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Effect of Heat Treatment on the Circular Dichroism Spectra of Bovine β Lactoglobulin A, B and C.

Manderson, Gavin LU ; Hardman, Mike J and and Creamer, Lawrie K (1999) In Journal of Agricultural and Food Chemistry 47(11). p.4557-4567
Abstract
Dilute solutions of -lactoglobulin (-Lg) A, B, and C were heated in phosphate buffer at temperatures between 40 and 94 C for 10 min, cooled, and analyzed using near-UV and far-UV circular dichroism (CD). The decrease in near-UV CD intensity at 293 nm (293) could be analyzed in terms of a two-state model, and the stability was -Lg C > -Lg A > -Lg B on the basis of the midpoint temperatures for samples heated at pH 6.7 and 7.4. However, the slopes of the curves at the midpoint temperature for variant A were generally less than those for -Lg B and -Lg C, indicating that the substitution of Val (-Lg A) for Ala (-Lg B or -Lg C) at position 118 had altered the entropic contribution to unfolding of the protein. The changes in CD at 270 nm... (More)
Dilute solutions of -lactoglobulin (-Lg) A, B, and C were heated in phosphate buffer at temperatures between 40 and 94 C for 10 min, cooled, and analyzed using near-UV and far-UV circular dichroism (CD). The decrease in near-UV CD intensity at 293 nm (293) could be analyzed in terms of a two-state model, and the stability was -Lg C > -Lg A > -Lg B on the basis of the midpoint temperatures for samples heated at pH 6.7 and 7.4. However, the slopes of the curves at the midpoint temperature for variant A were generally less than those for -Lg B and -Lg C, indicating that the substitution of Val (-Lg A) for Ala (-Lg B or -Lg C) at position 118 had altered the entropic contribution to unfolding of the protein. The changes in CD at 270 nm (270), an index of significant alteration to disulfide bond dihedral angles, occurred at higher temperatures than those for the 293 results. The far-UV CD showed some small changes as a consequence of heat treatment, and the shifts at 205 nm ([]205) fitted a two-state model. Plotting the changes in both 293 and []205 against the loss of nativelike and sodium dodecyl sulfate-monomeric protein (assessed by polyacrylamide gel electrophoresis) showed a strong 1:1 relationship between 293 or []205 and the loss of nativelike -Lg. These results indicated that the initial irreversible stage in the heat-induced aggregation of -Lg (nativelike monomer to unfolded monomer) altered the chirality of the environment of Trp19 and modified the secondary structure of -Lg slightly. The differences in the behavior of variants A-C were explicable on the basis of generalized electrostatic and hydrophobicity effects as well as specific amino acid effects. (Less)
Please use this url to cite or link to this publication:
author
publishing date
type
Contribution to journal
publication status
published
subject
keywords
Thermal denaturation, circular dichroism, aggregate formation, disulfide-linked aggregates, -lactoglobulin variants
in
Journal of Agricultural and Food Chemistry
volume
47
issue
11
pages
4557 - 4567
publisher
The American Chemical Society
external identifiers
  • scopus:0033230053
ISSN
0021-8561
DOI
10.1021/jf981291m
language
English
LU publication?
no
id
a4c5a10e-8dca-4ddb-b871-a9ac97bb1406 (old id 1115669)
date added to LUP
2008-07-08 11:23:14
date last changed
2017-07-23 03:34:30
@article{a4c5a10e-8dca-4ddb-b871-a9ac97bb1406,
  abstract     = {Dilute solutions of -lactoglobulin (-Lg) A, B, and C were heated in phosphate buffer at temperatures between 40 and 94 C for 10 min, cooled, and analyzed using near-UV and far-UV circular dichroism (CD). The decrease in near-UV CD intensity at 293 nm (293) could be analyzed in terms of a two-state model, and the stability was -Lg C > -Lg A > -Lg B on the basis of the midpoint temperatures for samples heated at pH 6.7 and 7.4. However, the slopes of the curves at the midpoint temperature for variant A were generally less than those for -Lg B and -Lg C, indicating that the substitution of Val (-Lg A) for Ala (-Lg B or -Lg C) at position 118 had altered the entropic contribution to unfolding of the protein. The changes in CD at 270 nm (270), an index of significant alteration to disulfide bond dihedral angles, occurred at higher temperatures than those for the 293 results. The far-UV CD showed some small changes as a consequence of heat treatment, and the shifts at 205 nm ([]205) fitted a two-state model. Plotting the changes in both 293 and []205 against the loss of nativelike and sodium dodecyl sulfate-monomeric protein (assessed by polyacrylamide gel electrophoresis) showed a strong 1:1 relationship between 293 or []205 and the loss of nativelike -Lg. These results indicated that the initial irreversible stage in the heat-induced aggregation of -Lg (nativelike monomer to unfolded monomer) altered the chirality of the environment of Trp19 and modified the secondary structure of -Lg slightly. The differences in the behavior of variants A-C were explicable on the basis of generalized electrostatic and hydrophobicity effects as well as specific amino acid effects.},
  author       = {Manderson, Gavin and Hardman, Mike J and and Creamer, Lawrie K},
  issn         = {0021-8561},
  keyword      = {Thermal denaturation,circular dichroism,aggregate formation,disulfide-linked aggregates,-lactoglobulin variants},
  language     = {eng},
  number       = {11},
  pages        = {4557--4567},
  publisher    = {The American Chemical Society},
  series       = {Journal of Agricultural and Food Chemistry},
  title        = {Effect of Heat Treatment on the Circular Dichroism Spectra of Bovine β Lactoglobulin A, B and C.},
  url          = {http://dx.doi.org/10.1021/jf981291m},
  volume       = {47},
  year         = {1999},
}