Light scattering bile salt micelles

M Janich, J Graener, J Lange, R Neubert. Extended light-scattering investigations on dihydroxy bile salt micelles in low-salt aqueous solutions. J Phys Chem B 102 5957-5962, 1998. 

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). 

CrystaUisation of biliary cholesterol monohydrate is a multiphase process not yet fuUy understood [60]. Bile is normally supersaturated with respect to cholesterol [61] which is solubilised by bile salts (the soluble end product of cholesterol metabolism, such as sodium glycocholate and sodium taurocholate [9]) within micelles, whose solubilising capacity is considerably increased by the incorporation of phosphohpid molecules such as lecithin [62]. Biliary vesicles contain virtually no bile salts but may accumulate cholesterol up to a cholesterol/phosphohpid ratio of 2 1 (by phospholipid transfer to micelles) [63]. These thermodynamically unstable (but kinetically stabilised) vesicles then aggregate and nucleate cholesterol crystals [64,65]. The mechanism of this crucial miceUe-to-vesicle transition has been the subject of various physicochemical studies, including, e.g. calorimetric, turbidimetric, dynamic light and neutron scattering methods [66-69]. 

In a light-scattering study of dihydroxy bile salts, Kratohvil and Del-licolli (120) estimated the fractional micellar charge, pjn, of NaTDC in 0.15 M NaCl from Debye plots. Here p represents the number of fundamental charges per micelle and n the number of monomer ions per micelle. Since m is the number of counterions bound to a micelle, then pin is equal to 1 — in/n. The fractional micellar charge pin was 0.29 in 0.15 M NaCl. From the present data pin for zero excess counterion (i.e., in water) concentration is 0.77. 

Vesicle formation in aqueous mixtures of lecithin and bile salt that takes place upon dilution with water has been studied intensively by means of time-resolved scattering methods (static and d5mamic light scattering, SANS), and it has been concluded that this transition takes place via elongated micelles and disklike micelles as intermediate structvu es. ... 

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