Premium
Structural properties and photophysical behavior of conformationally constrained hexapeptides functionalized with a new fluorescent analog of tryptophan and a nitroxide radical quencher
Author(s) -
Venanzi Mariano,
Valeri Alessandro,
Palleschi Antonio,
Stella Lorenzo,
Moroder Luis,
Formaggio Fernando,
Toniolo Claudio,
Pispisa Basilio
Publication year - 2004
Publication title -
biopolymers
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/bip.20110
Subject(s) - chemistry , nitroxide mediated radical polymerization , chromophore , moiety , side chain , stereochemistry , fluorescence , tryptophan , residue (chemistry) , photochemistry , amino acid , organic chemistry , radical polymerization , polymerization , biochemistry , physics , quantum mechanics , polymer
The influence of the conformational properties on the photophysics of two de novo designed hexapeptides was studied by spectroscopic measurements (ir, NMR, steady‐state, and time resolved fluorescence) and molecular mechanics calculations. The peptide sequences comprise two nonproteinogenic residues: a β‐(1‐azulenyl)‐ L ‐alanine (Aal) residue, obtained by formally functionalizing the Ala side chain with the azulene chromophore, and a C α ‐tetrasubstituted α‐amino acid (TOAC), incorporating a nitroxide group in a cycloalkyl moiety. Aal represents a new fluorescent, quasi‐isosteric Trp analog and TOAC a stable radical species, frequently used as a paramagnetic probe in biochemical studies. The peptide chains differ in the sequence position of the two probes and are heavily based on Aib (α‐aminoisobutyric acid) residues to generate conformationally restricted helical structures, as confirmed by both spectroscopic and computational results. The conformationally controlled, excited state interactions, determining the photophysical relaxation of the Aal*/TOAC pair, are also discussed. © 2004 Wiley Periodicals, Inc. Biopolymers, 2004