Structural properties and photophysical behavior of conformationally constrained hexapeptides functionalized with a new fluorescent analog of tryptophan and a nitroxide radical quencher
✍ Scribed by Mariano Venanzi; Alessandro Valeri; Antonio Palleschi; Lorenzo Stella; Luis Moroder; Fernando Formaggio; Claudio Toniolo; Basilio Pispisa
- Publisher
- Wiley (John Wiley & Sons)
- Year
- 2004
- Tongue
- English
- Weight
- 183 KB
- Volume
- 75
- Category
- Article
- ISSN
- 0006-3525
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✦ Synopsis
Abstract
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