Abstract
AbstractMolecular mass of a biomolecule is characterized in mass spectroscopy by the monoisitopic mass M~mono~ and the average isotopic mass M~av~. We found that peptide masses mapped on a plane made by two parameters derived from M~mono~ and M~av~ 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 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 = (2C - 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, and likely a signature of its emergence in abiotic synthesis. The linear correlation between M~av~ and M~mono~ reduces the complexity of polypeptide molecules, which may have increased the rate of their abiotic production. This, in turn may have influenced the selection of these 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 the Galaxy.
Highlights
Molecular mass (MM) of a biopolymer is a distribution containing information on the exact masses and abundances of all stable isotopes of the constituent elements
The molecular mass of a biomolecule is characterized by the monoisitopic mass Mmono and the average isotopic mass Mav
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
Summary
Molecular mass (MM) of a biopolymer is a distribution containing information on the exact masses and abundances of all stable isotopes of the constituent elements. The five constituent elements C, H, O, N and S encompass 12 stable isotopes, the five lightest isotopes being dominant. The full description of the peptide MM is a combination of the five variable coefficients of a brutto-formula (c, h, o, n and s), 12 constant isotope masses and seven relative abundances of less abundant isotopes, which are variable to some extent. MM of a biopolymer is characterized by two constant values, the monoisotopic mass Mmono and the average isotopic mass Mav. Reduction of the dimensionality to two affords easy visualization on a two dimensional (2D) plot using derivatives of the two mass values as axes [1].
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