Publications by authors named "Michael J Russell"

66 Publications

Surgical management of Graves' disease: historical context and single institution experience.

N Z Med J 2022 02 4;135(1549):43-49. Epub 2022 Feb 4.

FRACS, Breast, Endocrine, Laparoscopic and Melanoma Surgeon, Department of General Surgery, Waitematā DHB, Auckland.

Aim: To describe indications and outcomes of total thyroidectomy for Graves' disease in a large New Zealand endocrine surgery unit, and to compare these results to international studies.

Methods: We analysed a prospectively collected database to describe the indications and outcomes of surgery for Graves' disease between December 2001 and January 2021.

Results: Among 64 patients who underwent total thyroidectomy at our tertiary centre for Graves' hyperthyroidism, Graves' ophthalmopathy and patient preference/aversion to radioactive iodine were the most common indications for surgery. Total thyroidectomy resulted in long-term control of thyrotoxicosis in all patients. There were no incidences of recurrent laryngeal nerve injury. One patient (1.6%) suffered permanent hypoparathyroidism.

Conclusion: Total thyroidectomy is a safe and effective treatment for Graves' disease. In our population, total thyroidectomy functions as a second-line treatment for Graves' disease.
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February 2022

Cobalt: A must-have element for life and livelihood.

Proc Natl Acad Sci U S A 2022 01;119(3)

Dipartimento di Chimica, Università degli Studi di Torino, 10125 Torino, Italy;

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http://dx.doi.org/10.1073/pnas.2121307119DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8784093PMC
January 2022

Cellular remains in a ~3.42-billion-year-old subseafloor hydrothermal environment.

Sci Adv 2021 Jul 14;7(29). Epub 2021 Jul 14.

Department of Geology, University of Johannesburg, Johannesburg, South Africa.

Subsurface habitats on Earth host an extensive extant biosphere and likely provided one of Earth's earliest microbial habitats. Although the site of life's emergence continues to be debated, evidence of early life provides insights into its early evolution and metabolic affinity. Here, we present the discovery of exceptionally well-preserved, ~3.42-billion-year-old putative filamentous microfossils that inhabited a paleo-subseafloor hydrothermal vein system of the Barberton greenstone belt in South Africa. The filaments colonized the walls of conduits created by low-temperature hydrothermal fluid. Combined with their morphological and chemical characteristics as investigated over a range of scales, they can be considered the oldest methanogens and/or methanotrophs that thrived in an ultramafic volcanic substrate.
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http://dx.doi.org/10.1126/sciadv.abf3963DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8279515PMC
July 2021

The "Water Problem"(), the Illusory Pond and Life's Submarine Emergence-A Review.

Life (Basel) 2021 May 10;11(5). Epub 2021 May 10.

Dipartimento di Chimica, Università degli Studi di Torino, via P. Giuria 7, 10125 Turin, Italy.

The assumption that there was a "water problem" at the emergence of life-that the Hadean Ocean was simply too wet and salty for life to have emerged in it-is here subjected to geological and experimental reality checks. The "warm little pond" that would take the place of the submarine alkaline vent theory (AVT), as recently extolled in the journal Nature, flies in the face of decades of geological, microbiological and evolutionary research and reasoning. To the present author, the evidence refuting the warm little pond scheme is overwhelming given the facts that (i) the early Earth was a water world, (ii) its all-enveloping ocean was never less than 4 km deep, (iii) there were no figurative "Icelands" or "Hawaiis", nor even an "Ontong Java" then because (iv) the solidifying magma ocean beneath was still too mushy to support such salient loadings on the oceanic crust. In place of the supposed warm little pond, we offer a well-protected mineral mound precipitated at a submarine alkaline vent as life's womb: in place of lipid membranes, we suggest peptides; we replace poisonous cyanide with ammonium and hydrazine; instead of deleterious radiation we have the appropriate life-giving redox and pH disequilibria; and in place of messy chemistry we offer the potential for life's emergence from the simplest of geochemically available molecules and ions focused at a submarine alkaline vent in the Hadean-specifically within the nano-confined flexible and redox active interlayer walls of the mixed-valent double layer oxyhydroxide mineral, fougerite/green rust comprising much of that mound.
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http://dx.doi.org/10.3390/life11050429DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8151828PMC
May 2021

Six 'Must-Have' Minerals for Life's Emergence: Olivine, Pyrrhotite, Bridgmanite, Serpentine, Fougerite and Mackinawite.

Life (Basel) 2020 Nov 19;10(11). Epub 2020 Nov 19.

Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109, USA.

