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1.
Photochem Photobiol ; 81(6): 1439-46, 2005.
Article in English | MEDLINE | ID: mdl-16117565

ABSTRACT

The scope of photobiological processes that involve absorbers within a protein matrix may be limited by the vulnerability of the peptide group to attack by highly reactive redox centers consequent upon electronic excitation. We have explored the nature of this vulnerability by undertaking comprehensive product analyses of aqueous photolysates of 12 N-p-toluenesulfonyl peptides with systematically selected structures. The results indicate that degradation includes a major pathway that is initiated by intramolecular electron transfer in which the peptide bond serves as electron donor, and the data support the likelihood of a relay process in dipeptide derivatives.


Subject(s)
Peptides/metabolism , Photochemistry , Tosyl Compounds/chemistry , Electrons , Molecular Structure , Tosyl Compounds/classification , Tosyl Compounds/metabolism
2.
Chem Commun (Camb) ; (22): 2838-9, 2003 Nov 21.
Article in English | MEDLINE | ID: mdl-14651130

ABSTRACT

Photo-excited N-tosyl derivatives of phenylalanyl- and, more particularly, O-methyltyrosylmethylamides undergo electron transfer from aryl to tosyl groups whereas the photo-degradation of aliphatic analogues is initiated by electron transfer from the peptide bond, suggesting the latter as one possible reason for the rapid turnover of the D1 protein in biological water oxidation when the essential mediating role of tyrosine 116 in the PSII complex is inhibited.


Subject(s)
Amides/chemistry , Peptides/chemistry , Peptides/metabolism , Photolysis , Photosynthesis , Tyrosine/metabolism , Water/metabolism , Electron Transport , Molecular Structure , Tyrosine/chemistry , Water/chemistry
3.
Org Biomol Chem ; 1(6): 965-72, 2003 Mar 21.
Article in English | MEDLINE | ID: mdl-12929635

ABSTRACT

Selectivity in abiotic condensations of amino acids remains controversial and stereochemically little explored. We find that competitive activated couplings of N-acyl derivatives of glycine, alanine, valine, proline and phenylalanine with binary, ternary and quaternary mixtures of amides and esters of the same group of amino acids show little selectivity among the reactants, except with respect to configuration, where a consistent and significant preference for heterochiral outcomes, mostly > 80%, is observed. One possible explanation of this selectivity predicts a predisposition to homochiral coupling under conditions that would require the two carboxyl functions to be co-facial in the activated complex.


Subject(s)
Amino Acids/metabolism , Peptides/chemical synthesis , Stereoisomerism , Amino Acids/chemistry , Molecular Structure
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