ЧЕЛОВЕЧЕСКИЙ ФИБРИНОГЕН

Химические свойства

White or grayish amorphous substance.

Использование

Diagnostic aid (vascular patency); radioactive agent.

Определение

A sterile fraction of normal human blood plasma, dried from the frozen state. In solution, it has the property of being converted into insoluble fibrin when thrombin is added. It is an essential factor in the blood-clotting mechanism.

Общее описание

Fibrinogen, or Factor I, is a blood protein that is involved in clotting and is converted to fibrin by thrombin. Fibrinogen has an approximate molecular weight of 340 kDa

Методы очистки

A likely impurity is plasminogen. It is purified by glycine precipitation [Mosesson & Sherry Biochemistry 5 2829 1966] to obtain fractions 1-2, then further purified [Blomb.ck & Blomb.ck Arkiv Kemi 10 415 1956] and contaminating plasminogen is removed by passage through a lysine-Sepharose column. Such preparations are at least 95% clottable as determined by Mosesson and Sherry's method (above ref.) in which the OD280 is measured before and after clotting with 5 Units/mL of thrombin (> 3000U/mg). All fibrinogen preparations are treated with calf intestinal alkaline phosphatase to convert any fibrinogen peptide-AP to fibrinogen peptide-A by removing serine-bound phosphate. Solutions are then lyophilised and stored at -20o. [Higgins & Shafer J Biol Chem 256 12013 1981.] It is sparingly soluble in H2O. Aqueous solutions are viscous with isoelectric point at pH 5.5. It is readily denatured by heating above 56o or by chemical agents, e.g. salicylaldehyde, naphthoquinone sulfonates, ninhydrin or alloxan. [Edsall et al. J Am Chem Soc 69 2731 1947, Purification: Cama et al. Naturwissenschaften 48 574 1961, Lorand & Middlebrook Science 118 515 1953, cf. Fuller in Methods Enzymol 163 474 1988.] For plasminogen-deficient fibrinogen from blood plasma, the anticoagulated blood is centrifuged and the plasma is frozen and washed with saline solution. It is treated with charcoal, freeze-thawed and dialysed versus Tris/NaCl buffer. [Maxwell & Nikel Biochemical Preparations 12 16 1968.]