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I voted. It feels good to get it done, even if my son is going to "cancel my vote."

One of my happiest memories as a child is when my parents would drive back from voting - they always took me along - and my mother, a swing voter, would tell my father that she "canceled his vote," by voting for the Democrat.

In the good old family tradition, my oldest son announced he would be "cancelling my vote."

All three of us here at home, and the son away who will be voting in PA, are voting straight Democratic for all candidates, from Biden/Harris on down, but I voted against all three ballot initiatives on the NJ ballot, including the one that would legalize marijuana.

I don't believe that people should go to jail for possessing, smoking or even (privately) growing it, but I don't want legal pot stores here.

My son was a little upset with me and gave me the "alcohol is worse than pot" lecture that one hears, and while I'm not sure that the premise of that argument is wrong, I retorted that pancreatic cancer is worse than breast cancer, but this doesn't support an argument to make breast cancer easier to get. (To my knowledge, he has never smoked pot, but I don't want to make it easier for him to try.)

(He didn't like that.)

But the important point is that both my wife and dropped our ballots in the special drop boxes NJ has distributed, and there's two more votes for Joe and Kamala, and for the rest of the Democratic ticket, and two more to go from my family, my vote cancelling son and my "no pot on the ballot" son in PA.

I feel great!

Editors of the prestigious scientific journal Nature endorse Joe Biden!

Nature has been very active recently - for a very clear reason - in encouraging scientists to get political. Now there's this, another unprecedented US Presidential endorsement from a major scientific journal, following NEJM:

Why Nature supports Joe Biden for US president.

We cannot stand by and let science be undermined. Joe Biden’s trust in truth, evidence, science and democracy make him the only choice in the US election.

On 9 November 2016, the world awoke to an unexpected result: Donald Trump had been elected president of the United States.

This journal did not hide its disappointment. But, Nature observed, US democracy was designed with safeguards intended to protect against excesses. It is founded on a system of checks and balances that makes it difficult for a president to exercise absolute power. We were hopeful that this would help to curb the damage that might result from Trump’s disregard for evidence and the truth, disrespect for those he disagrees with and toxic attitude towards women.

How wrong we turned out to be.

No US president in recent history has so relentlessly attacked and undermined so many valuable institutions, from science agencies to the media, the courts, the Department of Justice — and even the electoral system. Trump claims to put ‘America First’. But in his response to the pandemic, Trump has put himself first, not America.

His administration has picked fights with the country’s long-standing friends and allies, and walked away from crucial international scientific and environmental agreements and organizations: notably, the 2015 Paris climate accord; the Iran nuclear deal; the United Nations’ science and education agency UNESCO; and even, unthinkable in the middle of a pandemic, the World Health Organization (WHO).

Challenges such as ending the COVID-19 pandemic, tackling global warming and halting the proliferation and threat of nuclear weapons are global, and urgent. They will not be overcome without the collective efforts of the nation states and international institutions that the Trump administration has sought to undermine.

On the domestic front, one of this administration’s most dangerous legacies will be its shameful record of interference in health and science agencies — thus undermining public trust in the very institutions that are essential to keeping people safe...

...Joe Biden must be given an opportunity to restore trust in truth, in evidence, in science and in other institutions of democracy, heal a divided nation, and begin the urgent task of rebuilding the United States’ reputation in the world.

I'm quite sure it's open sourced, and the full endorsement can be read at the Nature website.

The outcome of world history very much depends on this election. As the job of the scientist is to engage with reality, to analyze it, to report it, and indeed to predict outcomes, these actions by the premier journals of the scientific community are of paramount importance.

A comprehensive quantification of global nitrous oxide sources and sinks

The paper I'll discuss in this post is this one: A comprehensive quantification of global nitrous oxide sources and sinks (Tian, H., Xu, R., Canadell, J.G. et al. Nature 586, 248–256 (2020))

Nitrous oxide, N2O, laughing gas, has always been a part of the nitrogen cycle, but with the invention of the Haber-Bosch process in the early 20th century, on which our modern food supply depends, the equilibrium has been severely disturbed. Since, like CFC's, nitrous oxide is both a greenhouse gas and an ozone depletion agent. I'm sure I've written in this space and elsewhere about this serious environmental issue, since it worries me quite a bit. So this paper in Nature caught my eye. The authors are a consortium of scientists from around the world, who have assembled what may be the most detailed account of accumulations of this gas in the atmosphere.

The abstract is open sourced, and may be found at the link in the paper. It is worth pointing out the cogent portions of it however:

Analysis of process-based model estimates reveals an emerging N2O–climate feedback resulting from interactions between nitrogen additions and climate change. The recent growth in N2O emissions exceeds some of the highest projected emission scenarios3,4, underscoring the urgency to mitigate N2O emissions.

From the introduction to the paper:

Nitrous oxide (N2O) is a long-lived stratospheric ozone-depleting substance and greenhouse gas with a current atmospheric lifetime of 116 ± 9 years1. The concentration of atmospheric N2O has increased by more than 20% from 270 parts per billion (ppb) in 1750 to 331 ppb in 2018 (Extended Data Fig. 1), with the fastest growth observed in the past five decades5,6. Two key biochemical processes—nitrification and denitrification—control N2O production in both terrestrial and aquatic ecosystems and are regulated by multiple environmental and biological factors including temperature, water and oxygen levels, acidity, substrate availability7 (which is linked to nitrogen fertilizer use and livestock manure management) and recycling8,9,10. In the coming decades, N2O emissions are expected to continue to increase as a result of the growing demand for food, feed, fibre and energy, and an increase in sources from waste generation and industrial processes4,11,12. Since 1990, anthropogenic N2O emissions have been reported annually by Annex I Parties to the United Nations Framework Convention on Climate Change (UNFCCC). More recently, over 190 national signatories to the Paris Agreement have been required to report biannually their national greenhouse-gas inventory with sufficient detail and transparency to track progress towards their nationally determined contributions. However, these inventories do not provide a full picture of N2O emissions owing to their omission of natural sources, the limitations in methodology for attributing anthropogenic sources, and missing data for a number of key regions (for example, South America and Africa)2,9,13. Moreover, a complete account of all human activities that accelerate the global nitrogen cycle and that interact with the biochemical processes controlling the fluxes of N2O in both terrestrial and aquatic ecosystems is required2,8. Here we present a comprehensive, consistent analysis and synthesis of the global N2O budget across all sectors, including natural and anthropogenic sources and sinks, using both bottom-up and top-down methods and their cross-constraints. Our assessment enhances understanding of the global nitrogen cycle and will inform policy development for N2O mitigation, which could help to curb warming to levels consistent with the long-term goal of the Paris Agreement.

The authors refer to "bottom up" analyses, which consists basically of multiple source terms such as known emissions, modeling of agricultural inputs based on field measurements, etc., and "top down" analyses which consist of measurements coupled to transport flux modeling. The utilize 43 N2O "flux estimates" 30 of which are "bottom up," 5 of which are "top down" and 8 models.

They write:

With this extensive data and bottom-up/top-down framework, we established comprehensive global and regional N2O budgets that include 18 sources and various different chemical sinks. These sources and sinks are further grouped into six categories (Fig. 1, Table 1): (1) natural sources (no anthropogenic effects) including a very small biogenic surface sink; (2) perturbed fluxes from ecosystems induced by changes in climate, carbon dioxide (CO2) and land cover; (3) direct emissions from nitrogen additions in the agricultural sector (agriculture); (4) other direct anthropogenic sources—including fossil fuel and industry, waste and waste water, and biomass burning; (5) indirect emissions from ecosystems that are either downwind or downstream from the initial release of reactive nitrogen into the environment—including N2O release after transport and deposition of anthropogenic nitrogen via the atmosphere or water bodies as defined by the Intergovernmental Panel on Climate Change (IPCC)14; and (6) the atmospheric chemical sink, for which one value is derived from observations and the other is derived from the inversion models

This cartoon figure gives a feel for sources:

Fig. 1: Global N2O budget for 2007–2016.

The caption:

The coloured arrows represent N2O fluxes (in Tg N yr−1 for 2007–2016) as follows: red, direct emissions from nitrogen additions in the agricultural sector (agriculture); orange, emissions from other direct anthropogenic sources; maroon, indirect emissions from anthropogenic nitrogen additions; brown, perturbed fluxes from changes in climate, CO2 or land cover; green, emissions from natural sources. The anthropogenic and natural N2O sources are derived from bottom-up estimates. The blue arrows represent the surface sink and the observed atmospheric chemical sink, of which about 1% occurs in the troposphere. The total budget (sources + sinks) does not exactly match the observed atmospheric accumulation, because each of the terms has been derived independently and we do not force top-down agreement by rescaling the terms. This imbalance readily falls within the overall uncertainty in closing the N2O budget, as reflected in each of the terms. The N2O sources and sinks are given in Tg N yr−1. Copyright the Global Carbon Project.

A Tg - terragram - is, of course, a million metric tons.

