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Electron spin resonance of TOAC labeled peptides: Folding transitions and high frequency spectroscopy
Author(s) -
McNulty Joseph C.,
Silapie Jennifer L.,
Carnevali Maia,
Farrar Christian T.,
Griffin Robert G.,
Formaggio Fernando,
Crisma Marco,
Toniolo Claudio,
Millhauser Glenn L.
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<479::aid-bip1023>3.0.co;2-f
Subject(s) - chemistry , nitroxide mediated radical polymerization , electron paramagnetic resonance , crystallography , folding (dsp implementation) , site directed spin labeling , helix (gastropod) , amino acid , peptide , guanidine , resonance (particle physics) , spin label , stereochemistry , nuclear magnetic resonance , organic chemistry , biochemistry , ecology , physics , radical polymerization , particle physics , biology , snail , electrical engineering , copolymer , engineering , polymer
The unnatural, conformationally constrained nitroxide amino acid TOAC (2,2,6,6‐tetramethylpiperidine‐1‐oxyl‐4‐amino‐4‐carboxylic acid) stabilizes helical structure and provides a means for studying rigidly spin labeled peptides by electron spin resonance (ESR). Two new directions in TOAC research are described. The first investigates intermediates formed during α‐helix unfolding. Double TOAC labeled α‐helical peptides were unfolded at low temperature in aqueous solution with increasing concentrations of guanidine hydrochloride. Comparison of ESR spectra from two doubly labeled peptides suggests that 3 10 ‐helix emerges as an intermediate. The second research direction involves the use of high frequency ESR (140 GHz) at low temperature to assess dipolar couplings and, hence, distances between TOAC pairs in a series of 3 10 ‐helical peptides. Preliminary simulations suggest that high frequency ESR is able to extract correct distances between 6 and 11 Å. In addition, the spectra appear to be very sensitive to the relative orientation of the TOAC labels. © 2001 John Wiley & Sons, Inc. Biopolymers (Pept Sci) 55: 479–485, 2000