Heparin binding strength

Other recent NMR investigations of the interaction between heparin polymers and different protein receptors have focused on the heparin binding to full-length Tau systems.29 In this particular example, the strength and location of the interactions was investigated, as well as the structural consequences derived from this important molecular interaction. 

The diversions concerning the effect of heparin on platelet adhesion may probably be attributed to the different binding strengths of heparin to the polymer. When heparin is, at least to some extent, leaking into the bloodstream, the platelet adhesion... 

The theory and application of this fluorescence method have been discussed in detail by LePecq and others (3,8). The assay requires that there is sufficient ionic strength to minimize ionic binding (e.g., O.IM sodium chloride), that the pH is 4-10, that no heavy metals are present, that the fluorescence is not enhanced on binding to other excipients (e.g., proteins) and that at least portions of the nucleic acids are not complexed. These requirements can usually he met when dealing with recombinant products in some cases the samples must he manipulated to create the appropriate conditions. In the intercalative method of dye binding, proteins rarely interfere with the assay, and procedures have been developed to remove the few interferences they may cause (e.g., the use of heparin or enzymatic digestion of the protein 9). 

After the initial experimental conditions have been chosen with respect to kinetics and concentrations of ligands and immobilized heparin, variations in buffer composition, such as magnesium ion concentration, pH, and total ionic strength, can be examined. Finally, a measurement of the nonspecific binding of the system should also be made. 

The viscosity of heparin, measured under conditions of low shear stress, varies with the nature and concentration of counter-ions present (Na+, K+, Cs+, Mg +, Ba +, or Cu ). The viscosity decreases with increasing shear stress and this effect is reduced with an increased ionic strength. C.d. spectroscopic studies indicate that the binding of Cu + to heparin differs from that of other cations. 

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