Oriented bilayers

In the remainder of this section, we compare EISFs and Lorentzian line widths from our simulation of a fully hydrated liquid crystalline phase DPPC bilayer at 50°C with experiments by Kdnig et al. on oriented bilayers that, in order to achieve high degrees of orientation, were not fully hydrated. We consider two sets of measurements at 60°C on the IN5 time-of-flight spectrometer at the ILL one in which the bilayer preparations contained 23% (w/w) pure D2O and another in which bilayer orientation was preserved at 30% D2O by adding NaCl. The measurements were made on samples with two different orientations with respect to the incident neutron beam to probe motions either in the plane of the bilayers or perpendicular to that plane. 

Fig. 2 Mechanically oriented bilayer samples as a membrane model for ssNMR. (a) Illustration of the hydrated lipid bilayers with MAPs embedded, the glass supports, and the insulating wrapping, (b) A real sample consists of 15 stacked glass slides, (c) Schematic solid-state 19F-NMR lineshapes from an oriented CF3-labelled peptide (red), and the corresponding powder lineshape from a non-oriented sample (grey), (d) Illustration of typical orientational defects in real samples - the sources of powder contribution in the spectra...

Compared to the sizes of living cells,1 IUV and LUV resemble the dimensions of enveloped viruses (ranging from 80 to 400 nm) [94], while GUVs resemble typical bacteria and erythrocytes (1-7 pm). Eukaryotic cells tend to be even larger (10-30 pm in animals, 10-100 pm in plants). These dimensions imply that, except for viruses or specific sub-cellular membranes, flat bilayers are the only relevant membrane models. Hence, macroscopically oriented bilayers on solid supports (see... 

Naito A (2009) Structure elucidation of membrane-associated peptides and proteins in oriented bilayers by solid-state NMR spectroscopy. Solid State Nucl Mag 36 67-76... 

Electron microscopy easily yields structural images of cast bilayer films. Figure 6 shows a scanning electron microscope (SEM) image of the cross section of the bilayer film of CgAzoCioN+Br prepared by the simple casting of water solution. From the presence of well developed layers parallel to die film plane, it can be assumed that the cast film was composed from multiple highly oriented bilayers. 

The interaction of various cholesterol ancestors with lipid membranes on oriented bilayers has also been studied by 2H- and 31P-NMR [100]. 

In Figs. 12 and 13, structures determined in oriented bilayer samples and under MAS conditions are shown, respectively. If available, PDB codes are given. The first structure... 

Fig. 12. Structures determined by solid-state NMR in oriented bilayers. The PDB file numbers are shown, see text for details. (Adapted from Ref. 12.)...

Sanders CR, Schwonek JP (1992) Characterization of magnetically orientable bilayers in miKtures of dihexanoylphosphatidylcholine and dimyristoylphosphatidylcholine by solid-state NMR. Biochemistry 31 8898-8905... 

A. Filippov, G. Oradd, G. Lindblom, The effect of cholesterol on the lateral diffusion of phospholipids in oriented bilayers, Biophys. J., 2003, 84, 3079-3086. 

L.C. phases which form along water dilution lines. The simulation of NMR line shapes of unoriented PL bilayers in the L phase and of oriented bilayers in both L and Lp phases was performed through van Faassen s method it was demonstrated that this method, used for dimyristoylPC (DMPC) and dipal-mitoylPC (DPPC) PLs bilayers, involving only numerical integration, is less computationally consuming than other approaches. 

Thus, the hydrophilic head group and hydrophobic tail of lipids ensure assembly into the oriented bilayer array of cell membranes. The amphiphilic sheet, bilayer, and vesicle are now familiar mofits in biomimetic materials and structures. Synthetic liposomes are employed as biocompatible, biodegradable drug-delivery vehicles. Amphiphile assemblies may serve as templates mono-disperse nanoparticles are synthesized inside reverse micelles, and inorganic structures and materials such as ceramic tubules or mesoporous silica are formed around tubular micelles, rather as inorganics are patterned by vesicles in the formation of the exoskeletons of radiolarians and diatoms. 

Our BAE measurements indicate that the molecules in the first layer lie nearly fiat on the surface, while the molecules in the second layer are pointing more toward the surface normal. The structure of the second layer is, however, very diffeient from a homeotropically oriented bilayer of the bulk smectic phase which would give 2,bulk f °- Assuming that the molecular angular distribution /(0) is constant during the entire deposition of the... 