Life cannot emerge on a planet or moon without the appropriate electrochemical disequilibria and the minerals that mediate energy-dissipative processes. Here, it is argued that four minerals, olivine ([Mg>Fe]SiO), bridgmanite ([Mg,Fe]SiO), serpentine ([Mg,Fe,]SiO[OH)]), and pyrrhotite (FeS), are an essential requirement in planetary bodies to produce such disequilibria and, thereby, life. Yet only two minerals, fougerite ([FeFeOH]·[(CO)·3HO]) and mackinawite (Fe[Ni]S), are vital-comprising precipitate membranes-as initial "free energy" conductors and converters of such disequilibria, i.e., as the initiators of a CO-reducing metabolism. The fact that wet and rocky bodies in the solar system much smaller than Earth or Venus do not reach the internal pressure (≥23 GPa) requirements in their mantles sufficient for producing bridgmanite and, therefore, are too reduced to stabilize and emit CO-the staple of life-may explain the apparent absence or negligible concentrations of that gas on these bodies, and thereby serves as a constraint in the search for extraterrestrial life. The astrobiological challenge then is to search for worlds that (i) are large enough to generate internal pressures such as to produce bridgmanite or (ii) boast electron acceptors, including imported CO, from extraterrestrial sources in their hydrospheres.
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http://dx.doi.org/10.3390/life10110291DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7699418PMC
November 2020

Chemobrionics: From Self-Assembled Material Architectures to the Origin of Life.

Artif Life 2020 22;26(3):315-326. Epub 2020 Jul 22.

University of Szeged, Department of Physical Chemistry and Materials Science.

Self-organizing precipitation processes, such as chemical gardens forming biomimetic micro- and nanotubular forms, have the potential to show us new fundamental science to explore, quantify, and understand nonequilibrium physicochemical systems, and shed light on the conditions for life's emergence. The physics and chemistry of these phenomena, due to the assembly of material architectures under a flux of ions, and their exploitation in applications, have recently been termed chemobrionics. Advances in understanding in this area require a combination of expertise in physics, chemistry, mathematical modeling, biology, and nanoengineering, as well as in complex systems and nonlinear and materials sciences, giving rise to this new synergistic discipline of chemobrionics.
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http://dx.doi.org/10.1162/artl_a_00323DOI Listing
January 2021

Simulating Serpentinization as It Could Apply to the Emergence of Life Using the JPL Hydrothermal Reactor.

Astrobiology 2020 03;20(3):307-326

Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California.

The molecules feeding life's emergence are thought to have been provided through the hydrothermal interactions of convecting carbonic ocean waters with minerals comprising the early Hadean oceanic crust. Few laboratory experiments have simulated ancient hydrothermal conditions to test this conjecture. We used the JPL hydrothermal flow reactor to investigate CO reduction in simulated ancient alkaline convective systems over 3 days (T = 120°C,  = 100 bar, pH = 11). H-rich hydrothermal simulant and CO-rich ocean simulant solutions were periodically driven in 4-h cycles through synthetic mafic and ultramafic substrates and Fe>Ni sulfides. The resulting reductants included micromoles of HS and formate accompanied possibly by micromoles of acetate and intermittent minor bursts of methane as ascertained by isotopic labeling. The formate concentrations directly correlated with the CO input as well as with millimoles of Mg ions, whereas the acetate did not. Also, tens of micromoles of methane were drawn continuously from the reactor materials during what appeared to be the onset of serpentinization. These results support the hypothesis that formate may have been delivered directly to a branch of an emerging acetyl coenzyme-A pathway, thus obviating the need for the very first hydrogenation of CO to be made in a hydrothermal mound. Another feed to early metabolism could have been methane, likely mostly leached from primary CH present in the original Hadean crust or emanating from the mantle. That a small volume of methane was produced sporadically from the CO-feed, perhaps from transient occlusions, echoes the mixed results and interpretations from other laboratories. As serpentinization and hydrothermal leaching can occur wherever an ocean convects within anhydrous olivine- and sulfide-rich crust, these results may be generalized to other wet rocky planets and moons in our solar system and beyond.
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http://dx.doi.org/10.1089/ast.2018.1949DOI Listing
March 2020

Fougerite: the not so simple progenitor of the first cells.

Interface Focus 2019 Dec 18;9(6):20190063. Epub 2019 Oct 18.

Aix Marseille Université, CNRS, BIP (UMR 7281), Marseille, France.

We here review the extraordinary mineralogical properties of green rusts and their naturally occurring form, fougerite, and discuss the pertinence of these properties within the alkaline hydrothermal vent (AHV) hypothesis for life's emergence. We put forward an extended version of the AHV scenario which enhances the conformity between extant life and its earliest progenitor by extensively making use of fougerite's mechanistic and catalytic particularities.
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http://dx.doi.org/10.1098/rsfs.2019.0063DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6802129PMC
December 2019

Prospecting for life.

Interface Focus 2019 Dec 18;9(6):20190050. Epub 2019 Oct 18.

NASA Astrobiology Institute, NASA Ames Research Center, Moffett Field, CA, USA.

