Human fibrinogen heterogeneities: determination of the major Aalpha chain derivatives in blood

Most plasma fibrinogen molecules, when analyzed by Na Dod SO4 polyacrylamide gel electrophoresis migrate in three major positions, designated bands I, II, and III, respectively. Band I reflects the presence of intact molecules, whereas bands II and III represent molecules containing catabolic Aalpha chain fragments. In order to establish the Aalpha chain composition of band II molecules, we analyzed plasma fraction I-6 which consists amost exclusively of material migrating in this band position. Analyses of ancrod- and of reptilase-treated samples by Na Dod SO4 polyacrylamide gel electrophoresis and gel scanning densitometry permitted assessment of the Aalpha chain composition of fraction I-6. We found that an Aalpha chain derivative, termed Aalpha/4, comprises more than 70% of the Aalpha chain population of I-6. Consistent with this finding and with studies showing that band II molecules were the most abundant species of catabolic derivatives in plasma, Aalpha/4 was shown to be the most abundant of the Aalpha chain (core) fragments in blood.