生物金属与胆固醇相互作用的经验势函数计算

流行病学调查和医学实验均证实，以胆固醇在动脉血管壁沉着、形成病灶及纤维增生使管壁变硬为特征的动脉粥样硬化（AS），与血中某些金属元素的水平密切相关＊．一些临床医学观测报道了冠心病患者血中金属元素铜、锌、铬、钢等的水平与胆固醇含量变化的关系［2－6］，以期通过改善人体内微量元素的失调来抑制AS的发生和发展．AS患者血中生物金属铜、锌、铬、锅水平与胆固醇含量有关，可能意味着两者存在某种相互作用制约关系．本文通过金属一胆固醇间、胆固醇分子间、受金属离子影响的胆固醇分子间的各种模型构造，选用恰当的经验势函数…     

Steady-state oxidation of cholesterol catalyzed by cholesterol oxidase in lipid bilayer membranes on platinum electrodes

Cholesterol oxidase is immobilized in electrode-supported lipid bilayer membranes. Platinum electrodes are initially modified with a self-assembled monolayer of thiolipid. A vesicle fusion method is used to deposit an outer leaflet of phospholipids onto the thiolipid monolayer forming a thiolipid/lipid bilayer membrane on the electrode surface. Cholesterol oxidase spontaneously inserts into the electrode-supported lipid bilayer membrane from solution and is consequently immobilized to the electrode surface. Cholesterol partitions into the membrane from buffer solutions containing cyclodextrin. Cholesterol oxidase catalyzes the oxidation of cholesterol by molecular oxygen, forming hydrogen peroxide as a product. Amperometric detection of hydrogen peroxide for continuous solution flow experiments are presented, where flow was alternated between cholesterol solution and buffer containing no cholesterol. Steady-state anodic currents were observed during exposures of cholesterol solutions ranging in concentration from 10 to 1000 μM. These data are consistent with the Michaelis-Menten kinetic model for oxidation of cholesterol as catalyzed by cholesterol oxidase immobilized in the lipid bilayer membrane. The cholesterol detection limit is below 1 μM for cholesterol solution prepared in buffered cyclodextrin. The response of the electrodes to low density lipoprotein solutions is increased upon addition of cyclodextrin. Evidence for adsorption of low density lipoprotein to the electrode surface is presented.     

Oxidase/peroxidase bilayer-modified electrodes as sensors for lactate,pyruvate, cholesterol and uric acid

Enzyme heterobilayer-modified electrodes were fabricated by successively covalently binding to the surface of a tin(IV) oxide plate horseradish peroxidase (HRP), then an oxidase (lactate, pyruvate or cholesterol oxidase or uricase), which liberates hydrogen peroxide by reaction with the respective substrate. The cooperative action of oxidase-HRP leads to an efficient amperometric sensor system with the minimum amount of enzyme immobilized on an electrode.     

含胆汁酸和胆固醇的双亲性聚合物的研究进展

胆固醇和胆汁酸是广泛存在于自然界中的天然物质 ,生物相容性好 ,被广泛地用于高分子的疏水性改性 ,得到的双亲性聚合物 ,在水相中可以自组装或自聚集成纳米粒子。本文综述了含胆固醇或胆汁酸的双亲性聚合物的最新研究进展以及它们在药物载体系统中的应用。     

Effect of cholesterol or phospholipid incorporation on the chemical stability of the muramyldpeptide derivative B30-MDP in mixed vesicles

Application of the muramyldipeptide derivative B30-MDP to liposomal vaccines will aid in the development of improved high immunogenicity vaccines. To give full play to the effectiveness of B30-MDP as a liposomal vaccine, it is important to evaluate the effect of cholesterol, dimyristoylphosphatidylcholine (DMPC) or distearoylphosphatidylcholine (DSPC) incorporation on the chemical stability of B30-MDP and physicochemical properties of B30-MDP/lipid mixed vesicles from the view point of pharmaceutics.The observed degradation rate constants of B30-MDP by hydrolysis in B30-MDP/cholesterol mixed vesicles were increased with increasing concentration of cholesterol, however, those in B30-MDP/DMPC and B30-MDP/DSPC mixed vesicles were unchanged with increasing concentration of DMPC and DSPC. The degradation behavior of B30-MDP was then compared with physicochemical properties of B30-MDP/lipid mixed vesicles, such as membrane fluidity and particle size. It was apparent that the degradation of B30-MDP in B30-MDP/cholesterol mixed vesicles was influenced by the particle size, but not by the fluidity of the membranes. In the case of B30-MDP/phospholipid mixed vesicles, MDP/phospholipid mixed vesicles, the degradation of B30-MDP was not influenced by either the membranes' fluidity or the particle size of the mixed vesicles.It is considered that the degradation of B30-MDP in the mixed vesicles is dependent on the membrane state, and the addition of cholesterol to B30-MDP vesicle inhibits the mutual interaction of MDP regions, whereas the addition of phospholipids hardly influences the mutual interaction of MDP regions, possibly owing to phase separation between B30-MDP and phospholipids.     

