肝素钠分子结构.docVIP

/wiki/Heparin DESCRIPTION Heparin is a heterogenous group of straight-chain anionic mucopolysaccharides, called glycosaminoglycans having anticoagulant properties. Although others may be present, the main sugars occurring in heparin are: (1) α-L-iduronic acid 2-sulfate, (2) 2-deoxy-2-sulfamino-α-D-glucose 6-sulfate, (3) ?-D-glucuronic acid, (4) 2-acetamido-2-deoxy-α-D-glucose, and (5) α-L-iduronic acid. These sugars are present in decreasing amounts, usually in the order (2) (1) (4) (3) (5), and are joined by glycosidic linkages, forming polymers of varying sizes. Heparin is strongly acidic because of its content of covalently linked sulfate and carboxylic acid groups. In heparin sodium, the acidic protons of the sulfate units are partially replaced by sodium ions. Structure of Heparin Sodium (representative subunits): Heparins ? Sections ? Structure Structure - Activity Relationships Metabolism Pharmacology Biochemical Mechanism of Action Low-Molecular-Weight Heparins ? ??? Heparin - Structure ??????? Heparin is a mucopolysaccharide with a molecular weight ranging from 6,000 to 40,000 Da. The average molecular of most commercial heparin preparations is in the range of 12,000 - 15,000. The polymeric chain is composed of repeating disaccharide unit of D-glucosamine and uronic acid linked by 1ˉˉ4 interglycosidic bond. The uronic acid residue could be either D-glucuronic acid or L-iduronic acid. (Structure below) Few hydroxyl groups on each of these monosaccharide residues may be sulfated giving rise to a polymer with that is highly negatively charged. The average negative charge of individual saccharide residues is about 2.3. ?? ???? ?? ???? ??? Structure - Activity Relationship ?? ???? The key structural unit of heparin is a unique pentasaccharide sequence (below). This sequence consists of three D-glucosamine and two uronic acid residues. The central D-glucosamine residue contains a unique 3-O-sulfate moiety that is rare outside of this sequence. Four