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PubMed1996

Dynamics of the fetal adrenal, cholesterol, and apolipoprotein B responses to antenatal betamethasone therapy.

OBJECTIVE: Prior studies suggest that fetal plasma cholesterol is regulated in part by the rate of uptake and utilization of low-density lipoprotein cholesterol by the fetal adrenals for use in steroid biosynthesis. Direct evidence for this phenomenon and the kinetics of this process is, however, virtually impossible to obtain in a controlled experiment in the developing human. In the current study we sought to take advantage of the anticipated transient inhibition of the hypothalamic-pituitary-adrenal axis that occurs after antenatal therapy with glucocorticosteroids, to evaluate the temporal relationship between fetal adrenal steroids and plasma lipoprotein cholesterol levels in umbilical cord blood at delivery. STUDY DESIGN: Umbilical cord serum was obtained at delivery from 136 infants (30.5 +/- 2.7 weeks' gestation) who previously had been treated in utero with betamethasone, 12 mg per 12 or 24 hours for one or two doses and from 308 preterm infants (30.5 +/- 2.1 weeks) who had not been exposed to such therapy. We quantified the concentrations of dehydroepiandrosterone sulfate and cortisol as representative fetal adrenal steroids and also measured the total cholesterol and apolipoprotein B; the relationship between the steroids and lipids as a function of the interval between initial treatment and delivery was analyzed. RESULTS: Umbilical cord levels of dehydroepiandrosterone sulfate and cortisol were significantly reduced within the first 24 hours after initial treatment and remained significantly lower than in control infants through 4 days after initial treatment. In contrast, serum levels of cholesterol were significantly increased 3 to 4 days after treatment but fell on day 5. Serum levels of apolipoprotein B generally followed the same pattern as cholesterol. Cholesterol levels also were higher than normal in infants delivered >1 week after initial betamethasone treatment. CONCLUSIONS: The results of this study are consistent with the view that the plasma cholesterol pool in the fetus is regulated, at least in part, by the rate of uptake of low-density lipoprotein cholesterol and utilization by the fetal adrenals as substrate for steroidogenesis. Betamethasone also may influence cholesterol and lipoprotein synthesis in the fetus.

Apolipoproteins B↗
PubMed2002

Rapid transbilayer movement of spin-labeled steroids in human erythrocytes and in liposomes.

The transbilayer movement and distribution of spin-labeled analogs of the steroids androstane (SLA) and cholestane (SLC) were investigated in the human erythrocyte and in liposomes. Membranes were labeled with SLA or SLC, and the analogs in the outer leaflet were selectively reduced at 4C using 6-O-phenylascorbic acid. As shown previously, 6-O-phenylascorbic acid reduces rapidly nitroxides exposed on the outer leaflet, but its permeation of membranes is comparatively slow and thus does not interfere with the assay. From the reduction kinetics, we infer that transbilayer movement of SLA in erythrocytes is rapid at 4C with a half-time of approximately 4.3 min and that the probe distributes almost symmetrically between both halves of the plasma membrane. We have no indication that a protein-mediated transport is involved in the rapid transbilayer movement of SLA because 1) pretreatment of erythrocytes with N-ethyl maleimide affected neither flip-flop nor transbilayer distribution of SLA and 2) flip-flop of SLA was also rapid in pure lipid membranes. The transbilayer dynamics of SLC in erythrocyte membranes could not be resolved by our assay. Thus, the rate of SLC flip-flop must be on the order of, or even faster than, that of probe reduction rate on the exoplasmic leaflet (half-time approximately 0.5 min). The results are discussed with regard to the transbilayer dynamics of cholesterol.

Androstanes↗
PubMed1990

Microimmiscibility and three-dimensional dynamic structures of phosphatidylcholine-cholesterol membranes: translational diffusion of a copper complex in the membrane.