A Selective Cholesterol Biosensor Based on Composite Film Modified Electrode for Amperometric Detection

An amperometric cholesterol biosensor based on immobilization of cholesterol oxidase in a Prussian blue (PB)/polypyrrole (PPy) composite film on the surface of a glassy carbon electrode was fabricated. Hydrogen peroxide produced by the enzymatic reaction was catalytically reduced on the PB film electrode at 0 V with a sensitivity of 39 μA (mol/L)^?1. Cholesterol in the concentration range of 10^?5 ? 10^?4 mol/L was determined with a detection limit of 6 × 10^?7 mol/L by amperometric method. Normal coexisting compounds in the bio‐samples such as ascorbic acid and uric acid do not interfere with the determination. The excellent properties of the sensor in sensitivity and selectivity are attributed to the PB/PPy layer modified on the sensor.     

High performance liquid chromatographic separation of cholesterol oxidation products

Summary A fast, sensitive, high performance liquid chromatographic method for the simultaneous determination of cholesterol hydroperoxides and other major oxysterols, using two different detection systems (ultraviolet at 210 nm and light scattering), is here described. The hydroperoxy derivatives were obtained by cholesterol photoxidation, isolated by thin layer chromatography and joined with a standard mixture of 10 oxysterols (epoxy, hydroxy and keto derivatives). Aliquots were directly injected onto a 5-μm particle size, 25×0.46 cm i.d. Spherisorb S5 CN normal phase column, usingn-hexane/anhydrous ethanol (97:3, v/v) as mobile phase and a flow rate of 0.8 mL min⁻¹. This method allowed, in a single isocratic analysis, the separation and quantification of the primary and secondary cholesterol oxidation products in 30 minutes. The light scattering detector was particularly useful for the determination of nonderivatized 5,6-epoxides and cholestane-3β,5α,6β-triol. The sensitivity of both detectors was very similar for most of the oxysterols, except for the 5,6-epoxides and the 7-ketocholesterol. The method suitability for the determination of cholesterol oxidation products in food matrices was successfully tested on a saponified lipid extract from egg yolk powder.     

Synthesis of two glycolipid antigens of the causative agent of Lyme disease

As a prelude to development of a human vaccine against Lyme disease, the first chemical synthesis of glycolipid antigens of Borrelia burkholderi is reported. First, cholesteryl β-d-galactopyranoside was synthesized and was converted to partially protected congeners having the HO-6 group of the galactose moiety unprotected. Treatment of these intermediates with palmitic and oleic acid, respectively, under dehydrative conditions followed by removal of the protecting groups afforded cholesteryl 6-O-palmitoyl/oleoyl-β-d-galactopyranosides that were identical to the glycolipids isolated from B. burkholderi.     

Carotenoid incorporation into microsomes: yields, stability and membrane dynamics

The carotenoids beta-carotene (BC), lycopene (LYC), lutein (LUT), zeaxanthin (ZEA), canthaxanthin (CTX) and astaxanthin (ASTA) have been incorporated into pig liver microsomes. Effective incorporation concentrations in the range of about 1-6 nmol/mg microsomal protein were obtained. A stability test at room temperature revealed that after 3 h BC and LYC had decayed totally whereas, gradually, CTX (46%), LUT (21%), ASTA (17%) and ZEA (5%) decayed. Biophysical parameters of the microsomal membrane were changed hardly by the incorporation of carotenoids. A small rigidification may occur. Membrane anisotropy seems to offer only a small tolerance for incorporation of carotenoids and seems to limit the achievable incorporation concentrations of the carotenoids into microsomes. Microsomes instead of liposomes should be preferred as a membrane model to study mutual effects of carotenoids and membrane dynamics.     

A new strategy based on cholesterol-functionalized iron oxide magnetic nanoparticles for determination of polycyclic aromatic hydrocarbons by high-performance liquid chromatography with cholesterol column

This study reported for the first time the use of cholesterol-functionalized magnetic nanoparticles (Fe₃O₄@SiO₂@Chol) for the determination of polycyclic aromatic hydrocarbons (PAHs) in traditional Chinese medicine samples (TCMs) by high performance liquid chromatography (HPLC) coupled with fluorescence detection. The method was efficient, environmentally friendly, and fast. The solvent consumption of the proposed column is only half of the conventional column but with higher efficiency. Influencing factors, including sorbent amount, desorption solvent, sample volume and extraction time, were investigated in detail. Under the optimum conditions, good linearity (R² > 0.991) was obtained over the range of 5–400 ng g⁻¹, with limits of detection (LOD) 0.75, 0.50, 1.0, 0.56, 0.60, 0.84 and 0.80 ng g⁻¹ for anthracene, fluoranthene, pyrene, chrysene, benzo[a]anthracene, benzo(b)fluoranthene and benzo(k)fluoranthene, respectively.