Temperature-Dependent Helix−Coil Transition of an Alanine Based Peptide
- 23 August 2001
- journal article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 123 (38) , 9235-9238
- https://doi.org/10.1021/ja0158814
Abstract
The helix−coil transition of a synthetic α-helical peptide (the d-Arg peptide), Ac-YGG(KAAAA)3-CO-d-Arg-CONH2, was studied by static far-UV circular dichroism (CD) and time-resolved infrared spectroscopy coupled with the laser-induced temperature-jump technique for rapid relaxation initiation. Equilibrium thermal unfolding measurements of the d-Arg peptide monitored by CD spectroscopy reveal an apparent two-state helix−coil transition, with a thermal melting temperature around 10 °C. Time-resolved infrared (IR) measurements following a laser-induced temperature jump, however, reveal biphasic (or multiphasic) relaxation kinetics. The fast phase rises within the 20 ns response time of the detection system. The slow phase has a decay lifetime of ∼140 ns at 300 K and exhibits monotonic temperature dependence with an apparent activation energy around 15.5 kcal/mol.Keywords
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