Isotopic analyses can show the sources, by the way, of N2O. For example, N2O in the troposphere is slightly enriched in the O17 isotope, which is believed to be connected with interactions of atmospheric ammonia and the dangerous fossil fuel combustion waste NO2. The origin of the anomalous or “mass‐independent” oxygen isotope fractionation in tropospheric N2O (Crutzen, et al., Geophys. Res. Lett. Volume 28, Issue 3 1 February 2001 Pages 503-506)

In the paper under discussion there is a rather large table l will not reproduce here that breaks down various source inputs and outputs, natural and anthropogenic. The mean value for concentrations of nitrous oxide in the atmosphere have risen from a mean value of 1,462 Tg, 1.462 billion tons, to a mean value in the period between 2007 and 2016 of 1,555 Tg, 1.555 billion tons, an increase of 93 million tons.

A breakdown of inputs represented graphically:

Fig. 2: Regional N2O sources in the decade 2007–2016.

The caption:

The Earth’s ice-free land is partitioned into ten regions: North America, South America, Europe, Middle East, Africa, Russia, East Asia, South Asia, Southeast Asia and Oceania. Each subplot shows the emissions from five sub-sectors using bottom-up approaches, followed by the sum of these five categories using bottom-up approaches (blue) and the estimates from top-down approaches (yellow). Bottom-up and top-down estimates of ocean emissions are shown at the bottom left (from bottom to top, lighter to darker, the contributions from the 30°–90° N, 30° S–30° N and 90°–30° S regions). Error bars indicate the spread between the minimum and the maximum values. The centre map shows the spatial distribution of 10-year average N2O emissions from land and ocean based on the land and ocean models. Per capita N2O emission (kg N per capita per year) during 2007–2016 is shown in Supplementary Fig. 2. The map was created using ESRI ArcMap 10.4.1.

Fig. 3: Ensembles of regional anthropogenic N2O emissions over the period 1980–2016.

The caption:

The bar chart in the centre shows the accumulated changes in regional and global N2O emissions during the study period of 1980–2016. Error bars indicate the 95% confidence interval for the average of accumulated changes. The Mann–Kendall test was performed to examine a monotonic increasing or decreasing trend in the estimated ensemble N2O emissions globally and for each region over the period 1980–2016. The accumulated changes were calculated from the linear regressed annual change rate (Tg N yr−2) multiplied by 37 years. All regions except Southeast Asia show a significant increasing or decreasing trend in the estimated ensemble N2O emissions during the study period . *P < 0.05.


Fig. 4: Historical and projected global anthropogenic N2O emissions and concentrations.

a–d, Global anthropogenic N2O emissions (a, b) and concentrations (c, d) compared to the four RCPs in the IPCC assessment report 5 (a, c; ref. 2) and the new marker scenarios based on the SSPs used in CMIP6 (b, d; ref. 48). The historical emissions data are represented as the mean of the bottom-up and top-down estimates of anthropogenic N2O emissions, whereas the historical atmospheric concentration data are from the three available observation networks: AGAGE, NOAA, and CSIRO. Top-down anthropogenic emissions were calculated by subtracting natural fluxes derived from bottom-up approaches. To aid the comparison, the four RCPs were shifted down so that the 2005 value is equal to the 2000–2009 average of the mean of top-down and bottom-up estimates. The SSPs are harmonized3 to match the historical emissions used in CMIP649; Extended Data Fig. 10 shows the unharmonized data.

These IPCC reports by the way, are bitterly comical in all of their optimistic scenarios, "RCP" Representative Concentration Pathways. Things are not even "business as usual" as described in the early editions. Things are worse than business as usual.

This is true here. The authors write:

Observed atmospheric N2O concentrations are beginning to exceed predicted levels across all scenarios. Emissions need to be reduced to a level that is consistent with or below that of RCP 2.6 or SSP 1−2.6 in order to limit warming to well below the 2 °C target of the Paris Agreement. Failure to include N2O within climate mitigation strategies will necessitate even greater abatement of CO2 and methane. Although N2O mitigation is difficult because nitrogen is the key limiting nutrient in agricultural production, this study demonstrates that effective mitigation actions have reduced emissions in some regions—such as Europe—through technological improvements in industry and improved efficiency of nitrogen use in agriculture.

Nitrous oxide will support combustion; it is an oxidizing gas. In theory it would be reduced by fire, but in general, combustion also generates significant higher nitrates, NO and NO2 which are ultimately transformed into N2O.

The main sink is photolytic, at wavelengths below 230 nm, which is in the UV range. Singlet oxygen, a high energy state of oxygen gas, also can destroy N2O. It is also generated by radiation, as well as some chemical means.

In recent years, I have come to think of air as a working fluid in Brayton cycle/combined cycle power plants. I've returned to an old idea about which I thought much in the 1990s and early 2000's - although they were not directed at that time to Brayton cycles, but rather as Rankine cycles, which is to use highly radioactive materials as heat transfer agents, in those days, salts in the liquid phase, in these days salts and metals in the vapor phase. Under these circumstances, new sinks for highly stable or highly problematic greenhouse and ozone depleting agents, as well as particulates, might represent a new sink for not just nitrous oxide, but others.

I trust you are enjoying a safe, productive, and enjoyable weekend.

Electrochemical oxidation of 243Am(III) in nitric acid by a terpyridyl-derivatized electrode.

The paper I'll discuss in this post came out about 5 years ago, but somehow I missed it. The paper is: Electrochemical oxidation of 243Am(III) in nitric acid by a terpyridyl-derivatized electrode (Christopher J. Dares1, Alexander M. Lapides1, Bruce J. Mincher2, Thomas J. Meyer1,* Science Vol. 350, Issue 6261, pp. 652-655).

I've written several times about the element amercium, in this space, most recently about its separation from its f-series cogener, europium.

Liquid/Liquid Extraction Kinetics for the separation of Americium and Europium. The process described therein is a solvent based process, but utilizes specialized membranes. As I noted at that time, there are several drawbacks to the process.

However americium is potentially valuable fuel, particularly because of its nonproliferation value, since burning it will generate the heat generating isotope plutonium 238, (via the decay of Cm-242, formed from the decay of Am-242) which when added to other plutonium isotopes, can make them all useless in nuclear weapons.

It turns out, on further inspection, that Am-242 and its nuclear isomer Am-242m - both of which are highly fissionable - are among the best possible breeder fuels, having a high neutron multiplicity, meaning they can serve to transmute uranium into plutonium, greatly expanding the immediate availability of nuclear energy while avoiding isotope separations.

Here is the plot of the neutron multiplicity for the fission of Am-242(m):

Evaluated Nuclear Data File (ENDF) Retrieval & Plotting ("Neutron induced nubar." )

This spectrum, which is from the ENDF nuclear data files is clearly not highly resolved, to be sure, and surely represents a kind of average. It is undoubtedly difficult to obtain highly purified Am-242m for experimental verification. An interesting approach to obtaining it in high isotopic has been proposed, owing to its possible utility in making very small nuclear reactors for medical or space applications: Detailed Design of 242mAm Breeding in Pressurized Water Reactors (Leonid Golyand, Yigal Ronen & Eugene Shwageraus, Nuclear Science and Engineering, 168:1, 23-36 (2011)). To my knowledge, however, this proposal has never been reduced to practice.

There are very few nuclei that exhibit this high a multiplicity, over 3 neutrons per fission at any incident neutron energy. To my immediate knowledge, the only such nuclei is plutonium-241, and this over a fairly narrow range of incident neutron energies in the epithermal region.

I also discussed the critical masses of americium isotopes in this space: Critical Masses of the Three Accessible Americium Isotopes. In a fast nuclear spectrum, americium-241, the common americium isotope produced in the common thermal nuclear reactors that dominate the commercial nuclear industry, particularly in used fuel that has been stored for decades without reprocessing, is fissionable and thus is a potential nuclear fuel in its own right.

A "refinement" of some nuclear physics parameters relevant to the use of americium as a nuclear fuel was published about 13 years ago as of this writing, by scientists at Los Alamos: Improved Evaluations of Neutron-Induced Reactions on Americium Isotopes (P. Talou,*† T. Kawano, and P. G. Young, Nuclear Science and Engineering 155, 84–95 2007).

In a fast nuclear reactor, neutrons have an energy of 1 to 2 MeV whereas in a thermal reactor, the neutron speed is taken to be the kinetic energy of molecules in air, generally taken as 0.0253 eV, almost 100 million times lower energy. Thermalized neutrons tend to be absorbed without fission in americium-241, whereas at higher energy, they tend to fission. The following graphics from this paper show that for a region of neutrons well above the thermal region, but in the general region with the fission to capture ratio climbs:

The next graphic, from the same paper, shows that the neutron induced fission of americium-241, like its capture product, americium-242(m), has a very high neutron multiplicity, meaning that it is also an excellent breeder fuel under these conditions:

Even limited to the left most region of this graphic, which is actually the region in which "fast" reactors work, the multiplicity is shown to be above 3 neutrons/fission. The graph indicates that were the fusion people ever able to run a fusion reactor, where neutrons emerge with an incredible 14 MeV energy, and chose to use a hybrid approach fusion/fission approach to solve the unaddressed problem of heat transfer, americium could provide very high neutron fluxes to do incredible amounts of the valuable work that neutrons can do.

The next question is "How much Americium is Available?"

