Fibrin

Fibrin (also called Factor Ia) is a fibrous, non-globular protein involved in the clotting of blood.

Hereditary abnormalities of fibrinogen (the gene is carried on chromosome 4) are both quantitative and qualitative in nature and include afibrinogenaemia, hypofibrinogenaemia, dysfibrinogenaemia, and hypodysfibrinogenemia.

Fibrin from various different animal sources is generally glycosylated with complex type biantennary asparagine-linked glycans.

Variety is found in the degree of core fucosylation and in the type of sialic acid and galactose linkage.

[5][6] Fibrin assembly facilitates intermolecular antiparallel C-terminal alignment of gamma-chain pairs, which are then covalently 'cross-linked' by factor XIII ('plasma protransglutaminase') or XIIIa to form 'gamma-dimers'.

Composition of a fresh thrombus at microscopy, HE stain , showing nuclear debris in a background of fibrin and red blood cells .
Micrograph showing fibrin (dark pink amorphous material) in a blocked vein surrounded by extravasated red blood cells (right of image). An artery (left of image) and the amnion (far left of image) is also seen. Placenta in a case of fetal thrombotic vasculopathy . H&E stain .
From Fibrinogen to Fibrin with the help of Thrombin and Factor XIII .
Cross-linking by thrombin and stabilization by activated factor XIII
Crystal structure of the double-d fragment from human fibrin