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Cysteine‐linked aromatic nitriles as UV resonance Raman probes of protein structure
Author(s) -
Weeks Colin L.,
Jo Hyunil,
Kier Brandon,
DeGrado William F.,
Spiro Thomas G.
Publication year - 2012
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.3167
Subject(s) - chemistry , raman spectroscopy , resonance (particle physics) , cysteine , photochemistry , absorption band , nitrile , organic chemistry , physics , particle physics , optics , enzyme
Nitriles introduced into peptides and proteins can serve as useful vibrational spectroscopic probes, because the nitrile C ≡ N stretch is well isolated from backbone and sidechain vibrational bands. Aromatic nitriles offer large νC ≡ N absorption intensity in infrared spectra and resonance enhancement in Raman spectra with ultraviolet excitation. We report the ultraviolet resonance Raman spectra of cyanophenylalanine attached to cysteine, through linkage reactions that are applicable to cysteine residues in proteins. Excitation profiles are reported, and the νC ≡ N detection limit is estimated to be 5 µ m . The band position is sensitive to solvent polarity and especially to strong H‐bonding. The derivatization of mastoparan X peptide at introduced cysteine residues demonstrated the effectiveness of a cyanophenylcysteine probe in reporting the lowered environmental polarity when the peptide was incorporated into liposomes. For an asymmetrical cyanophenyl derivative, 2‐CBCys, the intensity ratio of asymmetric and symmetric ring modes, ν8 b and ν8 a , was found to respond to solvent polarity and not to H‐bonding. Copyright © 2012 John Wiley & Sons, Ltd.