Kessler - who writes frequently on the subject of denaturing nuclear materials to make them useless for weapons applications - addressed this issue about 12 years ago in this paper: G. Kessler (2008) Proliferation Resistance of Americium Originating from Spent Irradiated Reactor Fuel of Pressurized Water Reactors, Fast Reactors, and Accelerator-Driven Systems with Different Fuel Cycle Options, Nuclear Science and Engineering, 159:1, 56-82.

According to the IAEA calculations he referenced in this paper, as of 2005, there were about 106 MT in used nuclear fuel all around the world. During storage of used nuclear fuel, especially MOX fuel, but not limited in any sense to it, the amount of americium rises because of the decay of its precursor, plutonium-241, Pu-241, which has a half-life of 14.29 years, and which invariably accumulates as a nuclear reactor operates. Ten years after removal from an active core, about 61.6% of the Pu-241 in the fuel will still be present, with the balance having decayed to Am-241. Because of anti-nuclear fear and ignorance, which is quite literally killing the world we know and love, we now have unprocessed used nuclear fuel that has been stored for 40 years or more, without having been processed, albeit this without killing anyone. Forty year old used nuclear fuel will still contain 14.4% of the Pu-241 originally in it, but will obviously have more americium than it did when it was removed from the reactor. (The half-life of Am-241 is 432.6 years.) It seems reasonable to me that we may have more than 200 MT of americium available. This is not a lot of material, but it is significant. The energy content of this much americium, fully fissioned, is very roughly equal to about 10% to 20% of the annual energy demand of the United States. This much americium is certainly not enough to address any more than a tiny fraction of the completely unaddressed climate crisis, but on the other hand, the high neutron multiplicity can certainly accelerate the rate at which we can accumulate fissionable nuclei that are the only viable option for doing anything about climate change. (And let's be clear. Right now we are doing less than nothing to address climate change.) The amount of americium available to use is certainly enough to run 10 to 20 nuclear reactors running exclusively on americium.

Kessler's paper offered some calculations of the isotopic vectors of the Americium available in different fuel scenarios and presented them graphically. In connection with the thermal neutron spectrum graphics he writes:

Figure 2 shows the isotopic ratios of 241Am, 242mAm, and 243Am for a variety of different fuel cycle options in the spent-fuel elements of a modern PWR for a cooling time of 10 yr after discharge.18–24 Options A and B represent low-enriched-uranium LEU fuel after a burnup between 33 and 50 GWd/t…

...In options C, D, and E, either reenriched reprocessed uranium ~RRU! ~option C! or natural uranium or RRU both together with plutonium options D and E! are used…

...In options F and G, RRU or thorium is mixed with plutonium and MAs in order to incinerate both plutonium and MAs in PWRs.

Figure 2:

The graphic refers to a 10 year cooling period, and again, many used nuclear fuels are much older, with the result that the percentage of Am-241 in these cases would be more enriched in Am-241 with respect to the other isotopes.

Kessler offers similar analysis in various fast neutron cases which I will not discuss here. Very few of these types of reactors have operated commercially, although the advent of small modular "breed and burn" reactors, which Kessler does not address, will likely change this. Kessler also doesn't address a case which in my imagination would be superior to all solid fuel cases, specifically liquid metal fuels, a case that was abandoned in the 1960s because of the relatively primitive state of materials science in those days but is certainly worth reexamining 60 years later, given significant advances in that science.

Anyway, in writing this post, and researching it, I have convinced myself once in for all, that my previous feeling that it was a disgrace to let Pu-241 decay into Am-241 was wrong. I have changed my mind: Am-241 is more valuable than Pu-241, even accepting the high value of Pu-241.

This brings me to the Science paper referenced at the outset of this post:

Americium in its chemistry is dominated by the +3 oxidation state, and in this state, it behaves very much like the lanthanide f elements. Significant quantities of the lower lanthanide f elements are formed via nuclear fission, from lanthanum itself up to and including gadolinium.

The process described in the above referenced Science paper uses electrochemistry to make americium behave more like uranium, neptunium, and plutonium, in exhibiting oxidation states higher than +3, and thus having far different properties than the lanthanides.

From the paper's introduction:

Nuclear energy continues to be an attractive large-scale energy source due to its high power density and lack of carbon emissions (1). However, there are drawbacks to its expanded use, including the management of used fuel and high-level waste (HLW) (2, 3). The presence of the minor actinide americium in the nuclear waste stream greatly limits the storage capacity of geologic repositories due to heat production, especially from 241Am, which is a major contributor to the long-term radiotoxicity of HLW. Closed nuclear fuel recycling schemes that improve uranium efficiency and minimize the volume of HLW are under development in nuclear energy programs worldwide. In these schemes, Am must be separated from the lanthanides before transmutation because their high-neutron cross sections would otherwise disrupt the fission efficiency of the recycled fuel. Some schemes also separate Am from curium to facilitate radiologically safe fuel fabrication (4).

Partitioning of Am from the lanthanides is arguably the most difficult separation in radiochemistry. The stable oxidation state of Am in aqueous, acidic solutions is Am(III). With its ionic radius comparable to the radii of the trivalent lanthanide ions, its coordination chemistry is similar, leaving few options for separation. One approach is the use of soft donor ligands that exploit the slightly more diffuse nature of the actinide 5f-orbitals over the harder lanthanide 4f-orbitals. This provides a stronger, more covalent bond between actinides and N-donor ligands. Notable progress has been made in complexation-based strategies, but considerable challenges have been encountered when attempting to adapt their narrow pH range requirements for process scale-up, stimulating efforts to find alternatives. Another approach is oxidation and separation using the higher oxidation states of Am (5, 6). Unlike the lanthanides, with the exception of the ceric cation, Am(III) can be oxidized and forms [AmVO2]+ and [AmVIO2]2+ complex ions in acidic media. The high oxidation state ions could be separated from the lanthanides by virtue of their distinct charge densities using well-developed solvent extraction methods (4)...

Although solvent extraction method are in fact, well developed, it does not follow that they are the best approach to separations of the elements in used nuclear fuel. If I were to look at electrochemical oxidation of americium, I would also look at electrochemical based separation, including an analogue to the separation of nucleic acids and proteins, electrophoretic migration through gels, or liquid/liquid, gel, or solid based ion selective membranes.

The beauty of electrochemistry is that it avoids the use of reagents. the wide use of primitive solvent extraction methods in the mid to late 20th century led to problematic situations like the Hanford tanks about which very stupid anti-nukes carry on endlessly even as they completely ignore, with contempt for humanity, the millions upon millions of people killed every damned year, at a rate if about 19,000 human beings per day, from dangerous fossil fuel waste.

More excerpts of text in the paper:

Penneman and Asprey first reported the generation of Am(V) and Am(VI) in the 1950s (7). Determination of the formal reduction potentials has relied on both direct electrochemical measurements and indirect calorimetry. Formal potentials for the Am(IV/III) couple were evaluated in the 1960s and 1970s in concentrated phosphoric acid solutions (≈2 to 15 M) with Am(IV) stabilized and Am(V) destabilized by phosphate coordination, decreasing the driving force for disproportionation (8–12). Am(IV) is also stabilized in mildly acidic, concentrated fluoride solutions (13). Reported values for the Am(IV/III) potential have varied from as low as 2.2 V to as high as 2.9 V, with the standard value of 2.62 V versus the saturated calomel electrode (SCE) in 1 M perchloric acid...

...Oxidizing Am(III) in noncomplexing media is hampered by the high potential for the intermediate Am(IV/III) couple (Fig. 1) (15). Only a limited number of chemical oxidants, including persulfate and bismuthate, have been explored for this purpose (16). Oxidation by persulfate gives sulfate as a by-product, which complicates subsequent vitrification of the waste (17). Bismuthate suffers from very low solubility, necessitating a filtration step that complicates its removal (16). Adnet and co-workers have patented a method for the electrochemical generation of high-oxidation-state Am in nitric acid solutions (18), based on earlier results by Milyukova et al. (19, 20), who demonstrated Am(III) oxidation to Am(VI) in acidic persulfate solutions with Ag(I) added as an electron transfer mediator with Eo[Ag(II/I)] = 1.98 V versus SCE...

The fact that the authors are embracing the cultural mentality of so called "nuclear waste," rather than the recovery of valuable nuclear materials, has no bearing on the quality of their science. I just have to say that.

The redox potentials of americium:

The caption:

Fig. 1 Latimer diagram for Am in 1 M perchloric acid. Potentials listed are V versus the SCE.

The authors proposed the use of a new type of electrode, an organic/indium tin oxide electrode, to oxidize americium. Here is a a cartoon representation of this electrode:

The caption:

Fig. 2 Molecular structure of p-tpy on the surface of an ITO particle with the protonation state depicted as expected in neutral pH.

(Left) A simple molecular illustration. (Right) A density functional theory–optimized p-tpy structure with pyridine rings oriented to show the potential tridentate bonding motif, ideally placed on a surface.

