The Jahn-Teller effect of the Cr(2+) ion in aqueous solution: Ab initio QM/MM molecular dynamics simulations

The hydration structure of Cr(2+) has been studied using molecular dynamics (MD) simulations including three-body corrections and combined ab initio quantum mechanical/molecular mechanical (QM/MM) MD simulations at the Hartree-Fock level. The structural properties are determined in terms of radial distribution functions, coordination numbers, and several angle distributions. The mean residence time was evaluated for describing ligand exchange processes in the second hydration shell. The Jahn-Teller distorted octahedral [Cr(H(2)O)(6)](2+) complex was pronounced in the QM/MM MD simulation. The first-shell distances of Cr(2+) are in the range of 1.9-2.8 A, which are slightly larger than those observed in the cases of Cu(2+) and Ti(3+). No first-shell water exchange occurred during the simulation time of 35 ps. Several water-exchange processes were observed in the second hydration shell with a mean residence time of 7.3 ps.     

Inhibition of acyl-coenzyme A:cholesterol acyltransferase stimulates cholesterol efflux from macrophages and stimulates farnesoid X receptor in hepatocytes

We investigated the mechanism of spontaneous cholesterol efflux induced by acyl-coenzyme A:cholesterol acyltransferase (ACAT) inhibition, and how an alteration of cholesterol metabolism in macrophages impacts on that in HepG2 cells. Oleic acid anilide (OAA), a known ACAT inhibitor reduced lipid storage substantially by promotion of cholesterol catabolism and repression of cholesteryl ester accumulation without further increase of cytotoxicity in acetylated low-density lipoprotein-loaded THP-1 macrophages. Analysis of expressed mRNA and protein revealed that cholesterol 7alpha-hydroxylase (CYP7A1), oxysterol 7alpha- hydroxylase (CYP7B1), and cholesterol 27-hydroxylase (CYP27) were highly induced by ACAT inhibition. The presence of a functional cytochrome P450 pathway was confirmed by quantification of the biliary cholesterol mass in cell monolayers and extracelluar medium. Notably, massively secreted biliary cholesterol from macrophages suppressed the expression of CYP7 proteins in a farnesoid X receptor (FXR)-dependent manner in HepG2 cells. The findings reported here provide new insight into mechanisms of spontaneous cholesterol efflux, and suggest that ACAT inhibition may stimulate cholesterol-catabolic (cytochrome P450) pathway in lesion-macrophages, in contrast, suppress it in hepatocyte via FXR induced by biliary cholesterol (BC).     

Hydrolysis of titanium sulphate compounds

The influence of TiOSO₄ and free sulphuric acid concentrations in the starting solution on the degree of titanyl sulphate conversion to hydrated titanium dioxide and post-hydrolytic sulphuric acid was studied. Titanyl sulphate solution, an intermediate product in the commercial preparation of titanium dioxide pigments by sulphate route, was used. It was found that the degree of hydrolysis markedly depends on the studied parameters. The lower was the content of TiOSO₄ in the starting solution, the higher conversion was achieved. The degree of hydrolysis at the final stage varied between 81 % (420 g TiOSO₄ dm⁻³, 216 g H₂SO₄ dm⁻³) and 92 % (300 g TiOSO₄ dm⁻³, 216 g H₂SO₄ dm⁻³). The same relation was obtained when changing the concentration of free H₂SO₄ in the starting solution. The degree of hydrolysis at the final stage varied between 49 % (261 g H₂SO₄ dm⁻³, 340 g TiOSO₄ dm⁻³) and 96 % (136 g H₂SO₄ dm⁻³, 340 g TiOSO₄ dm⁻³). The particle size of the obtained hydrated titanium dioxide (HTD) also depends on the initial solution composition. Presented at the 34th International Conference of the Slovak Society of Chemical Engineering, Tatranské Matliare, 21–25 May 2007.     

