Dynamics of the spontaneous formation of a planar phospholipid bilayer: A new approach by simultaneous electrical and optical measurements

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Title
Dynamics of the spontaneous formation of a planar phospholipid bilayer: A new approach by simultaneous electrical and optical measurements
Author
氏名 FUJIWARA Hisashi
ヨミ フジワラ ヒサシ
別名 藤原 久志
氏名 FUJIHARA Masayuki
ヨミ フジハラ マサユキ
別名 藤原 昌幸
氏名 ISHIWATA Takashi
ヨミ イシワタ タカシ
別名 石渡 孝
Subject
lipid bilayers
biomembranes
capacitance
capacitors
Abstract

An artificial lipid bilayer in planar form, well known as bilayer lipid membrane (BLM), spontaneously forms from a lipid droplet (L-α-phosphatidylcholine in n-decane and chloroform in this work) in an aperture of a thin partition in aqueous solution. The thinning dynamics of the lipid droplet or membrane has been studied by simultaneous capacitance and image recording, because the lipid membrane sandwiched by aqueous solutions can be considered as a parallel-plate capacitor. The simultaneous measurements have revealed the two-step thinning of the lipid membrane from its specific capacitance value: first, the initial droplet thins to yield a membrane of about 100 nm thickness (0.02 μF/cm2), and second, within this thin lipid membrane, a lipid bilayer of 4 nm thickness (0.42 μF/cm2) suddenly emerges and grows, keeping a bilayer structure. In addition, the simultaneous measurements have a time stamp, and thus can determine the trigger moment of the bilayer formation. The revealed dynamics provides the first quantitative support for a “zipper” mechanism [H. T. Tien and E. A. Dawidowicz, J. Colloid Interface Sci. 22, 438 (1966)]; in the mechanism, the first thinning results in a sandwich consisting of the organic solvent between two adsorbed lipid monolayers whose distance is the order of 100 nm, and then a chance contact of both monolayers initiates the formation and growth of a lipid bilayer in a zipper-like manner. However, because of the existence of the two solvent–water interfaces containing surface-active molecules, phospholipids, this work claims that the zipper mechanism should be modified in view of the Marangoni effect. The simultaneous measurements have also revealed the adjacency effect, namely, that only the prebilayer region just adjacent to the bilayer changes into a bilayer. The present formation and growth of a lipid bilayer, including the adjacency effect, can be explained by the classic nucleation theory of two-dimensional crystallization. BLM systems with the simultaneous measurements can be considered as a useful environment for the study of soft-matter chemical physics.

Description Peer Reviewed
Journal Title
The Journal of Chemical Physics
Volume
119
Issue
13
Spage
6768
Epage
6775
Published Date
2003-10-01
Publisher
American Institute of Physics
ISSN
0021-9606
NCID
AA00694991
Language
eng
NIIType
Journal Article
Text Version
出版社版
Rights
Copyright 2003 American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.The following article appeared in J. Chem. Phys. 119, 6768 (2003) and may be found at http://dx.doi.org/10.1063/1.1605372.
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