A word on indium tin oxide: This compound is found in pretty much every touch screen in the world. It is also widely used in some types of solar cells. In the past, at DU, I used to engage a dumb "renewables will save us" anti-nuke in discussion of the fact - facts matter - that the world supply of indium is limited, and therefore any so called "renewable energy" technology based on it is, um, well, not in fact "renewable." Ultimately this person bored me to death, and I put him or her on my lovely "ignore" list, since there is no value in engaging people who simply repeat distortions and outright lies over and over, in a Trumpian fashion. The fact remains supplies of indium are limited. It is considered a "critical material" of concern to people who study such things. The world does risk running out of it. The difference, of course, between cell phones and solar cells and nuclear fuel reprocessing plants do not require large amounts of mass, since the environmental superiority of nuclear fuel to all other energy forms derives entirely from its enormous energy to mass ratio. In fact, indium is a minor fission product found in used nuclear fuel, and more than enough can easily be recovered from such a fuel to make these electrodes. I am not endorsing these particular types of electrodes by the way; I'm not sure that nitric acid solutions are in fact the best approach to nuclear fuel reprocessing; there are strong arguments that they are not. The point is, that in comparison to the requirements of solar cells and cell phones, the requirement for indium in this case, were it to go commercial - and it never may do so - is trivial.

Some graphics on the electrochemical results obtained in working with the electrode:

The caption:

Fig. 3 Electrochemical oxidation of 0.43 mM Am(III) in 0.1 M nitric acid with 0.9 M sodium nitrate using a p-tpy–derivatized ITO electrode.

(Left) Am speciation measured by visible spectroscopy in a 1-cm cuvette at an applied potential of 1.8 V versus SCE. The appearance of Am(V), concurrent loss of Am(III), and overall mass balance are plotted. (Right) Electrochemical Am oxidation scheme involving a p-tpy–derivatized electrode.

The authors remark on the effect of radiation on these solutions:

Autoreduction by radiolytic intermediates provides an explanation for only partial oxidation of Am(III) to Am(V) and Am(VI) at the electrolysis steady state, as observed here. Quantitating the extent of autoreduction and its role in defining the electrolysis steady state are important elements in possible electrochemical/separation schemes for Am. Compared with chemical oxidation, the electrochemical procedure offers the advantage of avoiding complications from oxidizing agents and their reduced forms (16).

Radiolysis of water by Am generates one-electron reducing agents such as H atoms and two-electron reducing agents such as hydrogen peroxide, as well as other redox transients (35). The concentration of radiolysis products varies linearly with total Am concentration, with zero-order reduction kinetics observed for the appearance or disappearance of Am species. Under these conditions, rate constants for these Am species during autoreduction can therefore be derived from the slopes of concentration-time plots (36, 37).

Radiolytically produced one-electron and two-electron reductants provide independent pathways for Am(VI) reduction, with an overall rate constant for Am(VI) loss of 23.4 × 10−6 s−1 (fig. S10). The Am(IV) produced from the two-electron reduction of Am(VI) by radiolytic intermediate or intermediates, presumably H2O2, rapidly disproportionates to Am(V) and Am(III). The reduction of Am(V) to Am(IV) or Am(III) is slow on this time scale (fig. S10).

It seems to me, perhaps naively, that this issue might be addressed by continuous separation, by methods to which I alluded above, to continuous separations, driving the equilibrium. Part of the problem might be addressed by putting beta emitting species - which in real life would be present anyway - in the solution, but no matter.

Some more commentary:

Electrolysis of an 84 μM solution of Am(III) at 2.25 V, 130 mV below the Am(IV/III) couple, gives Am(V) and Am(VI), both of which grow linearly in concentration with time (Fig. 4). After 1 hour, the increase in Am(VI) remains linear but with a noticeable decrease in rate. The growth in Am(V) also slows after 1 hour, eventually leveling off to reach a steady-state concentration of 30 μM. After 13 hours of electrolysis, the composition of the solution was 9 μM (11%) Am(III), 45 μM (54%) Am(V), and 30 μM (36%) Am(VI).

Figure 4:

The caption:

Fig. 4 Electrochemical oxidation of 84 μM Am(III) in 0.1 M nitric acid with 0.9 M sodium nitrate using a p-tpy–derivatized ITO electrode at an applied potential of 2.25 V versus SCE.

(Left) Am speciation as measured by visible spectroscopy in a 50-cm waveguide. (Right) Visible spectra of species before controlled potential electrolysis and after 13 hours of electrolysis with highlighted speciation changes.

The authors conclude:

Our results demonstrate low-potential oxidation of Am(III) to Am(VI) in noncoordinating solutions at high-surface-area metal oxide electrodes derivatized with a surface-bound terpyridine ligand. The mechanism appears to involve surface binding of Am(III) and oxidation to Am(IV) followed by further oxidation to Am(V) with release as [AmO2]+. Electrochemical oxidation is in competition with autoreduction by radiolysis intermediates, with Am(VI) more susceptible to reduction than Am(V).

This is an interesting little paper. I very much enjoyed going through it as well as thinking a little more deeply about the entire subject of americium, which might prove a valuable tool in saving the world via the use of nuclear energy.

While considering all of this, I have to say what's always on my mind:

To my way of thinking, opposition to nuclear energy - even though such opposition appears often on my end of the political spectrum - is criminally insane.

Right now, hurricanes are marching, year after year, all over the United States and other parts of the world. Vast forests, farms and homes have burned all over the Western United States this year, droughts are destroying crops as are things like derechos. We do not record the number of people killed by extreme heat events, but the scientific literature suggests these numbers are rather large, and we have seen the most extreme temperatures ever recorded in 2020. Insects that spread infections are appearing at ever higher latitudes...

The list of the scale of what we are experiencing from climate change goes on and on and on...

And yet...and yet...and yet...I hear from people that "nuclear power is too dangerous." Compared to what?

Let's be clear on something, OK? Opposition to nuclear energy is as ridiculous and as absurd as refusing to wear masks in the Covid-19 epidemic because of political orthodoxy; similarly it kills people. Many of us on the left should examine and confront our own anti-science political orthodoxy, much as old white men like myself need to examine and confront our suppressed racist rationalizations.

Questioning ourselves is something we all must do; because we cannot hope to struggle to achieve the status of being moral human beings without doing so.

Nuclear energy need not be entirely risk free to be vastly superior to everything else; it only needs to be vastly superior to everything else, which it is. It is immoral to oppose nuclear energy.

I trust that you will have a safe, yet rewarding weekend.

How Trump damaged science -- and why it could take decades to recover.

This is a news item in the current issue of the scientific journal Nature: How Trump damaged science — and why it could take decades to recover. (Jeff Toleffson, Nature News October, 6, 2020)

I don't believe a subscription is required.

Some excerpts from this rather long news story, necessarily long since so much damage has been done.

Some excerpts:

People packed in by the thousands, many dressed in red, white and blue and carrying signs reading “Four more years” and “Make America Great Again”. They came out during a global pandemic to make a statement, and that’s precisely why they assembled shoulder-to-shoulder without masks in a windowless warehouse, creating an ideal environment for the coronavirus to spread.

US President Donald Trump’s rally in Henderson, Nevada, on 13 September contravened state health rules, which limit public gatherings to 50 people and require proper social distancing. Trump knew it, and later flaunted the fact that the state authorities failed to stop him. Since the beginning of the pandemic, the president has behaved the same way and refused to follow basic health guidelines at the White House, which is now at the centre of an ongoing outbreak. As of 5 October, the president was in a hospital and was receiving experimental treatments.

Trump’s actions — and those of his staff and supporters — should come as no surprise. Over the past eight months, the president of the United States has lied about the dangers posed by the coronavirus and undermined efforts to contain it; he even admitted in an interview to purposefully misrepresenting the viral threat early in the pandemic. Trump has belittled masks and social-distancing requirements while encouraging people to protest against lockdown rules aimed at stopping disease transmission. His administration has undermined, suppressed and censored government scientists working to study the virus and reduce its harm. And his appointees have made political tools out of the US Centers for Disease Control and Prevention (CDC) and the Food and Drug Administration (FDA), ordering the agencies to put out inaccurate information, issue ill-advised health guidance, and tout unproven and potentially harmful treatments for COVID-19.

“This is not just ineptitude, it’s sabotage,” says Jeffrey Shaman, an epidemiologist at Columbia University in New York City, who has modelled the evolution of the pandemic and how earlier interventions might have saved lives in the United States. “He has sabotaged efforts to keep people safe.”

The statistics are stark. The United States, an international powerhouse with vast scientific and economic resources, has experienced more than 7 million COVID-19 cases, and its death toll has passed 200,000 — more than any other nation and more than one-fifth of the global total, even though the United States accounts for just 4% of world population...

...As he seeks re-election on 3 November, Trump’s actions in the face of COVID-19 are just one example of the damage he has inflicted on science and its institutions over the past four years, with repercussions for lives and livelihoods. The president and his appointees have also back-pedalled on efforts to curb greenhouse-gas emissions, weakened rules limiting pollution and diminished the role of science at the US Environmental Protection Agency (EPA). Across many agencies, his administration has undermined scientific integrity by suppressing or distorting evidence to support political decisions, say policy experts.

“I’ve never seen such an orchestrated war on the environment or science,” says Christine Todd Whitman, who headed the EPA under former Republican president George W. Bush.

