title: Effect of membrane lipid order on the degree of freezing damage of thylakoid membranes.
abstract: The extent of freezing damage of the photosynthetic apparatus of isolated thylakoid membranes, control and after modification of their membrane fatty acid acyl chain order by cholesterol and benzyl alcohol, was studied. The photochemical activity of photosystems I and II and the energy transfer between the main pigment protein complexes had been determined. Cholesterol-treated membranes are less susceptible to freezing damage, expressed by minor changes of the photochemical activity and retaining the 77K fluorescent characteristics. Benzyl alcohol incorporation enhanced the degree of freezing damage. The photochemical activity of both photosystems was severely decreased (by 80%) and considerable changes in the fluorescent properties were observed, mainly in the pigment pool associated with Photosystem I. The effects of different freezing media (artificial stroma medium, trehalose, glycine betaine and NaCl) were compared in respect to the maintaining of the activity of photosynthetic apparatus.
authors.affiliation: Institute of Biophysics, Bulgarian Academy of Asciences, Acad. G. Bonchev str. Bl. 21, 1113 Sofia, Bulgaria. popova@obzor.bio21.bas.bg
authors.forename: A V
authors.initials: AV
authors.lastname: Popova
authors.forename: M Y
authors.initials: MY
authors.lastname: Velitchkova
mesh_terms: D019905:Benzyl Alcohol; D002784:Cholesterol; D003451:Cryoprotective Agents; D005615:Freezing; D008560:Membrane Fluidity; D018532:Pisum sativum; D010788:Photosynthesis; D020524:Thylakoids
chemical_list: D003451:Cryoprotective Agents; D002784:Cholesterol; D019905:Benzyl Alcohol