31P solid-state NMR on skeletal muscle of wild and farmed Atlantic salmon

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Thermotropic Behavior of a Cationic Surfactant in the Adsorbed and Micellar State: An NMR Study

Knowledge about how temperature affects the internal structure and dynamics of surfactant aggregates can lead to a better understanding of their behavior in complex environments and processes. ¹³C chemical shifts of the cationic surfactant tetradecytrimethylammonium bromide (TTAB) in micellar solution and when adsorbed on silica particles are recorded in the temperature range 8–78 °C, and give information on the conformation of the alkyl chain carbons. Adsorbed TTAB has conformational disorder similar to free TTAB at about 70 °C, with an increase in the rate of conformational changes occurring above 50 °C. Furthermore, no significant change in TTAB adsorption density was observed in the temperature range studied, and the results indicate a bilayer arrangement of the adsorbed surfactants. The number of <i>gauche</i> conformers increases linearly with temperature for the alkyl chain carbons in TTAB micelles. However, the total increase in <i>gauche</i> conformers is significantly smaller for micellar than for adsorbed TTAB within the temperature range studied. The fraction of micellized TTAB molecules in solution is found to increase with temperature

Experimental Determination of Water Molecular Orientation near a Silica Surface Using NMR Spectroscopy

After nearly a century of research on water properties at interfaces it has become clear that water adopts a highly ordered structure near a solid surface. However, to date, the exact orientations and structures of water molecules adjacent to a solid surface remain within the realm of theoretical simulation. In this paper, the average orientation of water molecules near a silica surface is determined experimentally for the first time using a sample where silica surfaces are similarly oriented with respect to an external magnetic field. By allowing only water with increased ordering to remain in the closed system, the water ¹H magnetic resonance corresponds to an orientation-dependent doublet. From its orientation dependence, the average angle between the silica surface and the water ¹H–¹H vector is assessed to 78° at ambient conditions. This orientation is found to apply to tetrahedrally coordinated water molecules not directly adjacent the surface and suggests that water in subsequent layers adopt a low-energy structure with a significantly increased lifetime compared to bulk water structures. Despite preferred spatial orientations, the water molecules exhibit a relatively high degree of motional freedom

Effects and Location of Coplanar and Noncoplanar PCB in a Lipid Bilayer: A Solid-State NMR Study

Coplanar and noncoplanar polychlorinated biphenyls (PCBs) are known to have different routes and degree of toxicity. Here, the effects of noncoplanar PCB 52 and coplanar PCB 77 present at 2 mol % in a model system consisting of POPC liposomes (50% hydrated) are investigated by solid-state ¹³C and ³¹P NMR at 298 K. Both PCBs intercalate horizontally in the outer part of the bilayer, near the segments of the acyl chain close to the glycerol group. Despite similar membrane locations, the coplanar PCB 77 shows little effect on the bilayer properties overall, except for the four nearest neighboring lipids, while the effect of PCB 52 is more dramatic. The first ∼2 layers of lipids around each PCB 52 in the bilayer form a high fluidity lamellar phase, whereas lipids beyond these layers form a lamellar phase with a slight increase in fluidity compared to a bilayer without PCB 52. Further, a third high mobility domain is observed. The explanation for this is the interference of several high fluidity lamellar phases caused by interactions of PCB 52 molecules in different leaflets of the model bilayer. This causes formation of high curvature toroidal region in the bilayer and might induce formation of channels

Chlorpromazine interaction with glycerophospholipid liposomes studied by magic angle spinning solid state 13C-NMR and differential scanning calorimetry

AbstractPhosphatidylserine (PS) extracted from pig brain and synthetic dipalmitoylphosphatidylcholine (DPPC) and dimyristoylphosphatidylcholine (DMPC) were used to make DPPC/DMPC and DPPC/PS large unilamellar liposomes with a diameter of ∼1 μm. Chlorpromazine-HCl (CPZ), an amphipathic cationic psychotropic drug of the phenothiazine group, is known to partition into lipid bilayer membranes of liposomes with partition coefficients depending on the acyl chain length and to alter the bilayer structure in a manner depending on the phospholipid headgroups. The effects of adding CPZ to these membranes were studied by differential scanning calorimetry and proton cross polarization solid state magic angle spinning 13C-nuclear magnetic resonance spectroscopy (CP-MAS-13C-NMR). CP-MAS-13C-NMR spectra of the DPPC (60%)/DMPC (40%) and the DPPC (54%)/DMPC (36%)/CPZ (10%) liposomes, show that CPZ has low or no interaction with the phospholipids of this neutral and densely packed bilayer. Conversely, the DPPC (54%)/PS (36%)/CPZ (10%) bilayer at 25°C demonstrates interaction of CPZ with the phospholipid headgroups (PS). This CPZ interaction causes about 30% of the acyl chains to enter the gauche conformation with low or no CPZ interdigitation among the acyl chains at this temperature (25°C). The DPPC (54%)/PS (36%)/CPZ (10%) bilayer at a sample temperature of 37°C (TC=31.2°C), shows CPZ interdigitation among the phospholipids as deduced from the finding that ∼30% of the phospholipid acyl chains carbon resonances shift low-field by 5–15 ppm

31P solid-state NMR on skeletal muscle of wild and farmed Atlantic salmon

Over the past 50 years, 31P NMR has proven a powerful tool for obtaining information on cellular biochemistry. Here we use this technique for the first time to study intracellular phosphorous metabolites in skeletal muscle tissue of wild and farmed salmon, to investigate possible effects due to differences in diet and way of life. The wild salmon sample shows a significantly more diverse composition of metabolites compared to the farmed salmon sample. The differences are evident in the entire spectrum, including regions displaying resonances from phosphomonoesters and sugar phosphates, as well as other molecules important for phospholipid metabolism. It is demonstrated that 31P MAS NMR can be used to study a broad range of phosphorus metabolites ex vivo, which can give useful information, both on its own or as a supplement to other extraction-based analyses. Further 31P MAS NMR investigations on farmed salmon raised under different controlled conditions may give important insights into the broad array of health issues seen in farmed salmon

31P solid-state NMR on skeletal muscle of wild and farmed Atlantic salmon

Over the past 50 years, 31P NMR has proven a powerful tool for obtaining information on cellular biochemistry. Here we use this technique for the first time to study intracellular phosphorous metabolites in skeletal muscle tissue of wild and farmed salmon, to investigate possible effects due to differences in diet and way of life. The wild salmon sample shows a significantly more diverse composition of metabolites compared to the farmed salmon sample. The differences are evident in the entire spectrum, including regions displaying resonances from phosphomonoesters and sugar phosphates, as well as other molecules important for phospholipid metabolism. It is demonstrated that 31P MAS NMR can be used to study a broad range of phosphorus metabolites ex vivo, which can give useful information, both on its own or as a supplement to other extraction-based analyses. Further 31P MAS NMR investigations on farmed salmon raised under different controlled conditions may give important insights into the broad array of health issues seen in farmed salmon