[Electrophoretic fractions and NH2-terminal amino acids of high-molecular tryptic fragments of fibrinogen and fibrin].

The electrophoretic and NH2-terminal analyses were performed for D and E fragments obtained by tryptic digestion of bovine fibrinogen and fibrin under various conditions. The preparations of fragment D were heterogeneous, they were separated by polyacrylamide gel electrophoresis into a number of electrophoretic components with molecular weight ranging from 65 000 to 85 000. NH2-terminal analysis revealed from 6 to 8 NH2-terminal amino acids: Ser, Gly, Thr, Asp, Gly, Lys, Gln, Asn. Their composition and quantitative ratios were found to vary depending on the conditions of the fragment D production. The electrophoregrams showed that with Ca++ in the medium the enzymatic splitting of fibrinogen was limited. Fragment D obtained from fibrinogen without Ca++ was electrophoretically rather similar to that obtained from fibrinogen at Ca++ optimal concentration. Taking into consideration a very high specific anti-coagulational activity of these two fragment D preparations, one may conclude that both the polymerized state of protein molecules and the presence of Ca++ stabilize the specific molecular structure, that favorus the preservation of specific inhibitory activity in fragment D. According to the NH2-terminal analysis data, fragment E derived from fibrinogen hydrolyzed in the presence of Ca++ optimal concentration is also heterogeneous. The following amino acids were found: Tyr, Lys, His (main ones) and Gly, Ser, Thr, Val (minor ones). As to molecular weight determined by electrophoresis, fragment E appears to be homogeneous.