Saturated and unsaturated phosphatidylcholine (PC)-cholesterol membranes have been studied, with a special attention paid to fluid-phase immiscibility in cis-unsaturated phosphatidylcholine (PC)-cholesterol membranes as previously proposed and to the three-dimensional structure of the membrane. The investigation was carried out with dual probes: a membrane-soluble, square-planar copper complex, (3-ethoxy-2-oxobutyraldehyde bis(N4,N4-dimethylthiosemicarbazonato]copper(II) (CuKTSM2), and one of several nitroxide radical lipid-type spin-labels. Bimolecular collision rates between metal ion and spin-label were determined by measuring the nitroxide spin-lattice relaxation times (T1's) in the presence and absence of CuKTSM2 by use of saturation-recovery ESR techniques, and from these measured rates, translational diffusion coefficients of CuKTSM2 were estimated. Profiles of the collision rate across the membrane bilayer were obtained with Tempocholine phosphatidic acid ester, 5-doxylstearic acid, 16-doxylstearic acid, and cholesterol-type spin-labels as a function of cholesterol mole fraction, length and unsaturation of acyl chains, and temperature. In the liquid-crystalline phase of saturated PC membranes, incorporation of cholesterol decreases the collision rate at all depths in the membrane, and the effect of cholesterol is smallest in the middle of the bilayer. In trans-unsaturated PC membranes, a cholesterol-induced decrease of the collision rate was also observed, except in the head-group regions. In cis-unsaturated PC membranes, virtually no effect of cholesterol was observed on the collision rate, either with phospholipid-type spin-labels or with cholesterol-type spin-labels. This result is in clear contrast with our previous observation, in which the effect of cholesterol in cis-unsaturated PC membranes is small on the alkyl-chain motion of phospholipid-type spin-labels but large on the wobbling rotational diffusion of cholesterol-type spin-labels [Pasenkiewicz-Gierula, M., Subczynski, W. K., & Kusumi, A. (1990) Biochemistry 29, 4059-4069]. A model is proposed to explain these results in which the fluid-phase immiscibility is prevalent in cis-unsaturated PC-cholesterol membranes, but where cholesterol-rich (cholesterol oligomeric) domains are small (several lipids) and/or of short lifetime (10(-9) s to less than 10(-7) s). It is suggested that this microimmiscibility arises from the structural nonconformability between the rigid cholesterol ring structure and the rigid bend at the cis double bonds in PC alkyl chains.(ABSTRACT TRUNCATED AT 400 WORDS)

Androstanes↗
PubMed2002

The differential apoA-I enrichment of prebeta1 and alphaHDL is detectable by gel filtration separation.

The aim of the study was to assess the isolation of HDL by fast protein liquid chromatography (FPLC) to perform kinetics studies of apolipoprotein (apo)A-I-HDL labelled with a stable isotope. Comparison between FPLC and ultracentrifugation has been made. ApoA-I-HDL kinetics were studied by infusion of [5.5.5-(2)H(3)]leucine for 14 h in five subjects. Using FPLC, prebeta(1) HDL and alphaHDL (HDL(2) and HDL(3)) were separated from 200 microl of plasma samples. Total HDL was isolated by sequential ultracentrifugation (HDL-UC). The tracer-to-tracee ratio was higher in prebeta(1) HDL than in total HDL-UC. The higher leucine enrichment found in total HDL-UC compared to alphaHDL suggested the existence of a mixture of apoA-I-HDL sub-classes. From this difference in enrichments, the turnover rate of total HDL-UC, usually assumed to be alphaHDL, was probably overestimated in previous studies. To our knowledge, this study is the first report which provides a convenient tool to distinguish enrichments of apoA-I in prebeta(1) HDL and alphaHDL from total HDL previously used for kinetic measurements. This original and new method should help to understand the kinetics of HDL in humans and the reverse cholesterol transport dynamics.

Apolipoprotein A-I↗
PubMed2006

[Distribution of systemic vascular resistance disorders and its related factors in Hebei province].

OBJECTIVE: To analyze the distribution features of systemic vascular resistance (SVR) disorder in healthy subjects in Hebei province. METHODS: SVR and systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP), pulse pressure (PP), heart rate (HR), cardiac output (CO), cardiac index (CI), stroke volume (SV), stroke index (SI), left ventricular ejection time (LVET), left cardiac work (LCW) and cardiovascular function were determined with Bioz. com Cardio Dynamics. Total cholesterol (TC), triglyceride (TG) and influencing factor were tested by automated hematology analyzer in 999 healthy subjects living in Hebei province. RESULTS: SVR disorder gradually increased with the ageing in healthy subjects and the prevalences of SVR disorders was higher among females than among males (P < 0.001). SVR was positively correlated with SBP, DBP, MAP, PP, LVET, body mass index (BMI), TC, and TG, and was inversely associated with HR, CO, CI, SV, SI, LCW, and arterial compliance (AC). CO and MAP were independent influencing factors with SVR. CONCLUSION: SVR disorder is associated with age, sex, and blood pressure in populations in Hebei province and may be a marker of vascular injury.