Books with titles like 'The Call of the Wild' seemed to set a path for a life. Thus, I would be an explorer-a plan that did not work out so well, at least at first. On leaving school I got a job as a 'Works Chemist Improver', testing Ni catalysts for the hydrogenation of phenol to cyclohexanol. Taking night classes I passed enough exams to study geology at Queen Mary College, London. Armed thus I travelled to the Solomon Islands where geology is a 'happening'! Next was Canada to visit a mine sunk into a 1.5 billion year old Pb-Zn orebody precipitated from submarine hot springs. At last I reached the Yukon to prospect for silver. Thence to Ireland researching what I also took to be 'exhalative' (i.e. hot spring-related) Pb-Zn orebodies. While there in 1979, the discovery of 350°C metal-bearing acidic waters issuing from submarine Black Smoker chimneys in the Pacific sent us searching for fossil examples in the Irish mines. However, the chimneys we found were more like chemical gardens than Black Smokers, a finding that made us think about the emergence of life. After all, what better for life's emergence than to have a membrane comprising Fe minerals dosed with Ni in our chimneys to mediate the 'hydrogenation' of CO-life's job anyway. Indeed, such a membrane would keep redox and pH disequilibria at bay, just like biological membranes. At the same time, my field research among Alpine ophiolites-ocean floor mafic rocks obducted to the Alps-indicated that alkaline waters bearing H and CH were a result of serpentinization, a process that must have operated in all ocean floors over all time. Thus it was that we could predict the Lost City hydrothermal field 10 years before its discovery in the North Atlantic in the year 2000. Lost City comprises a number of alkaline springs at up to 90°C that produce carbonate and brucite (Mg[OH]) chimneys. We had surmised that Ni-enriched FeS chimneys would have precipitated at comparable alkaline springs issuing into a metal-rich carbonic ocean on the very early Earth (inducing membrane potentials comparable to those capable of succouring all life, and presumably, sufficient to drive life into being). However, our laboratory precipitates also revealed green rust, thought to be the precursor to the magnetite now comprising the Archaean Banded Iron Formations. We now look upon green rust, also known as fougèrite, as the tangible, base fractal of life.
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http://dx.doi.org/10.1098/rsfs.2019.0050DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6802130PMC
December 2019

Redox and pH gradients drive amino acid synthesis in iron oxyhydroxide mineral systems.

Proc Natl Acad Sci U S A 2019 03 25;116(11):4828-4833. Epub 2019 Feb 25.

NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109.

Iron oxyhydroxide minerals, known to be chemically reactive and significant for elemental cycling, are thought to have been abundant in early-Earth seawater, sediments, and hydrothermal systems. In the anoxic Fe-rich early oceans, these minerals would have been only partially oxidized and thus redox-active, perhaps able to promote prebiotic chemical reactions. We show that pyruvate, a simple organic molecule that can form in hydrothermal systems, can undergo reductive amination in the presence of mixed-valence iron oxyhydroxides to form the amino acid alanine, as well as the reduced product lactate. Furthermore, geochemical gradients of pH, redox, and temperature in iron oxyhydroxide systems affect product selectivity. The maximum yield of alanine was observed when the iron oxyhydroxide mineral contained 1:1 Fe(II):Fe(III), under alkaline conditions, and at moderately warm temperatures. These represent conditions that may be found, for example, in iron-containing sediments near an alkaline hydrothermal vent system. The partially oxidized state of the precipitate was significant in promoting amino acid formation: Purely ferrous hydroxides did not drive reductive amination but instead promoted pyruvate reduction to lactate, and ferric hydroxides did not result in any reaction. Prebiotic chemistry driven by redox-active iron hydroxide minerals on the early Earth would therefore be strongly affected by geochemical gradients of E, pH, and temperature, and liquid-phase products would be able to diffuse to other conditions within the sediment column to participate in further reactions.
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http://dx.doi.org/10.1073/pnas.1812098116DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6421445PMC
March 2019

Why the Submarine Alkaline Vent is the Most Reasonable Explanation for the Emergence of Life.

Bioessays 2019 01 15;41(1):e1800208. Epub 2018 Nov 15.

California Institute of Technology, JPL/NASA, 4800 Oak Grove Drive, M/S 183-601, Pasadena, California.

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http://dx.doi.org/10.1002/bies.201800208DOI Listing
January 2019

Green Rust: The Simple Organizing 'Seed' of All Life?

Life (Basel) 2018 Aug 27;8(3). Epub 2018 Aug 27.

Planetary Chemistry and Astrobiology, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109-8099, USA.

Korenaga and coworkers presented evidence to suggest that the Earth's mantle was dry and water filled the ocean to twice its present volume 4.3 billion years ago. Carbon dioxide was constantly exhaled during the mafic to ultramafic volcanic activity associated with magmatic plumes that produced the thick, dense, and relatively stable oceanic crust. In that setting, two distinct and major types of sub-marine hydrothermal vents were active: ~400 °C acidic springs, whose effluents bore vast quantities of iron into the ocean, and ~120 °C, highly alkaline, and reduced vents exhaling from the cooler, serpentinizing crust some distance from the heads of the plumes. When encountering the alkaline effluents, the iron from the plume head vents precipitated out, forming mounds likely surrounded by voluminous exhalative deposits similar to the banded iron formations known from the Archean. These mounds and the surrounding sediments, comprised micro or nano-crysts of the variable valence Fe/Fe oxyhydroxide known as green rust. The precipitation of green rust, along with subsidiary iron sulfides and minor concentrations of nickel, cobalt, and molybdenum in the environment at the alkaline springs, may have established both the key bio-syntonic disequilibria and the means to properly make use of them-the elements needed to effect the essential inanimate-to-animate transitions that launched life. Specifically, in the submarine alkaline vent model for the emergence of life, it is first suggested that the redox-flexible green rust micro- and nano-crysts spontaneously precipitated to form barriers to the complete mixing of carbonic ocean and alkaline hydrothermal fluids. These barriers created and maintained steep ionic disequilibria. Second, the hydrous interlayers of green rust acted as engines that were powered by those ionic disequilibria and drove essential endergonic reactions. There, aided by sulfides and trace elements acting as catalytic promoters and electron transfer agents, nitrate could be reduced to ammonia and carbon dioxide to formate, while methane may have been oxidized to methyl and formyl groups. Acetate and higher carboxylic acids could then have been produced from these C1 molecules and aminated to amino acids, and thence oligomerized to offer peptide nests to phosphate and iron sulfides, and secreted to form primitive amyloid-bounded structures, leading conceivably to protocells.
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http://dx.doi.org/10.3390/life8030035DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6161180PMC
August 2018

