Cation-dependent light-induced structural changes in visual receptor membranes |
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Authors: | S P Verma L J Berliner I C Smith |
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Affiliation: | Division of Biological Sciences National Research Council of Canada Ottawa, Ont, K1A OR6, Canada |
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Abstract: | A stearamide spin probe was used to study the light-induced structural changes in Rod Outer Segment Membranes in the presence of sodium and calcium ions. The correlation time (τC) for the reorientation of the probe was calculated in the dark and light. In the presence of sodium ions, τC = 3.3 × 10?9 sec in the dark, and 2.7 × 10?9sec in the light while the opposite was noticed in the presence of calcium ions, τC = 2.9 × 10?9 sec in the dark and 3.6 × 10?9 sec in the light. The correlation times for reorientation of the probe were also calculated in aqueous glycerol solutions of varying viscosities at 20°C. Comparison of the values of τC (dark and light) suggests a change in local mobility in the ROS corresponding to a macroscopic viscosity difference of approximately 150 cp. The significance of calcium ion interaction with negatively charged groups and the formation of a Schiff base is emphasized. |
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