Sulfonate salts of the therapeutic agent dapsone: 4‐[(4‐aminophenyl)sulfonyl]anilinium benzenesulfonate monohydrate and 4‐[(4‐aminophenyl)sulfonyl]anilinium methanesulfonate monohydrate

Dapsone, formerly used to treat leprosy, now has wider therapeutic applications. As is the case for many therapeutic agents, low aqueous solubility and high toxicity are the main problems associated with its use. Derivatization of its amino groups has been widely explored but shows no significant therapeutic improvements. Cocrystals have been prepared to understand not only its structural properties, but also its solubility and dissolution rate. Few salts of dapsone have been described. The title salts, C₁₂H₁₃N₂O₂S⁺·C₆H₅O₃S⁻·H₂O and C₁₂H₁₃N₂O₂S⁺·CH₃SO₃⁻·H₂O, crystallize as hydrates and both compounds exhibit the same space group (monoclinic, P2₁/n). The asymmetric unit of each salt consists of a 4‐[(4‐aminophenyl)sulfonyl]anilinium monocation, the corresponding sulfonate anion and a water molecule. The cation, anion and water molecule form hydrogen‐bonded networks through N—H…O=S, N—H…O_water and O_water—H…O=S hydrogen bonds. For both salts, the water molecules interact with one sulfonate anion and two anilinium cations. The benzenesulfonate salt forms a two‐dimensional network, while the hydrogen bonding within the methanesulfonate salt results in a three‐dimensional network.     

Oxidative status of human low density lipoprotein isolated by anion-exchange high-performance liquid chromatography--assessment by total hydroxyoctadecadienoic acid, 7-hydroxycholesterol, and 8-iso-prostaglandin F(2alpha)

This study aims to measure the oxidative status of LDL from human plasma (n=26) as assessed by biomarkers for lipid peroxidation, total hydroxyoctadecadienoic acid (tHODE), 7alpha- and 7beta-hydroxycholesterol (t7-OHCh), and 8-iso-prostaglandin F(2alpha) (t8-iso-PGF(2alpha)) after subfractionation of LDL with an anion-exchange HPLC (AE-HPLC). LDL was separated and quantified by AE-HPLC as LDL-1, LDL-2, and LDL-3 in the order of the anionic charge of the LDL particles. The concentrations of tHODE, t7-OHCh, and t8-iso-PGF(2alpha) in both plasma and LDL subfractions were assessed after reduction and saponification. In this method, the free and ester forms of hydroperoxides, ketones, and hydroxides of linoleic acid and cholesterol are measured as tHODE and t7-OHCh, respectively. It was found that tHODE significantly correlated with the proportion of LDL-2 and LDL-3 as well as with the concentration of malondialdehyde-modified LDL in plasma. Further, by the analyses of LDL subfractions, the concentrations of tHODE, t8-iso-PGF(2alpha), and t7-OHCh in LDL-3 were found to be significantly higher than those in LDL-1 and LDL-2. These results clearly indicate that the extent of oxidation increases in the order of LDL-1相似文献   

Interaction of Polyunsaturated Fatty Acids with Cholesterol: A Role in Lipid Raft Phase Separation

Unequal affinity between lipids has been hypothesized to be a mechanism for the formation of microdomains/rafts in membranes. Our studies focus upon the interaction of cholesterol with polyunsaturated fatty acid (PUFA)-containing phospholipids. They support the proposal that steric incompatibility of the rigid steroid moiety for highly disordered PUFA chains, in particular docosahexaenoic acid (DHA), provides a sensitive trigger for lateral segregation of lipids into PUFA-rich/sterol-poor and PUFA-poor/sterol-rich regions. Solid state ²H NMR and x-ray diffraction (XRD) demonstrate that the solubility of cholesterol is reduced in 1-palmitoyl-2-docosahexaenoyl-phosphatidylethanolamine (16-0:22:6PE) bilayers. In mixed membranes of phosphatidylethanolamine (PE) with the lipid raft forming molecules egg sphingomyelin (SM) and cholesterol, diminished affinity of the sterol for 16:0-22:6PE relative to 1-palmitoyl-2-oleoylphosphatidylethanolamine (16:0-18:1PE) is identified by ²H NMR order parameters and detergent extraction. Phase separation of the PUFA-containing phospholipid from SM/cholesterol rafts is the implication, which may be associated with the myriad of health benefits of dietary DHA.     

