EXPLORING THE PEPTIDE 3(10)-HELIX-REVERSIBLE-ARROW-ALPHA-HELIX EQUILIBRIUM WITH DOUBLE-LABEL ELECTRON-SPIN-RESONANCE

Over the last several years we have used spin labeling as a means for exploring the structure of helical peptides. Two nitroxide labels are engineered into a peptide sequence and distances are ranked with elect ron spin resonance (ESR). We have found that there is a significant am ount of 3(10)-helix in 16-residue model peptides containing only L-ami no acids. This review covers several facets of the methodology includi ng spin labeling strategy, interpretation of ESR spectra and the influ ence of molecular dynamics on the spectral line shapes. Also covered a ve recent findings of a length-dependent 3 (10)-helix --> alpha-helix transition and the role of Arg(+) in the stabilization of specific hel ix structures. (C) 1995 John Wiley & Sons, Inc.