On the Natural History of Flavin-Based Electron Bifurcation.

Front Microbiol 2018 3;9:1357. Epub 2018 Jul 3.

CNRS, BIP, UMR 7281, IMM FR3479, Aix-Marseille University, Marseille, France.

Electron bifurcation is here described as a special case of the continuum of electron transfer reactions accessible to two-electron redox compounds with redox cooperativity. We argue that electron bifurcation is foremost an electrochemical phenomenon based on (a) strongly inverted redox potentials of the individual redox transitions, (b) a high endergonicity of the first redox transition, and (c) an escapement-type mechanism rendering completion of the first electron transfer contingent on occurrence of the second one. This mechanism is proposed to govern both the traditional quinone-based and the newly discovered flavin-based versions of electron bifurcation. Conserved and variable aspects of the spatial arrangement of electron transfer partners in flavoenzymes are assayed by comparing the presently available 3D structures. A wide sample of flavoenzymes is analyzed with respect to conserved structural modules and three major structural groups are identified which serve as basic frames for the evolutionary construction of a plethora of flavin-containing redox enzymes. We argue that flavin-based and other types of electron bifurcation are of primordial importance to free energy conversion, the quintessential foundation of life, and discuss a plausible evolutionary ancestry of the mechanism.
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http://dx.doi.org/10.3389/fmicb.2018.01357DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6037941PMC
July 2018

Frankenstein or a Submarine Alkaline Vent: Who is Responsible for Abiogenesis?: Part 2: As life is now, so it must have been in the beginning.

Bioessays 2018 08 4;40(8):e1700182. Epub 2018 Jul 4.

Planetary Chemistry and Astrobiology, Sec. 3225 MS:183-301, Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, 91109-8099, USA.

We argued in Part 1 of this series that because all living systems are extremely far-from-equilibrium dynamic confections of matter, they must necessarily be driven to that state by the conversion of chemically specific external disequilibria into specific internal disequilibria. Such conversions require task-specific macromolecular engines. We here argue that the same is not only true of life at its emergence; it is the enabling cause of that emergence; although here the external driving disequilibria, and the conversion engines needed must have been abiotic. We argue further that the initial step in life's emergence can only create an extremely simple non-equilibrium "seed" from which all the complexity of life must then develop. We assert that this complexity develops incrementally and progressively, each step tested for value added "in flight." And we make the case that only the submarine alkaline hydrothermal vent (AHV) model has the potential to satisfy these requirements.
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http://dx.doi.org/10.1002/bies.201700182DOI Listing
August 2018

Frankenstein or a Submarine Alkaline Vent: Who Is Responsible for Abiogenesis?: Part 1: What is life-that it might create itself?

Bioessays 2018 07 5;40(7):e1700179. Epub 2018 Jun 5.

Planetary Chemistry and Astrobiology, Jet Propulsion Laboratory California Institute of Technology, Pasadena, CA, 91109-8099, USA.

Origin of life models based on "energized assemblages of building blocks" are untenable in principle. This is fundamentally a consequence of the fact that any living system is in a physical state that is extremely far from equilibrium, a condition it must itself build and sustain. This in turn requires that it carries out all of its molecular transformations-obligatorily those that convert, and thereby create, disequilibria-using case-specific mechanochemical macromolecular machines. Mass-action solution chemistry is quite unable to do this. We argue in Part 2 of this series that this inherent dependence of life on disequilibria-converting macromolecular machines is also an obligatory requirement for life at its emergence. Therefore, life must have been launched by the operation of abiotic macromolecular machines driven by abiotic, but specifically "life-like", disequilibria, coopted from mineral precipitates that are chemically and physically active. Models grounded in "chemistry-in-a-bag" ideas, however energized, should not be considered.
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http://dx.doi.org/10.1002/bies.201700179DOI Listing
July 2018

Ingested bread clip as an unexpected diagnostic tool.

N Z Med J 2018 03 23;131(1472):90-96. Epub 2018 Mar 23.

Department of General Surgery, Christchurch Hospital, Christchurch.

