VCD spectroscopic properties of the β‐hairpin forming miniprotein CLN025 in various solvents

Abstract Electronic and vibrational circular dichroism are often used to determine the secondary structure of proteins, because each secondary structure has a unique spectrum. Little is known about the vibrational circular dichroic spectroscopic features of the β‐hairpin. In this study, the VCD spectral features of a decapeptide, YYDPETGTWY (CLN025), which forms a stable β‐hairpin that is stabilized by intramolecular weakly polar interactions and hydrogen bonds were determined. Molecular dynamics simulations and ECD spectropolarimetry were used to confirm that CLN025 adopts a β‐hairpin in water, TFE, MeOH, and DMSO and to examine differences in the secondary structure, hydrogen bonds, and weakly polar interactions. CLN025 was synthesized by microwave‐assisted solid phase peptide synthesis with N α ‐Fmoc protected amino acids. The VCD spectra displayed a (−,+,−) pattern with bands at 1640 to 1656 cm −1 , 1667 to 1687 cm −1 , and 1679 to 1686 cm −1 formed by the overlap of a lower frequency negative couplet and a higher frequency positive couplet. A maximum IR absorbance was observed at 1647 to 1663 cm −1 with component bands at 1630 cm −1 , 1646 cm −1 , 1658 cm −1 , and 1675 to 1680 cm −1 that are indicative of the β‐sheet, random meander, either random meander or loop and turn, respectively. These results are similar to the results of others, who examined the VCD spectra of β‐hairpins formed by D Pro‐Xxx turns and indicated that observed pattern is typical of β‐hairpins. © 2009 Wiley Periodicals, Inc. Biopolymers 93: 442–450, 2010. This article was originally published online as an accepted preprint. The “Published Online” date corresponds to the preprint version. You can request a copy of the preprint by emailing the Biopolymers editorial office at biopolymers@wiley.com