title: In situ AFM imaging of apolipoprotein A-I directly derived from plasma HDL.
abstract: The major apolipoproteins of plasma lipoproteins play vital roles in the structural integrity and physiological functions of lipoproteins. More than ten structural models of apolipoprotein A-I (apoA-I), the major apolipoprotein of high-density lipoprotein (HDL), have been developed successively. In these models, apoA-I was supposed to organize in a ring-shaped form. To date, however, there is no direct evidence under physiological condition.
  
  
  
  Here, atomic force microscopy (AFM) was used to in situ visualize the organization of apoA-I, which was exposed via depletion of the lipid component of plasma HDL pre-immobilized on functionalized mica sheets.
  
  
  
  For the first time, the ring-shaped coarse structure and three detailed structures (crescent-shaped, gapped "O"-shaped, and parentheses-shaped structures, respectively) of apoA-I in plasma HDL, which have the ability of binding scavenger receptors, were directly observed and quantitatively measured by AFM. The three detailed structures probably represent the different extents to which the lipid component of HDL was depleted. Data on lipid depletion of HDL may provide clues to understand lipid insertion of HDL.
  
  
  
  These data provide important information for the understanding of the structure/maturation of plasma HDL. Moreover, they suggest a powerful method for directly visualizing the major apolipoproteins of plasma lipoproteins or the protein component of lipoprotein-like lipid-protein complexes.
authors.affiliation: Nanoscale Science and Technology Laboratory, Institute for Advanced Study, Nanchang University, Nanchang, Jiangxi 330031, PR China; College of Life Sciences, Nanchang University, Nanchang, Jiangxi 330031, PR China.
authors.forename: Chaoye
authors.initials: C
authors.lastname: Gan
authors.affiliation: Nanoscale Science and Technology Laboratory, Institute for Advanced Study, Nanchang University, Nanchang, Jiangxi 330031, PR China.
authors.forename: Zhexuan
authors.initials: Z
authors.lastname: Wang
authors.affiliation: Nanoscale Science and Technology Laboratory, Institute for Advanced Study, Nanchang University, Nanchang, Jiangxi 330031, PR China; College of Life Sciences, Nanchang University, Nanchang, Jiangxi 330031, PR China. Electronic address: dr_yongchen@hotmail.com.
authors.forename: Yong
authors.initials: Y
authors.lastname: Chen
mesh_terms: D000538:Aluminum Silicates / Q000737:chemistry; D016632:Apolipoprotein A-I / Q000097:blood* / Q000737:chemistry*; D003902:Detergents / Q000737:chemistry; D006801:Humans; D008075:Lipoproteins, HDL / Q000097:blood* / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D017830:Octoxynol; D011092:Polyethylene Glycols / Q000737:chemistry; D011485:Protein Binding; D011487:Protein Conformation; D013329:Structure-Activity Relationship
chemical_list: C505693:APOA1 protein, human; D000538:Aluminum Silicates; D016632:Apolipoprotein A-I; D003902:Detergents; D008075:Lipoproteins, HDL; D011092:Polyethylene Glycols; D017830:Octoxynol; C010615:Nonidet P-40; C011934:mica
keywords: Apolipoproteins; Atomic force microscopy (AFM); High-density lipoprotein (HDL); Nonidet P-40 (NP-40); Plasma lipoproteins; Scavenger receptors; apoA-I