Temperature dependence of the thermodynamics of helix-coil transition.
The temperature-induced helix to coil transition in a series of host peptides was monitored using circular dichroism spectroscopy (CD) and differential scanning calorimetry (DSC). Combination of these two techniques allowed direct determination of the enthalpy of helix-coil transition for the studied peptides. It was found that the enthalpy of the helix-coil transition differs for different peptides and this difference is related to the difference in the temperature for the midpoint of helix-coil transition. The enthalpy of the helix-coil transition decreases with the increase in temperature, thus providing the first experimental estimate for the heat capacity changes upon helix-coil transition, DeltaC(p). The values for DeltaC(p) of helix-coil transition are found to be negative, which is in contrast to the positive DeltaC(p) for protein unfolding. Analysis suggests that this negative DeltaC(p) of helix-coil transition is due to the exposure of the polar peptide backbone to solvent upon helix unfolding.
Richardson
John M
JM
Department of Biochemistry and Molecular Biology H171, Pennsylvania State University College of Medicine, 500 University Drive, Hershey, PA 17033-2390, USA.
Makhatadze
George I
GI
D000595:Amino Acid Sequence; D002152:Calorimetry, Differential Scanning; D002942:Circular Dichroism; D008969:Molecular Sequence Data; D017433:Protein Structure, Secondary; D011506:Proteins / Q000737:chemistry*; D013696:Temperature; D013816:Thermodynamics; D014461:Ultracentrifugation
D011506:Proteins