A series of eight cyclic penta- and hexapeptides with hydrogen-bonded β- and γ-turn structures have been investigated by FTIR and CD spectroscopy. The analysis of the amide I band contour (1700-1600 cm-1) by Fourier self-deconvolution and nonlinear curve-fitting shows that infrared spectroscopy is a useful method in detecting H-bonded β- and γ-turns. FTIR spectra of the studied peptides were recorded both in TFE and in DMSO. It has been found that well-established β-turns give rise to characteristic acceptor amide I bands between 1642 and 29 cm-1, while bands appearing at ∼ 1650 cm-1 and 1625-15 cm-1 are due to acceptor amide carbonyls of weakly and strongly H-bonded γ-turns, respectively. The low-frequency component bands are often weaker or missing in the spectra obtained in DMSO, the changes in the relative band intensities can be explained on the basis of the different solvating property of the two solvents. CD spectra obtained in TFE were in general in good agreement with the IR spectroscopic data, indicating a mixture of conformers comprising more or less well defined turns. Previous NMR and MD studies on these cyclic peptides made possible the assignment of acceptor amide I component bands to particular carbonyls involved in intramolecular H-bonds.
|Number of pages||14|
|Journal||Spectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy|
|Publication status||Published - May 1998|
ASJC Scopus subject areas
- Analytical Chemistry
- Atomic and Molecular Physics, and Optics