Adolescent↗
PubMedDate not supplied

[Lipid peroxidation processes and the dynamics of shifts in the cholesterol level in plasma and erythrocytes under the influence of low-frequency acoustic oscillations].

Distinct alterations in lipid peroxidation, in content of alpha-tocopherol and cholesterol fractions were observed in rat blood plasma and erythrocyte membranes after long-term low-frequency acoustic oscillations (105 decibels, diurnally, within 3 months). Under these conditions activities of superoxide dismutase and erythrocyte Na+, K+-ATPase were also altered. The rate and direction of the enzymatic activity alterations correlated with the duration of the acoustic oscillation exposure and the patterns studied. Enrichment of blood plasma and erythrocyte membranes with alpha-tocopherol within 2-4 weeks of the acoustic oscillation is considered as an important phenomenon.

Animals↗
PubMedDate not supplied

[The effect of protamine on cholesterol, triglycerides and blood serum proteins during the dynamics of experimental hypercholesterolemia].

Content of total proteins, cholesterol, and triglycerides was studied in the blood serum and lipoprotein fractions of rabbits after administration of protamine within 1, 3 and 7 months of hypercholesterolemia development. The protamine effect was accompanied by "equalization" of cholesterol and triglyceride concentrations, as compared with their alteration in hypercholesterolemia, by stabilization of their content in various periods of the disease, but at the higher level than that of intact animals. The phenomenon observed occurred mainly in lipid components of LDL and VLDL subfractions. Analysis of alterations in the content of cholesterol and proteins in HDL and apo B-containing fractions showed that administration of protamine during long-term hypercholesterolemia led to development of antiatherogenic symptoms. Proatherogenic alterations in lipoprotein composition, developed during hypercholesterolemia, appear to be inhibited by protamine.

Animals↗
PubMed1977

Dynamic mechanical properties of atherosclerotic aorta. A correlation between the cholesterol ester content and the viscoelastic properties of atherosclerotic aorta.

The effect of cholesterol and cholesterol ester content of aortas on the dynamic mechanical properties of these tissues was studied in rabbits during development of atherosclerosis. The disease was induced by feeding a 1.5% cholesterol diet for six weeks. At two week intervals, an equal number of control and experimental animals were sacrificed and their aortas were collected. After grading the aortas for lesions, one-half of each aorta was used for the determination of cholesterol and cholesterol ester content while the other half was used for the determination of viscoelastic properties. The viscoelastic properties were determined in both the longitudinal and the tangentail direction of the aortas. The results showed that cholesterol feeding had no effect on the longitudinal dynamic Young's modulus of the aortas. On the other hand, the tangential dynamic Young's modulus of the aortas was found to be very much influenced by the cholesterol diet. After the first two weeks of cholesterol feeding, the tangential dynamic Young's modulus was found to be increased markedly with time. At the end of the 6-week period, the average value of the tangential Young's moduli was 4.0 X 10(6) dynes/cm2 in the cholesterol-fed group while in the control group it remained 2.7 X 10(6) dynes/cm2. This increase in the tangential Young's moduli showed a remarkable correlation with the increase in the cholesterol ester content of the aortas. The cholesterol est content of aortas, like the tangential Young's modulus, remained unaffected during the first two weeks of cholesterol feeding. But after the first two weeks, a rapid increase in the cholesterol ester content was observed which coincided with an almost identical increase in the tangential Young's modulus values. It is concluded that during the early stages of atherosclerosis, the cholesterol ester content of aortas exerts a significant influence on the tangential dynamic Young's modulus of aortas. The serum levels of cholesterol and cholesterol ester, although increased steadily with the cholesterol feeding, did not show any direct correlation with the viscoelastic properties of the aortas.

Animals↗
PubMed2004

Combined Monte Carlo and molecular dynamics simulation of hydrated 18:0 sphingomyelin-cholesterol lipid bilayers.

