|
The Saffman–Delbrück model describes a lipid membrane as a thin layer of viscous fluid, surrounded by a less viscous bulk liquid. This picture was originally proposed to determine the diffusion coefficient of membrane proteins, but has also been used to describe the dynamics of fluid domains within lipid membranes. The Saffman–Delbrück formula is often applied to determine the size of an object embedded in a membrane from its observed diffusion coefficient, and is characterized by the weak logarithmic dependence of diffusion constant on object radius. ==Origin== In a three-dimensional highly viscous liquid, a spherical object of radius ''a'' has diffusion coefficient : by the well-known Stokes–Einstein relation. By contrast, the diffusion coefficient of a circular object embedded in a two-dimensional fluid diverges; this is Stokes' paradox. In a real lipid membrane, the diffusion coefficient may be limited by: # the size of the membrane # the inertia of the membrane (finite Reynolds number) # the effect of the liquid surrounding the membrane Philip Saffman and Max Delbrück calculated the diffusion coefficient for these three cases, and showed that Case 3 was the relevant effect.〔(P. G. Saffman and M. Delbrück, ''Brownian motion in biological membranes'', Proc. Nat. Acad. Sci., USA, vol. 72 p. 3111–3113 1975 )〕 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「Saffman–Delbrück model」の詳細全文を読む スポンサード リンク
|