This is from Christie Todd Whitman, who in the Bush administration was certainly a previous "worst ever" administrator of that agency, refusing to do a damned thing about climate change. Even a Republican with as a pathetic view of environmental issues can be outraged by Trump.

...All the while, the president has peddled chaos and fear rather than facts, as he advances his political agenda and discredits opponents. In dozens of interviews carried out by Nature, researchers have highlighted this point as particularly worrisome because it devalues public trust in the importance of truth and evidence, which underpin science as well as democracy.

“It’s terrifying in a lot of ways,” says Susan Hyde, a political scientist at the University of California, Berkeley, who studies the rise and fall of democracies. “It’s very disturbing to have the basic functioning of government under assault, especially when some of those functions are critical to our ability to survive.”...

There's plenty here, read it and weep...

Why Nature needs to cover politics now more than ever

An Editorial in Nature has recently discussed why scientists must be politically engaged: Why Nature needs to cover politics now more than ever.

It's open sourced; no subscription is required.

For convenience, some excerpts:

Since Nature’s earliest issues, we have been publishing news, commentary and primary research on science and politics. But why does a journal of science need to cover politics? It’s an important question that readers often ask.

This week, Nature reporters outline what the impact on science might be if Joe Biden wins the US presidential election on 3 November, and chronicle President Donald Trump’s troubled legacy for science. We plan to increase politics coverage from around the world, and to publish more primary research in political science and related fields.

Science and politics have always depended on each other. The decisions and actions of politicians affect research funding and research-policy priorities. At the same time, science and research inform and shape a spectrum of public policies, from environmental protection to data ethics. The actions of politicians affect the higher-education environment, too. They can ensure that academic freedom is upheld, and commit institutions to work harder to protect equality, diversity and inclusion, and to give more space to voices from previously marginalized communities. However, politicians also have the power to pass laws that do the opposite.

The coronavirus pandemic, which has taken more than one million lives so far, has propelled the science–politics relationship into the public arena as never before, and highlighted some serious problems. COVID-related research is being produced at a rate unprecedented for an infectious disease, and there is, rightly, intense worldwide interest in how political leaders are using science to guide their decisions — and how some are misunderstanding, misusing or suppressing it...

...Perhaps even more troubling are signs that politicians are pushing back against the principle of protecting scholarly autonomy, or academic freedom. This principle, which has existed for centuries — including in previous civilizations — sits at the heart of modern science.

Today, this principle is taken to mean that researchers who access public funding for their work can expect no — or very limited — interference from politicians in the conduct of their science, or in the eventual conclusions at which they arrive. And that, when politicians and officials seek advice or information from researchers, it is on the understanding that they do not get to dictate the answers...

... Last year, Brazil’s President Jair Bolsonaro sacked the head of the country’s National Institute for Space Research because the president refused to accept the agency’s reports that deforestation in the Amazon has accelerated during his tenure. In the same year, more than 100 economists wrote to India’s prime minister, Narendra Modi, urging an end to political influence over official statistics — especially economic data — in the country.

And just last week, in Japan, incoming Prime Minister Yoshihide Suga rejected the nomination of six academics, who have previously been critical of government science policy, to the Science Council of Japan. This is an independent organization meant to represent the voice of Japanese scientists. It is the first time that this has happened since prime ministers started approving nominations in 2004...

An Enantioefficient Synthesis of Ergocryptine w/Direct Synthesis of the (+) Lysergic Acid Component.

The paper I'll discuss in this post is 16 years old. It is this one: Enantioefficient Synthesis of α-Ergocryptine:  First Direct Synthesis of (+)-Lysergic Acid (István Moldvai, Eszter Temesvári-Major, Mária Incze, Éva Szentirmay, Eszter Gács-Baitz, and Csaba Szántay The Journal of Organic Chemistry 2004 69 (18), 5993-6000)

This is the structure of ergocryptine as drawn in this paper:

When this molecule is brominated, using N-bromosuccinimde, it is called bromocryptine, which is a drug used to treat Parkinson's disease, a few types of substance abuse diseases, and, interestingly, Type 2 diabetes.


Recently, in this space, I referred to the latter molecule in a paper about the relationship between microbial fuel cells and Parkinson's disease in connection with electron transfer, and I remarked that I'd informed my sons and my son's girlfriend, that the structure of the upper ring system, which is obviously peptide derived from the amino acids valine, leucine and proline, had a hemiacetal structure.

That post (uncorrected) is here: Electron Shuttling in Parkinson's Disease Elucidated by Microbial Fuel Cells.

Thankfully I was corrected by a correspondent, our leader in this forum in fact, who noted that this is in fact not a hemiacetal, but is rather an orthohemiaminal.

To be frank, I can't recall running across too many orthoaminals, but I assumed, correctly, that somewhere that there was a synthesis of this molecule, which is a derivative of lysergic acid, the famous precursor to LSD which was discovered at Sandoz by Albert Hoffman, whose serious scientific work work on ergot alkaloids includes a synthesis of the upper ring system, a paper which I will cite below. The paper cited above at the outset includes a direct synthesis of lysergic acid and an improved synthesis of Hoffman's synthesis of the upper ring system.

Orthoaminals seem to be relatively rare in the literature, a quick search in Google scholar in my hands produced less than 100 hits. It is thus somewhat surprising that Hoffman's generation of that structure was not all that elaborate from what I can pick out of the German text.

First the introductory text from the paper cited at the outset:

Ergot alkaloids, of which lysergic acid is representative, are particularly important as they possess the widest spectrum of biological activity found in any family of natural products”.1 One of the biologically most important ergot alkaloids is α-ergocryptine (1). Its semisynthetic derivative, the so-called bromocryptine, is one of the most widely used drugs in this family (e.g., as a prolactin inhibitor, or an anti-Parkinsonian).2 Great efforts have been devoted to the synthesis of ergot alkaloids during the second half of the last century. Conceptually, retrosynthetic cleavage of the central amide bond devides the problem into two parts, the synthesis of the lysergic acid and of the peptide dilactam moiety.

The first synthesis of racemic lysergic acid was effected by Woodward and Kornfeld in 1956.3,16 One of their main problems was to prepare ring C from the otherwise easily accessible 3-indolepropionic acid (3), since the ring closure of the corresponding acid chloride occurred at the more reactive pyrrole ring instead of the benzene ring. Thus the Woodward group reduced the pyrrole ring, the amine was protected by benzoylation, and thereafter the ring closure took place regioselevtively as desired. The drawback of this approach is that sooner or later the pyrroline moiety must be reoxidized to a pyrrole ring. It is difficult to perform an enantioefficient synthesis as well, since the method involves introduction of an unnecessary chiral center by the reduction. The earlier described resolution of racemic compound needs further and rather inconvenient steps.4 So far the total synthesis of (±)-2a has been achieved by nine groups, but the number of publications dealing with the synthetic efforts is much higher. Among these approaches one can find about a dozen methods trying to construct the ergoline ring, some of which were successful; others remained at the level of attempt.5 Seven of the nine successful syntheses used the reduced indoline derivative as the starting compound. Oppolzer et al.3 performed the first total synthesis avoiding the reduction step, but their procedure again cannot be scaled up. A second approach to the racemic acid was published recently.6

We decided to construct the ergoline skeleton starting from indole, thus avoiding the reoxidation problem, and at the same time making an enantioefficient synthesis possible.7

An ideal starting material was the so-called Uhle's ketone (4a) having the intact indole ring, although the original synthesis of 4a is rather tedious. Uhle commenced with acetylation and subsequent bromination, and he claimed that the derived bromo-derivative 4b could be subjected successfully to a substitution reaction with various amines.9 Early in the seventies Bowman and co-workers reinvestigated a few results of Uhle's synthesis and established that one of the key steps, alkylation of several types of amines with 4b, always failed.10 The approach starting from 4a by Stoll used the Stobbe condensation as a key step, but the reaction sequence could not be carried out,11 thus the synthesis of lysergic acid starting from Uhle's ketone remained a challenge.

How they did it:

The caption:

Scheme 2.  Synthesis of 4-Bromo-Uhle's Ketone (4g) from 3a

a Reagents and conditions:  (a) (1) powdered KOH + Piv-Cl, CH2Cl2 + THF, (2) SOCl2, (3) AlCl3 + ClCH2COCl, CH2Cl2 (43%, overall); (b) ref 15 (85%); (c) HO(CH2)2OH, p-TSA, benzene, reflux, 6 h (81%); (d) MeNH2, CHCl3, 10−15 °C, 3−4 h (88%); (e) aq HCl (1 M), acetone, rt, 3 h (97%).

The caption:

Scheme 3.  Synthesis of Tetracyclic Ketone [(+)-7]a

a Reagents and conditions:  (a) 5 + 4d, toluene, 48 h, rt (35%); (b) 5 + 4g, THF, 24 h, rt (56%); (c) MeNH2, benzene, 10−15 °C, 1 h (80%); (d) aq HCl (6 M), 35−40 °C, 1 h then (e) 6c in CHCl3, LiBr + TEA, 0−5 °C, 12 h (60%, 2 steps); (f) ( − )-dibenzoyl-l-tartaric acid, CH3CN + H2O (1:1) (38%).

