Abstract
The viscosity of heparin solution was investigated under conditions of low shear stress between 0.0193 and 0.222 dyne cm^β2^, in water, in the presence of various cations (Na^+^, K^+^, Cs^+^, Mg^2+^, Ba^2+^, Cu^2+^) and at several pH's. The viscosity was found to decrease with in creasing shear stress. Shear dependence was greatest in the absence of added salts, and decreased as the ionic strength increased.
Differences in viscosity in the presence of various cations appear to be related to the binding affinity of these cations to heparin. Viscosity studies of the periodate oxidation of heparin confirmed that heparin contains vicinal hydroxyl groups in its primary structure.
Circular dichroism spectra of the same heparin solutions were also studied. The binding process between Cu^2+^ and heparin appears to be different from that of other divalent ions. A reduction in the pitch of the helix would qualitatively explain the conformational changes that occur on binding Cu^2+^ to heparin. These changes are reversible on removal of Cu^2+^ and replacement with Na^+^. The circular dichroism spectrum was virtually lost for periodateoxidized heparin.