Hydrodynamic volume equivalence ratio

The ratio of the molecular weights of two homopolymers eluted at the same solvent volume is defined as the hydrodynamic volume equivalence ratio (equivalence ratio for short). 

In this review we have briefly discussed the theoretical and experimental aspects of both Newtonian and non-Newtonian viscosities of polymer solutions. To protein chemists one of the interesting developments is no doubt the re-examination of the (Newtonian) viscosity treatments of protein solutions. There are many assumptions involved in the effective use of intrinsic viscosity measurements for evaluating the asymmetry of the protein molecules, however attractive the conventional treatment may have appeared for the past two decades. Carefully interpreted, the intrinsic viscosity (at zero gradient) can still provide a reasonable estimate of the axial ratios of the protein molecules. The concept of equivalent hydrodynamic volume, sound in principle, has put the viscometry of protein solutions in a proper perspective, although the quantitative aspects of this new approach still... 

Secondly, the use of Simha s viscosity increments for protein molecules implies automatically that the shape of the molecule can be approximated by an equivalent hydrodynamic ellipsoid having the same volume as that of the protein. The uncertainty involved in this second assumption is not just a problem of hydration. Even if the degree of hydration were precisely known and even if F and Fsp were identical the axial ratio as determined from the intrinsic viscosity may still not represent the real molecule. 

The compaction behavior is also indicated by the effective volume fraction of an aggregate (pejf (Fig- 5), calculated from the aspect ratio of an equivalent ellipsoid. The shear-rale dependence on effective volume fraction was small so that a maximum compaction was not observed even at high shear rates. Again, higher shear rates required for higher compaction may violate model assumptions, such as Stokes regime for the hydrodynamics and the conditions for the overdamped motion. 

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