title: EPR spin labeling measurements of thylakoid membrane fluidity during barley leaf senescence.
abstract: Physical properties of thylakoid membranes isolated from barley were investigated by the electron paramagnetic resonance (EPR) spin labeling technique. EPR spectra of stearic acid spin labels 5-SASL and 16-SASL were measured as a function of temperature in secondary barley leaves during natural and dark-induced senescence. Oxygen transport parameter was determined from the power saturation curves of the spin labels obtained in the presence and absence of molecular oxygen at 25°C. Parameters of EPR spectra of both spin labels showed an increase in the thylakoid membrane fluidity during senescence, in the headgroup area of the membrane, as well as in its interior. The oxygen transport parameter also increased with age of barley, indicating easier diffusion of oxygen within the membrane and its higher fluidity. The data are consistent with age-related changes of the spin label parameters obtained directly by EPR spectroscopy. Similar outcome was also observed when senescence was induced in mature secondary barley leaves by dark incubation. Such leaves showed higher membrane fluidity in comparison with leaves of the same age, grown under light conditions. Changes in the membrane fluidity of barley secondary leaves were compared with changes in the levels of carotenoids (car) and proteins, which are known to modify membrane fluidity. Determination of total car and proteins showed linear decrease in their level with senescence. The results indicate that thylakoid membrane fluidity of barley leaves increases with senescence; the changes are accompanied with a decrease in the content of car and proteins, which could be a contributing factor.
authors: Department of Plant Physiology and Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University in Krakow, Ul. Gronostajowa, 7, 30-387 Krakow, Poland.
authors: Ivan
authors: I
authors: Jajić
authors: Department of Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University in Krakow, Ul. Gronostajowa, 7, 30-387 Krakow, Poland.
authors: Anna
authors: A
authors: Wiśniewska-Becker
authors: Department of Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University in Krakow, Ul. Gronostajowa, 7, 30-387 Krakow, Poland.
authors: Tadeusz
authors: T
authors: Sarna
authors: Department of Plant Physiology and Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University in Krakow, Ul. Gronostajowa, 7, 30-387 Krakow, Poland.
authors: Małgorzata
authors: M
authors: Jemioła-Rzemińska
authors: Department of Plant Physiology and Biochemistry, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University in Krakow, Ul. Gronostajowa, 7, 30-387 Krakow, Poland. Electronic address: kazimierzstrzalka@gmail.com.
authors: Kazimierz
authors: K
authors: Strzałka
mesh_terms: D001692:Biological Transport; D002338:Carotenoids; D002734:Chlorophyll / Q000378:metabolism; D002851:Chromatography, High Pressure Liquid; D003624:Darkness; D004578:Electron Spin Resonance Spectroscopy; D001467:Hordeum / Q000378:metabolism*; D008560:Membrane Fluidity; D010100:Oxygen / Q000378:metabolism; D018515:Plant Leaves / Q000254:growth & development* / Q000378:metabolism*; D010940:Plant Proteins / Q000378:metabolism; D012399:Rotation; D013113:Spin Labels; D013696:Temperature; D020524:Thylakoids / Q000378:metabolism*; D013997:Time Factors
chemical_list: D010940:Plant Proteins; D013113:Spin Labels; D002734:Chlorophyll; D002338:Carotenoids; D010100:Oxygen
keywords: Fluidity; Oxygen transport parameter; Senescence; Spin labeling; Thylakoid membrane