Dual Role of Hydrophobic Racemic Thioesters of alpha-Amino Acids in the Generation of Isotactic Peptides and Co-peptides in Water; Implications for the Origin of Homochirality

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TitreDual Role of Hydrophobic Racemic Thioesters of alpha-Amino Acids in the Generation of Isotactic Peptides and Co-peptides in Water; Implications for the Origin of Homochirality
Type de publicationJournal Article
Nouvelles publications2010
AuteursIllos, RA, Clodic G, Bolbach G, Weissbuch I, Lahav M
JournalOrigins of Life and Evolution of Biospheres
Volume40
Fascicule1
Pagination51-63
Année de publicationFeb
Numéro0169-6149
Accession NumberISI:000274142200006
Résumé

Thioesters of alpha-amino acids are considered as plausible monomers for the generation of the primeval peptides. DL-Leucine-thioethyl esters (LeuSEt), where the L-enantiomer was tagged with deuterium atoms, undergo polycondensation in water or in bicarbonate or imidazole buffer solutions to yield mainly heterochiral (atactic) peptides and diketopiperazine, as analyzed by MALDI-TOF and ESI mass-spectrometry. In variance, when polymerization of DL(d(10))-Leu, first activated with N,N'-carbonyldiimidazole, then initiated with ethanethiol or with DL(d(3))-LeuSEt yielded a library of peptides Lip to 30 detectable residues where those of homochiral sequence (isotactic) are the dominant diastereoisomers. At these conditions, racemic beta-sheets are formed and operate as stereoselective templates in the process of chain-elongation. Isotopic L:L(d(10))-Leu co-peptides were obtained in the polymerization of L(d(10))-Leu with L-LeuSEt. By contrast, mixtures of oligo-D-Leu and oligo-L(d(10))-Leu were obtained in the polymerization of mixtures of D-LeuSEt with activated L(d(10))-Leu. Isotactic co-peptides containing Leu and Val residues were formed in the polymerization of mixtures of activated DL(d(g))-Val with DL(d(3))-LeuSEt in water, implying that the racemic P-sheets exert regio-enantio-selection but not chemo-selection. A reaction pathway is suggested, where LeuSEt operates both as initiator of the reaction as well as a multimer.

URL<Go to ISI>://000274142200006
DOI10.1007/s11084-009-9186-1
Importer un fichierDual Role of Hydrophobic Racemic Thioesters of alpha-Amino Acids in the Generation of Isotactic Peptides and Co-peptides in Water; Implications for the Origin of Homochirality
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