Comparative 2H- and 31P-NMR study on the properties of palmitoyllysophosphatidylcholine in bilayers with gramicidin, cholesterol and dipalmitoylphosphatidylcholine

The stoichiometric palmitoyllysophosphatidylcholine (lysoPC)/gramicidin (4:1, mol/mol) lamellar complex (Killian, J.A., De Kruijff, B., Van Echteld, C.J.A., Verkleij, A.J., Leunissen-Bijvelt, J. and De Gier, J. (1983) Biochim. Biophys. Acta 728, 141-144) is a useful model system to investigate the various aspects of lipid protein interactions. To study the effect of gramicidin on local order and motion of 1-palmitoyl-sn-glycero-3-phosphocholine (lysoPC) we employed 31P and 2H nuclear magnetic resonance (NMR) using selectively deuterated lysoPC's and we compared the results to those obtained for lysoPC in bilayers with cholesterol (1:1, mol/mol) and dipalmitoylphosphatidylcholine (DPPC) (1:4, mol/mol). 2H-NMR experiments on acyl chain deuterated lysoPC showed similar quadrupole splittings in the liquid crystalline state for the lysoPC/DPPC and the lysoPC/gramicidin samples. In the lysoPC/cholesterol sample an increase of the quadrupole splitting was found. T1 measurements showed that gramicidin decreases the lysoPC acyl chain motion, especially at the C12 position. In the lysoPC/cholesterol sample an increase of motion was observed as compared to lysoPC in fluid bilayers of DPPC. 31P-NMR and 2-H-NMR measurements of lysoPC, deuterated at the alpha- and beta-position of the choline moiety, indicated an increase in headgroup flexibility in all samples as compared to the parent compound DPPC. In addition, a change in headgroup conformation was observed. The alpha- and beta-segments in all samples exhibited concerted motion. It was found that also in the polar headgroup gramicidin induces a decrease of the rate of motion.     

Elevated choline concentration in neonatal plasma

Plasma choline concentrations were measured in humans, rats, and rabbits within the first few hours of life, before any food was ingested. Neonatal animals and humans had markedly elevated plasma choline levels compared to adult animals or humans. Possible mechanisms responsible for this elevation are discussed and possible consequences for brain function, lung function, and growth are presented.     

The Ultrastructure of the Glandular Trichomes of Solanum tuberosum

The potato plant has two types of glandular trichomes whichwere investigated by electron microscopy. One type has a eight celled globular head on a neck cell anda stalk cell Each glandular cell has many rather large vacuoles,a large nucleus, many ribosomes and mitochondria, a few Golgibodies, and darkly coloured, often irregular plastids (chloroplasts).The plastids are mostly located near the axial cell wall borderinga large central intercellular space filled with secretion materialThe plastids are assumed to participate in the formation ofthe secretion material, which reacts positively to esterasetests. The outer wall is covered by a thin cuticle. The other type has a club-shaped multicellular head on a singlestalk cell. The cytoplasmic features in the cells are similarto those of the globular-headed trichome, except that they possesslarge central vacuoles and randomly distributed plastids. Centricendoplasmic reticulum has been observed in young cells. Intercellularspaces develop between the cells and into the outer wall, whichis thus split into two. Whereas the older glandular cells reactpositively to tests for esterase, the secretion material itselfis pectinaceous and reacts negatively. The outer wall is cutinizedand covered by a cuticle. Solanum tuberosum L., potato, glandular trichomes, ultrastructure     

Electrogenic membrane transport in plants a review

This review treats some examples of electrogenic transport across the outer plasmamembrane (plasmalemma) of plant cells. The selection includes primary active uniport by membrane ATPases (e.g., the proton pump), secondary active transport of hexoses by proton-dependent cotransport, and passive uniport of amines. Primacy is given to the presentation of electrophysiological data and to the discussion of voltage-dependence of the transport mechanisms.Lecture from the Annual Meeting of the Deutsche Gesellschaft für Biophysik at Konstanz