Donovan J W, Mihalyi E
Proc Natl Acad Sci U S A. 1974 Oct;71(10):4125-8. doi: 10.1073/pnas.71.10.4125.
Solutions of fibrinogen show two endothermal (denaturing) transitions, at 61 degrees and at 100 degrees , when heated in a differential scanning calorimeter. Similar transitions are observed for a mixture of the fragments D and E obtained by limited proteolysis of fibrinogen. Isolated fragment E shows only a single transition, at 97 degrees . The independent thermal denaturation of these portions of fibrinogen supports the three-nodular model proposed for fibrinogen. The D and E subunits retain their characteristic denaturation behavior when fibrinogen is clotted by thrombin addition, but over a period of about one hundred times the clotting time, the denaturation temperature of the D subunit increases by 9 degrees and its enthalpy of denaturation by one-third. Since this change takes place in the absence of Factor XIII activity, and its rate is proportional to thrombin concentration, it is presumed to be mediated by a proteolytic cleavage distinct from those which liberate the A and B fibrinopeptides.
在差示扫描量热仪中加热时,纤维蛋白原溶液在61度和100度出现两个吸热(变性)转变。对通过纤维蛋白原有限蛋白酶解获得的片段D和E的混合物也观察到类似的转变。分离出的片段E仅在97度出现单一转变。纤维蛋白原这些部分的独立热变性支持了为纤维蛋白原提出的三结节模型。当通过添加凝血酶使纤维蛋白原凝结时,D和E亚基保留其特征性变性行为,但在约凝血时间的一百倍时间内,D亚基的变性温度升高9度,其变性焓增加三分之一。由于这种变化在缺乏因子XIII活性的情况下发生,且其速率与凝血酶浓度成正比,推测它是由不同于释放A和B纤维蛋白肽的蛋白水解切割介导的。