The fluidity of chloroplast thylakoid membranes and their constituent lipids: A comparative study by ESR |
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Authors: | Roger G Hiller John K Raison |
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Institution: | 1. School of Biological Sciences, Macquarie University, North Ryde, 2113 Australia;2. Plant Physiology Group, CSIRO Division of Food Research, North Ryde, 2113 Australia |
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Abstract: | Comparative measurements were made of the fluidity of chloroplast thylakoids, total membrane lipids and polar lipids utilizing the order parameter and motion of spin labels.No significant differences were found in the fluidity of membranes or total membrane lipids from a wild type and a mutant barley (Hordeum vulgare chlorina f2 mutant) which lacks chlorophyll and a 25 000 dalton thylakoid polypeptide. Redistribution of intrinsic, exoplasmic face (EF) membrane particles by unstacking thylakoid membranes in low salt medium also had no effect on membrane fluidity. However, heating of isolated thylakoids decreased membrane fluidity.The fluidity of vesicles composed of membrane lipids is much greater than that of the corresponding membranes. Fluidity of the membranes, however, increased during greening indicating that the rigidity of the membranes, compared with that of total membrane lipids, is not caused by chlorophyll or its associated peptides. It is concluded that the restriction of motion in the acyl chains in the thylakoids is not caused by chlorophyll or the major intrinsic polypeptide but by some other protein components. |
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Keywords: | Chloroplast Thylakoid membrane Membrane lipid Spin labeling (Hordeum vulgare) ESR electron spin resonance LHCP light-harvesting chlorophyll protein SDS sodium dodecyl sulphate |
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