SrB4 O7 : Eu磷光粉的制备及其发光性能

采用高温固相法合成了SrB₄O₇ : Eu荧光粉,并研究了不同原料、掺杂浓度、煅烧温度等因素对其发光性能的影响。发射光谱测试结果表明:SrB₄O₇ : Eu荧光粉的最佳Eu掺杂浓度为2%左右,进一步增大掺杂浓度会导致浓度猝灭。煅烧温度对基质组成影响较大,随着温度的升高,基质中BO₄四面体所占比例增大,有利于Eu³⁺离子的还原。以水合硼酸锶为原料制得样品的发光强度高于以SrCO₃和H₃BO₃为原料制得样品的发光强度。     

Effect of Hydrated Ionic Liquid on Photocycle and Dynamics of Photoactive Yellow Protein

The mechanism by which proteins are solvated in hydrated ionic liquids remains an open question. Herein, the photoexcitation dynamics of photoactive yellow protein dissolved in hydrated choline dihydrogen phosphate (Hy[ch][dhp]) were studied by transient absorption and transient grating spectroscopy. The photocyclic reaction of the protein in Hy[ch][dhp] was similar to that observed in the buffer solution, as confirmed by transient absorption spectroscopy. However, the structural change of the protein during the photocycle in Hy[ch][dhp] was found to be different from that observed in the buffer solution. The known change in the diffusion coefficient of the protein was apparently suppressed in high concentrations of [ch][dhp], plausibly due to stabilization of the secondary structure.     

Polysaccharide Structures and Their Hypocholesterolemic Potential

Several classes of polysaccharides have been described to have hypocholesterolemic potential, namely cholesterol bioaccessibility and bioavailability. This review will highlight the main mechanisms by which polysaccharides are known to affect cholesterol homeostasis at the intestine, namely the effect (i) of polysaccharide viscosity and its influence on cholesterol bioaccessibility; (ii) on bile salt sequestration and its dependence on the structural diversity of polysaccharides; (iii) of bio-transformations of polysaccharides and bile salts by the gut microbiota. Different quantitative structure–hypocholesterolemic activity relationships have been explored depending on the mechanism involved, and these were based on polysaccharide physicochemical properties, such as sugar composition and ramification degree, linkage type, size/molecular weight, and charge. The information gathered will support the rationalization of polysaccharides’ effect on cholesterol homeostasis and highlight predictive rules towards the development of customized hypocholesterolemic functional food.     

Determination of fatty acid compositions and cholesterol levels of some freshwater fish living in Porsuk Dam,Turkey

We determined the oil content, fatty acid composition, and cholesterol content of common carp (Cyprinus carpio), crucian carp (Carassius carassius), chub (Leusiscus cephalus), and tench (Tinca tinca) by GLC. The saturated fatty acids (SFA), monounsaturated fatty acids (MUFA), and polyunsaturated fatty acids (PUFA) levels were found to be 36.49%, 31.92%, 31.59% in common carp; 32.92%, 32.21%, and 34.87% in crucian carp; 36.19%, 32.91%, and 30.90% in chub; and 32.86%, 30.77%, and 36.37% in tench, respectively. The cholesterol (mg/100 g oil) levels of common carp, crucian carp, chub, and tench were determined by GLC methods as 119 ± 2.64 mg, 170.37 ± 2.36 mg, 94.68 ± 3.13 mg, and 179.84 ± 6.75 mg, respectively. Thus, the cholesterol contents of the analyzed freshwater fish species were low but their PUFA contents and nutritional values were high. Published in Khimiya Prirodnykh Soedinenii, No. 1, pp. 15–17, January–February, 2009.