= Fibrinopeptide B
{c}
<Fibrinopeptide B> is the 14-<amino acid> <peptide> that <thrombin> releases from the <N-terminus> of each B-beta chain of human <fibrinogen>. Cleavage exposes the B knob on the remaining <fibrin> molecule, allowing a <fibrin knob-hole interaction>. Each <fibrinogen> molecule contains two B-beta chains and can therefore release two copies of <Fibrinopeptide B>.<Fibrinopeptides A and B release in the process of surface fibrin formation by Tomas Riedel and others>[Introduction: twofold chain composition, 14-residue peptide and B-knob exposure]{ref}
Its release need not track <Fibrinopeptide A> release identically. A study comparing dissolved and surface-adsorbed <fibrinogen> incubated the preparations with <thrombin> and measured the released <peptides> by <high-performance liquid chromatography>. Surface-bound preparations released <Fibrinopeptide B> without the characteristic solution-phase lag; densely adsorbed preparations could release more <Fibrinopeptide B> than <Fibrinopeptide A>.<Fibrinopeptides A and B release in the process of surface fibrin formation by Tomas Riedel and others>[Methods: polystyrene wells and HPLC; Abstract and Figures4–5: altered lag and release proportions]{ref}
The experiment shows why a measured <fibrinopeptide> ratio needs its reaction conditions. Molecular presentation at a surface changes access to cleavage sites, so a typical sequence observed in solution should not be turned into an unconditional rule for every preparation.
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