Photon correlation spectroscopy has been used for studying the processes of asphaltene aggregation and flocculation in hydrocarbon solutions. The kinetics of asphaltene flocculation and the stability of asphaltene aggregates are strongly affected by the nature of the solvent. A simple theoretical model has been developed in order to interpret the experimental results.

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Motivated by controversies in the literature on the microscopic and mesoscopic structure of some aqueous solutions, we have performed static and dynamic light-scattering experiments in aqueous solutions of 3-methylpyridine (3MP) and tertiary butyl alcohol (TBA). In addition to the microscopic concentration fluctuations we have found the presence of reproducible mesoscopic inhomogeneities, which become especially pronounced below room temperature. We find that the observed inhomogeneities are near-spherical Brownian aggregates of a size from a hundred to a few hundred nm. We speculate that these aggregates are long-lived metastable clathrate-like precursors triggered by minute traces of impurities in these solutions.

Thermal denaturation and aggregation of beta(L)-crystallin from bovine lens have been studied using differential scanning calorimetry (DSC) and dynamic light scattering (DLS). According to the DLS data, the distribution of the beta(L)-crystallin aggregates by their hydrodynamic radius (R(h)) remains monomodal to the point of precipitating aggregates (sodium phosphate, pH 6.8; 100 mM NaCl; 60 degrees C). The size of the start aggregates (R(h,0)) and duration of the latent stage (t(0)) leading to the formation of the start aggregates have been determined from the light scattering intensity versus the hydrodynamic radius plots and the dependences of R(h) on time. The R(h,0) value remains constant at variation of the beta(L)-crystallin concentration, whereas the t(0) value increases with diminishing beta(L)-crystallin concentration. The suppression of beta(L)-crystallin aggregation by alpha-crystallin is connected with the decrease in the R(h,0) value and increase in the t(0) value. In the presence of alpha-crystallin the aggregate population is split into two components. The first component is represented by stable aggregates whose size remains constant in time. The aggregates of the other kind grow until they reach the size characteristic of aggregates prone to precipitation. The DSC data show that alpha-crystallin has no appreciable influence on thermal denaturation of beta(L)-crystallin.