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The molecular orientation of 6-F-cholesterol in dimyristoylphosphatidylcholine (DMPC) bilayers is studied by using [super 19]F chemical shift anisotropy, [super 2]H NMR and C-F rotational echo double resonance (REDOR) experiments. The studies have shown that the dynamic properties of 6-F-cholesterol in dimyristoylphosphatidylcholine are similar to those of unmodified cholesterol and hence the introduction of a fluorine atom at C6 has no effect on cholesterol dynamics in membranes.

Determining how the regulation of cellular processes is impacted in cystic fibrosis (CF) is fundamental to understanding disease pathology and to identifying new therapeutic targets. In this study, unesterified cholesterol accumulation is observed in lung and trachea sections obtained from CF patients compared with non-CF tissues, suggesting an inherent flaw in cholesterol processing. An alternate staining method utilizing a fluorescent cholesterol probe also indicates improper lysosomal storage of cholesterol in CF cells. Excess cholesterol is also manifested by a significant increase in plasma membrane cholesterol content in both cultured CF cells and in nasal tissue excised from [cftr.sup.-/-] mice. Impaired intracellular cholesterol movement is predicted to stimulate cholesterol synthesis, a hypothesis supported by the observation of increased de novo cholesterol synthesis in lung and liver of [cftr.sup.-/-] mice compared with controls. Furthermore, pharmacological inhibition of cholesterol transport is sufficient to cause CF-like elevation in cytokine production in wild-type cells in response to bacterial challenge but has no effect in CF cells. These data demonstrate via multiple methods in both cultured and in vivo models that cellular cholesterol homeostasis is inherently altered in CF. This perturbation of cholesterol homeostasis represents a potentially important process in CF pathogenesis.

Pig kidney [Na.sup.-]/[K.sup.+]-ATPase is reconstituted into unilammelar vesicles of endogenous lipids mimicking the natural membrane to gain insight into the role of cholesterol. It is found that in the vicinity of the critical mole fractions, where superlattice formation can occur, minute changes in cholesterol concentration produce abrupt changes in the membrane organization, increasing interdomain surfaces.

The relationship between the molecular organization of lipid headgroups and activity of surface-acting enzyme is studied using a bacterial cholesterol oxidase as a model. The findings from the study reveal that headgroup superlattice domains exist in lipid bilayers and that they may play a crucial role in modulating the activity of enzymes acting on the cell membrane surface.

The molecular organization of cholesterol in phosphatidylethanolamines (PEs) that vary in their degree of acyl chain unsaturation were investigated. The findings indicate that both headgroup structure and acyl chain unsaturation modulate cholesterol solubility within membranes, which might have implications for lipid phase separation, raft formation, and membrane function.

The effects of its metabolites, ceramide and ceramide phosphate, on the activity and fatty acid specificity of lecithin-cholestrol acyltransferase (LCAT) in vitro are investigated. The results indicate that the activity and fatty acid specificity of LCAT may be altered during the inflammatory response.

Oxycholesterols (OS) are formed from cholesterol or its immediate precursors by enzymatic or free radical action in vivo or might be derived from food. A review of the most-important aspects of OS cytotoxic activities, in particular its influence on HMG-CoA reductase activity, antiproliferative action and apoptosis based on experimental results is presented.

Studies are conducted to verify that the kinetics of microsolubilization of dimyristoylphosphatidylcholine (DMPC) multilamellar vesicles by apolipopretein A-I (apoA-I) is dramatically affected by varying oxysterol chemical structure, sterol concentration and the lipid phase state of DMPC. It is observed that some oxysterols increase the rate of microsolubilization while some oxysterols greatly inhibit it.

The study focuses on the potential influence that insoluble calcite seeds might play in the crystallization of cholesterol monohydrate. The theoretical and experimental approach brings us closer to a molecular scale by which one can understand that the energetic barriers to cholesterol nucleation can be reduced by some physiological conditions.

It is shown that cholesterol can bind to the intercalated bilayer, providing a route for its insertion into inorganic solids. An analysis of the alkyl chains of an intercalated bilayer is studied.

