S-Nitrosoglutathione Alters Fibrin Architecture Figure 1. Fibrin polymerization, GSNO targets and fibrin structural elements imaged by multiphoton microscopy. Panel A shows a schematic of fiber formation. Fibrinogen is a bisymmetrical molecule consisting of three pairs of polypeptide chains (Aa, Bb, c)2 held together by 29 disulfide bonds. It has a trinodal structure, with central E domain containing N-terminal regions of all six chains connected, by two coiled coils, to two end D domains containing the carboxy-terminal ends of the Bb and c chains. The carboxy-terminal portion of the Aa chain folds back from the D PLOS ONE | www.plosone.org 3 August 2012 | Volume 7 | Issue 8 | e43660