Thermodynamics of mucopolysaccharide–dye binding. III. Thermodynamic and cooperativity parameters of acridine orange–heparin system

摘要: Binding isotherms for acridine orange (AO)–heparin systems can be evaluated solely on the basis of quantitative fluorescence spectroscopic measurements. The evaluation thermodynamic parameters indicates that interactions AO with heparins from several animal sources are similar to each other in magnitude. is highly exothermic (ΔH = −6 kcal mol−1) and stabilized by dye–polymer dye–dye (coopertive) interactions, as well entropic factors (ΔS +7 e.u.). predominant stabilizing factor appears electrostatic attraction between cation heparin polyanion, although important well. At 24°C value cooperative binding constants various range 8.8 11.3 × 105M−1, corresponding a free energy −8 mol−1. degree cooperativity, which direct measure interaction, varies polymer:dye ratio; theoretical this variation remains elucidated. Electrophoretic data indicate sample consists mixture species, its own charge density. This precludes definitive interpretation observed small differences values among samples until resolved into components.