Comparison of NH exchange and circular dichroism as techniques for measuring the parameters of the helix-coil transition in peptides

被引:161
作者
Rohl, CA [1 ]
Baldwin, RL [1 ]
机构
[1] STANFORD UNIV,DEPT BIOCHEM,SCH MED,STANFORD,CA 94305
关键词
D O I
10.1021/bi9706677
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Circular dichroism and NH exchange are compared directly as techniques for measuring helix content in peptides and the parameters of the helix-coil transition, To cover a broad range of helix contents, alanine-based peptides with chain lengths varying from 12 to 22 residues are examined over the temperature range from 0.6 to 26.9 degrees C in 1 M sodium chloride, (H2O)-H-2. Helix-coil transition theory independently fits both circular dichroism and exchange data, but the helix contents measured by exchange are larger than those measured by circular dichroism, The two techniques are brought into agreement by removing the assumption that the intrinsic chemical exchange rate in the helix is the same as the exchange rate measured for short unstructured model peptides. This modification allows the circular dichroism and NH exchange data to be described by the same set of helix parameters and indicates that the intrinsic exchange rate in the presence of helical structure is reduced approximately 17% relative to the rates measured in unstructured models. To test the possibility that this effect is electrostatic in origin, the sensitivity of the exchange reaction to ionic strength is determined. A substantial dependence of exchange rate on ionic strength is found, but the form of the dependence is complex. In studies of the exchange rates of native proteins, the exchange-competent form of the protein is assumed to exchange with the same rate constant as a blocked dipeptide with the identical amino acid sequences. Our result suggests that this assumption will be seriously in error in some case because of charge effects in the protein.
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收藏
页码:8435 / 8442
页数:8
相关论文
共 28 条
  • [1] PRIMARY STRUCTURE EFFECTS ON PEPTIDE GROUP HYDROGEN-EXCHANGE
    BAI, YW
    MILNE, JS
    MAYNE, L
    ENGLANDER, SW
    [J]. PROTEINS-STRUCTURE FUNCTION AND GENETICS, 1993, 17 (01): : 75 - 86
  • [2] PROTEIN STABILITY PARAMETERS MEASURED BY HYDROGEN-EXCHANGE
    BAI, YW
    MILNE, JS
    MAYNE, L
    ENGLANDER, SW
    [J]. PROTEINS-STRUCTURE FUNCTION AND BIOINFORMATICS, 1994, 20 (01) : 4 - 14
  • [3] DERIVATIVE SPECTROSCOPY APPLIED TO TYROSYL CHROMOPHORES - STUDIES ON RIBONUCLEASE, LIMA BEAN INHIBITORS, INSULIN, AND PANCREATIC TRYPSIN-INHIBITOR
    BRANDTS, JF
    KAPLAN, LJ
    [J]. BIOCHEMISTRY, 1973, 12 (10) : 2011 - 2024
  • [4] STABILITY OF ALPHA-HELICES
    CHAKRABARTTY, A
    BALDWIN, RL
    [J]. ADVANCES IN PROTEIN CHEMISTRY, VOL 46, 1995, 46 : 141 - 176
  • [5] AROMATIC SIDE-CHAIN CONTRIBUTION TO FAR-ULTRAVIOLET CIRCULAR-DICHROISM OF HELICAL PEPTIDES AND ITS EFFECT ON MEASUREMENT OF HELIX PROPENSITIES
    CHAKRABARTTY, A
    KORTEMME, T
    PADMANABHAN, S
    BALDWIN, RL
    [J]. BIOCHEMISTRY, 1993, 32 (21) : 5560 - 5565
  • [6] CHAKRABARTTY A, 1994, PROTEIN SCI, V3, P843
  • [7] LARGE DIFFERENCES IN THE HELIX PROPENSITIES OF ALANINE AND GLYCINE
    CHAKRABARTTY, A
    SCHELLMAN, JA
    BALDWIN, RL
    [J]. NATURE, 1991, 351 (6327) : 586 - 588
  • [8] DOIG AJ, 1995, PROTEIN SCI, V4, P1325, DOI 10.1002/pro.5560040708
  • [9] DOIG AJ, 1994, BIOCHEMISTRY-US, V33, P3396, DOI 10.1021/bi00177a033
  • [10] ENGLANDER SW, 1984, Q REV BIOPHYS, V16, P521