The Energy Landscape of Unsolvated Peptides: Helix Formation and Cold Denaturation in Ac-A4G7A4 + H+
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- 作者：Brian S. Kinnear ; Matthew R. Hartings ; and Martin F. Jarrold
- 刊名：Journal of the American Chemical Society
- 出版年：2002
- 出版时间：April 24, 2002
- 年：2002
- 卷：124
- 期：16
- 页码：4422 - 4431
- 全文大小：292K
- 年卷期：v.124,no.16(April 24, 2002)
- ISSN：1520-5126
文摘
Ion mobility measurements and molecular dynamics simulations were performed for unsolvatedA4G7A4 + H+ and Ac-A4G7A4 + H+ (Ac = acetyl, A = alanine, G = glycine) peptides. As expected, A4G7A4+ H+ adopts a globular conformation (a compact, random-looking, three-dimensional structure) over theentire temperature range examined (100-410 K). Ac-A4G7A4 + H+ on the other hand is designed to havea flat energy landscape with a marginally stable helical state. This peptide shows at least four differentconformations at low temperatures (<230 K). The two conformations with the largest cross sections areattributed to 
chars/alpha.gif" BORDER=0>- and partial chars/pi.gif" BORDER=0 >-helices, while the one with the smallest cross section is globular. The othermain conformation may be partially helical. Ac-A4G7A4 + H+ becomes predominantly globular at intermediatetemperatures and then becomes more helical as the temperature is raised further. This unexpected behaviormay be due to the helix having a higher vibrational entropy than the globular state, as predicted by somerecent calculations (Ma, B.; Tsai, C.-J.; Nussinov, R. Biophys. J. 2000, 79, 2739-2753).
chars/alpha.gif" BORDER=0>- and partial chars/pi.gif" BORDER=0 >-helices, while the one with the smallest cross section is globular. The othermain conformation may be partially helical. Ac-A4G7A4 + H+ becomes predominantly globular at intermediatetemperatures and then becomes more helical as the temperature is raised further. This unexpected behaviormay be due to the helix having a higher vibrational entropy than the globular state, as predicted by somerecent calculations (Ma, B.; Tsai, C.-J.; Nussinov, R. Biophys. J. 2000, 79, 2739-2753).