The caption:

Scheme 4.  Synthesis of (+)-Lysergic Acid (2a) from (+)-7a

a Reagents and conditions:  (a) (+)-7 + 8, t-BuOK, THF + t-BuOH, 0 °C, 20 min then + H2O, −5 °C (77%); (b) aq HCl (2 M), reflux, 30 min (13%); (c) NaOMe, MeOH, 70−75 °C, 30 min (70%); (d) HCl/MeOH (6.7 M), 75−80 °C, 45 min (72%); (e) aq NaOH (5 M), MeOH, 70−80 °C, 2.5 h then aq HCl (6 M) to pH 6.5 (54%).

When I was a kid, I used to do a fair amount of amino acid related synthetic chemistry, and so I tend to see amino acids in everything. I always saw the tryptophan in the structure of lysergic acid, and I remember chatting with a friend of mine the way one does in the lab and speculating that they cyclization to what I now know as Uhle's ketone could be accomplished by having the tryptophan side chain acylate the benzogroup of the indole ring. This would retain the necessary stereochemistry at the nitrogen, free of charge. I was a stupid and naďve kid, since there is no way to assure the regiochemistry of actually accomplishing this, but it's not like it was even a remotely serious conversation.

It turns out however, as is referenced in this paper, that Rappaport group did synthesize a stereochemically pure Uhle's ketone using a serine starting material: Enantiospecific Synthesis of (R)-4-Amino-5-oxo-1,3,4,5-tetrahydrobenz[cdindole, an Advanced Intermediate Containing the Tricyclic Core of the Ergots] (Clarence R. Hurt, Ronghui Lin, and Henry Rapoport The Journal of Organic Chemistry 1999 64 (1), 225-233)

Here is the route, beginning with the (complex) synthesis of bromotryptophan in such a way as to assure regiospecificity for the cyclization.

The caption:

Scheme 2.  Synthesis of d-(+)-4-Bromotryptophan

The serine in this scheme is the molecule numbered 12; it is protected as a MOM (methoxymethyl) acetal of formaldehyde. (I should have used that protecting group more often; but I was a stupid kid).

Uhle's ketone:

The caption:

Scheme 4.  Synthesis of Tricyclic α-Amino Ketonea

a Both (±) and (+) compounds were prepared; only the (+) form is shown.

Anyway, about that orthohemiaminal. I kind of thought it would be very difficult to make, but it looks like it sort of falls out in this elegant synthesis by Albert Hofmann and his coworkers. The text is in German:

Die Synthese der Alkaloide der Ergotoxin‐Gruppe. 70. Mitteilung über Mutterkornalkaloide (P. A. Stadler St. Guttmann H. Hauth R. L. Huguenin Ed. Sandrin G. Wersin H. Willems A. Hofmann, Helv Chim Acta Volume 52, Issue 6 1969 Pages 1549-1564)

In this picture, the awkwardly drawn molecule 10 with the ridiculously long amide bond spontaneously arranges to the orthohemiaminal, 11.

The text describing this reaction is in German, so one can either look at the pictures or muddle through translating the German.

The German Text:

Die Dioxopiperazine wurden mit dem S-( +)-Isopropyl-benzyloxy-malonsauremonoathylester- chlorid 8 unter den Reaktionsbedingungen, wie sie im experimentellen Teil am Beispiel des Ergocristins beschrieben sind, umgesetzt. Die resultierenden Acyldioxopiperazine 10 a)-d), die wenig stabil sind, wurden nicht isoliert, sondern zwecks Abspaltung der Benzyl- Schutzgruppe sogleich niit Pd-Katalysator und Wasserstoff behandelt . Die primar entstehenden Isopropyl-hydroxy-malonyl-dioxopiperazine cyclisieren sich spontan unter Bildung der entsprechenden Cyclocarbonsiiureatliylester 11 a)-d). Die Cyclolbildung erfolgt stereospezifisch, indem jeweils nur die eine der an C-12' epimeren Formen, namlich diejenige mit der tertiaren Hydroxylgruppe in a-Stellung gebildet wird.

My translation:

The dioxopiperazine was reacted with the S-(+)-isopropylbenzyoxymonoethyl ester chloride using the reaction conditions used for example in experiments for the ergocristins previously described. The resulting acyloxopiperazine 10 a)-d) are only weakly stable and were not isolated, but were hydrogenated over Pd/C to remove the benzyl protecting group. The resulting isopropyl-hydroxy-malonyl-dioxopiperazines cyclize spontaneously to form the corresponding cyclocarboxylic acid ethyl esters 11 a) -d). The cyclol formation takes place stereospecifically; only the one of the forms of the epimer at C-12 ', namely the one with the tertiary hydroxyl group is formed

The emphasis is mine.

So much for the difficulty of forming a orthohemiaminal.

On a day like this, where one thinks, given the nutcase in the White House, that one must be hallucinating, must be on a bad trip, it was probably appropriate to stumble upon some lysergic acid chemistry while trying to think about electron transfer in Parkinson's disease and in microbial fuel cells.

Have a nice day tomorrow.

Biden is going to need to seriously disinfect the White House when he moves in.

He should also take care of any Covid residues.

Using Corn Cob Derived Biomaterials to Remove Heavy Metals and Kill Bacteria in Contaminated Water.

The paper I'll discuss in this post is this one: Polyethylenimine-Grafted-Corncob as a Multifunctional Biomaterial for Removing Heavy Metal Ions and Killing Bacteria from Water (Qin Meng, Shengdong Wu, and Chong Shen Industrial & Engineering Chemistry Research 2020 59 (39), 17476-17482).

With a little bit of googling, it appears to me that the world produces about 1.1 billion tons of corn each year, presumably measured as grain. According to the introduction of the above cited paper, which I will excerpt, corn cobs, which are generally discarded, account for a mass 1/4 as large as the grain itself, somewhere around 250 million tons. From a table in the paper, that I'll reproduce from the paper, it appears that corncobs are about 43% carbon, meaning that somewhere around 100 to 110 million tons of carbon can be obtained from corncobs.

While we are engaged in Godotian waiting for the grand so called "renewable energy" nirvana that has not come, is not here, and won't come, we are currently dumping about 35 billion tons of the dangerous fossil fuel waste carbon dioxide into the planetary atmosphere.

The interesting product discussed in this paper will not sequester all that much carbon in use, even if - as surely will not happen - all the corn cobs in the world were utilized to make the biomaterial discussed herein. Nevertheless this is carbon captured from the air, and every little bit counts. In theory, at least, carbon captured from corn cobs and sequestered as value added products might remove a billion tons every decade, not all that much, but nothing at which to sneeze. Thus this is an interesting little paper.

The corn cobs in this paper are functionalized, as noted in the title, with polyethylenimine, which is a polymer synthesized by chain ring opening of aziridine, the simplest nitrogen organic heterocycle, a cyclic molecule having two carbons, five hydrogens and one nitrogen. Aziridine is generally made via various routes from ethylene. All, or almost all, of the world's ethylene is obtained from dangerous fossil fuels. However many other starting materials are certainly possible on an industrial scale. Syngas is a mixture of hydrogen and carbon oxides - generally the monoxide - which can be made from pretty much any carbon containing material and water, including carbon dioxide with the agency of heat, nuclear heat if one is seeking a carbon free route. There are many routes to ethylene from syngas. My personal favorite proceeds via the intermediate dimethyl ether, which I personally believe should be the core chemical portable energy medium in a sustainable world. It is described here: Direct Conversion of Syngas into Methyl Acetate, Ethanol, and Ethylene by Relay Catalysis via the Intermediate Dimethyl Ether (Zhou et al., Angew. Chem. Int. Ed. 2018, 57, 12012 –12016)

Ethylene can also be made via the partial hydrogenation of acetylene, and acetylene can be made from multiple carbon sources by many means, notably heating a carbon source with calcium metal, albeit with varying degrees of efficiency. The calcium hydroxides produced in such a process can be useful for carbon dioxide capture from either air or from combustion gases or reformer gases.

Thus it is theoretically possible to derive the corn cob derived product described here entirely from carbon dioxide in the air, although any polyethylenimine used for these purposes would merely sequester dangerous fossil fuel derived carbon.

Here is the cartoon accompanying the abstract of the paper:

From the paper's introduction:

Corn is one of the most widely grown grain crops throughout the world and is mostly planted in the United States, China, and Brazil.(1) However, corncob, accounting for a quarter of the total quanity of corn, is usually discarded as agricultural waste.(2) In fact, corncob can be a good biomass that is low-cost, green, and reliable. There is an increasing interest in adding value to corncob, such as applications in the production of bioethanol,(3) furfural,(4) fermentable sugars,(5) and succinic acid.(6)

By now, corncob-based biochars, corncob mixtures, and even corncob itself have been developed into biosorbents for removal of heavy metal ions from aqueous solution. For example, calcined corncob biochars showed maximum adsorption capabilities of less than 40 mg/g for Cu2+,(7) Pb2+,(8) and Cd2+,(8) while the acrylonitrile modification on the biochars improved the Cd2+ adsorption capacity to 85.6 mg/g.(2) In addition, a mixture of tea waste, corncob, and sawdust had adsorptive capacities of 39.5, 94.0, and 41.5 mg/g for Cu2+, Pb2+, and Cd2+.(9) Interestingly, Garg et al. reported that corncob itself could remove 105.6 mg/g of Cd2+ from aqueous solution,(10) even more potent than the biochars and mixtures. Nevertheless, the adsorptive capabilities of these biosorbents are not high because the mechanism was dominated by physisorption via the weak van der Waals force between the metal ions and corncob surface(8) due to the lack of functional groups on the sorbents.