We describe a case where a bread clip has in fact became lodged adjacent to a portion of small bowel affected by a deposit of previously undiagnosed metastatic serous carcinoma of likely ovarian origin.
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March 2018

Oesophageal adenocarcinoma associated with a right-sided aortic arch.

ANZ J Surg 2019 01 30;89(1-2):127-129. Epub 2017 Nov 30.

Department of General Surgery, Christchurch Hospital, Christchurch, New Zealand.

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http://dx.doi.org/10.1111/ans.14127DOI Listing
January 2019

Nitrogen Oxides in Early Earth's Atmosphere as Electron Acceptors for Life's Emergence.

Astrobiology 2017 Oct 12;17(10):975-983. Epub 2017 Oct 12.

5 Jet Propulsion Laboratory, California Institute of Technology , Pasadena, California.

We quantify the amount of nitrogen oxides (NOx) produced through lightning and photochemical processes in the Hadean atmosphere to be available in the Hadean ocean for the emergence of life. Atmospherically generated nitrate (NO) and nitrite (NO) are the most attractive high-potential electron acceptors for pulling and enabling crucial redox reactions of autotrophic metabolic pathways at submarine alkaline hydrothermal vents. The Hadean atmosphere, dominated by CO and N, will produce nitric oxide (NO) when shocked by lightning. Photochemical reactions involving NO and HO vapor will then produce acids such as HNO, HNO, HNO, and HONO that rain into the ocean. There, they dissociate into or react to form nitrate and nitrite. We present new calculations based on a novel combination of early-Earth global climate model and photochemical modeling, and we predict the flux of NOx to the Hadean ocean. In our 0.1-, 1-, and 10-bar pCO models, we calculate the NOx delivery to be 2.4 × 10, 6.5 × 10, and 1.9 × 10 molecules cm s. After only tens of thousands to tens of millions of years, these NOx fluxes are expected to produce sufficient (micromolar) ocean concentrations of high-potential electron acceptors for the emergence of life. Key Words: Nitrogen oxides-Nitrate-Nitrite-Photochemistry-Lightning-Emergence of life. Astrobiology 17, 975-983.
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http://dx.doi.org/10.1089/ast.2016.1473DOI Listing
October 2017

The Possible Emergence of Life and Differentiation of a Shallow Biosphere on Irradiated Icy Worlds: The Example of Europa.

Astrobiology 2017 Dec 10;17(12):1265-1273. Epub 2017 Oct 10.

1 Jet Propulsion Laboratory, California Institute of Technology , Pasadena, California.

Irradiated ice-covered ocean worlds with rocky mafic mantles may provide the conditions needed to drive the emergence and maintenance of life. Alkaline hydrothermal springs-relieving the geophysical, thermal, and chemical disequilibria between oceans and tidally stressed crusts-could generate inorganic barriers to the otherwise uncontrolled and kinetically disfavored oxidation of hydrothermal hydrogen and methane. Ionic gradients imposed across these inorganic barriers, comprising iron oxyhydroxides and sulfides, could drive the hydrogenation of carbon dioxide and the oxidation of methane through thermodynamically favorable metabolic pathways leading to early life-forms. In such chemostatic environments, fuels may eventually outweigh oxidants. Ice-covered oceans are primarily heated from below, creating convection that could transport putative microbial cells and cellular cooperatives upward to congregate beneath an ice shell, potentially giving rise to a highly focused shallow biosphere. It is here where electron acceptors, ultimately derived from the irradiated surface, could be delivered to such life-forms through exchange with the icy surface. Such zones would act as "electron disposal units" for the biosphere, and occupants might be transferred toward the surface by buoyant diapirs and even entrained into plumes. Key Words: Biofilms-Europa-Extraterrestrial life-Hydrothermal systems. Astrobiology 17, 1265-1273.
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http://dx.doi.org/10.1089/ast.2016.1600DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5729856PMC
December 2017

Methane: Fuel or Exhaust at the Emergence of Life?

Astrobiology 2017 Oct 26;17(10):1053-1066. Epub 2017 Sep 26.

