翻訳と辞書
Words near each other
・ Memecylon rostratum
・ Memecylon rotundatum
・ Memecylon royenii
・ Memecylon sessilicarpum
・ Memecylon sisparense
・ Membrane analogy
・ Membrane androgen receptor
・ Membrane biology
・ Membrane biophysics
・ Membrane bioreactor
・ Membrane bound polyribosome
・ Membrane channel
・ Membrane computing
・ Membrane contact site
・ Membrane corticosteroid receptor
Membrane curvature
・ Membrane dipeptidase
・ Membrane distillation
・ Membrane electrode assembly
・ Membrane emulsification
・ Membrane estrogen receptor
・ Membrane fluidity
・ Membrane fouling
・ Membrane fusion protein
・ Membrane gas separation
・ Membrane glucocorticoid receptor
・ Membrane glycoproteins
・ Membrane keyboard
・ Membrane lipids
・ Membrane method


Dictionary Lists
翻訳と辞書 辞書検索 [ 開発暫定版 ]
スポンサード リンク

Membrane curvature : ウィキペディア英語版
Membrane curvature
Membrane curvature is the geometrical measure or characterization of the curvature of membranes.
The membranes can be naturally occurring or man-made (synthetic). An example of naturally occurring membrane is the lipid bilayer of cells, also known as cellular membranes.〔(【引用サイトリンク】url=http://www.samuelfurse.com/2011/12/curvy-biology/ )〕 Synthetic membranes can be obtained by preparing aqueous solutions of certain lipids. The lipids will then "aggregate" and form various phases and structures. According to the conditions (concentration, temperature, ionic strength of solution, etc.) and the chemical structures of the lipid, different phases will be observed. For instance, the lipid POPC (palmitoyl oleyl phosphatidyl choline) tends to form lamellar vesicles in solution, whereas smaller lipids (lipids with shorter acyl chains, up to 8 carbons in length), such as detergents, will form micelles if the CMC (critical micelle concentration) is reached.
==Basic Geometry of Curvature==
A biological membrane is commonly described as a two-dimensional surface, which spans a three-dimensional space. So, to describe membrane shape, it is not sufficient to determine the membrane curling that is seen in a single cross-section of the object, because in general there are two curvatures that characterize the shape each point in space. Mathematically, these two curvatures are called the principal curvatures, c1 and c2, and their meaning can be understood by the following thought experiment. If you cross-section the membrane surface at a point under consideration using two planes that are perpendicular to the surface and oriented in two special directions called the principal directions, the principal curvatures are the curvatures of the two lines of intercepts between the planes and the surface which have almost circular shapes in close proximity to the point under consideration. The radii of these two circular fragments, R1 and R2, are called the principal radii of curvature, and their inverse values are referred to as the two principal curvatures.〔Spivak, M. ''A Comprehensive Introduction to Differential Geometry'' (Brandeis University, Waltham,1970)〕
c1 = 1/R1
c2 = 1/R2
The principal curvatures C1 and C2 can vary arbitrarily and thereby give origin to different geometrical shapes, such as cylinder, plane, sphere and saddle. Analysis of the principal curvature is important, since a number of biological membranes possess shapes that are analogous to these common geometry staples. For instance, prokaryotic cells such as cocci, rods, and spirochette display the shape of a sphere, and the latter two the shape of a cylinder. Erythrocytes, commonly referred to as red blood cells, have the shape of a saddle, although these cells are capable of some shape deformation. The table below lists common geometric shapes and a qualitative analysis of their two principal curvatures.
Even though often membrane curvature is thought to be a completely spontaneous process, thermodynamically speaking there must be factors actuating as the driving force for curvature to exist. Currently, there are some postulated mechanisms for accepted theories on curvature; nonetheless, undoubtedly two of the major driving forces are lipid composition and proteins embedded and/or bound to membranes.

抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)
ウィキペディアで「Membrane curvature」の詳細全文を読む



スポンサード リンク
翻訳と辞書 : 翻訳のためのインターネットリソース

Copyright(C) kotoba.ne.jp 1997-2016. All Rights Reserved.