ISSN:
1573-0689
Keywords:
31P-NMR
;
photosynthetic membranes
;
phase transitions
;
glycerol effect
;
freeze-drying
;
non-lamellar phases
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
,
Physics
Notes:
Abstract 31P-NMR spectra at 162 MHz were used to monitor phase changes of wheat thylakoid membranes as a function of temperature. At room temperature the31P-NMR line was a superposition of anisotropic component characteristic of phospholipid lamellar phase and isotropic line due to inorganic phosphorus or small membrane vesicles arising as an effect of preparation. For temperatures higher than +35 °C an increase of the isotropic component occurs, which is irreversible as the sample is cooled. For the temperatures between +55 °C and +60 °C the presence of the hexagonal phase cylinders is suggested, as monitored by phosphorus lineshape. However, the addition of glycerol stimulates a formation of the isotropic phase. The effect of reconstitution of freeze-dried thylakoid membranes by addition of water or water-glycerol medium to the sample was examined. As lyophilizate was gradually diluted, the increase of isotropic line component was observed. For thylakoid membranes suspended in D2O at the highest dilution examined, the line contribution due to small membrane fragments is not greater than 50%, but in presence of glycerol, this contribution could reach 70%. This suggests that the presence of glycerol increases the formation of the small membrane particles as the thylakoid membrane is reconstituted from lyophilizate. The wheat thylakoid membranes reconstituted from lyophilizate show, in comparison to native membranes, the increased contribution of small membrane vesicles. Moreover, the31P -NMR spectra suggest the appearance of the hexagonal phase cylinders even at +50 °C.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00705595
Permalink