Effect of temperature and pH on the aggregation and the surface hydrophobicity of bovine Delta k-casein

Delta *k-Casein ( Delta *k-CN) aggregation by heating has been studied at pH 7.2 and 5.2 using UV-visible spectrophotometry, sodium dodecyl sulfate polyacrylamide gel electrophoresis, spectrofluorometric study of the 1--8 aniline naphtalene sulfonate (ANS)-- Delta *k-CN binding and circular dichrois...

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Bibliographic Details
Published in:Colloid and polymer science 2008-10, Vol.286 (12), p.1369-1378
Main Authors: Risso, Patricia H, Borraccetti, Domingo Mariano, Araujo, Cesar, Hidalgo, Maria Eugenia, Gatti, Carlos A
Format: Article
Language:English
Subjects:
Agglomeration
Aggregates
Aniline
Binding
Electrophoresis
Heating
Sodium
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Summary:Delta *k-Casein ( Delta *k-CN) aggregation by heating has been studied at pH 7.2 and 5.2 using UV-visible spectrophotometry, sodium dodecyl sulfate polyacrylamide gel electrophoresis, spectrofluorometric study of the 1--8 aniline naphtalene sulfonate (ANS)-- Delta *k-CN binding and circular dichroism (CD) spectroscopy. The aggregation process to form aggregates like micelles or submicelles and the structural characteristics of these aggregates were pH dependent. Far-UV CD showed that the aggregates obtained by heating presented changes in the Delta *k-CN secondary structure. Near-UV CD spectra showed a certain degree of tertiary organization in the Tyr environment for the protein heated or unheated, only at pH 5.2. ANS binding at both pH was quite different and depends on the self-association process. Heating produced exposition of hydrophobic binding sites only at pH 7.2, including those in the neighborhood of the Delta *k-CN Trp residue.
ISSN:0303-402X
DOI:10.1007/s00396-008-1906-y