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Titolo:
Interaction of the neuronal marker dye FM1-43 with lipid membranes - Thermodynamics and lipid ordering
Autore:
Schote, U; Seelig, J;
Indirizzi:
Univ Basel, Bioctr, Dept Biophys Chem, CH-4056 Basel, Switzerland Univ Basel Basel Switzerland CH-4056 ys Chem, CH-4056 Basel, Switzerland
Titolo Testata:
BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES
fascicolo: 1, volume: 1415, anno: 1998,
pagine: 135 - 146
SICI:
0005-2736(199812)1415:1<135:IOTNMD>2.0.ZU;2-7
Fonte:
ISI
Lingua:
ENG
Soggetto:
FROG NEUROMUSCULAR-JUNCTION; PHOSPHOLIPID HEAD GROUPS; CHARGE-SHIFT PROBES; MAGNETIC-RESONANCE; LATERAL INTERACTIONS; PHOSPHATIDYLCHOLINE; BILAYERS; BINDING; HEADGROUP; CONFORMATION;
Keywords:
lipid ordering; thermodynamics; neuronal marker dye; FM1-43;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Life Sciences
Citazioni:
35
Recensione:
Indirizzi per estratti:
Indirizzo: Seelig, J Univitzerlandioctr, Dept Biophys Chem, Klingelbergstr 70, CH-4056 Basel, Sw Univ Basel Klingelbergstr 70 Basel Switzerland CH-4056 asel, Sw
Citazione:
U. Schote e J. Seelig, "Interaction of the neuronal marker dye FM1-43 with lipid membranes - Thermodynamics and lipid ordering", BBA-BIOMEMB, 1415(1), 1998, pp. 135-146

Abstract

The fluorescent dye FM1-43 labels nerve terminals in an activity-dependentfashion and has been found increasingly useful in exploring the exo- and endocytosis of synaptic vesicles and other cells by fluorescence methods. The dye distributes between the aqueous phase and the lipid membrane but the physical-chemical parameters characterizing the adsorption/ partition equilibrium have not yet been determined. Fluorescence spectroscopy alone is notsufficient for a detailed elucidation of the adsorption mechanism since the method can be applied only in a rather narrow low-concentration window. In addition to fluorescence spectroscopy, we have therefore employed high sensitivity isothermal titration calorimetry (ITC) and deuterium magnetic resonance (H-2-NMR). ITC allows the measurement of the adsorption isotherm up to 100 mu M dye concentration whereas H-2-NMR provides information on the location of the dye with respect to the plane of the membrane. Dye adsorption/partition isotherms were measured for neutral and negatively-charged phospholipid vesicles. A non-linear dependence between the extent of adsorptionand the free dye concentration was observed. Though the adsorption was mainly driven by the insertion of the non-polar part of the dye into the hydrophobic membrane interior, the adsorption equilibrium was further modulated by an electrostatic attraction/repulsion interaction of the cationic dye (z= +2) with the membrane surface. The Gouy-Chapman theory was employed to separate electrostatic and hydrophobic effects. After correcting for electrostatic effects, the dye-membrane interaction could be described by a simplepartition equilibrium (X-b =Kc(dye)) with a partition constant of 10(3)-10(4) M-1, a partition enthalpy of Delta H = -2.0 kcal/mol and a free energy of binding of Delta G = -7.8 kcal/mol. The insertion of FM1-43 into lipid membranes at room temperature is thus an entropy-driven reaction following the classical hydrophobic effect. Deuterium nuclear magnetic resonance provided insight into the structural changes of the lipid bilayer induced by theinsertion of FM1-43. The dye disturbed the packing of the fatty acyl chains and decreased the fatty acyl chain order. FM1-43 also induced a conformational change in the phosphocholine headgroup. The P--N+ dipole was parallelto the membrane surface in the absence of dye and was rotated with its positive end towards the water phase upon dye insertion. The extent of rotation was, however, much smaller than that induced by other cationic molecules of similar charge, suggesting an alignment of FM1-43 such that the POPC phosphate group is sandwiched by the two quaternary FM1-43 ammonium groups. Insuch an arrangement the two cationic charges counteract each other in a rotation of the P--N+ dipole. (C) 1998 Elsevier Science B.V. All rights reserved.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 28/09/20 alle ore 20:25:49