Electrochemistry of membrane proteins and protein–lipid assemblies

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Structure and kinetics of lipid–nucleic acid complexes

The structure and function of lipid-based complexes (lipoplexes) have been widely investigated as cellular delivery vehicles for nucleic acids—DNA and siRNA. Transfection efficiency in applications such as gene therapy and gene silencing has been clearly linked to the local, nano-scale organization of the nucleic acid in the vehicle, as well as to the global properties (e.g. size) of the carriers. This review focuses on both the structure of DNA and siRNA complexes with cationic lipids, and the kinetics of structure evolution during complex formation.     

Surface chemistry of lipid raft and amyloid Aβ (1-40) Langmuir monolayer

Lipid rafts being rich in cholesterol and sphingolipids are considered to provide ordered lipid environment in the neuronal membranes, where it is hypothesized that the cleavage of amyloid precursor protein (APP) to Aβ (1-40) and Aβ (1-42) takes place. It is highly likely that the interaction of lipid raft components like cholesterol, sphingomylein or GM1 leads to nucleation of Aβ and results in aggregation or accumulation of amyloid plaques. One has investigated surface pressure-area isotherms of the lipid raft and Aβ (1-40) Langmuir monolayer. The compression-decompression cycles and the stability of the lipid raft Langmuir monolayer are crucial parameters for the investigation of interaction of Aβ (1-40) with the lipid raft Langmuir monolayer. It was revealed that GM1 provides instability to the lipid raft Langmuir monolayer. Adsorption of Aβ (1-40) onto the lipid raft Langmuir monolayer containing neutral (POPC) or negatively charged phospholipid (DPPG) was examined. The adsorption isotherms revealed that the concentration of cholesterol was important for adsorption of Aβ (1-40) onto the lipid raft Langmuir monolayer containing POPC whereas for the lipid raft Langmuir monolayer containing DPPG:cholesterol or GM1 did not play any role. In situ UV-vis absorption spectroscopy supported the interpretation of results for the adsorption isotherms.     

Reduction of irradiation off-odor and lipid oxidation in ground beef by α-tocopherol addition and the use of a charcoal pack

A combination of a charcoal pack during irradiation and α-tocopherol addition into ground beef was applied to eliminate an irradiation characteristic off-odor and to retard the lipid oxidation caused by the irradiation process. Ground beef was mixed with 200 ppm α-tocopherol and gamma irradiated with 0, 5, and 10 kGy with or without a charcoal pack present during the irradiation treatment. The pH of the control group was lower than that of α-tocopherol and charcoal pack treatment initially but increased rapidly and showed higher pH at day 7. Addition of α-tocopherol with or without charcoal pack addition showed lower 2-thiobarbituric acid reactive substances values in irradiated ground beef at days 3 and 7 compared to those without addition. The color of ground beef was not significantly affected by the treatment. However, odor preference result showed that 10 kGy-irradiated ground beef with a combination of charcoal pack and α-tocopherol addition had higher scores than the control group regardless of irradiation. Solid-phase microextraction (SPME) gas chromatograph/mass spectrometry (GC/MS) analysis identified various volatile compounds that were created by irradiation of ground beef. These compounds were reduced or eliminated when a charcoal pack was used during the irradiation process. The results of the present study imply that combination of packaging with a charcoal pack during the irradiation process and addition of α-tocopherol into ground beef is a good method to effectively eliminate an irradiation off-odor and retard the lipid oxidation development in ground beef caused by irradiation.     

Stereoselective syntheses of γ-alkyl (aryl)-α,β-dihydroxy-γ-butyrolactones and naturally occurring lipid guggultetrol

γ-Oxo-butyramides derived from tartaric acid serve as excellent precursors for the synthesis of γ-alkyl (aryl)-α,β-dihydroxy-γ-butyrolactones and for the synthesis of tetrols containing three contiguous stereogenic centres. The methodology presented here is general for the synthesis of γ-alkyl (aryl)-α,β-dihydroxy-γ-butyrolactones. Utility of the chiral building block was demonstrated by the synthesis of naturally occurring lipid guggultetrol.     