Polyethylenimine (PEI), a polymer that contains a large amount of primary and secondary amine side groups, can bind to heavy metal ions via chelating forces.(11) The strong binding forces of chelation attributed to the high adsorptive capability (>100 mg/g) of PEI modified materials such as bacterial cellulose,(12) P84 nanofiltration membrane,(13) chitin,(14) and magnetic nanoparticles(15) to heavy metal ions. In addition, PEI also displayed wide-spectrum antimicrobial effects(16) due to its cation property, so that the PEI-grafted materials (e.g., polyurethane ureteral stents) showed potent antibacterial ability in medical applications.(17,18) Economically, PEI is a bulk chemical that is much cheaper than other materials such as silver nanoparticles.
Because of these properties of PEI, this paper aims to develop a multifunctional material via grafting PEI on corncob. The PEI-modified corncob is expected to perform functions like removing heavy metal ions and killing bacteria. As the two aspects are critical and usually coexist in treatment of polluted water, multifunctional PEI-g-OC should be a useful biomaterial in the application of water treatment, e.g., portable devices for water purification. The PEI-g-OC performs significant advantages on cheapness, lightweight and environmental-friendliness over chemical synthetic materials.

A cartoon about the route to the product, a photograph of the starting materials, intermediate and product, and some spectra:

The caption:

Figure 1. Preparation and characterization of PEI-g-OC. (A) Preparation procedure of PEI-g-OC. (B–D) Morphology, FTIR spectra, and thermogravimetric curves of corncob, oxidized corncob (OC), and PEI-g-OC.

A table of the elemental composition of the final product and the intermediates, giving a feel, as mentioned above, for the carbon sequestration capability of these materials:

Copper, for which toxicity is concentration dependent, is pretty much found in all potable water from piping, cadmium and lead to varying degrees from historic solders and or leachate from landfills, cadmium from discarded nickel cadmium batteries, and - increasingly in the future - from discarded CIGS type photovoltaic devices, both portable (as in old calculators and toys) and/or solar cells.

An idea of the capacity of these materials for heavy metals, in this case cadmium, copper and lead:

The caption:

Figure 2. Effect of pH and other metal ions on adsorption of heavy metal ions. (A) Effect of pH on the adsorptive capability of PEI-g-OC in water. m/v = 0.1 g/L. Concentration of heavy metal ions is 5 mg/L. (B) Effect of Na+, Ca2+ and Mg2+ (10 mM) on the adsorptive capability of PEI-g-OC. pH at 5 for Pb2+ and pH at 5.5 for Cd2+ and Cu2+. m/v = 0.1 g/L.

Langmuir and Freundlich isotherms, which are technical measurements of evaluating surface chemistry:

The caption:

Figure 3. Adsorption of heavy metal ions on PEI-g-OC. (A) Time-dependent adsorption on PEI-g-OC in water. Concentration of heavy metal ions is 10 mg/L. (B) Adsorption isotherm of heavy metal ions on PEI-g-OC in water (t = 12 h). pH at 5 for Cu2+ and pH at 5.5 for Cd2+ and Pb2+. m/v = 0.1 g/L.

The antibacterial properties of the PEI impregnated corn cob material was determined against E. coli, P. aeruginosa, and S. aureus:

The caption:

Figure 4. PEI-g-OC killed viable bacteria. Bacteria on the tissue culture plate surface (A–C) and PEI-g-OC (D–F, green channel; G–I, red channel). Green: viable bacteria stained by SYTO 9. Red: dead bacteria stained by propidium iodide. Scale bar = 5 μm.

The caption:

Figure 5. Antibacterial activity of the PEI-g-OC. Bacterial viability after challenged with 104 CFU/ml of P. aeruginosa, S. aureus, or E. coli for 12 h. OC = oxidized corncob; TCPS = tissue culture plate surface.

The authors determined that the product was reusable:

The caption:

Figure 6. Reuse of PEI-g-OC on removal of heavy metal ions. Concentration of heavy metal ions is 10 mg/L. m/v = 1 g/L.

The paper's conclusion:

PEI-g-OC that was developed from agricultural waste of corncob presented high adsorptive capabilities to Cu2+, Cd2+ and Pb2+ at 159.5, 212.6, and 224.0 mg/g in water. Moreover, the PEI-g-OC could potently kill the model bacteria of S. aureus, P. aeruginosa, and E. coli with MIC at 3.5, 12.0, and 8.5 mg/mL. The multifunction of PEI-g-OC in killing bacteria and removing heavy metal ions indicated its potential application in water treatment.

It is notable that products like these that capture metals can be utilized to create low grade ores. The inexhaustibility of uranium resources is tied to precisely such an approach.

It's an interesting little paper.

I wish you a safe, healthy and enjoyable Sunday afternoon.

Electron Shuttling in Parkinson's Disease Elucidated by Microbial Fuel Cells.

The paper I'll discuss in this post is this one: Deciphering Electron-Shuttling Characteristics of Parkinson’s Disease Medicines via Bioenergy Extraction in Microbial Fuel Cells (Chen et al, Industrial & Engineering Chemistry Research 2020 59 (39), 17124-17136.

Since my regular journal reading list - the reading list for pleasure, as opposed for my paid work - often includes journals focusing on issues relating to energy and the environment, I often come across papers relating to microbial fuel cells. I tend not to read these papers in any level of detail, since my main focus is on carbon dioxide issues and high temperature thermal schemes, but my general feeling is that they may prove to be a way to recover some energy in water treatment systems while simultaneously cleaning up the water.

The current issue of Industrial & Engineering Chemistry Research is about biomass utilization, a topic which is of very high interest to me, since it is one route - certainly not the only route - to capture of carbon dioxide from the air, a topic which will be of extreme importance in the future given our ongoing failure to do anything even remotely practical to address climate change.

In spite of my low passing interest in microbial fuel cells, this particular article caught my eye because my oldest son, a designer/artist, has an independent interest in neurobiology as it relates to perception and in general, to mood and to consciousness itself. In addition my youngest son's girlfriend is studying neurobiological psychology. Also any paper that intrinsically brings together two very disparate scientific issues is immediately interesting.

From the introductory text:

Due to gradual exhaustion of fossil fuels over the globe, exploring green sustainability and renewable energy applications has become an important issue. In particular, bioenergy could be regenerated without secondary pollution and thus be considered as the most environmentally friendly renewable energy in the world. Among them, microbial fuel cells (MFCs) as bioelectrochemical systems utilize electroactive microbes to directly oxidize organics, converting chemical energy to be bioelectricity. In addition, provided that specific microbes were selected for bioelectric generation in MFCs, exogenous supplementation of energy nutrients or electron shuttles (ESs) could significantly enhance electron-transport phenomena, leading to remarkable rises in bioelectricity generation.(1) To improve the power-generating efficiency, augmentation of exogenous ESs as “electrochemical catalysts” to MFCs was found to be very electroactive to promote electron transfer efficiency for power generation.(2) Owing to electron-shuttling characteristics, phenolic derivatives could form stable “radical-resonant” intermediates to promote the electron transfer for redox reaction(s). Such stable and reversible transferring capabilities could take place via electron/radical delocalization within the chemical structure through the resonance effects.(3) As a matter of fact, such a resonance effect could stably take place at the benzene ring of the aromatic structure. That is, the benzene ring of the aromatic structure may be one of the necessary criteria to initiate the electron-shuttling capability to be effectively expressed. In addition, regarding the electrochemical characterization of different functional group(s) (e.g., hydroxyl (−OH), amine (−NH2), carboxy (−COOH)) on the benzene ring, as O and N are more electronegative than C, this leads to their strong tendency as antioxidants...

... Moreover, for dihydroxyl (diOH)-bearing aromatics, compared to meta-isomers, ortho- or para-dihydroxyl (diOH) substituent-bearing phenolics possessed more promising electrochemical activities for electron-shuttling.(5,6) For example, the literature(7) further mentioned that accumulation of azo dye-decolorized metabolites (DMs) could catalytically stimulate the efficiency of electron transfer, thereby enhancing the bioelectricity generation of MFCs. However, microbial decolorization of azo dyes would generate aromatic amine (−NH2) intermediates,(8) inevitably leading to possible concerns of secondary pollution to the environment...

...Recently, the study(10) has also evaluated ortho-diOH-substituents (e.g., o-diOH-bearing dopamine (DA) and epinephrine (EP)), showing that such neurotransmitter-related chemicals could significantly mediate electrochemical properties, thereby effectively promoting bioelectricity generation in MFCs. It was also suspected that such electron-mediating capabilities were strongly associated with neurotransmission among neurons, muscle cells, or gland cells. For example, DA is an endogenous hormone and neurotransmitter in the human brain and body. It is released from presynaptic neurons to synaptic cleft and binds to postsynaptic receptors to causes actions of postsynaptic cells, in turn promoting transmission among postsynaptic cells.(11)...