We have carried out atomic level molecular dynamics and Monte Carlo simulations of hydrated 18:0 sphingomyelin (SM)-cholesterol (CHOL) bilayers at temperatures of 20 and 50 degrees C. The simulated systems each contained 266 SM, 122 CHOL, and 11861 water molecules. Each simulation was run for 10 ns under semi-isotropic pressure boundary conditions. The particle-mesh Ewald method was used for long-range electrostatic interactions. Properties of the systems were calculated over the final 3 ns. We compare the properties of 20 and 50 degrees C bilayer systems with each other, with experimental data, and with experimental and simulated properties of pure SM bilayers and dipalmitoyl phospatidyl choline (DPPC)-CHOL bilayers. The simulations reveal an overall similarity of both systems, despite the 30 degrees C temperature difference which brackets the pure SM main phase transition. The area per molecule, lipid chain order parameter profiles, atom distributions, and electron density profiles are all very similar for the two simulated systems. Consistent with simulations from our lab and others, we find strong intramolecular hydrogen bonding in SM molecules between the phosphate ester oxygen and the hydroxyl hydrogen atoms. We also find that cholesterol hydroxyl groups tend to form hydrogen bonds primarily with SM carbonyl, methyl, and amide moieties and to a lesser extent methyl and hydroxyl oxygens.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1999

Role of cholesterol ester mass in regulation of secretion of ApoB100 lipoprotein particles by hamster hepatocytes and effects of statins on that relationship.

Our understanding of the factors that regulate the secretion of apoB100 lipoproteins remains incomplete with considerable debate as to the role, if any, for cholesterol ester in this process. This study examines this issue in primary cultures of hamster hepatocytes, a species in which both cholesterol and apoB100 metabolism are very similar to man. Addition of oleate to medium increased the mass of triglyceride and cholesterol ester within the hepatocyte and also increased the secretion of triglycerides, cholesterol ester, and apoB100 into the medium. Next, the responses of hamster hepatocytes to addition of either an HMG-CoA reductase inhibitor (lovastatin) or an acyl-CoA cholesterol acyltransferase inhibitor (58-035) to the medium, with or without added oleate, were determined. Effects of either agent were only evident in the oleate-supplemented medium in which cholesterol ester mass had been increased above basal. If oleate was not added to the medium, neither agent reduced apoB100 secretion; equally important, over the 24-hour incubation, neither agent, at the concentration used, produced any detectable change in intracellular cholesterol ester mass. However, in contrast to the estimates of mass, which were unchanged, under the same conditions radioisotopic estimates of cholesterol ester synthesis were markedly reduced. Any conclusion as to the relation of cholesterol ester mass to apoB100 secretion would therefore depend on which of the 2 methods was used. Overall, the data indicate a close correlation between the mass of cholesterol ester within the hepatocyte and apoB100 secretion from it and they go far to explain previous apparently contradictory data as to this relation. More importantly, though, taken with other available data, they indicate that the primary response of the liver to increased delivery of lipid is increased secretion rather than decreased uptake. These results point, therefore, to a hierarchy of hepatic responses to increased flux of fatty acids and increased synthesis of cholesterol that in turn suggests a more dynamic model of cholesterol homeostasis in the liver than has been appreciated in the past.

Animals↗
PubMed2001

Combined Monte Carlo and molecular dynamics simulation of hydrated lipid-cholesterol lipid bilayers at low cholesterol concentration.

We have applied a hybrid equilibration and sampling procedure for the atomic level simulation of a hydrated lipid bilayer to systems consisting of dipalmitoyl phosphatidylcholine (DPPC) and cholesterol, and palmitoyl-oleyl phosphatidylcholine (POPC) at low (approximately 6%) cholesterol concentration. The procedure is applied to bilayers of 94 molecules of DPPC, 6 molecules of cholesterol, and 3205 water molecules, and to bilayers of 120 molecules of POPC, 8 molecules of cholesterol, and 4268 water molecules, at a temperature of 325 K. After equilibration, three separate 400-ps continuous molecular dynamics runs, separated by 10,000 configurational bias Monte Carlo steps, were carried out for each system. Properties of the systems were calculated and averaged over the three separate runs. Results of the simulations are presented and compared with experimental data and with other recent simulations of DPPC and cholesterol, and of pure DPPC, and pure POPC. Certain properties of the bilayers are indistinguishable from cholesterol-free bilayers, including lateral diffusion and electron density. Other properties, most notably the order parameter profile, show the effect of cholesterol even at low concentrations.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed2006

Comparative molecular dynamics study of lipid membranes containing cholesterol and ergosterol.

