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Interaction between TOAC free radical and photoexcited triplet chromophores linked to peptide templates
Author(s) -
Corvaja Carlo,
Sartori Elena,
Toffoletti Antonio,
Formaggio Fernando,
Crisma Marco,
Toniolo Claudio
Publication year - 2000
Publication title -
peptide science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.556
H-Index - 125
eISSN - 1097-0282
pISSN - 0006-3525
DOI - 10.1002/1097-0282(2000)55:6<486::aid-bip1024>3.0.co;2-c
Subject(s) - chemistry , electron paramagnetic resonance , radical , nitroxide mediated radical polymerization , photochemistry , triplet state , excited state , chromophore , intramolecular force , quenching (fluorescence) , peptide , crystallography , stereochemistry , fluorescence , nuclear magnetic resonance , molecule , radical polymerization , organic chemistry , atomic physics , polymerization , biochemistry , physics , quantum mechanics , polymer
The intramolecular quenching of photoexcited triplet states by free radicals linked to peptide templates was studied by time‐resolved electron paramagnetic resonance (EPR) with pulsed laser excitation. The systems investigated are 3 10 ‐helix forming peptides, having in the amino acid sequence the free radical 2,2,6,6‐tetramethylpiperidine‐1‐oxyl‐4‐amino‐4‐carboxylic acid (TOAC) and a triplet precursor, such as Bin, Bpa, or Trp, incorporated at different relative positions. Upon interaction with the excited triplet the TOAC radical spin sublevel populations assume values that differ from the Boltzmann equilibrium values. This spin polarization effect produces EPR lines in emission whose time evolution reflects the triplet quenching rate. In particular, in a series of peptides labeled with Bpa and TOAC at successive positions in the 3 10 ‐helix, radical‐triplet interaction was observed in all cases. However, for the peptide where Bpa and TOAC are at positions 2 and 4 the rate of triplet quenching is lower than for the other peptides in the series. In addition, the radical‐excited triplet complex in the quartet spin state was observed in a peptide containing fullerene (C 60 ) as a triplet precursor and TOAC. © 2001 John Wiley & Sons, Inc. Biopolymers (Pept Sci) 55: 486–495, 2000