Study On The Interaction Between Hemoglobin And Didodecyldimethylammonium Bromide

Hemoglobin(Hb),a tetramer protein with an Mr of approximately 67 kDa,is composed of twoαand twoβsubunits.It is an important functional protein for reversible oxygen carrying and storage,as well as a model protein with highα-helical content.However,Hb in outer cells and its ramification could permeate into the blood system and produce the side effect to certain extent.In everyday's life many washes are widely used,and the surfactant could permeate into the people's body by the food chain,which may cause the change of protein's stucture and result in the illness produced.At present,the health problem caused by the surfactant are concerned more and more.Didodecyldimethylammonium bromide(DDAB) is an ionic surfactant with double chain,it was composed by hydrophilic group and hydrophobic group.According to the hydrophobic force,DDAB could form the self-assembled supermolecular structure,such as micelle, microemulsion and vesicle.In this thesis,the interaction between Hb and DDAB was investigated by electrochemistry method,UV-vis spectra,fluorescence spectra and circular dichroism spectra.The results may help to understand the mechanism of surfactant-protein interaction,especially the effect of surfactant molecule on protein structure.Firstly,a modified electrode was prepared by sequentially dropping DDAB of different concentration and Hb solution on pyrolytic graphite electrode.The electrochemical property of the modified electrode was studied by cyclic voltammetry.The data analyzed with Laviron model shown that with increasing the DDAB concentration,the heme released from hemoglobin,so that the electrochemical reaction changed from a double-electron process to a single-electron process.Secondly,the interaction between Hb and DDAB was investigated by UV-vis spectra,fluorescence spectra and circular dichroism spectra. Experimental results showed that the binding of DDAB to Hb induced a conformation change of Hb,which was further proved by the quantitative analysis of CD spectra.The data of UV-vis and fluorescence spectra indicated that the changes of microenvironment of Hb were induced by the binding of DDAB.The parameters of thermodynamics suggested that the type of interaction between DDAB and Hb was mainly hydrophobic force.