A light-scattering study of the effect of calcium chloride on the molecular weight of busycon hemocyanin

M.Constance Loeffler, Shian-shi Su, Norman C. Li, Edward F. Casassa
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引用次数: 4

Abstract

Solutions of Busycon canaliculatum have been studied by light scattering. In 0.05 M Trizma buffer + 0.1 M NaCl at pH 7.0 at 14°, the weight-average molecular weight is 8.9 X 106. In the presence of added CaCl2 (0.02 M), the molecular weight of the protein increases to 10.7 X 106, and the second virial coefficient is reduced. At pH 9.95, the molecular weights with and without 0.02 M CaCl2, are 3.7 X 106 and 1.3 X 106, respectively; and the effect of Ca++ in reducing the second virial coefficient is much greater than at pH 7.0. These results can be understood on the basis that at pH 7.0, Ca++ increases the association of hemocyanin, by binding and intermolecular linkage through the carboxyl groups of protein side chains. At pH 9.95, amino groups are deprotonated and therefore also become available for Ca++ binding. The relative effect of Ca++ in enhancing the association of hemocyanin therefore becomes greater at the higher pH.

氯化钙对水仙桃血青素分子量影响的光散射研究
用光散射法研究了水仙花的解法。在0.05 M Trizma缓冲液+ 0.1 M NaCl, pH 7.0,温度14°条件下,分子量为8.9 X 106。在CaCl2 (0.02 M)的存在下,蛋白质的分子量增加到10.7 X 106,第二维里系数降低。在pH 9.95时,加入0.02 M CaCl2和不加入0.02 M CaCl2的分子量分别为3.7 X 106和1.3 X 106;Ca++对第二维里系数的降低作用远大于pH 7.0时。这些结果可以理解为,在pH 7.0时,Ca++通过蛋白质侧链的羧基结合和分子间连锁增加了血青素的结合。在pH值为9.95时,氨基被去质子化,因此也可以与Ca++结合。因此,在较高的pH值下,Ca++在促进血青素结合方面的相对作用变得更大。
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