Avtor/Urednik		Svetek, J; Schara, M; Nemec, M; Nothnagel, EA
Naslov		Osmolality effects on membrane transport properties and membrane domain structure measured in maize root tissue in situ by spin proble EPR
Tip		članek
Vir		Acta Pharm
Vol. in št.		Letnik 44, št. 4
Leto izdaje		1994
Obseg		str. 297-307
Jezik		slo
Abstrakt		The osmotic effect of the medium on the maize root tissue and cell membrane was studied by electron paramagnetic resonance (EPR) methods which provide a nondestructive assessment of the structure and transport properties of the cell membranes in situ in the tissue. Kinetic EPR imaging was used to evaluate the tissue and membrane permeabilities for small uncharged spin labeled molecules of Tempol (1-oxyl-2,2,6,6-tetramethyl-4-hydroxypiperidine). Additionally the line shapes of complex superimposed EPR spectra of the spin labeled methyl esters of palmitic acid (methyl ester of 5- and 13-doxyl palmitic acid, MeFASL(10,3) and MeFASL(2,11)), incorporated into the membranes in the root tissue, were analyzed in terms of different ordering and dynamics of particular membrane domains. Increased osmolality of the medium induced elevated penetration rates of Tempol molecules into the tissue and also increased the permeability of the cell membrane. A detailed evaluation of the model based on the reduction kinetics of Tempol coupled to the cylindrical geometry of the root showed that, besides an increase of the cell membrane permeability the largest contribution to the overall penetration rates into the tissue are due to the osmotic contractions of the protoplast, which gives rise to the volume increase of the aqueous compartments within the cell wall boundary as well as to the effective surface area available for the relatively fast diffusion of Tempol into the tissue. The results imply that osmotic conditions have a relatively small influence on the permeability of the membrane in the hypotonic range, while the hypertonic medium induces a significant increase of membrane permeability.(trunc.)
Deskriptorji		CORN CELL MEMBRANE PERMEABILITY ELECTRON SPIN RESONANCE SPECTROSCOPY OSMOLAR CONCENTRATION SPIN LABELS PIPERIDINES PALMITIC ACIDS