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Effect of anions on the denaturation and aggregation of β‐Lactoglobulin as measured by differential scanning microcalorimetry
Author(s) -
McPhail Deborah,
Holt Carl
Publication year - 1999
Publication title -
international journal of food science and technology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.831
H-Index - 96
eISSN - 1365-2621
pISSN - 0950-5423
DOI - 10.1046/j.1365-2621.1999.00316.x
Subject(s) - chemistry , isoelectric point , isothermal microcalorimetry , phosphate , divalent , denaturation (fissile materials) , electrolyte , salt (chemistry) , chromatography , protein aggregation , phosphate buffered saline , imidazole , inorganic chemistry , whey protein , nuclear chemistry , biochemistry , organic chemistry , electrode , quantum mechanics , enthalpy , enzyme , physics
Summary Profound differences in the rate of aggregation and denaturation among β‐lactoglobulin samples from different sources can be reduced or even eliminated by dialysis of the samples first against a phosphate buffer. Visual evidence and thermograms indicated a reduced rate of aggregation in a phosphate buffered salt solution compared to the salt solution alone. The same effect was not achieved by another divalent tetrahedral ion, sulphate, nor by imidazole‐buffered NaCl. Replacement of the background electrolyte by Na acetate had no discernible effect on the thermogram in the phosphate buffer. Phosphate is particularly good at buffering the protein solution at neutral pH at elevated temperature so the main effect is to maintain the net protein charge. In the imidazole and unbuffered media, the protein can move towards its isoelectric point and although the protein is more stable, aggregation is faster. It is speculated that there might also be a specific interaction of the phosphate anion with a cation‐rich region of the β‐lactoglobulin surface which could also inhibit aggregation at elevated temperatures.