O. Thiebaut, H. Bock, E. Grelet, Eace-on oriented bilayer of two discotic columnar liquid crystals for tn-ganic donor-acceptor heterojunctiotL J. Am. Chem. Soc. 132, 6886-6887... 

Membranes and model membranes exhibit liquid crystalline behavior and this has been exploited in a number of studies to obtain valuable information on the structure and dynamics of membrane associated peptides and proteins as well as on the interaction of the peptides with the membranes themselves. NMR spectroscopy of nuclei such as proton, carbon, deuterium, nitrogen and phosphorus has been utilized for such purposes. Structure elucidation of membrane-associated peptides and proteins in oriented bilayers by solid-state NMR spectroscopy has been reviewed. A survey on the use of static uniaxially oriented samples for structural and topological analysis of membrane-associated polypeptides is available. The theoretical background has been dealt with and a number of examples of applications provided. In addition, ongoing developments combining this method with information from solution NMR spectroscopy and molecular modelling as well as exploratory studies using dynamic nuclear polarization solid-state NMR have been presented. The use of N chemical shift anisotropy, dipolar interactions and the deuterium quadrupolar split-... 

The influence of polyacrylic add (PAA) with small concentrations (l-4mol%) on the change of the phase state, lateral diffusion of these lipids in lamellar phase and transmembrane water diffusion in macroscopically oriented bilayers of lipid-water systems formed by dimiristoylphosphatidylcholine (DMPQ and dioleoylphosphatidylcholine were studied. Measurements were... 

Khare, R. S., Worthington, C. R. An X-Ray Diffraction Study of Sphingomyelin-Cholesterol Interaction in Oriented Bilayers. Mol. Cryst. Liq. Cryst. 38, 195 (1977)... 

Many authors have described structural transitions in dilute lamellar phases under the influence of shear. For example, Roux and co-workers (19) studied different dilute lamellar phases which were stabilized by undulation forces and contained flat bilayers with defects, at rest. With increasing shear rates, these bilayers undergo a transition into relatively monodisperse multilamellar vesicles above a characteristic shear rate. The size of the formed vesicles is indirectly proportional to the shear rate. Beyond a second characteristic shear rate, the vesicles are again transformed into flat oriented bilayers. These results were explained in terms of a balance between shear stress and elastic forces which come from the bending and the Gaussian moduli of the bilayers. The same authors observed a similar sequence with increasing shear rate for other lamellar phases. It was found... 

H 1 000 High resolution spectra Chemical shift, 7- T High sensitivity Natural abundance Reasonable spectra with small vesicles, micelles, high speed MAS or MAS of oriented bilayers Several relaxation mechanisms Overlapping resonances Dynamic properties Lipid diffusion... 

In principle, a single three-dimensional correlation spectrum of an oriented sample of a uniformly N labelled protein provides sufficient information in the form of orientationally dependent frequencies for each amide site to determine the complete structure of the polypeptide backbone. The two-dimensional iH-i-TsT heteronuclear dipolar- N chemical shift PISEMA spectrum in Figure 5A was obtained from a uniformly i-TsT labelled sample of the 50-residue fd coat protein in oriented bilayers it contains resonances from all of the amide backbone (and side-chain) nitrogen sites. The resonances in the box in the upper left are largely from residues in the... 

Michalek et al. have determined the high-resolution structure of huntingtin 1-17 using a combination of solution and solid state NMR spectroscopy both in micelles and in oriented phosphatidylcholine bilayers. ssNMR was used to identify specific parts of the structure in the orientated bilayer with angular restraints was obtained using labelled with and at selected sites. 

On the basis of X-ray diffraction studies, the ultrastructure of chloroplast membrane has been analyzed by Kreutz - s, and the subject reviewed by him. Using the freeze-etching technique, Muehlethaler has suggested a picture for the thylakoid membrane based upon the bimolecular leaflet model. The salient feature in all these proposed models lies in their oriented bilayer lipid core, onto which other important cellular constituents, such as proteins and pigments, may interact through either ionic or van der Waals attraction, or both. Muehlethaler s interpretation is of special interest, in view of the experiments using the pigmented... 

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