2 CNRS/Aix-Marseille University , BIP UMR 7281, IMM FR 3479, Marseille, France.

As many of the methanogens first encountered at hydrothermal vents were thermophilic to hyperthermophilic and comprised one of the lower roots of the evolutionary tree, it has been assumed that methanogenesis was one of the earliest, if not the earliest, pathway to life. It being well known that hydrothermal springs associated with serpentinization also bore abiotic methane, it had been further assumed that emergent biochemistry merely adopted and quickened this supposed serpentinization reaction. Yet, recent hydrothermal experiments simulating serpentinization have failed to generate methane so far, thus casting doubt on this assumption. The idea that the inverse view is worthy of debate, that is, that methanotrophy was the earlier, is stymied by the "fact" that methanotrophy itself has been termed "reverse methanogenesis," so allotting the methanogens the founding pedigree. Thus, attempting to suggest instead that methanogenesis might be termed reverse methanotrophy would require "unlearning"-a challenge to the subconscious! Here we re-examine the "impossibility" of methanotrophy predating methanogenesis as in what we have termed the "denitrifying methanotrophic acetogenic pathway." Advantages offered by such thinking are that methane would not only be a fuel but also a ready source of reduced carbon to combine with formate or carbon monoxide-available in hydrothermal fluids-to generate acetate, a target molecule of the first autotrophs. And the nitrate/nitrite required for the putative oxidation of methane with activated NO would also be a ready source of fixed nitrogen for amination reactions. Theoretical conditions for such a putative pathway would be met in a hydrothermal green rust-bearing exhalative pile and associated chimneys subject to proton and electron counter gradients. This hypothesis could be put to test in a high-pressure hydrothermal reaction chamber in which a cool carbonate/nitrate/nitrite-bearing early acidulous ocean simulant is juxtaposed across a precipitate membrane to an alkaline solution of hydrogen and methane. Key Words: Green rust-Methanotrophy-Nitrate reduction-Emergence of life. Astrobiology 17, 1053-1066.
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http://dx.doi.org/10.1089/ast.2016.1599DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5655419PMC
October 2017

Sex and Electrode Configuration in Transcranial Electrical Stimulation.

Front Psychiatry 2017 14;8:147. Epub 2017 Aug 14.

Center for Neuroscience, University of California, Davis, Davis, CA, United States.

Transcranial electrical stimulation (tES) can be an effective non-invasive neuromodulation procedure. Unfortunately, the considerable variation in reported treatment outcomes, both within and between studies, has made the procedure unreliable for many applications. To determine if individual differences in cranium morphology and tissue conductivity can account for some of this variation, the electrical density at two cortical locations (temporal and frontal) directly under scalp electrodes was modeled using a validated MRI modeling procedure in 23 subjects (12 males and 11 females). Three different electrode configurations (non-cephalic, bi-cranial, and ring) commonly used in tES were modeled at three current intensities (0.5, 1.0, and 2.0 mA). The aims were to assess the effects of configuration and current intensity on relative current received at a cortical brain target directly under the stimulating electrode and to characterize individual variation. The different electrode configurations resulted in up to a ninefold difference in mean current densities delivered to the brains. The ring configuration delivered the least current and the non-cephalic the most. Female subjects showed much less current to the brain than male subjects. Individual differences in the current received and differences in electrode configurations may account for significant variability in current delivered and, thus, potentially a significant portion of reported variation in clinical outcomes at two commonly targeted regions of the brain.
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http://dx.doi.org/10.3389/fpsyt.2017.00147DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5558260PMC
August 2017

The H-bond network surrounding the pyranopterins modulates redox cooperativity in the molybdenum-bisPGD cofactor in arsenite oxidase.

Biochim Biophys Acta 2016 09 17;1857(9):1353-1362. Epub 2016 May 17.

CNRS, Aix-Marseille Univ, BIP UMR 7281, IMM FR 3479, 31 chemin J. Aiguier, 13402 Marseille Cedex 20, France. Electronic address:

While the molybdenum cofactor in the majority of bisPGD enzymes goes through two consecutive 1-electron redox transitions, previous protein-film voltammetric results indicated the possibility of cooperative (n=2) redox behavior in the bioenergetic enzyme arsenite oxidase (Aio). Combining equilibrium redox titrations, optical and EPR spectroscopies on concentrated samples obtained via heterologous expression, we unambiguously confirm this claim and quantify Aio's redox cooperativity. The stability constant, Ks, of the Mo(V) semi-reduced intermediate is found to be lower than 10(-3). Site-directed mutagenesis of residues in the vicinity of the Mo-cofactor demonstrates that the degree of redox cooperativity is sensitive to H-bonding interactions between the pyranopterin moieties and amino acid residues. Remarkably, in particular replacing the Gln-726 residue by Gly results in stabilization of (low-temperature) EPR-observable Mo(V) with KS=4. As evidenced by comparison of room temperature optical and low temperature EPR titrations, the degree of stabilization is temperature-dependent. This highlights the importance of room-temperature redox characterizations for correctly interpreting catalytic properties in this group of enzymes. Geochemical and phylogenetic data strongly indicate that molybdenum played an essential biocatalytic roles in early life. Molybdenum's redox versatility and in particular the ability to show cooperative (n=2) redox behavior provide a rationale for its paramount catalytic importance throughout the evolutionary history of life. Implications of the H-bonding network modulating Molybdenum's redox properties on details of a putative inorganic metabolism at life's origin are discussed.
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http://dx.doi.org/10.1016/j.bbabio.2016.05.003DOI Listing
September 2016

Chemical Gardens as Flow-through Reactors Simulating Natural Hydrothermal Systems.

J Vis Exp 2015 Nov 18(105). Epub 2015 Nov 18.

NASA Jet Propulsion Laboratory, California Institute of Technology; NASA Astrobiology Institute, Icy Worlds.

