Lipid solid interfaces

Among the above hypotheses, effects of lipids (4-17,59-62, 69-71,155-159), formaldehyde (160-166), and gas-solid interface TMJ appear to be very important in Gadoid fishes. Denaturation of myofibrillar proteins caused by free fatty acids and/or lipid peroxides must occur during frozen storage. To prove this, Jarenback and Liljemark have shown by electron microscopy that, in muscle stored frozen with added linoleic and linolenic hydroperoxides, myosin became resistant to extraction with salt solution (168). 

To investigate in more details the mechanisms of the interaction of proteins and peptides with membranes, Scheidt et al. discussed the advantages and disadvantages of using lipid modified pseudopeptides to study their interactions with lipid membranes and the aid of solid-state NMR. In the same direction go developments of defined transmembrane peptides with covalently modified acyl chains to investigate interactions of proteins and lipids at the lipid-protein interface as reviewed by Nyholm et al. ... 

Marsh D, Horvath LI (1998) Structure, dynamics and composition of the lipid-protein interface. Perspectives from spin-labelling. Biochim Biophys Acta 1376(3) 267-296 Watts A (1998) Solid-state NMR approaches for studying the interaction of peptides and proteins with membranes. Biochim Biophys Acta 1376(3) 297-318 White SH, Wimley WC (1998) Hydrophobic interactions of peptides with membrane interfaces. Biochim Biophys Acta 1376(3) 339-352... 

Langmuir-Blodgett Films via Electrostatic Control of the Lipid/Water Interface, Thin Solid Films, 133 51 (1985)... 

While the v-a plots for ionized monolayers often show no distinguishing features, it is entirely possible for such to be present and, in fact, for actual phase transitions to be observed. This was the case for films of poly(4-vinylpyri-dinium) bromide at the air-aqueous electrolyte interface [118]. In addition, electrostatic interactions play a large role in the stabilization of solid-supported lipid monolayers [119] as well as in the interactions between bilayers [120]. 

In this chapter we describe the basic principles involved in the controlled production and modification of two-dimensional protein crystals. These are synthesized in nature as the outermost cell surface layer (S-layer) of prokaryotic organisms and have been successfully applied as basic building blocks in a biomolecular construction kit. Most importantly, the constituent subunits of the S-layer lattices have the capability to recrystallize into iso-porous closed monolayers in suspension, at liquid-surface interfaces, on lipid films, on liposomes, and on solid supports (e.g., silicon wafers, metals, and polymers). The self-assembled monomolecular lattices have been utilized for the immobilization of functional biomolecules in an ordered fashion and for their controlled confinement in defined areas of nanometer dimension. Thus, S-layers fulfill key requirements for the development of new supramolecular materials and enable the design of a broad spectrum of nanoscale devices, as required in molecular nanotechnology, nanobiotechnology, and biomimetics [1-3]. 

Most important for many applications of S-layer lattices in molecular nanotechnology, biotechnology, and biomimetics was the observation that S-layer proteins are capable of reassembling into large coherent monolayers on solid supports (e.g., silicon wafers, polymers, metals) at the air/water interface and on Langmuir lipid films (Fig. 6) (see Sections V and VIII). 

In the first step, lipid model membranes have been generated (Fig. 15) on the air/liquid interface, on a glass micropipette (see Section VIII.A.1), and on an aperture that separates two cells filled with subphase (see Section VIII.A.2). Further, amphiphilic lipid molecules have been self-assembled in an aqueous medium surrounding unilamellar vesicles (see Section VIII.A.3). Subsequently, the S-layer protein of B. coagulans E38/vl, B. stearother-mophilus PV72/p2, or B. sphaericus CCM 2177 have been injected into the aqueous subphase (Fig. 15). As on solid supports, crystal growth of S-layer lattices on planar or vesicular lipid films is initiated simultaneously at many randomly distributed nucleation... 

