ELECTROSPRAY-IONIZATION MASS-SPECTROMETRY FACILITATES DETECTION OF FIBRINOGEN (B-BETA-14ARG-]CYS) MUTATION IN A FAMILY WITH THROMBOSIS

We report the first direct detection of a fibrinogen mutation by elect rospray ionisation mass spectrometry. The propositus, from a family wi th a history of thrombosis, came to attention after a pulmonary emboli sm subsequent to a spontaneous abortion. Prolonged thrombin (41 s) and reptilase times (26 s) together with an impairment of fibrinopeptide B release suggested a mutation at the thrombin cleavage site of the B beta chain. Direct mass analysis of purified fibrin chains from a thro mbin induced clot showed that 50% of the B beta chains remained unclea ved. The measured mass of the mono sialo isoform of this uncleaved cha in was 54150 Da, compared to a value of 54198 Da for normal B beta cha ins. This decrease of 48 Da in the intact protein is indicative of eit her a B beta 14 Arg to Cys, or Arg to Leu substitution. Heterozygosity for the B beta 14 Arg --> Cys mutation was verified by PCR amplificat ion and DNA sequence analysis.