Lateral heterogeneity of polar lipids in the thylakoid membranes of spinach chloroplasts

Isolated appressed and non‐appressed membrane fractions of spinach thylakoids have been subjected to lipid class and fatty acid composition analyses. The ratio of monogalactosyldiacylglycerol to digalactosyldiacylglycerol was much higher in the fractions obtained from the appressed membranes compared with those derived from non‐appressed membranes. Moreover, appressed thylakoids contained a larger amount of anionic lipids in comparison with non‐appressed thylakoids. No major differences were observed in the fatty acid composition between the thylakoid fractions. The results are discussed in terms of the possible significance of lipid heterogeneity in the chloroplast thylakoid membrane.