Understanding the Enhanced Magnetic Response of Aminocholesterol Doped Lanthanide-Ion Chelating Phospholipid Bicelles (original) (raw)
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Magnetic Resonance in Chemistry, 2004
We report the utilization of magnetically aligned phospholipid bilayers (bicelles) to study the effects of cholesterol in phospholipid bilayers for both chain perdeuterated DMPC and partially deuterated a-[2,2,3,4,4,6-d 6 ]-cholesterol using 2 H solid-state NMR spectroscopy. The quadrupolar splittings at 40 • C were 25.5 and 37.7 kHz, respectively, for the 2,4-2 H eq and 2,4-2 H ax deuterons when the bilayer normal of the discs was aligned perpendicular to the static magnetic field. The quadrupolar splittings were doubled when Yb 3+ ions were added to flip the bicelles 90 • such that the bilayer normal was colinear with the magnetic field. The results suggest that cholesterol is incorporated into the bicelle discs. For chain perdeuterated DMPC-d 54 , incorporated into DMPC-DHPC bicelle discs, the individual quadrupolar splittings of the methylene and methyl groups doubled on going from the perpendicular to the parallel alignment. Also, the presence of cholesterol increased the overall ordering of the acyl chains of the phospholipids. S CD i calculations were extracted directly from the 2 H quadrupolar splittings of the chain perdeuterated DMPC. The order parameter, S CD i , calculations clearly indicated an overall degree of ordering of the acyl chains in the presence of cholesterol. We also noted a disordering effect at higher temperatures. This study demonstrates the ease with which 2 H order parameters can be calculated utilizing magnetically aligned phospholipid bilayers when compared with randomly dispersed membrane samples.
Biochimica et Biophysica Acta (BBA) - Biomembranes, 2005
X-band EPR spectroscopy has been employed to study the dynamic properties of magnetically aligned phospholipid bilayers (bicelles) utilizing a variety of phosphocholine spin labels (n-PCSL) as a function of cholesterol content. The utilization of both perpendicular and parallel aligned bicelles in EPR spectroscopy provides a more detailed structural and orientational picture of the phospholipid bilayers. The magnetically aligned EPR spectra of the bicelles and the hyperfine splitting values reveal that the addition of cholesterol increases the phase transition temperature and alignment temperature of the DMPC/DHPC bicelles. The corresponding molecular order parameter, S mol , of the DMPC/DHPC bicelles increased upon addition of cholesterol. Cholesterol also decreased the rotational motion and increased the degree of anisotropy in the interior region of the bicelles. This report reveals that the dynamic properties of DMPC/DHPC bicelles agree well with other model membrane systems and that the magnetically aligned bicelles are an excellent model membrane system. D
Physical chemistry chemical physics : PCCP, 2017
Lanthanide ion (Ln(3+)) chelating amphiphiles are powerful molecules for tailoring the magnetic response of polymolecular assemblies. Mixtures of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-dimyristoyl-sn-glycero-3-phospho-ethanolamine-diethylene triaminepentaacetate (DMPE-DTPA) complexed to Ln(3+) deliver highly magnetically responsive bicelles. Their magnetic properties are readily tuned by changing the bicellar size or the magnetic susceptibility Δχ of the bilayer lipids. The former technique is intrinsically bound to the region of the phase diagram guarantying the formation of bicelles. Methods aiming towards manipulating the Δχ of the bilayer are comparatively more robust, flexible and lacking. Herein, we synthesized a new Ln(3+) chelating phospholipid using glutamic acid as a backbone: DMPE-Glu-DTPA. The chelate polyhedron was specifically engineered to alter the Δχ, whilst remaining geometrically similar to DMPE-DTPA. Planar asymmetric assemblies hundreds of na...
Small angle x-ray scattering studies of magnetically oriented lipid bilayers
Biophysical Journal, 1995
Magnetically oriented lipid/detergent bilayers are potentially useful for studies of membrane-associated molecules and complexes using x-ray scattering and nuclear magnetic resonance (NMR). To establish whether the system is a reasonable model of a phospholipid bilayer, we have studied the system using x-ray solution scattering to determine the bilayer thickness, interparticle spacing, and orientational parameters for magnetically oriented lipid bilayers. The magnetically orientable samples contain the phospholipid L-a-dilauroylphosphatidylcholine (DLPC) and the bile salt analog 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxy-1 -propanesulfonate (CHAPSO) in a 3:1 molar ratio in 70% water (w/v) and are similar to magnetically orientable samples used as NMR media for structural studies of membrane-associated molecules. A bilayer thickness of 30 A was determined for the DLPC/CHAPSO particles, which is the same as the bilayer thickness of pure DLPC vesicles, suggesting that the CHAPSO is not greatly perturbing the lipid bilayer. These data, as well as NMR data on molecules incorporated in the oriented lipid particles, are consistent with the sample consisting of reasonably homogeneous and well dispersed lipid particles. Finally, the orientational energy of the sample suggests that the size of the cooperatively orienting unit in the samples is 2 x 107 phospholipid molecules.