FIGURE 2.1 A side view of the structure of the prototype G-protein-coupled, 7TM receptor rhodopsin. The x-ray structure of bovine rhodopsin is shown with horizontal gray lines, indicating the limits of the cellular lipid membrane. The retinal ligand is shown in a space-filling model as the cloud in the middle of the structure. The seven transmembrane (7TM) helices are shown in solid ribbon form. Note that TM-III is rather tilted (see TM-III at the extracellular and intracellular end of the helix) and that kinks are present in several of the other helices, such as TM-V (to the left), TM-VI (in front of the retinal), and TM-VII. In all of these cases, these kinks are due to the presence of a well-conserved proline residue, which creates a weak point in the helical structure. These kinks are believed to be of functional importance in the activation mechanism for 7TM receptors in general. Also note the amphipathic helix-VIII which is located parallel to the membrane at the membrane interface. 

As for the mechanical response of thin lipid films, surface pressure(fl)-surface area(A) characteristics of lipid monolayer at air/water interface have been well studied under quasi-static conditions. It has been established that different phases are observed for the ensemble of lipid molecules in a two-dimensional arrangement, similarly to the gas, liquid, and solid phases and some other intermediate phases as in three-dimensional molecular assemblies. 

In the case of alkanes, the distance between the molecules in the solid phase is ca. 5 A, while it is 5-6 A in the case of the liquid phase. The distance between molecules in the gas phase, in general, is ca. I ()()() /3 = 10 times larger than in the liquid phase (water volume of 1 mol water = 18 cc volume of 1 mol gas = 22.4 L). In fact, mono-molecular film studies are the only direct method of obtaining such information at the interfaces of lipids. Considering that, only microgram quantities are enough for such information, the importance of such studies becomes clearly evident. 

The technique of fluorescence spectral measurements has become very sensitive over the past decade. In order to obtain more information on the surface monolayers, a new method based on fluorescence was developed. It consisted of placing the monolayer trough on the stage of an epifluorescence microscope, with doped low concentration of fluorescent lipid probe. Later, ordered solid-liquid coexistence at the water-air interface and on solid substrates were reported. The theory of domain shapes has been extensively described by this method. 

Fig. 6.9. A Spontaneous Raman spectrum of d62-DPPC lipids and its decomposition into Lorentzian line profiles. B Normalized multiplex CARS spectra (dots) of a planar-supported bilayer and monolayer formed by d62-DPPC on a glass-water interface for parallel-polarized input beams, together with the fit using the center frequency and line width parameters extracted from the decomposition analysis in (A) (solid line). The spectrum exposure time was 0.64 s. Error bars indicate the shot-noise standard deviation (Copyright American Chemical Society [70])...

J. Kim, G. Kim, and P. S. Cremer, Investigations of water structure at die solid/liquid interface in the presence of supported lipid bilayers by vibrational sum frequency spectroscopy, Langmuir 17, 7255-7260(2001). 

Modern methods of vibrational analysis have shown themselves to be unexpectedly powerful tools to study two-dimensional monomolecular films at gas/liquid interfaces. In particular, current work with external reflection-absorbance infrared spectroscopy has been able to derive detailed conformational and orientational information concerning the nature of the monolayer film. The LE-LC first order phase transition as seen by IR involves a conformational gauche-trans isomerization of the hydrocarbon chains a second transition in the acyl chains is seen at low molecular areas that may be related to a solid-solid type hydrocarbon phase change. Orientations and tilt angles of the hydrocarbon chains are able to be calculated from the polarized external reflectance spectra. These calculations find that the lipid acyl chains are relatively unoriented (or possibly randomly oriented) at low-to-intermediate surface pressures, while the orientation at high surface pressures is similar to that of the solid (gel phase) bulk lipid. 

Volodkin DV, Michel M, Schaaf P et al (2008) Liposome embedding into polyelectrolyte multilayers a new way to create drug reservoirs at solid-liquid interfaces. In Liu AL (ed) Advances in planar lipid bilayers and hposomes. Elsevier, Amsterdam... 

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