Effects Of Nonidet P40 And Methyl-β-Cyclodextrin On Lipid Comosition And Protein Structure Of Low Density Lipoprotein

Low-density lipoprotein(LDL)is the main carrier of cholesterol transporting from the liver to peripheral tissues and cells,and is the primary risk factor for atherosclerotic diseases.At present,most of the research on LDL structure use X-ray diffraction,smallangle scattering,and transmission electron microscopy to characterize the structure of the major apolipoprotein(i.e.apoB-100)in LDL.However,these research methods generally have the defects of neglecting the physiological environment or composition of LDL.Regarding the study of LDL structure,one of the main challenges in the future is to elucidate the structural characteristics of apolipoproteins and lipids in LDL and their interactions.Depletion of the lipid component of LDL may help to address the abovementioned challenges.Ethyl phenyl polyethylene glycol(NP-40)and methyl-β-cyclodextrin(MβCD)are two mild lipid-depleting reagents commonly used in biological research to remove lipids from cells and other biological structures in different manners.However,it is not clear whether and how they remove lipids from LDL.In this experiment,LDL was treated with different concentrations of NP-40 and MβCD.The effects of NP-40 and MβCD on the lipid composition,morphology and physicochemical properties of LDL were detected by agarose gel electrophoresis,X-ray diffraction,dynamic light scattering,and atomic force microscope(AFM).Appropriate concentrations of NP-40 and MβCD caused the separation of the lipid component from the protein component in LDL,however,at a MβCD concentration of around 40-80 mM the charge property of the apolipoprotein is like that in native LDL.The treatments by 0.64% NP-40 and 100 mM MβCD induced the exposure of cyclic and globular structures of the apolipoprotein.However,MβCD had a higher cholesterol-depleting rate(92%)and a lower triglyceride-depleting rate(58%).The results show that both NP-40 and MβCD were able to eliminate the lipid component of LDL and that the protein structure of LDL was related to the lipid loss of LDL.In addition,this study shows that the combination of AFM and NP-40 treatment can detect the structure of a lipoprotein under physiological conditions and that the combination of agarose gel electrophoresis and MβCD treatment can separate apolipoproteins from LDL,which will provide new methods for future research.