The article discusses the synthesis, as well as the characterization of CHOBIMALT, a cholesterol-based detergent. The detergent is shown to highly enhance the thermal stability of hum an kappa opioid receptor type 1 on being added to the classical detergent micelles.

The time-resolved fluorescence anisotropy technique is employed to explain the interaction taking place between the bovine fibronectin type II (Fn2) protein PDC-109 and cholesterol. The rotational mobility of the cholesterol is shown to be highly reduced by the presence of the protein.

Site-directed mutagenesis is used for examining the ligand selectivity and in vivo function of the yellow fever mosquito sterol carrier protein-2 protein (AeSCP-2). Mutations to amino acids in AeSCP-2 known to interact with bound ligand has weakened NBD-cholesterol binding and overexpressing wild-type AeSCP-2 in the Aedes aegypti cultured Aag-2 cells has resulted in an increase in the level of incorporation of [[super 3]H] cholesterol.

Neutron diffraction is used for showing cholesterol' s orientational preference in different lipid bilayers. The results have provided credibility to DMPCEs aversion for polyunsaturated fatty acids (PUFAs), which has supported the notion that domain formation is primarily driven by lipids.

Cholesteric liquid crystals doped with reactive chiral compounds are used for describing a new approach to optical monitors for gases. The method is based on cholesteric pitch length changes caused by a change in helical twisting power and it is used for monitoring carbon dioxide via reversible carbamate formation and for oxygen using the irreversible oxidation of a chiral dithiol to a disulfide.

Site-specific fluorescence labeling with pyrene maleimide is employed to gain insight into the structure and conformation of the C-terminal domain (CT) of apolipoprotein E (apoE), which is a vital protein involved in cholesterol transport in the plasma and brain. The results indicated alternative use of pyrene fluorophores to obtain conformation information of proteins at physiologically relevant concentrations.

Free radical chain oxidation of highly oxidizable 7-dehydrocholesterol (7-DHC), initiated by 2,2'-azobis(4-methoxy-2,4-dimethylvaleronitrile), is performed in benzene and oxysterols derived from 7-DHC are isolated and characterized by NMR spectroscopy and mass spectroscopy. The studies have shown that the high reactivity of 7-DHC and the oxyterols generated from its peroxidation have played major roles in the pathogenesis of Smith-Lemli-Opitz syndrome, X-linked dominant chondrodysplasia punctata, and cerebrotendinous xanthomatosis, all of these being metabolic disorders characterized by an elevated level of 7-DHC.

Experimental studies were conducted to understand the interaction in apolipoprotein E, a key ligand for cholesterol homeostasis with ligand binding repeats in the LDL receptor family, LDLR, LRP, and VLDLR. Binding experiments with LA3-5 of LDLR and CR16-18 revealed that a conserved W25/D30 pair appears to be critical for high-affinity binding to ApoE(130-149) and that LA5 recognized a distinct epitope on ApoE that might only exist in the lipid-bound form.

The studies related to the electrical tuning of negative dielectric anisotropy (-[Delta][epsi]) cholesteric liquid crystals (CLCs) under the influence of ac and dc electric fields are presented. The generated CLC cells which are able to both red and blue tune might find potential applications in tunable optical filters, optical pressure/stress sensors, and tunable laser technologies.

The article studies the spatial heterogeneity of membrane lipids in context of cholesterol and phospholipid acyl-chain-dependent domain formation. Results highlight the important role of subphase factors and lipid head-group specificity in the formation and stability of cholesterol-dependent domains in cellular plasma membranes.

Syntaxin-1A, a part of the SNARE complex was reconstituted into lipid model membranes to show that syntaxin cluster formation depends on cholesterol in a lipid system that lacks sphingomyelin and hence does not form liquid-ordered phases that are commonly believed to represent lipid rafts in cell membranes. The cholesterol-induced clustering of syntaxin is found to be reversed by as little as 1-5 mol % of the regulatory lipid phosphatidylinositol 4,5-bisphosphate (PI-4,5-[P.sub.2]), and PI-4,5-[P.sub.2] is bound electrostatically to syntaxin mediated by the highly positively charged juxtamembrane domain of syntaxin.

