A Prebiotic Surface Catalysed  Photochemically Activated Synthesis of L-Cysteine

Aylward, Nigel

doi:10.2991/bep-16.2017.1

Cited by 2 publications

(4 citation statements)

References 7 publications

(9 reference statements)

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“…In the early Earth’s oceans, Fe 2+ would have been supplied through hydrothermal inputs and Fe 3+ (before the origin of life) could be produced by chemical oxidation in an anoxic setting . Iron (oxy)hydroxides can precipitate with various Fe(II)/(III) ratios which in turn impact their specific mineralogy, adsorption capacity, and reactivity; in this study, we chose to focus on the ferric and ferrous hydroxide end members to test the adsorption behavior of phosphate and AAs at pHs of 6 and 9 [relevant to the early Earth’s ocean and mixing zones near alkaline hydrothermal vents]. ,, Three prebiotically available AAs, containing amine and carboxylate functional groups but variable side chainseach with an affinity for metals that are commonly used by metalloenzymes and may therefore have been important for facilitating prebiotic reactions , were chosen for the study: histidine, arginine, and cysteine , (Figure A). Their side chains include an imidazole group, a guanidino group, and a sulfhydryl group, respectively.…”

Section: Introductionmentioning

confidence: 99%

Effects of Amino Acids on Phosphate Adsorption Onto Iron (Oxy)hydroxide Minerals under Early Earth Conditions

Flores

Martı́nez

Rodriguez

et al. 2021

ACS Earth Space Chem.

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Phosphate, an essential molecule in biochemistry, is not abundant in modern oceans and would have been even less abundant in early Earth’s oceans. One possible mechanism for concentrating phosphate for prebiotic reactions is adsorption onto iron (oxy)hydroxide minerals, which would have precipitated from interactions between iron-rich oceans of the early Earth and near neutral-alkaline hydrothermal fluids. In this work, we synthesized ferrous and ferric (oxy)hydroxides to test their adsorptivity toward phosphate under early Earth oceanic conditions (anoxic, dissolved Fe2+, pH 6–9, and low phosphate levels). Prebiotically relevant amino acids (cysteine, histidine, and arginine) were added to test their effect on phosphate adsorption. Colorimetry techniques coupled with nuclear magnetic resonance and statistical analysis were utilized to determine how experimental conditions influenced the adsorption reaction. We observed an 80–90% reduction of ferric to ferrous iron minerals in the presence of cysteine; we hypothesize that iron and cysteine underwent a redox reaction to produce cystine. In addition, phosphate was readily adsorbed onto iron (oxy)hydroxide minerals, but their efficacy depended on the iron redox state and pH at which the minerals were precipitated. Phosphate adsorption was the greatest with ferrous (oxy)hydroxide minerals precipitated at pH 9, reaching a maximum average adsorption of 45%. Under these conditions, the addition of organics significantly enhanced phosphate adsorption by an additional ∼30%; differences due to the amino acid side chain were not statistically significant. This work shows how environmental conditions (redox state, pH, and presence of organics) influenced adsorption in a simulated mineral system; such systems merit further study under increasingly complex conditions in order to better understand phosphate dynamics on wet-rocky worlds such as early Earth or Mars.

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Section: Introductionmentioning

confidence: 99%

Effects of Amino Acids on Phosphate Adsorption Onto Iron (Oxy)hydroxide Minerals under Early Earth Conditions

Flores

Martı́nez

Rodriguez

et al. 2021

ACS Earth Space Chem.

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“…Mg.porphin is a powerful catalyst able to form charge transfer complexes with a n umber of different kinds of molecules [15][16]. With ethyne the ligand is positively charged (0.08) and the porphin has a negative charge [17]. The acetylene sets as l igand with a l inear H-C ≡ C-H structure as shown.…”

Section: Total Energies (Hartrees)mentioning

confidence: 99%

“…acetyl-5-dehydro-5-methyl cyclopent-2-en-1-yl.porphin may be excited to a higher energy state where it is bonded to the nitrogen atom of a pyrrole unit, as Mg.1,4-acetyl-5-dehydro-5-methyl cyclopent-2en-1-yl.porphin → Mg.1,porphin. 4-acetyl-5-dehydro-5-methylcyclopent-2-en-N1-yl (17). [14]…”

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confidence: 99%

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A Computational Study of a Prebiotic Synthesis of the Steroid Progesterone (C and D Rings)

Aylward

2020

Wseas Transactions on Biology and Biomedicine

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The magnesium ion metalloporphyrin complex is shown to bind the ligands propyne (p) and ethyne (e) on the metal or nitrogen pyrrole sites as a two site catalyst in their copolymerization. The order of addition of the monomers is (pepee). The steroid ring D (pep) is formed first from the propyne adduct bound t o the metal site and the but-diene adduct bound to the N-site. The optimal orientation of these adducts determines the β-orientation of the 17-substituent. Further reaction with hydroxyl radicals allows this to be a 17 β-acetyl substituent. Further addition of two ethyne monomers forms an N-diene cyclopentene derivative able to cyclise to form the steroid ring C (pee) with a trans conformation and a 13-β methyl substituent. The reactions have been shown to be feasible from the overall enthalpy changes in the ZKE approximation at the HF and MP2 /6-31G* level, and with acceptable activation energies.

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A Prebiotic Surface Catalysed Photochemically Activated Synthesis of L-Cysteine

Cited by 2 publications

References 7 publications

Effects of Amino Acids on Phosphate Adsorption Onto Iron (Oxy)hydroxide Minerals under Early Earth Conditions

Effects of Amino Acids on Phosphate Adsorption Onto Iron (Oxy)hydroxide Minerals under Early Earth Conditions

A Computational Study of a Prebiotic Synthesis of the Steroid Progesterone (C and D Rings)

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