Sterol molecules are essential for maintaining the proper structure and function of eukaryotic cell membranes. The influence of cholesterol (the principal sterol of higher animals) on the lipid bilayer properties was extensively studied by both experimental and simulation methods. In contrast, the effect of ergosterol (the principal fungal sterol) on the membrane structure and dynamics is much less recognized. This work presents the results of comparative molecular dynamics simulation of the hydrated dimyristoylphosphatidylcholine bilayer containing approximately 25 mol % of cholesterol or ergosterol. A detailed analysis of the molecular properties (e.g., bilayer thickness, lipid order, diffusion, intermolecular interactions, etc.) of both sterol-induced liquid-ordered membrane phases is presented. Presence of sterols in the membrane significantly changes its property, especially fluidity and molecular packing. Moreover, in accordance with the experiments, our calculations show that, compared to cholesterol, ergosterol has higher ordering effect on the phospholipid acyl chains. This different influence on the properties of the lipid bilayer stems from differences in conformational freedom of sterol side chains. Additionally, obtained models of lipid membranes containing human and fungal sterols, constituting the result of our work, can be also utilized in other chemotherapeutic studies on interaction of selected ligands (e.g., antifungal compounds) with membranes.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1992

Deuteron nuclear magnetic resonance study of the dynamic organization of phospholipid/cholesterol bilayer membranes: molecular properties and viscoelastic behavior.

The influence of cholesterol on the dynamic organization of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) bilayers was studied by deuteron nuclear magnetic resonance (2H NMR) using unoriented and macroscopically aligned samples. Analysis of the various temperature- and orientation-dependent experiments were performed using a comprehensive NMR model based on the stochastic Liouville equation. Computer simulations of the relaxation data obtained from phospholipids deuterated at the 6-, 13- and 14-position of the sn-2 chain and cholesterol labeled at the 3 alpha-position of the rigid steroid ring system allowed the unambiguous assignment of the various motional modes and types of molecular order present in the system. Above the phospholipid gel-to-liquid-crystalline phase transition, TM, 40 mol % cholesterol was found to significantly increase the orientational and conformational order of the phospholipid with substantially increased trans populations even at the terminal sn-2 acyl chain segments. Lowering the temperature continuously increases both inter- and intramolecular ordering, yet indicates less ordered chains than found for the pure phospholipid in its paracrystalline gel phase. Trans-gauche isomerization rates on all phospholipid alkyl chain segments are slowed down by incorporated cholesterol to values characteristic of gel-state lipid. However, intermolecular dynamics remain fast on the NMR time scale up to 30 K below TM, with rotational correlation times tau R parallel for DMPC ranging from 10 to 100 ns and an activation energy of ER = 35 kJ/mol. Below 273 K a continuous noncooperative condensation of both phospholipid and cholesterol is observed in the mixed membranes, and at about 253 K only a motionally restricted component is left, exhibiting slow fluctuations with correlation times of tau R perpendicular greater than 1 microsecond. In the high-temperature region (T greater than TM), order director fluctuations are found to constitute the dominant transverse relaxation process. Analysis of these collective lipid motions provides the viscoelastic parameters of the membranes. The results (T = 318 K) show that cholesterol significantly reduces the density of the cooperative motions by increasing the average elastic constant of the membrane from K = 1 x 10(-11) N for the pure phospholipid bilayers to K = 3.5 x 10(-11) N for the mixed system.

Cholesterol↗
PubMed2001

Steroidogenic acute regulatory protein binds cholesterol and modulates mitochondrial membrane sterol domain dynamics.

The steroidogenic acute regulatory protein (StAR) mediates the rate-limiting step of steroidogenesis, delivery of cholesterol to the inner mitochondrial membrane. However, the mechanism whereby cholesterol translocation is accomplished has not been resolved. Recombinant StAR proteins lacking the first N-terminal 62 amino acids comprising the mitochondrial-targeting sequence were used to determine if StAR binds cholesterol and alters mitochondrial membrane cholesterol domains to enhance sterol transfer. First, a fluorescent NBD-cholesterol binding assay revealed 2 sterol binding sites (K(d) values near 32 nm), whereas the inactive A218V N-62 StAR mutant had only a single binding site with 8-fold lower affinity. Second, NBD-cholesterol spectral shifts and fluorescence resonance energy transfer from StAR Trp residues to NBD-cholesterol showed (i) close molecular interaction between these molecules (R(2/3) = 33 A) and (ii) sensitized NBD-cholesterol emission from only one of the two sterol binding sites. Third, circular dichroism showed that cholesterol binding induced a change in StAR secondary structure. Fourth, a fluorescent sterol transfer assay that did not require separation of donor and acceptor mitochondrial membranes demonstrated that StAR enhanced mitochondrial sterol transfer as much as 100-fold and induced/increased the formation of rapidly transferable cholesterol domains in isolated mitochondrial membranes. StAR was 67-fold more effective in transferring cholesterol from mitochondria of steroidogenic MA-10 cells than from human fibroblast mitochondria. In contrast, sterol carrier protein-2 (SCP-2) was only 2.2-fold more effective in mediating sterol transfer from steroidogenic cell mitochondria. Taken together these data showed that StAR is a cholesterol-binding protein, preferentially enhances sterol transfer from steroidogenic cell mitochondria, and interacts with mitochondrial membranes to alter their sterol domain structure and dynamics.

