Si. Barry et al., OBTAINING THE CONCENTRATION-DEPENDENT DIFFUSION-COEFFICIENT FROM ULTRAFILTRATION EXPERIMENTS - APPLICATION TO HYALURONATE, Biopolymers, 39(1), 1996, pp. 1-11
A method for determining the concentration-dependent mutual diffusion
coefficient D(C) of a macromolecule-solvent combination over a wide ma
cromolecular concentration range is presented. All necessary data are
gathered from a single experiment, in which polymer concentration prof
iles are measured during one-dimensional dead-end ultrafiltration. Bas
ed on these profiles, the convection-diffusion equation is used to ded
uce the dependence of D on C. To demonstrate the utility of the approa
ch, studies using sodium hyaluronate dissolved in either 10 mM NaCl or
a phosphate buffer were carried out. For hyaluronate (HA) in 10 mM Na
Cl, the mutual diffusion coefficient varies approximately linearly wit
h concentration according to D(C) = 4.1 X 10(-6) C-0.96 cm(2)/s in the
range 0 less than or equal to C less than or equal to 0.6 mass %, for
C expressed in mass %. However, transition points (slope changes) in
the D(C) curve are present at C approximate to 0.7 mass % and C approx
imate to 1.4 mass %. For HA in the phosphate buffer, the mutual diffus
ion coefficient is well described by D(C) = 1.9 X 10(-6) C-0.825, for
0 less than or equal to C less than or equal to 1.8 mass %. These valu
es agree well with previously published data. The technique is robust,
and permits reasonably high polymer concentrations to be easily studi
ed. (C) 1996 John Wiley & Sons, Inc.