Temperature-dependent helix-coil transition of an alanine based peptide.
The helix-coil transition of a synthetic alpha-helical peptide (the D-Arg peptide), Ac-YGG(KAAAA)(3)-CO-D-Arg-CONH(2), 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 degrees 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 approximately 140 ns at 300 K and exhibits monotonic temperature dependence with an apparent activation energy around 15.5 kcal/mol.
Huang
C Y
CY
Department of Chemistry, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA.
Klemke
J W
JW
Getahun
Z
Z
DeGrado
W F
WF
Gai
F
F
D000409:Alanine / Q000737:chemistry*; D001120:Arginine / Q000737:chemistry; D002942:Circular Dichroism; D007700:Kinetics; D010455:Peptides / Q000737:chemistry*; D017510:Protein Folding; D017433:Protein Structure, Secondary; D017550:Spectroscopy, Fourier Transform Infrared; D013696:Temperature
D010455:Peptides; C019529:polyalanine; D001120:Arginine; D000409:Alanine