Structure-affinity Relationshipand Mechanism In The Interaction Of Flavonoids And Derivatives With Protein

Object: To study the mechanism and structure-affinity relationship of twenty-three flavonoids and four genistein derivatives on binding to protein under simulative physiological condition(p H=7.40).Methods: Fluorescence was used to determine fluorescent intensity of protein after interaction of this compounds,ultraviolet-visible(UV-vis)absorption spectra,synchronous fluorescence,three-dimensional fluorescence spectroscopy,circular dichroism were used to anlysis the characteristic conformational change of protein after interaction of this compounds,molecular docking techniques were furtherly performed to reveal the binding mode and binding affinity to protein.Resluts:1.Structure-affinity relationship and mechanism in the interaction of twenty-three flavonoids with human serum albumin,lysozyme,hyaluronidase The quenching mechanism of fluorescence of three proteins(human serum albumin,lysozyme,hyaluronidase)by twenty-three flavonoids were both static quenching process.The enthalpy change(?H),entropy change(?S),free energy change(?G)were both be negative,indicated that the binding process was spontaneous and the interaction between twenty-three flavonoids and human serum albumin,lysozyme,hyaluronidase were driven mainly by hydrogen bonds and van der Waals forces.The different structure of flavonoids affected on the binding capacity of flavonoids to protein.The methylation of hydroxyl groups in flavonoids slightly enhanced the affinities for proteins by 1-2 times.The hydroxyl group in the A-ring did not much affect the binding interaction.The hydroxyl group at 3' and 4' positions in the B-ring enhanced the affinities,the hydroxyl group at 5 positions in the A-ring and 3'positions in the B-ring both enhanced the affinities for this compounds interaction with three proteins,but the hydroxyl group at 5' positions in the B ring did not much affect the affinities of flavonols.The hydroxyl group at 5 positions in the A ring decreased the affinities of isoflavones.The glycosylation of flavonoids decreased the affinities for proteins depending on the conjugation site and the class of sugar moiety.Hydrogenation of the C2=C3 double bond for the reduction reaction decreased the affinities for flavonoids to three proteins.2.Structure-affinity relationship and mechanism in the interaction of four genistein derivatives with bovine serum albumin The intrinsic fluorescence of BSA was quenched by four genistein derivatives were due to the formation of the genisteins-BSA complex.Both static quenching and nonradiative energy transferring were confirmed to result in the fluorescence quenching.The enthalpy change(?H),ntropy change(?S),free energy change(?G)were both be negative,indicated that the binding process was spontaneous and the interaction between genistein derivatives and BSA were driven mainly by hydrogen bonds and van der Waals forces.Site marker competitive experiment indicated that the binding of genisteins to BSA primarily took place in the sub-domain?A.The results of synchronous fluorescence,UV-vis absorption spectra,three-dimensional fluorescence spectroscopy,circular dichroism showed that the presence of genisteins resulted in the change of secondary structure of BSA afer four genistein derivatives binding to BSA.Molecular docking was performed to reveal genistein derivatives could insert into hydrophobic cavity in BSA.The results revealed that genistein derivatives tended to bind with BSA mainly by hydrogen bond and hydrophobic interaction.Furthermore,the bind affinity ranked in the order GEN1> GEN> GEN4> GEN3> GEN2,the hydroxylation on ring A obviously enhanced the binding affinity.However,trifluoromethylation did not much affect the affinity,alkylation,esterification and difluoromethylation slightly enhanced the binding affinity.Conclution:1.The intrinsic fluorescence of three proteins(human serum albumin,lysozyme,hyaluronidase)were quenched by twenty-three flavonoids were due to the formation of the drug-protein complex,this was a static quenching procedure.The interaction between twenty-three flavonoids and three proteins were driven mainly by hydrogen bonds and hydrophobic interaction.The affinity of flavonoids and protein were closely related to the position,type and number of substituents on the mother's nucleus.2.The intrinsic fluorescence of BSA was quenched by four genistein derivatives were due to the formation of the drug-protein complex,this was a static quenching procedure.The interaction between four genistein derivatives and BSA were driven mainly by hydrogen bonds and hydrophobic interaction.The hydroxylation on ring A obviously enhanced the binding affinity.However,trifluoromethylation did not much affect the affinity,alkylation,esterification and difluoromethylation slightly enhanced the binding affinity.