Effect of sulfated polysaccharides on heat-induced structural changes in beta-lactoglobulin.
The mechanism that leads to a decreased aggregation of beta-lactoglobulin in the presence of dextran sulfate and lambda-carrageenan was investigated by assessing changes in the denaturation thermodynamics and protein structure. Differential scanning calorimetry results showed that the denaturation temperature (Tp) was about 4.6 degrees C higher in the presence of dextran sulfate, as compared with beta-lactoglobulin alone, whereas in the presence of lambda-carrageenan the difference in Tp was about 1.2 degrees C. Changes in protein structure studies using near-UV circular dichroism (CD) provided support for the calorimetric results. The transition midpoint (Tm) for denaturation of beta-lactoglobulin was about 5 degrees C higher in the presence of dextran sulfate than that found with beta-lactoglobulin alone and about 2 degrees C in the presence of lambda-carrageenan. Thermal modifications of the tertiary structure of beta-lactoglobulin were irreversible at temperatures above 67 degrees C; the addition of dextran sulfate reduced the extent of such modifications. Far-UV CD studies indicated that the addition of dextran sulfate or lambda-carrageenan did not affect secondary structure changes of beta-lactoglobulin upon heating. These studies indicate that dextran sulfate and lambda-carrageenan can enhance the stability of beta-lactoglobulin and thereby inhibit heat denaturation and aggregation.
Zhang
Guoyan
G
Department of Food Science, North Carolina State University, Raleigh, North Carolina 27695, USA.
Foegeding
E Allen
EA
Hardin
Charles C
CC
D002351:Carrageenan / Q000494:pharmacology*; D003911:Dextrans / Q000494:pharmacology*; D004355:Drug Stability; D006358:Hot Temperature; D007782:Lactoglobulins / Q000737:chemistry*; D011134:Polysaccharides / Q000494:pharmacology*; D011489:Protein Denaturation; D013431:Sulfates / Q000494:pharmacology*; D013816:Thermodynamics
D003911:Dextrans; D007782:Lactoglobulins; D011134:Polysaccharides; D013431:Sulfates; D002351:Carrageenan