Assaying the Gel Cell Size through Fluorescence Anisotropy Measurements.

Assessment of the gel structure and determination of the limitations of the rotational diffusion in the structural elements (cells) of the gel was achieved through studying changes in the fluorescence anisotropy in a series of luminophores as their molecular sizes and volumes increase. It has been found that small-sized fluorescent probes do not experience noticeable imposition from the gel environment, and the fluorescence anisotropy is quite adequately described by the Levshin-Perrin equation. However, starting from molecular overall size >2.1 nm, rotational diffusion of luminophores becomes stopped, which can be interpreted as the molecules getting stuck in the gel cells. The characteristic size of the dimethyl sulfoxide (DMSO)-MgSO₄ gel cell amounts to 2.3 nm. A modification of the Levshin-Perrin equation is obtained taking into account the statistical parameters of the gel cell.