Membrane during freezing, protein release

Figure 7. Electrophoretic patterns of proteins which are released from thyla-koids during freezing or exposure to 0°C in the presence of various solutes. The solute concentration before freezing is indicated under the gels. Freezing time was 3 hours at —25°C. After thawing, supernatant fluids from membranes were treated with sodium dodecylsulfate (SD) and mercaptoethanol then subjected to gel electrophoresis. Phe is sodium phenylpyruvate, Cap is sodium caprylate, lie is isoleucine. From Volger, Heber, and Berzborn (48).

Protein Release in Relation to Loss of Membrane Function. When thylakoids are frozen in the presence of sucrose, membrane function is preserved. If a cryotoxic salt such as NaCl is also present, retention of membrane functionality during freezing depends on the ratio of sucrose to salt (5). Loss of cyclic photophosphorylation is the most sensitive parameter of membrane inactivation. Photophosphorylation is largely lost before significant protein release from the membranes can be detected (Figure 8). Since photophosphorylation requires membranes with un-... 

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