Lipid molecular shape analysis

An extension of the Tanford s (1980) treatment of the shapes of micelles, based on the molecular-shape analysis and the concept of the shape parameter (ratio between the nonpolar and polar cross-section areas), was introduced by Israelachvili (1991) for a qualitative understanding of the topology of lipid aggregates with different lipid compositions. However, the liposome models are approximate, and a rigorous thermodynamic analysis fails because liposomes are not at the thermodynamic equilibrium. The rigorous analysis would yield a very narrow size distribution, which is never observed in practice, as well as the spontaneous formation, while a high-energy process is typically needed to produce liposomes. 

The spin label technique appeared to be very fruitful recently in research ofmembrane-carotenoids interaction. The shape of a spin probe ESR spectrum is sensitive to the rate of its molecular motion being directly dependent on the membrane fluidity determined by the rate of lipid molecular motion. Thus, the analysis of ESR spectra of spin labels doped into pigmented membranes would provide information on the carotenoid effect on particular regions of lipid bilayers, dependent on the type of probes applied, penetrating different membrane portions. Tfiis technique was applied to study an effect of xanthophylls and j8-carotene on fluidity of lipid membranes formed with several synthetic and nonsaturated phosphatidylcholines (Subczynski et al, 1991,1992,1993 StrzalkaandGruszecki, 1991, Yin and Subczynski, 1996, Wisniewska and... 

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