Binding pattern of ferrocyphen upon interaction with cetyltrimethyl ammonium bromide in the presence of urea

Cetyltrimethylammonium bromide (CTABr) have been titrated against Ferrocyphen (Dicyano-bis-(1, 10-phenanthroline) iron II complex) in aqueous solution as a function of urea concentration which gave a sigmoidal binding isotherm. A simple method was introduced for resolution and characterization of binding set on the basis of binding capacity concept to give hill coefficient > 1.0. Hill coefficient greater than one are the experimental hall mark of cooperativity in which initial binding events render subsequent binding events more favorable. The degree of cooperativity is sensitive to the concentration of urea. The results are interpreted in terms of dielectric constant and decrease in the hydrophobic interaction between the complex (ferrocyphen) and the surfactant monomers.   Key word: Binding isotherm, surfactant, cooperativity, hydrophobic ferrocyphen, binding capacity.