[Polarization fluorescence of chloroplasts oriented in polyacrylamide gel. Experiment and theoretical analysis]

Maize mesophyll chloroplasts were oriented in polyacrylamide gel upon squeezing of gel samples. Fluorescence polarization was measured as a function of the gel deformation parameter. Linearly polarized fluorescence spectra were recorded at -140 degrees. The results show that chloroplasts were oriented in polyacrylamide gel as effectively as in magnetic field. Theoretical models are analyzed for orientation of disc-shaped and rod-shaped chloroplasts. Of these two, only the model for disc-shaped chloroplasts can account for the experimental results. Based on experimental data, the approaches are proposed to estimate the order of alignment of thylakoid membranes within chloroplasts, and to calculate the angles made by transition dipoles with the thylakoid membrane plane. Internal structure of chloroplasts (alignment of thylakoid membranes) is shown to be unchanged upon squeezing of the gel samples.