This happens because albumin has acidic amino acids, like glutamate and aspartate, which have some carboxyl groups that are in the form of COO- or COOH.

这是因为白蛋白含有酸性氨基酸，比如谷氨酸与天冬氨酸，它们具有一些以COO-或COOH形式存在的羧基。