期刊
EUROPEAN BIOPHYSICS JOURNAL WITH BIOPHYSICS LETTERS
卷 40, 期 5, 页码 673-685出版社
SPRINGER
DOI: 10.1007/s00249-011-0673-8
关键词
Peptide dynamics; Folding; IR spectroscopy; Temperature jump; CD spectroscopy
类别
资金
- Ministry of Science and Culture of Hesse (HMWK)
- University of Frankfurt
The thermal stability and folding dynamics of polyglutamic acid were studied by equilibrium circular dichroism (CD), Fourier-transform infrared (FTIR), and time-resolved temperature-jump infrared (IR) spectroscopy. Polyglutamic acid (PGA) forms alpha-helical peptides in aqueous solution and is an ideal model system to study the helix-coil transition. Melting curves were monitored with CD and FTIR as a function of pD. At low pD, PGA aggregates at temperatures above 323 K, whereas at pD > 5, unfolding and refolding are reversible. At pD 5.4, a helix-coil transition occurs with a transition temperature T (m) of 307 K. At slightly higher pD of 6.2, the peptide conformation is already in a coil structure and only small conformational changes occur upon heating. We determined the equilibrium constant for the reversible helix-coil transition at pD 5.4. The dynamics of this transition was measured at single IR wavelengths after a nanosecond laser-excited temperature jump of a dagger T similar to 10 K. Relaxation constants decreased with increasing peptide temperature. Folding and unfolding rates as well as activation energies were extracted based on a two-state model. Our study shows how equilibrium and time-resolved infrared spectroscopic data can be combined to characterize a structural transition and to analyze folding mechanisms.
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