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 studie...

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Bibliographic Details
Published in:Journal of molecular biology 2004-01, Vol.335 (4), p.1029-1037
Main Authors: Richardson, John M, Makhatadze, George I
Format: Article
Language:English
Subjects:
Amino Acid Sequence
Calorimetry, Differential Scanning
Circular Dichroism
Molecular Sequence Data
Protein Structure, Secondary
Proteins - chemistry
Temperature
Thermodynamics
Ultracentrifugation
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Summary: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.
ISSN:0022-2836
DOI:10.1016/j.jmb.2003.11.027