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Fourier transform vibrational circular dichroism as a decisive tool for conformational studies of peptides containing tyrosyl residues
Author(s) -
Borics Attila,
Murphy Richard F.,
Lovas Sándor
Publication year - 2002
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/bip.10247
Subject(s) - chemistry , circular dichroism , vibrational circular dichroism , chromophore , protein secondary structure , crystallography , side chain , amide , peptide , stereochemistry , helix (gastropod) , solvent , photochemistry , organic chemistry , polymer , ecology , biochemistry , snail , biology
Previous UV–circular dichroism (UV–CD) and NMR studies showed that Ac‐EAAKA‐NH 2 has an α‐helical structure in 50% (v/v) aqueous trifluoroethanol. Replacement of Ala 1 to Ala 6 with Tyr results in spectra that show an apparent loss of helicity in the same solvent. This apparent loss of helicity could be attributed to the coupling of the tyrosyl side chain chromophore with the backbone amide. However, such electronic coupling does not affect the vibrational CD (VCD) spectra. The VCD spectra of the peptides with tyrosyl residues were identical to that of the peptide containing no Tyr, which shows the same α‐helical structure. Because it is now clear that Tyr replacement does not change the backbone conformation of peptides, UV–CD measurements should be complemented by VCD to determine the secondary structure when electronic effects can disturb the UV–CD spectrum of the inherent structure. © 2002 Wiley Periodicals, Inc. Biopolymers (Biospectroscopy) 72: 21–24, 2003