Calorimetric determination of the enthalpy change for the alpha-helix to coil transition of an alanine peptide in water

J M Scholtz; S Marqusee; R L Baldwin; E J York; J M Stewart; M Santoro; D W Bolen

doi:10.1073/pnas.88.7.2854

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Calorimetric determination of the enthalpy change for the alpha-helix to coil transition of an alanine peptide in water

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Calorimetric determination of the enthalpy change for the alpha-helix to coil transition of an alanine peptide in water

J M Scholtz, S Marqusee, R L Baldwin, E J York, J M Stewart, M Santoro and D W Bolen

Proceedings of the National Academy of Sciences - PNAS, Vol.88(7), pp.2854-2858

04/1991

DOI: 10.1073/pnas.88.7.2854

PMCID: PMC51338

PMID: 2011594

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Abstract

The enthalpy change (delta H) accompanying the alpha-helix to random coil transition in water has been determined calorimetrically for a 50-residue peptide of defined sequence that contains primarily alanine. The enthalpy of helix formation is one of the basic parameters needed to predict thermal unfolding curves for peptide helices and it provides a starting point for analysis of the peptide hydrogen bond. The experimental uncertainty in delta H reflects the fact that the transition curve is too broad to measure in its entirety, which precludes fitting the baselines directly. A lower limit for delta H of unfolding, 0.9 kcal/mol per residue, is given by assuming that the change in heat capacity (delta Cp) is zero, and allowing the baseline to intersect the transition curve at the lowest measured Cp value. Use of the van't Hoff equation plus least-squares fitting to determine a more probable baseline gives delta H = 1.3 kcal/mol per residue. Earlier studies of poly(L-lysine) and poly(L-glutamate) have given 1.1 kcal/mol per residue. Those investigations, along with our present result, suggest that the side chain has little effect on delta H. The possibility that the peptide hydrogen bond shows a correspondingly large delta H, and the implications for protein stability, are discussed.

Details

Title: Subtitle: Calorimetric determination of the enthalpy change for the alpha-helix to coil transition of an alanine peptide in water
Creators: J M Scholtz - Stanford University
S Marqusee - Stanford University
R L Baldwin - Stanford University
E J York - Stanford University
J M Stewart - Stanford University
M Santoro - Stanford University
D W Bolen - Stanford University
Resource Type: Journal article
Publication Details: Proceedings of the National Academy of Sciences - PNAS, Vol.88(7), pp.2854-2858
DOI: 10.1073/pnas.88.7.2854
PMID: 2011594
PMCID: PMC51338
NLM abbreviation: Proc Natl Acad Sci U S A
ISSN: 0027-8424
eISSN: 1091-6490
Publisher: National Academy of Sciences
Language: English
Date published: 04/1991
Academic Unit: Research Administration; Pharmaceutical Sciences and Experimental Therapeutics; Biochemistry and Molecular Biology; Chemistry
Record Identifier: 9984288718202771

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