Turns and Bends

Protein p-Structure Helix Random Turns and bends ... 

Figure 7.4 Curve-fitted amide I band of lysozyme in D2O T, turns and bends p, p-stmc-ture a, a-helix R, random coil configuration S, amino acid side-chain vibrations. From Stuart, B., Biological Applications of Infrared Spectroscopy, ACOL Series, WUey, Chichester, UK, 1997. University of Greenwich, and reproduced by permission of the University of Greenwich.

The component band at 1692 cm may be attributed to turns and bends in the peptide. Computer analysis shows that this band contributes to 11% to the total amide 1 band area. The band at 1675 cm (7% of the total band area) appears at a wavenumber commonly expected for a P-structure. The large component at 1653 cm appears at a wavenumber that may be attributed to unordered structures in the peptide. This band is the major component, forming 82% of the band area. Most small peptides show largely random structures, but this is not surprising because of the small size of such molecules, which limits the possibilities of forming structures such as a-helices which require a minimum number of amino acids to form. 

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