No abstract

No abstract

A series of sodium heparinate preparations have been characterised in terms of their ionogenic groups, utilizing a fluorescence titration technique. Single ion activity coefficients of the counterion were determined in pure polyelectrolyte solutions and polyelectrolyte/NaCl solutions. The results are discussed in relation to the anticoagulant activity of each heparin preparation. There appears to be a correlation between the linear charge parameter of the polyanion, and anticoagulant activity.Heparin is a naturally occurring mucopolysaccharide of molecular weight 5000-50 000. It is initially synthesized as an alternating copolymer of N-acetylglucosamine and glucuronic acid' but in subsequent pathways glucosamine residues are N-deacetylated and N-sulfated; glucuronic acid residues epimerise to iduronic acid which together with glucosamine are ester sulfated.2 T h e anticoagulant activity of heparin has been investigated by several researchers i n order t o correlate the biological role with polydispersity i n molecular size,3 variation in t h e ratio of glucuronic t o iduronic acid,4 alterations i n t h e a m o u n t of ester and N -~u l f a t i o n ,~ and differing degree of N-acetylation.6 Although these chemical and physical differences can affect t h e anticoagulant activity, at present none of these criteria have been shown t o be paramount, a n d for instance molecular weight dependence of anticoagulant activity has given rise to a number of conflicting report^.^,^,^ T h i s implies that the anticoagulant activity of heparin might be related t o a variety of chemical and physical factor^.^ In this present investigation, preparations of sodium salts of heparin were examined in an attempt to relate the cationic binding strength both in the pure polyelectrolyte system and also with a d d e d sodium chloride t o t h e anticoagulant activity of heparin. Stivala e t a l l o have already proposed that a correlation exists between Cu(I1) binding and t h e anticoagulant activity of heparin. Also it has been noted that a relationship exists between the counterion salt form of a heparin preparation a n d its efficacy as a prophylactic drug for d e e p venous thrombosis a n d local haematoma treatment."-13 There is, therefore, a necessity t o provide a better understanding of t h e parameters governing anticoagulant activity.It is generally known14 that polyelectrolytes characterised by t h e dimensionless linear charge parameter, 5,where e is t h e protonic charge, t is t h e bulk dielectric constant of the solvent, k is Boltzmann's constant, T i s the absolute temperature, and b is t h e average distance between charged groups on t h e polyelectrolyte chain; tcriticd is given by (zizP(-l, where zi is t h e charge carried by t h e counterion and zp is t h e charge carried by t h e charged site of the polyelectrolyte.T h e Manning model for the infinite line charge gives rise to limiting laws for thermodynamic parameters, and these laws received extensive experimental testing, a n d have been found t o give good agreeme...

No abstract

Pulse radiolysis and 60Co gamma-radiolysis have been used to study the effects of ionizing radiations on the protein-polysaccharide complex, chondromucoprotein. Both hydroxyl radicals and hydrated electrons readily react with the complex, with second-order rate-constants of 4-55 X 10(8)M-1s-1, respectively. Depolymerization of the carbohydrate component, which is initiated by reaction of OH, readily occurs after irradiation in aqueous solution, as is evidenced by an increase in the formation of reducing-end groups and a decrease in the viscosity of the solution. The ability of the anionic carbohydrate component to bind cationic counter-ions also decreases.