Author/Editor		Waugh, RE; Song, J; Svetina, S; Žekš, B
Title		Local and nonlocal curvature elasticity in bilayer membranes by tether formation from lecithin vesicles
Type		članek
Source		Biophys J
Vol. and No.		Letnik 61, št. 4
Publication year		1992
Volume		str. 974-82
Language		eng
Abstract		Bilayer membranes exhibit an elastic resistance to changes in curvature. This resistance depends both on the intrinsic stiffness of the constituent monolayers and on the curvature-induced expansion or compression of the monolayers relative to each other The monolayers are constrained by hydrophobic forces to remain in contact, but they are capable of independent lateral redistribution to minimize the relative expansion or compression of each leaflet. Therefore, the magnitude of the expansion and compression of the monolayers relative to each other depends on the integral of the curvature over the entire membrane capsule The coefficient characterizing the membrane stiffness resulting from relative expansion is the nonlocal bending modulus kr. Both the intrinsic (local) bending modulus (kc) and the nonlocal bending modulus (kr) can be measured by the formation of thin cy!indrical membrane strands (tethers) from giant phospholipid vesicles. Previously, we reported measurements ot kc based or, measurements of tether radius as a tunction of force (Song and Waugh, 1991, J. Biomech. Engr. 112:233). Further anaiysis has revealed that the contribution from the nonlocal bending stiffness can be detected by measuring the change in the aspiration pressure required to establish equilibrium with increasing tether length Using this approach we obtain a mean value for the nonlocal bending modulus k, of 4.1 x 10-19 J. The range of values is broad (1.1-10 1 x 10-19 J) and could reflect contributions other than simple mechanical equilibrium. Inclusion ot the nonlocal bending stiffness in the calculation of kc results in a value for thaf modulus of 1.20 +- 0.17 x 10-19 J; in close agreement with values obtained by other methods.
Descriptors		LIPID BILAYERS BIOPHYSICS ELASTICITY MEMBRANE FLUIDITY PHOSPHATIDYLCHOLINES THERMODYNAMICS