Here we report experimental simulations of hydrothermal chimney growth using injection chemical garden methods. The versatility of this type of experiment allows for testing of various proposed ocean / hydrothermal fluid chemistries that could have driven reactions toward the origin of life in environments on the early Earth, early Mars, or even other worlds such as the icy moons of the outer planets. We show experiments that include growth of chemical garden structures under anoxic conditions simulating the early Earth, inclusion of trace components of phosphates / organics in the injection solution to incorporate them into the structure, a switch of the injection solution to introduce a secondary precipitating anion, and the measurement of membrane potentials generated by chemical gardens. Using this method, self-assembling chemical garden structures were formed that mimic the natural chimneys precipitated at submarine hydrothermal springs, and these precipitates can be used successfully as flow-through reactors by feeding through multiple successive "hydrothermal" injections.
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http://dx.doi.org/10.3791/53015DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4692733PMC
November 2015

RNA Oligomerization in Laboratory Analogues of Alkaline Hydrothermal Vent Systems.

Astrobiology 2015 Jul 8;15(7):509-22. Epub 2015 Jul 8.

1 New York Center for Astrobiology, Rensselaer Polytechnic Institute , Troy, New York.

Discovering pathways leading to long-chain RNA formation under feasible prebiotic conditions is an essential step toward demonstrating the viability of the RNA World hypothesis. Intensive research efforts have provided evidence of RNA oligomerization by using circular ribonucleotides, imidazole-activated ribonucleotides with montmorillonite catalyst, and ribonucleotides in the presence of lipids. Additionally, mineral surfaces such as borates, apatite, and calcite have been shown to catalyze the formation of small organic compounds from inorganic precursors (Cleaves, 2008 ), pointing to possible geological sites for the origins of life. Indeed, the catalytic properties of these particular minerals provide compelling evidence for alkaline hydrothermal vents as a potential site for the origins of life since, at these vents, large metal-rich chimney structures can form that have been shown to be energetically favorable to diverse forms of life. Here, we test the ability of iron- and sulfur-rich chimneys to support RNA oligomerization reactions using imidazole-activated and non-activated ribonucleotides. The chimneys were synthesized in the laboratory in aqueous "ocean" solutions under conditions consistent with current understanding of early Earth. Effects of elemental composition, pH, inclusion of catalytic montmorillonite clay, doping of chimneys with small organic compounds, and in situ ribonucleotide activation on RNA polymerization were investigated. These experiments, under certain conditions, showed successful dimerization by using unmodified ribonucleotides, with the generation of RNA oligomers up to 4 units in length when imidazole-activated ribonucleotides were used instead. Elemental analysis of the chimney precipitates and the reaction solutions showed that most of the metal cations that were determined were preferentially partitioned into the chimneys.
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http://dx.doi.org/10.1089/ast.2014.1280DOI Listing
July 2015

From Chemical Gardens to Fuel Cells: Generation of Electrical Potential and Current Across Self-Assembling Iron Mineral Membranes.

Angew Chem Int Ed Engl 2015 Jul 12;54(28):8184-7. Epub 2015 May 12.

NASA Astrobiology Institute, JPL Icy Worlds, Pasadena, CA (USA).

We examine the electrochemical gradients that form across chemical garden membranes and investigate how self-assembling, out-of-equilibrium inorganic precipitates-mimicking in some ways those generated in far-from-equilibrium natural systems-can generate electrochemical energy. Measurements of electrical potential and current were made across membranes precipitated both by injection and solution interface methods in iron-sulfide and iron-hydroxide reaction systems. The battery-like nature of chemical gardens was demonstrated by linking multiple experiments in series which produced sufficient electrical energy to light an external light-emitting diode (LED). This work paves the way for determining relevant properties of geological precipitates that may have played a role in hydrothermal redox chemistry at the origin of life, and materials applications that utilize the electrochemical properties of self-organizing chemical systems.
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http://dx.doi.org/10.1002/anie.201501663DOI Listing
July 2015

The evolution of respiratory O2/NO reductases: an out-of-the-phylogenetic-box perspective.

J R Soc Interface 2014 Sep;11(98):20140196

Laboratoire de Bioénergétique et Ingénierie des Protéines UMR 7281 CNRS/AMU, FR3479, Marseille Cedex 20 13402, France

Complex life on our planet crucially depends on strong redox disequilibria afforded by the almost ubiquitous presence of highly oxidizing molecular oxygen. However, the history of O2-levels in the atmosphere is complex and prior to the Great Oxidation Event some 2.3 billion years ago, the amount of O2 in the biosphere is considered to have been extremely low as compared with present-day values. Therefore the evolutionary histories of life and of O2-levels are likely intricately intertwined. The obvious biological proxy for inferring the impact of changing O2-levels on life is the evolutionary history of the enzyme allowing organisms to tap into the redox power of molecular oxygen, i.e. the bioenergetic O2 reductases, alias the cytochrome and quinol oxidases. Consequently, molecular phylogenies reconstructed for this enzyme superfamily have been exploited over the last two decades in attempts to elucidate the interlocking between O2 levels in the environment and the evolution of respiratory bioenergetic processes. Although based on strictly identical datasets, these phylogenetic approaches have led to diametrically opposite scenarios with respect to the history of both the enzyme superfamily and molecular oxygen on the Earth. In an effort to overcome the deadlock of molecular phylogeny, we here review presently available structural, functional, palaeogeochemical and thermodynamic information pertinent to the evolution of the superfamily (which notably also encompasses the subfamily of nitric oxide reductases). The scenario which, in our eyes, most closely fits the ensemble of these non-phylogenetic data, sees the low O2-affinity SoxM- (or A-) type enzymes as the most recent evolutionary innovation and the high-affinity O2 reductases (SoxB or B and cbb3 or C) as arising independently from NO-reducing precursor enzymes.
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http://dx.doi.org/10.1098/rsif.2014.0196DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4233682PMC
September 2014

The drive to life on wet and icy worlds.