Biochimica et Biophysica Acta (BBA) - Biomembranes, 2001
This study reports the solid-state NMR spectroscopic characterization of a long chain phospholipid bilayer system which spontaneously aligns in a static magnetic field. Magnetically aligned phospholipid bilayers or bicelles are model systems which mimic biological membranes for magnetic resonance studies. The oriented membrane system is composed of a mixture of the bilayer forming phospholipid palmitoylstearoylphosphatidylcholine (PSPC) and the short chain phospholipid dihexanoylphosphatidylcholine (DHPC) that breaks up the extended bilayers into bilayered micelles or bicelles that are highly hydrated (approx. 75% aqueous). Traditionally, the shorter 14 carbon chain phospholipid dimyristoylphosphatidylcholine (DMPC) has been utilized as the bilayer forming phospholipid in bicelle studies. Alignment (perpendicular) was observed with a PSPC/DHPC q ratio between 1.6 and 2.0 slightly above T m at 50³C with 2 H and 31 P NMR spectroscopy. Paramagnetic lanthanide ions (Yb 3) were added to flip the bilayer discs such that the bilayer normal was parallel with the static magnetic field. The approx. 1.8 (PSPC/DHPC) molar ratio yields a thicker membrane due to the differences in the chain lengths of the DMPC and PSPC phospholipids. The phosphate-to-phosphate thickness of magnetically aligned PSPC/ DHPC phospholipid bilayers in the L K phase may enhance the activity and/or incorporation of different types of integral membrane proteins for solid-state NMR spectroscopic studies. ß 2001 Published by Elsevier Science B.V.
Solid State Nuclear Magnetic Resonance, 2003
Solid-state deuterium NMR spectroscopy was used to study the structural and dynamic properties of stearic acid-d 35 in magnetically aligned phospholipid bilayers as a function of temperature. Magnetically aligned phospholipid bilayers or bicelles are model systems, which mimic biological membranes for magnetic resonance studies. Paramagnetic lanthanide ions (Yb 3+ ) were added to align the bicelles such that the bilayer normal is colinear with the direction of the static magnetic field. The corresponding order parameters of the stearic acidd 35 probe were calculated and compared with values obtained from unoriented samples in the literature. The addition of cholesterol to the bicelle system decreases the fluidity of the phospholipid bilayers and increases the ordering of the acyl chains of stearic acid-d 35 . This study demonstrates the feasibility of utilizing magnetically aligned bicelles for calculating 2 H order parameter profiles for non-biological systems such as polymer-grafted membranes and Schiff's base complexes. r
Magnetically Aligned Bicelles To Study the Orientation of Lipophilic Ligands in Membrane Bilayers
Journal of Medicinal Chemistry, 2008
Magnetically aligned bicelles were used as a model membrane to study the orientation and dynamic properties of two cannabinoids (∆ 8 -THC and Me-∆ 8 -THC) using 31 P and 2 H NMR. The uniform alignment of the bicelles allowed us to obtain well resolved deuterium spectra from a solution NMR spectrometer. The preferred orientations of ∆ 8 -THC and Me-∆ 8 -THC were calculated on the basis of the measurements of individual quadrupolar splittings. Our results agree with previous experiments using multilamellar membranes as well as with molecular dynamics simulation data described here. In conjunction with our earlier report using small and fast tumbling bicelles, the present work of well aligned bicelles shows that bicelle preparations can provide either pseudoisotropic or anisotropic NMR spectra to study the conformation, orientation, and dynamic properties of ligands in membrane bilayers. Such data are of critical value for understanding the interactions of lipophilic drug molecules with membrane proteins.
Biochimica et Biophysica Acta (BBA) - Biomembranes, 2012
16-DSPC … 3-DC 3-DoxylCholestane 5-DSPC … A-ESR angle-resolved electron spin resonance AFD angle-resolved fluorescence depolarization BHT butylated hydroxytoluene DHPE-Bodipy N-(4,4-difluoro-5,7-dimethyl-4-bora-3a,4a-diaza-s-indacene-3-propionyl)-1,2dihexadecanoyl-sn-glycero-3-phosphoethanolamine (triethylammonium salt) DLPC 1,2-dilinoleoyl-sn-glycero-3-phosphocholine DOPC 1,2-dioleoyl-sn-glycero-3-phosphocholine DPH 1,6-diphenyl-1,3,5-hexatriene DPPC FCS fluorescence correlation spectroscopy FRET Förster resonance energy transfer GUV giant unilamellar vesicles HOPLPC
The Journal of chemical physics, 2014
Lipid-cholesterol interactions are responsible for different properties of biological membranes including those determining formation in the membrane of spatial inhomogeneities (lipid rafts). To get new information on these interactions, electron spin echo (ESE) spectroscopy, which is a pulsed version of electron paramagnetic resonance (EPR), was applied to study 3β-doxyl-5α-cholestane (DCh), a spin-labeled analog of cholesterol, in phospholipid bilayer consisted of equimolecular mixture of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine and 1,2-dioleoyl-sn-glycero-3-phosphocholine. DCh concentration in the bilayer was between 0.1 mol.% and 4 mol.%. For comparison, a reference system containing a spin-labeled 5-doxyl-stearic acid (5-DSA) instead of DCh was studied as well. The effects of "instantaneous diffusion" in ESE decay and in echo-detected (ED) EPR spectra were explored for both systems. The reference system showed good agreement with the theoretical prediction for the ...