INFRARED EVIDENCE OF A BETA-HAIRPIN PEPTIDE STRUCTURE IN SOLUTION

The IR spectrum of an 16-amino acid peptide corresponding, according t o NMR studies, to a beta-hairpin has been analysed, Two characteristic features distinguish its spectrum from that of an antiparallel beta-s heet: the low-frequency band that in a beta-sheet structure is located at approximate to 1632 cm(-1) appears here at approximate to 1620 cm( -1), and the high-frequency component does not undergo the isotopic sh ift typical of beta-sheet from 1690 to 1675 cm(-1) when transferred to D2O. The infrared characteristics associated with beta-hairpins have been described so far in two proteins, in one of which, whose three-di mensional structure is known from X-ray diffraction, a beta-hairpin ha s actually been detected.