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Irreversible heat denaturation of bovine α-lactalbumin

Published online by Cambridge University Press:  01 June 2009

Lesley C. Chaplin  and
Richard L. J. Lyster
Lesley C. Chaplin
Affiliation:
AFRC Food Research Institute (University of Reading), Shinfield, Reading RG2 9AT, UK
Richard L. J. Lyster
Affiliation:
AFRC Food Research Institute (University of Reading), Shinfield, Reading RG2 9AT, UK
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Summary

The irreversible heat denaturation of α-lactalbumin (α-la) in 0·1 M-phosphate, pH 7·0, at 100 °C was studied using polyacrylamide-gel electrophoresis (PAGE). PAGE revealed two groups of bands, one moving faster than native α-la and one slower, in addition to some denatured protein which remained at the origin and some residual native α-la. The faster group had unchanged molecular weight, but an increase in charge, partly due to hydrolysis of glutamine and asparagine residues. The slower group was shown by two-dimensional sodium dodecyl sulphate-PAGE to be oligomers of denatured α-la; formation of the smaller oligomers preceded the larger ones. The oligomers reverted to monomers in the presence of dithiothreitol, showing that they were disulphide-linked aggregates of denatured α-la. Immuno-blots of the gels showed that both fast and slow groups of bands had irreversibly lost most of the antigenicity of the native protein.

Type
Original Articles
Information
Journal of Dairy Research , Volume 53 , Issue 2 , May 1986 , pp. 249 - 258
Copyright
Copyright © Proprietors of Journal of Dairy Research 1986

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