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Reasons for the occurrence of the twenty coded protein amino acidsFactors involved in the selection of the 20 protein L-alpha-amino acids during chemical evolution and the early stages of Darwinian evolution are discussed. The selection is considered on the basis of the availability in the primitive ocean, function in proteins, the stability of the amino acid and its peptides, stability to racemization, and stability on the transfer RNA. It is concluded that aspartic acid, glutamic acid, arginine, lysine, serine and possibly threonine are the best choices for acidic, basic and hydroxy amino acids. The hydrophobic amino acids are reasonable choices, except for the puzzling absences of alpha-amino-n-butyric acid, norvaline and norleucine. The choices of the sulfur and aromatic amino acids seem reasonable, but are not compelling. Asparagine and glutamine are apparently not primitive. If life were to arise on another planet, it would be expected that the catalysts would be poly-alpha-amino acids and that about 75% of the amino acids would be the same as on the earth.
Document ID
19810061092
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Weber, A. L.
(Salk Institute for Biological Studies San Diego, CA, United States)
Miller, S. L.
(California, University La Jolla, CA, United States)
Date Acquired
August 11, 2013
Publication Date
August 1, 1981
Publication Information
Publication: Journal of Molecular Evolution
Volume: 17
Subject Category
Space Biology
Accession Number
81A45496
Funding Number(s)
CONTRACT_GRANT: NAGW-20
CONTRACT_GRANT: NSG-7627
Distribution Limits
Public
Copyright
Other

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