Investigation of pyridine carboxylic acids in CM2 carbonaceous chondrites: Potential precursor molecules for ancient coenzymes

Abstract

The distribution and abundances of pyridine carboxylic acids (including nicotinic acid) in eight CM2 carbonaceous chondrites (ALH 85013, DOM 03183, DOM 08003, EET 96016, LAP 02333, LAP 02336, LEW 85311, and WIS 91600) were investigated by liquid chromatography coupled to UV detection and high resolution Orbitrap mass spectrometry. We find that pyridine monocarboxylic acids are prevalent in CM2-type chondrites and their abundance negatively correlates with the degree of pre-terrestrial aqueous alteration that the meteorite parent body experienced. We also report the first detection of pyridine dicarboxylic acids in carbonaceous chondrites. Additionally, we carried out laboratory studies of proton-irradiated pyridine in carbon dioxide-rich ices (a 1:1 mixture) to serve as a model of the interstellar ice chemistry that may have led to the synthesis of pyridine carboxylic acids. Analysis of the irradiated ice residue shows that a comparable suite of pyridine mono-and dicarboxylic acids was produced, although aqueous alteration may still play a role in the synthesis (and ultimate yield) of these compounds in carbonaceous meteorites. Nicotinic acid is a precursor to nicotinamide adenine dinucleotide, a likely ancient molecule used in cellular metabolism in all of life, and its common occurrence in CM2 chondrites may indicate that meteorites may have been a source of molecules for the emergence of more complex coenzymes on the early Earth.

Two homologous series of alkylpyridines in the Murchison meteorite

“…In comparison, chemical oxidation process could be effected by OH radicals or aqueous alteration on the parent bodies, in which the progressive oxidation of methylene carbon yields alcohol to ketone followed by carboxylic acid (Cody and Alexander, 2005;Oba and Naraoka, 2006). The carbon double bond in unsaturated alkylpyridines would easily be oxidized to yield alkylpyridine carboxylic acids and dicarboxylic acids, being consistent with the reports that various alkylpyridine carboxylic acids are present in CCs (Stoks and Schwartz, 1982; Pizzarello et al, 2001;Smith et al, 2014).…”

VUV spectroscopy of an electron irradiated benzene : carbon dioxide interstellar ice analogue

“…Several experimental studies have looked at the formation of PAHs or benzene derivatives within interstellar ice analogues. [13][14][15] In particular, aromatic molecules with the carboxylic acid moiety (-COOH) have been studied because of their role as precursors to amino acids with non-aromatic carboxylic acids detected in the ISM in the form of formic acid (HCOOH) 16 and acetic acid (CH 3 -COOH). 17 Carboxylic acids with varying degrees of complexity have also been detected in the Tagish Lake, [18][19][20] Murchison 21,22 and Orgueil 22,23 carbonaceous meteorites.…”

Life's utilization of B vitamins on early Earth

“…Further support for the prebiotic synthesis of some B vitamins comes from their discovery in carbonaceous meteorites whose carbon content can reach as high as 3% and likely served as a major source of carbon to Earth (Botta & Bada, 2002). Vitamin B 3 , the structurally simplest B vitamin, and its nitrogen-heterocyclic analogs have been detected in multiple meteorites starting in the 1980s (Smith, Callahan, Gerakines, Dworkin, & House, 2014;Stoks & Schwartz, 1981), although a definite mechanism of formation remains to be determined. Porphyrins, despite their structural complexity, have also been found in numerous carbonaceous meteorites (Hodgson & Baker, 1969).…”