Basic Information
Abstract Number: 2110-3    
Author Name: Roman Zubarev Affiliation: Karolinska Institute
Session Title: Ralph N Adams Award
Event Type: Award
Event Title: Stable Isotopes and the Origin of Life
Presider(s): Li, Liang Start Time: 03:20 PM ( Slot # 5 )
Date: Wednesday, March 3rd, 2010 Location: 206A
Keywords: Mass Spectrometry

Abstract Content
Molecular mass of a biomolecule is characterized in mass spectroscopy by the monoisotopic mass Mmono and the average isotopic mass Mav. We found that peptide masses mapped on a plane made by two parameters derived from Mmono and Mav form a peculiar global feature in form of a ‘band gap’ 5-7 ppm wide stretching across the whole ‘peptide galaxy’, with a narrow (FWHM ≈0.2 ppm) line in the centre. The purpose of this study was to investigate possible reasons for the emergence of such a feature, provided it is not a random occurrence. It was found that the a priori probability of such a feature to emerge by chance is less than 1:100. Peptides contributing to the central line have elemental compositions following the rules S=0; Z = C – (N + H)/2 = 0, which nine out of 20 amino acid residues satisfy. The relative abundances of amino acids in the peptides contributing to the central line correlate with the consensus order of emergence of these amino acids, with ancient amino acids being overrepresented in on-line peptides.
Thus, the central line is a relic of ancient life. Since linear correlation between Mav and Mmono reduces the complexity of polypeptide molecules, and less complex molecules interconvert faster when isolated, the line could be a signature of abiotic synthesis of primordial biopolymers. Thus the complexity reduction may have influenced the selection of amino acid residues for terrestrial life. Assuming the line feature is not spurious, life has emerged from elements with isotopic abundances very close to terrestrial levels, which rules out most of our Galaxy.