The hydrodynamic characteristics of heparin fractions in a 0.2 M NaCl solution have been determined. Experimental values varied over the following ranges: the sedimentation coefficient (at 20.0 degrees C), 1.3
Three well-known representatives of the cyclodextrin family were completely characterized by molecular hydrodynamics methods in three different solvents. For the first time the possibility of an estimation of velocity sedimentation coefficients s between 0.15 and 0.5 S by the numerical solution of the Lamm equation is shown. Comparison of the experimental hydrodynamic characteristics of the cyclodextrins with theoretical calculations for toroidal molecules allows an estimation of the thickness of the solvent layers on the surface of cyclodextrin molecules.
The translational diffusion coefficient Do, the sedimentation coefficient So, and the intrinsic viscosity [q] of samples and fractions of poly(1-vinyl-2-pyrrolidone) were measured in a 0.1 M solution of sodium acetate in the molecular weight range 2 Q Ma Q 2200. For M > 4. lo4 the following relationships were obtained: [q] = 8,86-1 0 -5 * d " , Do = 2,42 -M-oss8, and So = 2,14 * lo-" * d-". For M < 4 * lo4 the corresponding relations are [q] = 5,O. 10-4*&s56, Do = 129. 10-4.M-0*s2 and S -1,15 -i0-l' The hydrodynamic invariant is A, = (3,2 f 025). lO-"J -K-' * m~!-"~ and the sedimentation parameter 8, = (i,3 f 0,17) * lo7 m~l -~" . The temperature coefficient of the intrinsic viscosity is negative, viz. Aln[q]/AT = -6.3 * K-'. The evaluation of the length of the Kuhn segment A and the hydrodynamic diameter d of chains representing the molecules of PVP in solution was conducted on the basis of the theory for the hydrodynamic properties of a wormlike necklace taking into account the excluded volume effects. The values of A agree with those obtained from the Burchard-Stockmayer-Fixman and Cowie-Bywater equations, A = (2,l f 0,3) nm and d = (0,5 f 0,13) nm.
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