Analysis of calcium phosphate cross-linkage in casein micelles by radioactive isotope Professor

用放射性同位素分析酪蛋白胶束中的磷酸钙交联教授

基本信息

批准号：
07660362
负责人：
AOKI Takayoshi
金额：
$ 1.34万
依托单位：
Kagoshima University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (C)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1996
项目状态：
已结题

项目摘要

Although calcium and inorganic phosphate (Pi) in bovine casein micelles were at equilibrium with those in soluble form, their properties have not yet been elucidated sufficiently. In this study, the behavior of calcium and Pi in casein micelles was studied using ^<45>Ca and ^<32>P by ultrafiltration, equilibrium dialysis and gel permeation HPLC in the presence of 6M urea. Approximately 30-40% of the calcium and Pi in bovine casein micelles were estimated to be hard to exchanged with those in soluble phase. Then, artificial casein micelles were prepared at a casein concentration of 2.5% with 30-40 mM calcium, 22-27 mM Pi and 10mM citrate using ^<45>Ca and ^<32>P.About 75 and 65% of micellar calcium and Pi in artificial casein micelles were exchanged after dialysis of artificial casein micelles against a simulated milk ultrafiltrate at 4ﾟC for 72h.The percentage of ^<45>Ca and ^<32>P in the fraction of casein aggregates cross-linked by micellar calcium phosphate were 26.9 and 27.6%, which decreased to about 10% after equilibrium dialysis against a simulated milk ultrafiltrate at 4ﾟC for 72h. The proportion of exchanged calcium and Pi in artificial casein micelles during dialysis for 72h were higher at 25ﾟC than at 4ﾟC,suggesting that the exchange of calcium and Pi between diffusible and micellar phases depended on temperature. The effects of calcium and Pi on the formation and properties of casein micelles were also examined using response surface analyzes. The results suggest that the exchange of calcium and phosphate between diffusible and micellar phases proceeds slowly, and a proportion of calcium and Pi in casein micelles is difficult to exchage.

尽管牛酪蛋白胶束中的钙和无机磷酸盐（Pi）与可溶形式的钙和无机磷酸盐（Pi）处于平衡状态，但它们的性质尚未得到充分阐明。在本研究中，使用^<45>研究了酪蛋白胶束中钙和Pi的行为。在6M尿素存在下通过超滤、平衡透析和凝胶渗透HPLC测定Ca和32 P大约30-40％。据估计，牛酪蛋白胶束中的钙和Pi很难与可溶相中的钙和Pi交换。然后，使用30-40mM钙、22-27mM Pi和10mM柠檬酸盐制备酪蛋白浓度为2.5%的人工酪蛋白胶束。 ^<45>Ca和^<32>P。人工酪蛋白胶束中的胶束钙和Pi的约75％和65％被交换人工酪蛋白胶束与模拟牛奶超滤液在 4°C 下透析 72 小时后。通过胶束磷酸钙交联的酪蛋白聚集体中 ^<45>Ca 和 ^<32>P 的百分比分别为 26.9% 和 27.6% ，在 4°C 下对模拟牛奶超滤液进行平衡透析后，该值下降至约 10% 72小时透析过程中人工酪蛋白胶束中钙和Pi的交换比例在25℃时高于4℃时，表明扩散相和胶束相之间的钙和Pi交换取决于温度和Pi。还使用响应表面颗粒检查了酪蛋白胶束的形成和性质，结果表明扩散相和胶束相之间存在钙和磷酸盐的交换。进展缓慢，酪蛋白胶束中的钙和Pi的比例难以交换。