Light scattering micelle size/shape

W. Brown, R. Johnsen, P. Stilbs, B. Lindman. Size and shape of nonionic amphiphile (Ci2Eg) micelles in dilute aqueous solutions as derived from quasielastic and intensity of light scattering, sedimentation and pulsed-field-gradient nuclear magnetic resonance self-diffusion data. J Phys Chem 87 4548-4553, 1983. 

With the development of new instrumental techniques, much new information on the size and shape of aqueous micelles has become available. The inceptive description of the micelle as a spherical agglomerate of 20-100 monomers, 12-30 in radius (JJ, with a liquid hydrocarbon interior, has been considerably refined in recent years by spectroscopic (e.g. nmr, fluorescence decay, quasielastic light-scattering), hydrodynamic (e.g. viscometry, centrifugation) and classical light-scattering and osmometry studies. From these investigations have developed plausible descriptions of the thermodynamic and kinetic states of micellar micro-environments, as well as an appreciation of the plurality of micelle size and shape. 

Schematic models for the expanded structure of bile acid-phosphatidylcholine mixed micelles are shown in Fig. 2B. The original model was proposed by Small in 1967 (S36). In this model the mixed micelle consisted of a phospholipid bilayer disk surrounded on its perimeter by bile acid molecules, which were oriented with their hydrophilic surhices in contact with aqueous solvent and their hydrophobic sur ces interacting with the hydrocarbon chains of the phosphohpid molecules. This model has recently been revised, based on further studies of mixed micelles using quasi-elastic light scattering spectroscopy (M20). In a new model for the molecular structure of bile acid-phospholipid mixed micelles. Mazer et al. (M20) propose a mixed disk, in which bile acids are found not only on the perimeter of phospholipid bilayers, but also incorporated within their interior in high concentrations (Fig. 2B). The size of these mixed micelles was estimated to be as high as 200 to 400 A in radius in some solutions, and disk-shaped particles in this size range were observed by transmission electron microscopy (M20). Micellar aggregates similar in size and structure to those found in model bile solutions have been demonstrated in dog bile (M22).

M21. Mazer, N. A., Carey, M. C., Kwasnick, R. F., and Benedek, G. B., Quasielastic light scattering studies of aqueous biliary lipid systems. Size, shape, and thermodynamics of bile salt micelles. Biochemistry 18, 3064-3075 (1979). 

Low angle light scattering experiments performed in these systems (162) prove that the photorheological effects described above are connected with changes of size and shape of the micelles in the isotropic concentration region in the presence of nonpolar rheologically active anthracenes and of the stilbene... 

Structural characterization of block copolymer aggregates by dynamic and static light scattering (DLS and SLS) in combination with small angle neutron scattering (SANS) at variable ionic strength and pH in the solution enables one to discriminate between frozen and dynamic (equilibrium) micelles. In particular, SANS provides direct information about the core size and shape because of relatively low scattering density of the corona. 

Various types of experiments (notably dynamic light scattering and neutron scattering) have revealed size, shape, and stability of C3Ms. The number of polymers in the micelle amounts to several tens. C3Ms are usually spherical, having radii of... 

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