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Resolution of Trp near UV CD spectra of calmodulin‐domain peptide complexes into the 1 L a and 1 L b component spectra
Author(s) -
Barth Andreas,
Martin Stephen R.,
Bayley Peter M.
Publication year - 1998
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/(sici)1097-0282(199806)45:7<493::aid-bip3>3.0.co;2-j
Subject(s) - spectral line , chemistry , nuclear magnetic resonance , physics , astronomy
Near uv CD spectra of Trp residues in proteins frequently show a complex line shape deriving from the overlap of 1 L a and 1 L b electronic transitions. This study presents an original empirical method of resolving these components, based on the near uv CD spectra of well‐defined complexes of calmodulin domains with target peptides containing a single Trp residue and derived from the skeletal muscle myosin light chain kinase target sequence. Spectra of 4 complexes were used to obtain the 1 L a and 1 L b component spectra that were then used to analyze further complexes. The broad and featureless 1 L a spectrum is centered at 279 nm, the 1 L b spectrum shows vibrational fine structure with maxima at 274.9, 281.5, and 289.8 nm. The CD spectrum of most complexes could successfully be fitted with one 1 L a and one 1 L b spectrum, the 1 L b spectrum being negative for all complexes but the 1 L a spectrum showing either positive or negative sign. Spectra of some complexes, however, failed to be adequately represented by only one 1 L a and one 1 L b spectrum. Instead, they could be fitted with one 1 L b spectrum and two 1 L a spectra with different sign and position. The method is successful in identifying and quantitating the relative intensities of a two‐component system, consistent with a single conformation for tryptophan in a protein, and provides a simple indication of cases where a more complicated explanation is required. © 1998 John Wiley & Sons, Inc. Biopoly 45: 493–501, 1998