Abstract: Screening tests and bioassay of von Willebrand's factor (platelet aggregating factor) in human and animal blood plasma are effected using a reagent of blood platelets and snake venom having a positive platelet aggregating cofactor effect. The reagent and tests may also suitably employ dried blood platelets. The reagent may comprise dried platelets and either ristocetin or active snake venom as the platelet aggregating cofactor.
Abstract: Sulfhydryl oxidase is isolated in substantially purified form by precipitating from whey a crude impure fraction of sulfhydryl oxidase, dissolving the crude sulfhydryl oxidase in a dilute neutral buffer solution, equilibrating to allow for dissociation of the dissolved sulfhydryl oxidase, separating the equilibrated sulfhydryl oxidase from molecularly larger materials, concentrating the resultant separated sulfhydryl oxidase and separating the concentrated sulfhydryl oxidase from molecularly smaller materials to isolate a substantially purified sulfhydryl oxidase enzyme having a specific activity at least about fifty times greater than the crude enzyme and about 3000 times greater than that in skim milk. The enzyme may be immobilized, for example, by attaching it to an inert support. Activity of the immobilized enzyme may be regenerated by treatment with an aqueous solution of ferrous ions.
Abstract: Milk having "cooked" flavor produced by heat treatment, such as ultra-high-temperature processing, is contacted with immobilized sulfhydryl oxidase to remove the "cooked" flavor.