L. Sun et al., DIFFUSION OF MIXED MICELLES OF BILE SALT-LECITHIN IN AMYLOPECTIN GELS- A FOURIER-TRANSFORM INFRARED MICROSPECTROSCOPY APPROACH, Biophysical chemistry, 61(2-3), 1996, pp. 143-150
Using Fourier transform infrared (FTIR) microspectroscopy the average
translational diffusion coefficients of bile salt-lecithin mixed micel
les diffusing in amylopectin gels of varying concentration were measur
ed, on the assumption that the diffusion coefficient was constant duri
ng diffusion. This assumption was examined based on quasielastic light
scattering (QLS) measurements of the change in the mixed micellar siz
e on dilution. The size increased significantly on dilution with a buf
fer without the bile salt, whereas the size was almost constant on dil
ution with a solution of the bile salt in the same buffer. Because bil
e salt molecules in intermicellar solution (being much smaller) diffus
e much faster than the mixed micelles, the mixed micelles in the diffu
sing front can be treated as if diluted with the bile salt solution. T
herefore their size will be constant during diffusion, validating the
assumption of a constant diffusion coefficient. Based on this it is po
ssible to show that the micelles diffuse with a diffusion coefficient
of similar to 10(-11) m(2) s(-1), independent (within experimental err
or) of the amylopectin gel concentration over the range 5%-10% w/w.