Correlation between biological activity of 30 S subunits of Escherichia coli ribosomes and their conformation changes revealed by optical mixing spectroscopy.

Spectral analysis of light scattered from solutions of 30 S subunits was performed by the method of regularization of the inverse spectral problem. The subunits observed under ionic conditions which preserved their biological activity (200 mM NH4Cl at 1 mM MgCl2) revealed a monodisperse pattern of scattering with diffusion constant D = (1.83 +/- 0.10) X 10(-7) cm2/s. The polydispersity and compaction of 30 S subunits were observed under inactivation ionic conditions (30 mM NH4Cl at 1 mM MgCl2). The number of compacted particles correlates with the irreversible loss of biological activity, the ability of 30 S subunits to bind specific tRNA.