...The major families of drugs to treat PD are dopamine agonists, Levodopa, and monoamine oxidase inhibitors (MAO-B inhibitors).(16,17) They are applied to different nerve conduction or neurotransmitting pathways to reduce symptoms of PD. In fact, as Levodopa and dopamine are electron-shuttling chemicals, it was thus proposed that the involvement or initiation of DA-associated chemicals with high bioelectrochemical-catalyzing activities seemed to be significant for disease medication. That was why this study selected seven representative medicines used in clinical treatment for comparative assessment (Figure 1; Table S1)...

Figure 1:

The caption:

Figure 1. Conceptual schematics of metabolic pathways associated with the treatment of Parkinson’s disease medicines: (a) levodopa (L-DOPA), (b) benserazide (BSZ), (c) entacapone (ETP), (d) rasagiline (RSL), (e) amantadine (AMTD), (f) apomorphine (APO), ropinirole (RPNR), bromocriptine (BM).

I sent my sons and my youngest son's girlfriend the following commentary when I emailed this paper to them:

In figure one, the molecule at the top, bromocriptine, labeled "BM," the lower fused ring system is bromolysergic acid, the upper ring system is actually a peptoid - a system that has a peptide structure that has been slightly modified.

The three amino acids in this interesting ring system are valine and isoleucine and proline. The carboxylic acid in proline has been reduced to an aldehyde and then formed into a structure called a "hemiacetal, connected to an oxygen from an oxidized form of valine, alpha hydroxyvaline, making the valine a "aminal." These types of lysergic acid/peptoid structures are very common in the ergot alkaloids, from which several major neuroactive, including neuromuscular active, drugs have been developed, including ergotamine, and methasergide for chronic headaches, ergonovine and methergine to induce labor, and of course, the chemically brominated bromocriptine, utilized in parkinson's.

LSD, and a few other hallucinogenic molecules are also derivatives of lysergic acid, of course.

The point is that all of these molecules act on neurotransmitters.

The microbial fuel cells utilized an electroactive organism, Aeromonas hydrophilia, which was originally obtained from a river in Taiwan. It apparently has been investigated for it's ability to decolorize waste water from dyeing plants in the textile industry.

Some more text this from the main body of the paper:

Among PD-associated medicines, both DA and EP contained ortho-dihydroxybenzene structures to show significant potentials to effectively augment bioelectricity formation in MFCs. To extensively confirm such phenomena, this work also quantitatively evaluated such electron-mediating characteristics of candidate chemicals [e.g., 10 typical PD-treating medicines (i.e., dopamine (DA), levodopa (L-DOPA), benserazide (BSZ), rasagiline (RSL), apomorphine (APO), entacapone (ETP), orphenadrine (OPD), amantadine (AMTD), ropinirole (RPNR), bromocriptine mesylate (BM)] which were thus chosen as model medicines for study. That is, such promoting capabilities were suspected to be strongly associated with medication power to treat PD. As DA and EP are crucial neurotransmitting-chemicals in the human brain, this study tended to uncover whether the medicines with redox-mediating capabilities for bioenergy extraction were possibly related to curative power to PD. This study would explore whether they could exhibit such reversible and stable electron-shuttling characteristics to stimulate bioenergy-extracting capabilities.

The authors found that L-Dopa, dopamine, and APO all gave enhanced electrochemical signals in the microbial fuel cell.

Some more figures from the text:

The caption:

Figure 2. Cyclic voltammetric profiles of scan cycle 50 for some neurotransmitters and Parkinson’s medicines (0.3 mM): (a) dopamine (DA), (b) levodopa (L-DOPA), (c) benserazide (BSZ), and (d) apomorphine (APO). (Note that, as BSZ was not so electrochemically sensitive to CV analysis, a higher concentration of 30 mM was chosen for testing.)

The caption:

Figure 4. MS/MS fragment analysis of apomorphine (APO) (a) before (powder) and (b) after (0.3 mM) cyclic voltammetry in treatment of 50 cycles (positive ion (+p); negative ion (−p)).

The authors utilized a high resolution mass spec, a Thermo Q Exactove Plus - an orbitrap mass spec - to study the products of the APO, apomorphine, in the fuel cell.

The caption:

Figure 4. MS/MS fragment analysis of apomorphine (APO) (a) before (powder) and (b) after (0.3 mM) cyclic voltammetry in treatment of 50 cycles (positive ion (+p); negative ion (−p)).

The authors studied the power density of the microbiological fuel cells in the presence of Parkinson's medications. Note that the units give a feel for the required size for these types of devices:

The caption:

Figure 5. Comparison of power-density profiles using 0.3 mM neurotransmitters and Parkinson’s medicines by two separate A. hydrophila NIU01-inoculated microbial fuel cells [blank (BK) was control MFC in the absence of test chemical; abbreviations denoted as benserazide (BSZ), apomorphine (APO), dopamine (DA), levodopa (L-DOPA), orphenadrine (OPD), amantadine (AMTD), and ropinirole (RPNR)].

The authors studied various hydroxybenzenes, a few of which are available from lignins, suggesting that the "black liquor" of paper making, which contains lignins, may be utilized in microbial fuel cell type systems to clean up the black liquor if the base can be neutralized. It should be said that lignins, I believe, will have many future uses in a post dangerous fossil fuel world, should one ever come to exist. I should note in the context of this paper, that one of the trihydroxybenzenes listed here, gallic acid, which can be obtained from wood, is a potential synthetic precursor to the neurologically active hallucinogen mescaline, in six - possibly fewer - steps, the point being that hydroxylated benzenes screw with your nerves. (The street drug known as Ecstasy or "Molly" is also a hydroxybenzene derivative, as is vanilla.)

The caption:

Figure 6. Cyclic voltammetric profiles of some model di- or trihydroxyl-based polyhydroxybenzenes (0.3 mM) at 50 cycles of CV scan: (a) catechol (1,2-DHB), resorcinol (1,3-DHB), and hydroquinone (1,4-DHB); and (b) pyrogallol (1,2,3-THB), phloroglucinol (1,3,5-THB), hydroxyhydroquinone (1,2,4-THB), and gallic acid (GA).

The caption:

Figure 7. Comparative profiles of power-density profiles using 0.3 mM dihydroxyl- or trihydroxyl-based polyhydroxybenzenes by (a) A. hydrophila NIU01-inoculated microbial fuel cells NIU01 and (b) mixed consortia-seeded microbial fuel cells (MFC-A) (blank (BK) denoted the control or test chemical-absent MFC; abbreviations denoted as catechol (1,2-DHB), resorcinol (1,3-DHB), hydroquinone (1,4-DHB), pyrogallol (1,2,3-THB), phloroglucinol (1,3,5-THB), hydroxyhydroquinone (1,2,4-THB), gallic acid (GA)).

This first-attempt study deciphered electrochemical characteristics of PD-associated medicines, implying that APO and BSZ for the medication of PD were strongly related to their redox-mediating capabilities. The most electrochemically promising species APO enhanced the activity of dopamine receptors, significantly augmenting the efficacy of PD medication. In addition, BSZ inhibited L-ADD activity in periphery for PD medication. Other medicines seemed not to be strongly associated with electrochemical activity for PD medication. To suggest feasible phenolics-containing organics as PD medicines, several model polyphenolics were compared for bioenergy-stimulating capabilities. In fact, hydroxyhydroquinone, pyrogallol, and hydroquinine were all electrochemically outstanding ESs (e.g., increased ca. 4–6 fold power generation in MFCs), implying that chemicals with such similar chemical structures should exhibit promising electrochemical characteristics for the medication of PD. In addition, this study also pointed out that MFC modules should be more promising bioelectrochemical devices to directly exhibit not only electrochemical properties but also the biocompatible nature of test chemical(s) for applications in biotechnology. This work also disclosed a guideline to disclose bioelectrochemical characteristics of chemical(s) associated with pharmaceutical capabilities, suggesting bioenergy stimulation as possible electrochemical means to catalyze drug medication.

A brief excerpt of the conclusion:

Regarding bioenergy stimulation, supplementing ortho- and para-polyhydroxybenzene chemicals to MFCs effectively augmented the performance of bioelectricity generation ca. 92–576%. Thus, polyhydroxybenzene-bearing aromatics could express significant electrochemical activity to improve bioelectricity-stimulating efficiency in MFCs. However, augmentation of non-polyphenolics-related chemicals to MFCs could not exhibit appropriate electrochemical characteristics to promote bioelectricity generation. It was suspected that supplementing ortho- or para-polyhydroxybenzene-based medicines (e.g., APO) for curative mediation of PD was very likely due to their bioenergy-stimulating capabilities.

An interesting and different approach to drug screening I think. Whether it would prove superior to other screening tools, I can't say. I haven't worked in neuroactive drug development, except for some very remotely related work on Alzheimer's medications and a few purely analytical programs for drugs utilized in PD.

Have a pleasant Sunday.
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