MOLECULAR-WEIGHT OF HUMAN-PLASMA FACTOR-VIII

Gel chromatography of human plasma on agarose resulted in elution of factor [F] VIII coagulant activity at the void volume under the following conditions: at 37.degree. C, with physiological concentrations of albumin and Ca ions and anticoagulation by benzamidine and diisopropylfluorophosphate; using citrated or heparinized plasma; and after prevention of disulfide bridge formation by blocking cysteine residues. Similar elutions were obtained with purified F VIII. The apparent MW of purified F VIII was decreased by relatively small changes of the medium: under mildly reducing conditions in which case the lowest MW form with measurable coagulant activity was about 480,000; after incubation and elution at high ionic strength (0.25 M CaCl2); and after dialysis and chromatography in acetate buffer at pH 6.0. The MW of purified F VIII apparently corresponds to the in vivo MW and alterations were apparently due to changes in the in vitro conditions.