Formation of an intramolecular cross-link in enzyme donor polypeptide fragments of .beta.-galactosidase, thereby forming a cyclic enzyme donor which is hindered from complementation with an enzyme acceptor fragment to form active of .beta.-galactosidase. The cyclic enzyme donor can be linearized by cleaving to restore complementation ability. Assays in which such cyclic enzyme donors are linearized by specific analytes are disclosed, as well as novel homobifunctional bis-maleimido cross-linking agents of the formula ##STR1## wherein R is hydroxy or acetate.
在
β-半乳糖苷酶酶给体
多肽片段中形成分子内交联,从而形成一个环状酶给体,该环状酶给体受到阻碍,无法与酶受体片段互补形成活性的
β-半乳糖苷酶。环状酶给体可以通过切割来线性化,恢复互补能力。揭示了通过特定分析物线性化这种环状酶给体的测定方法,以及新型的具有下列结构的同源双官能双马来
酰亚胺交联试剂:其中R为羟基或
乙酸根。