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Analysis of water self-diffusion in polycrystalline lamellar systems by pulsed field gradient nuclear magnetic resonance experiments (1993)

Coppola, L. ; La Mesa, C. ; Ranieri, G. A. ; [et al.]

College Park, Md. : American Institute of Physics (AIP)

The Journal of Chemical Physics 98 (1993), S. 5087-5090

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ISSN: 1089-7690

Source: AIP Digital Archive

Topics: Physics , Chemistry and Pharmacology

Notes: A study of the water self-diffusion in polycrystalline lamellar systems, by pulsed field gradient spin-echo (PFG-SE) nuclear magnetic resonance (NMR) experiments, is reported here. Our analysis confirmed the validity of previous equations for bidimensional water self-diffusion in lamellar lyomesophases and clarified their applicability limits. Depending on the diffusion experimental time range, two different procedures can be built up; for wide amplitude windows, the experimental diffusion coefficients are correlated to the fraction of bound water, whereas for short times it has been possible to point out the "obstruction factor'' to diffusion. Experimental support for the theoretical findings was inferred by investigation of the lamellar mesophase of the binary system water/sodium-bis-2-ethylhexyl sulfosuccinate (AOT). It confirmed the existence of some defects in the lamellae at water concentration higher than 70 wt. %.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1063/1.464964

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Effects of high electrolyte concentration on DPPC-multilayers: an ESR and DSC investigation (1994)

Sapia, P. ; Coppola, L. ; Ranieri, G. ; [et al.]

Springer

Colloid & polymer science 272 (1994), S. 1289-1294

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ISSN: 1435-1536

Keywords: Ionic strength ; DPPC ; multilayer ; ESR ; DSC

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Abstract The effects of salinity on the lateral headgroup interactions of dipalmitoylphosphatidylcholine (DPPC) molecules in fully hydrated multilayers have been investigated by spin label electron spin resonance (ESR) spectroscopy and differential scanning calorimetry (DSC). By increasing the NaCl concentration from 0 to 3 M in the multilayers' dispersion medium, the ESR measurements performed with the 5-stearic acid spin label and di-tert-butyl-nitroxide show an increase in the orientational degree of order of the lipid molecules, mainly in the gel phase, and a decrease of the membrane permeability. An upward shift from 31.5° to 36.5°C and from 40.5° to 41.9°C of the pre- and main DPPC phase transition temperatures, respectively, is observed with 5-SASL, while slightly higher values are detected with DTBN. Small effects are evident on the properties of the liquid crystalline phase of the DPPC multilayers. The DSC measurements also reveal an upward shift of the pre- and main transition temperatures. The shifts, however, are more marked if compared to the ones observed with the ESR technique. The findings suggest an increase in the packing density of the DPPC molecules in the multilayers in presence of high salt concentration. Dehydration of the DPPC interfacial region with a variation of the lateral electrostatic interactions between phospholipid polar heads trigger the phenomena observed.