Molecular dynamics simulations of the oxysterols are used in 1-palmitoyl 2-oleoyl phosphatidylcholine (POPC) bilayers to explain the structural origins for the differing effects of cholesterol and 25-hydroxycholesterol on bilayer properties. The studies have shown that direct membrane perturbation by side-chain oxysterols is vital and that these membrane perturbations have played a role in the oxysterol regulation of cholesterol homeostasis.

A series of experiments are performed that have shown that cholesterol lies flat in the midplane of 20:4-20:4PC (where PC is phoaphatidylcholine) bilayers. The diffraction measurements have shown that the tail of cholesterol resides at the center of the bilayer in both mono- and polyunsaturated PC lipids.

ent-Cholesterol is synthesized from commercially available (S)-citronellol. This synthesis has made ent-cholesterol more readily available for using as a probe of the function and metabolism of cholesterol.

The solution-state NMR method is used for studying the locational and orientational structure of cholesterol molecules and the cholesterol effects on the stiffness of the bilayer membrane in dimyristoylphosphatidylcholine (DMPC). The dynamic slowdown at high cholesterol concentrations is shown on the basis of the correlation times for nuclear Overhauser effect (NOE) as well as the broadening of the proton linewidths.

A study was conducted to explore the physical properties of bilayers of oxysterol (7-ketocholesterol), composed of the major lipid component of the cytoplasmic leaflet of the plasma membrane. The results provided insights into toxic effects of 7-ketocholesterol, which plays a significant role in antherosclerosis.

All-atom molecular dynamic simulation studies of a ternary mixture of 1-palmitoyl-2-oleoyl phosphatidylcholine (POPC), 1-palmitoyl-2-oleoyl phosphatidic acid (POPA), and cholesterol (CHOL) is presented. The results could provide insight into ternary mixture that could be useful for modulation of nicotinic acetylcholine receptor (nAChR) functions.

Time-of-flight secondary ion mass spectrometry (TOF-SMIS) is used for observing the label-free lipid localization determined by acyl chain saturation and its effect on cholesterol (CH) domain formation. The results have shown that the high saturation level of sphingomyelin (SM) acyl chains in the cellular membrane is an important driving force for SM colocalization with CH in lipid rafts.

Several molecular dynamics simulations of the bilayers containing mixtures of sphingomyelin and phosphatidylcholine with cholesterol were conducted. These systems are found to show various regions of liquid-liquid coexistence in them.

The aggregate formation among cholesterol molecules is revealed by [sup.1.H] and [sup.2.H] NMR solution-state self-diffusion and 1dimensional and 2 dimensional measurements. Cholesterol forms aggregates in the organic solvents that mimic the membrane bilayer hydrophobic core as chloroform and cyclohexane but it does not in 1-octanol.

Photoactivatable analogues 4-6 of cholesterol, having their cross-linking site in the ring D sterol region, are synthesized starting from bromotetralone through enantioselective Robinson annulation to enone 13 and Suzuki carbonylative coupling to the appropriate phenylboronic acid. Each of 4-6 is shown to substitute successfully for photoactivatable analogues 4-6 of cholesterol in an assay of apo A-I-induced cellular cholesterol efflux, indicating that these analogues equilibrated with photoactivatable analogues 4-6 of cholesterol in all major cellular pools.

The degree of homophospholipid association in bilayers containing AA, AB, and BB in the presence of a series of natural sterols whose hydrophobicity, shape, and ability to migrate within the hydrocarbon core of the bilayers has been varied, is examined. Nearest-neighbor recognition (NNR) showed, that cholesterol induces homophospholipid association in fluid bilayers made from exchangeable dimers AA, AB, and BB.

A study to identify and characterize the effects of various sterols including cholesterol, ergosterol by using fluorescence depolarization techniques is presented. The TMA-DPA a amphiphilic probe molecule detects the interaction between the rigid ring system of the sterols with the upper acyl chain region of the phospholipids.