Astrobiology 2014 Apr 3;14(4):308-43. Epub 2014 Apr 3.

1 NASA Astrobiology Institute , JPL Icy Worlds, USA .

This paper presents a reformulation of the submarine alkaline hydrothermal theory for the emergence of life in response to recent experimental findings. The theory views life, like other self-organizing systems in the Universe, as an inevitable outcome of particular disequilibria. In this case, the disequilibria were two: (1) in redox potential, between hydrogen plus methane with the circuit-completing electron acceptors such as nitrite, nitrate, ferric iron, and carbon dioxide, and (2) in pH gradient between an acidulous external ocean and an alkaline hydrothermal fluid. Both CO2 and CH4 were equally the ultimate sources of organic carbon, and the metal sulfides and oxyhydroxides acted as protoenzymatic catalysts. The realization, now 50 years old, that membrane-spanning gradients, rather than organic intermediates, play a vital role in life's operations calls into question the idea of "prebiotic chemistry." It informs our own suggestion that experimentation should look to the kind of nanoengines that must have been the precursors to molecular motors-such as pyrophosphate synthetase and the like driven by these gradients-that make life work. It is these putative free energy or disequilibria converters, presumably constructed from minerals comprising the earliest inorganic membranes, that, as obstacles to vectorial ionic flows, present themselves as the candidates for future experiments. Key Words: Methanotrophy-Origin of life. Astrobiology 14, 308-343. The fixation of inorganic carbon into organic material (autotrophy) is a prerequisite for life and sets the starting point of biological evolution. (Fuchs, 2011 ) Further significant progress with the tightly membrane-bound H(+)-PPase family should lead to an increased insight into basic requirements for the biological transport of protons through membranes and its coupling to phosphorylation. (Baltscheffsky et al., 1999 ).
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http://dx.doi.org/10.1089/ast.2013.1110DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3995032PMC
April 2014

Free energy conversion in the LUCA: Quo vadis?

Biochim Biophys Acta 2014 Jul 19;1837(7):982-8. Epub 2013 Dec 19.

Laboratoire de Bioénergétique et Ingénierie des Protéines UMR 7281 CNRS/AMU, FR3479, F-13402 Marseille Cedex 20, France. Electronic address:

Living entities are unimaginable without means to harvest free energy from the environment, that is, without bioenergetics. The quest to understand the bioenergetic ways of early life therefore is one of the crucial elements to understand the emergence of life on our planet. Over the last few years, several mutually exclusive scenarios for primordial bioenergetics have been put forward, all of which are based on some sort of empirical observation, a remarkable step forward from the previous, essentially untestable, ab initio models. We here try to present and compare these scenarios while at the same time discuss their respective empirical weaknesses. The goal of this article is to harness crucial new expertise from the entire field by stimulating a larger part of the bioenergetics community to become involved in "origin-of-energy-metabolism" research. This article is part of a Special Issue entitled: 18th European Bioenergetic Conference.
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http://dx.doi.org/10.1016/j.bbabio.2013.12.005DOI Listing
July 2014

Individual differences in transcranial electrical stimulation current density.

J Biomed Res 2013 Nov 25;27(6):495-508. Epub 2013 Oct 25.

Aaken Research Institute, Inc. Davis, CA 95616, USA;

Transcranial electrical stimulation (TCES) is effective in treating many conditions, but it has not been possible to accurately forecast current density within the complex anatomy of a given subject's head. We sought to predict and verify TCES current densities and determine the variability of these current distributions in patient-specific models based on magnetic resonance imaging (MRI) data. Two experiments were performed. The first experiment estimated conductivity from MRIs and compared the current density results against actual measurements from the scalp surface of 3 subjects. In the second experiment, virtual electrodes were placed on the scalps of 18 subjects to model simulated current densities with 2 mA of virtually applied stimulation. This procedure was repeated for 4 electrode locations. Current densities were then calculated for 75 brain regions. Comparison of modeled and measured external current in experiment 1 yielded a correlation of r = .93. In experiment 2, modeled individual differences were greatest near the electrodes (ten-fold differences were common), but simulated current was found in all regions of the brain. Sites that were distant from the electrodes (e.g. hypothalamus) typically showed two-fold individual differences. MRI-based modeling can effectively predict current densities in individual brains. Significant variation occurs between subjects with the same applied electrode configuration. Individualized MRI-based modeling should be considered in place of the 10-20 system when accurate TCES is needed.
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http://dx.doi.org/10.7555/JBR.27.20130074DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3841475PMC
November 2013
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