Author/Editor     Heinrich, V; Brumen, M; Heinrich, R; Svetina, S; Žekš, B
Title     Nearly spherical vesicle shapes calculated by use of spherical harmonics: axisymmetric and nonaxisymmetric shapes and their stability
Type     članek
Source     J Phys II
Vol. and No.     Letnik 2
Publication year     1992
Volume     str. 1081-108
Language     eng
Abstract     A theoretical approach to determine nearly spherical shapes of phospholipid vesicles is developed. The method is general in the sense that it does not depend on any symmetry restrictions. Equilibrium shapes are assumed to correspond to the rninimum of the membrane bending elastic energy at constant values of the membrane area, the vesicle volume and the difference of areas of the two leaflets of the phospholipid bilayer. The bending energy and the constraints are expanded up to fourth order terms in the deviation from a sphere, and in the subsequent calculations all terms up to the third order are included. The deviation is expressed as a series of spherical harmonics. It is shown that the stability of the solutions can be tested by inspecting the eigenvalues of the matrix of second derivatives of the bending energy with respect to independent amplitudes of spherical harmonics expansion. The method is applied to the calculation of axisymetric and nonaxisymetric shapes, and the influences of different approximations are discussed. It is shown that at variations of the leaflet area difference stable oblate and stable prolate shapes are transformed into each other in a continuous manner.
Descriptors     PHOSPHOLIPIDS
MEMBRANES
ELASTICITY
ENZYME STABILITY
MODELS, BIOLOGICAL