4-Chloro-7-nitrobenzofurazan↗
PubMed1989

The fidelity of response by 1-[4-(trimethylammonio)phenyl]-6-phenyl-1,3,5-hexatriene in time-resolved fluorescence anisotropy measurements on lipid vesicles. Effects of unsaturation, headgroup and cholesterol on orientational order and reorientational dynamics.

Time-resolved fluorescence anisotropy measurements on 1-[4-(tri-methylammonio)phenyl]-6-phenyl-1,3,5-hexatriene (TMA-DPH) molecules in lipid vesicles of palmitoyloleoylphosphatidylcholine (POPC), PC extracted from egg yolk (EggPC), dioleoyl-PC (DOPC), dilinoleoyl-PC (DLPC), phosphatidylglycerol extracted from egg yolk (EggPG), dioleoyl-PG (DOPG), sulfoquinovosyldiacylglycerol (SQDG) and digalactosyl-DG (DGDG) with and without cholesterol are presented. The observed intensity decay curves are analyzed simultaneously in terms of the Brownian rotational diffusion model. The analysis thus yields the isotropic fluorescence decay, the initial anisotropy r (0), the order parameters mean value of P2 and mean value of P4 as well as the diffusion coefficient of the long molecular axis. It is shown that increasing unsaturation in the acyl chains of the PC lipids results in an increase in the rotational diffusion rates of the probes and a decrease in the order parameter mean value of P2. However, the value of mean value of P4 remains unchanged. The corresponding orientational distribution function of the probes is bimodal, with fractions lying preferentially parallel and perpendicular to the local vesicle surface. Surprisingly, the fraction of probe molecules lying with their long axes parallel to the bilayer surface increases with increasing unsaturation with a concomitant narrowing in the width of the distribution of the fraction lying perpendicular to it. As expected, cholesterol is found to increase the order parameters in all the systems and to suppress the tendency of the molecules to lie parallel to the bilayer surface. Furthermore, the rotational diffusion coefficients of the probes is found to increase in all the systems except for DLPC. Interestingly, the effects of unsaturation on the reorientational dynamics of TMA-DPH molecules in the vesicle systems are opposite to those found in the corresponding planar multibilayers (Deinum et al. 1988), whereas the same cholesterol effect is observed for the two systems. Nevertheless, the TMA-DPH molecules exhibit higher diffusion coefficients in the vesicle than in the planar multibilayer systems. In addition, a unimodal distribution of the probe molecules is found in the multibilayer systems. The differences between the two systems are ascribed to the differences in the radius of curvature and the hydration of the bilayers. Lastly we rationalize the bimodal distribution of the TMA-DPH molecules in the vesicles in terms of their observed partition between the lipid and aqueous phases.

Cholesterol↗
PubMed2004

Molecular-level organization of saturated and polyunsaturated fatty acids in a phosphatidylcholine bilayer containing cholesterol.

Cholesterol's preference for specific fatty acid chains is investigated at the atomic level in a 20 ns molecular dynamics computer simulation of a lipid bilayer membrane consisting of cholesterol and 1-stearoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine (SDPC) in a 1:3 ratio. These simulations reproduce experimental measurements suggesting that cholesterol prefers to be solvated by saturated acyl chains and has a low affinity for polyunsaturated fatty acids. Analyses of the simulation trajectory provide a detailed picture of both the transverse and lateral structures of the lipid bilayer membrane, along with a description of lipid and cholesterol dynamics at high temporal resolution. Comparison with a previous simulation of a pure phospholipid bilayer allows an atomic-level description of the changes in membrane structure and dynamics resulting from incorporation of cholesterol. The observed differential cholesterol interactions with saturated and polyunsaturated lipids provide a mechanism for the formation of laterally inhomogeneous membranes; thus, the simulation provides molecular-level insight into the formation of lipid rafts.

Cholesterol↗