Effect Of Curcumin Structure On The Formation And Stability Of Hen Egg White Lysozyme Amyloid Fibril

Protein was mainly formed by element C,N,O,P and it participated in many physiological movement in organism.Its normal physiological function could be exhibited when the molecular chain of protein was in correct conformation.Toxic amyloid fibrils may be formed if the molecular chain of protein was misfold and the normal physiological function could not be exhibited.The formation of amyloid fibrils could induce a series of neurodegenerative diseases,such as Alzheimer’s disease,Huntington’s disease and so on.The design and synthesis of new compund which could prevent the formation of amyloid fibril or decompose the formed amyloid fibril was one of the study hot in this field.Curcumin molecule was formed by β-diketone and two O-methylate phenols and it could effectilvely inhibit the formation of amyloid fibril.However,the inhibitory mechanism was ambiguous until now.In this article,the effect of diketone and phenol on the formation of amyloid fibril was detaily studied.This thesis was divided into four chapters.Chapter 1: Introduction.The structural of protein,the formation process of amyloid fibril,the types of inhibitors and the interaction between drug and protein were briefly introduced.Chapter 2: The effect of diketone in curcumin on the formation of hen egg white lysozyme amyloid fibril.A new monoketone curcumin analogues(compound 1)was synthesized using vanillin and acetone as reactant.The result of amyloid fibrillation experiment showed that both curcumin and compound 1 could inhibit the formation of amyloid fibril of hen egg white lysozyme.However,the inhibition capacity of curcumin was greater than that of compound 1at the same concentration.The difference of inhibition capacity was mainly caused by the difference of molecule structure,which indicated that the diketone structure played a key role in the process of inhibiting amyloid fibrillation.The interaction between curcumin/compound1 and lysozyme was explored by fluorescence spectroscopy.The fluorescence quenching mechanism of curcumin/compound 1 on lysozyme was dynamic and static complex quenching,and the binding number was one.The interaction between curcumin and lysozyme was hydrogen bond and van der Waals force,and the interaction between compound 1 and lysozyme was hydrophobic force.Chapter 3: The effect of phenolic hydroxyl group in curcumin on the formation of hen egg white lysozyme amyloid fibril.A curcumin analogues(compound 2)without phenolic hydroxyl group was synthesized by 3,4-dimethoxybenzaldehyde and acetone.The result of amyloid fibrillation experiment showed that compound 2 could also inhibit the formation of amyloid fibril in a dose-dependent manner.However,its inhibitory effect was weaker than ofcurcumin/compound 1 at the same concentration,which means that phenolic hydroxyl group plays a key role in the process of inhibiting amyloid fibrillation.The interaction mechanism between compound 2 and lysozyme was explored by fluorescence spectroscopy.The quenching mechanism of compound 2 on lysozyme fluorecence was dynamic and static composite quenching,and the binding number was one.The interaction between compound 2 and lysozyme was hydrogen bond and van der Waals force.Chapter 4: The effect of curcumin/compound 1/compound2 on the stability of amyloid fibril.The ThT fluorescence intensity decreased immediately after adding curcumin/compound1/compound 2 into amyloid firil and there was no significant change with time,which indicated that they could not disaggregate amyloid fibril.The decreasing of ThT fluorescence intensity may be caused by the weakening of binding force between lysozyme amyloid fibril and ThT.The average particle size measured by DLS after adding curcmin/compound 1/compound 2 was not changed.The protein conformation measured by circular dichroism after adding curcumin/compound 1/compound2 was also not changed.All the resuls indicated that curcumin/compound 1/compound 2 could not disaggreate the mature amyloid fibril at the experimental condition.