title: Distribution and stable isotopic composition of amino acids from fungal peptaibiotics: assessing the potential for meteoritic contamination.
abstract: The presence of nonprotein α-dialkyl-amino acids such as α-aminoisobutyric acid (α-AIB) and isovaline (Iva), which are considered to be relatively rare in the terrestrial biosphere, has long been used as an indication of the indigeneity of meteoritic amino acids. However, recent work showing the presence of α-AIB and Iva in peptides produced by a widespread group of filamentous fungi indicates the possibility of a terrestrial biotic source for the α-AIB observed in some meteorites. We measured the amino acid distribution and stable carbon and nitrogen isotopic composition of four α-AIB-containing fungal peptides and compared this data to similar meteoritic measurements. We show that the relatively simple distribution of the C(4) and C(5) amino acids in fungal peptides is distinct from the complex distribution observed in many carbonaceous chondrites. We also identify potentially diagnostic relationships between the stable isotopic compositions of pairs of amino acids from the fungal peptides that may aid in ruling out fungal contamination as a source of meteoritic amino acids.
authors.affiliation: Goddard Center for Astrobiology and Solar System Exploration Division, NASA Goddard Space Flight Center, Greenbelt, Maryland 20771, USA. Jamie.Elsila@nasa.gov
authors.forename: Jamie E
authors.initials: JE
authors.lastname: Elsila
authors.forename: Michael P
authors.initials: MP
authors.lastname: Callahan
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Glavin
authors.forename: Jason P
authors.initials: JP
authors.lastname: Dworkin
authors.forename: Hans
authors.initials: H
authors.lastname: Brückner
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000737:chemistry; D000621:Aminoisobutyric Acids / Q000737:chemistry*; D005118:Extraterrestrial Environment; D005658:Fungi / Q000737:chemistry*; D007554:Isotopes / Q000737:chemistry*; D019110:Meteoroids; D008969:Molecular Sequence Data; D054848:Peptaibols / Q000737:chemistry*; D053719:Tandem Mass Spectrometry; D014633:Valine / Q000737:chemistry*
chemical_list: D000596:Amino Acids; D000621:Aminoisobutyric Acids; D007554:Isotopes; D054848:Peptaibols; C100049:2-aminoisobutyric acid; C032737:isovaline; D014633:Valine