Document Detail

The molecular-scale arrangement and mechanical strength of phospholipid/cholesterol mixed bilayers investigated by frequency modulation atomic force microscopy in liquid.
MedLine Citation:
PMID:  19509439     Owner:  NLM     Status:  MEDLINE    
Cholesterols play key roles in controlling molecular fluidity in a biological membrane, yet little is known about their molecular-scale arrangements in real space. In this study, we have directly imaged lipid-cholesterol complexes in a model biological membrane consisting of dipalmitoylphosphatidylcholine (DPPC) and cholesterols by frequency modulation atomic force microscopy (FM-AFM) in phosphate buffer solution. FM-AFM images of a DPPC/cholesterol bilayer in the liquid-ordered phase showed higher energy dissipation values compared to those measured on a nanoscale DPPC domain in the gel phase, reflecting the increased molecular fluidity due to the insertion of cholesterols. Molecular-resolution FM-AFM images of a DPPC/cholesterol bilayer revealed the existence of a rhombic molecular arrangement (lattice constants: a = 0.46 nm, b = 0.71 nm) consisting of alternating rows of DPPC and cholesterols as well as the increased defect density and reduced molecular ordering. The mechanical strength of a DPPC/cholesterol bilayer was quantitatively evaluated by measuring a loading force required to penetrate the membrane with an AFM tip. The result revealed the significant decrease of mechanical strength upon insertion of cholesterols. Based on the molecular-scale arrangement found in this study, we propose a model to explain the reduced mechanical strength in relation to the formation of lipid-ion networks.
Hitoshi Asakawa; Takeshi Fukuma
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't     Date:  2009-06-10
Journal Detail:
Title:  Nanotechnology     Volume:  20     ISSN:  1361-6528     ISO Abbreviation:  Nanotechnology     Publication Date:  2009 Jul 
Date Detail:
Created Date:  2009-06-17     Completed Date:  2009-08-13     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  101241272     Medline TA:  Nanotechnology     Country:  England    
Other Details:
Languages:  eng     Pagination:  264008     Citation Subset:  IM    
Frontier Science Organization, Kanazawa University, Kakuma-machi, 920-1192 Kanazawa, Japan.
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MeSH Terms
1,2-Dipalmitoylphosphatidylcholine / chemistry*
Cholesterol / chemistry*
Compressive Strength
Lipid Bilayers / chemistry*
Microscopy, Atomic Force / methods*
Models, Biological
Surface Properties
Reg. No./Substance:
0/Lipid Bilayers; 2644-64-6/1,2-Dipalmitoylphosphatidylcholine; 57-88-5/Cholesterol

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