Transport properties of fractal aggregates calculated by permeability

The Debye–Brinkman concept of treating polymer coils as uniformly permeable spheres is utilized for embryonic aggregates composed of less than a dozen or so primary particles. These can be the direct models for bioparticles or may be equivalent to multi-particle aggregates and macromolecules. The method is based on the calculation of permeability of the system contained inside the sphere circumscribed on the aggregate, which makes it possible to estimate the transport properties such as the translational and rotational diffusion coefficients and the intrinsic viscosity of bead models. With this method it is possible to describe properly the translational diffusion coefficient for the embryonic aggregates analyzed as compared to that deduced from the experimental values of sedimentation velocity. The results obtained for rotational diffusion coefficient and intrinsic viscosity of oligomers are close to that calculated by the Kirkwood–Riseman method using modified Oseen tensor with volume correction.