Chain termination in the oxidation of lipid models by α-tocopherol and its synthetic analog

The rate constants (k₁) and stoichiometric coefficients (f) of chain termination in the oxidation of lipid models (methyl esters of acids in the oleic series) by -tocopherol and its synthetic analog at 50°C were measured. The values of k₁ and f do not depend on the structure of the substituent R in the peroxide radical ROO of the lipid models undergoing oxidation, but the values of k₁ are determined by the conformation of the investigated phenols.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 29, No. 5, pp. 441–444, September–October, 1993.     

Aqueous dispersions of cubic lipid–water phases

Inverse lipid–water phases such as cubic phases can form kinetically stable dispersions by fragmentation in water. Cubic lipid phases can be dispersed by polar lipids favoring lamellar phases or by block copolymers, which can close the bilayer at the surface so that the hydrocarbon chain core is not exposed to water. Monodisperse particles based on glycerol monooleate, with their bilayer curved as the P-, D- or G-minimal surface, have been prepared in this way. Their inner bilayer conformation and outer shape have been examined, mainly by X-ray diffraction and cryo transmission electron microscopy. There is also a different type of cubic lipid bilayer particles with a periodicity in the micrometer range, which have been identified in phospholipid–water dispersions and in cell membrane assemblies. The mechanism behind formation in vivo of such cubic membranes, which also follow the P-, D- and G-surfaces, is discussed. Other lipid–water dispersions with lower symmetry are finally considered; dispersions formed by the inverse hexagonal phase and the dispersed state of a tetragonal bilayer structure formed by lung surfactants.     

A sophorose lipid from microbial conversion of oleyl alcohol

Man}'kindsofbiosurfactants-includingsophoroselipids,rhamnolipids,trehaloselipidsandlipopolysaccharideshavebeeninvestigatedin0urlaboratory'recently.l']SophoroselipidswereproducedbytheyeastTorumpsissP.l=IThemainproductofsophoroselipidsisalactonics0phoroselipidcontainingamono-unsatUratedl7-hydroxy-octadecenoicacidSl,whichisdifferentfromthesaturatedSlstrUctUre.I3]MethylsophoroselipidS2wasobtainedfromthelatterbymethy1ation.I']TheyeastTOruloPsissP.producedamixtureofsoph0roselipidsduringgrowtho…     

Determinations of combustion and formation enthalpies of C_(60)and C_(70)

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Formulation and evaluation of gel containing nanostructured lipid carriers of tretinoin–Epi-β-CD binary complex for topical delivery

The objective of present research work was to formulate and evaluate topical gel containing tretinoin–cyclodextrin (CD) binary complex loaded into nanostructured lipid carriers (NLCs). Use of cyclodextrin and nanolipid carrier together in a system produced a synergistic effect by increasing the drug release and skin permeation, thus improving the overall therapeutic effect. Two different cyclodextrins i.e. β-CD and its water soluble polymeric derivative epichlorohydrin-β-cyclodextrin (EPI-β-CD) were used to obtain binary inclusion complex of drug-cyclodextrin (D-CD) systems by two different techniques (kneading and co-evaporation). The prepared solid complexes were characterized by FTIR, DSC, XRD etc. and the best system was selected for loading into nanolipid carriers. NLC comprising glyceryl mono stearate (GMS) and oleic acid were obtained by slightly modified emulsification evaporation method. Four different formulations of NLCs were suitability characterized for particle size, zeta potential, entrapment efficiency, drug loading and drug release. EPI-β-CD was found to be more effective than β-CD in enhancing solubility and dissolution properties of tretinoin. The most effective NLC formulation was incorporated into carbopol hydrogel which showed better permeation properties than that of the reference gel (0.1%).     

Multicellular tumor spheroids bridge the gap between two-dimensional cancer cells and solid tumors: The role of lipid metabolism and distribution

Previous studies demonstrated that three-dimensional(3D) multicellular tumor spheroids(MCTS) could more closely mimic solid tumors than two-dimensional(2D) cancer cells in terms of the spatial structure, extracellular matrix-cell interaction, and gene expression pattern. However, no study has been reported on the differences in lipid metabolism and distribution among 2D cancer cells, MCTS, and solid tumors. Here, we used Hep G2 liver cancer cell lines to establish these three cancer models. The ...     

Synthesis and characterization of β-diketonato- and phenoxoderivatives of mono(dizirconium-ennea-isopropoxy)copper(II)

Summary -Diketonato- and phenoxo-derivatives of mono(dizirconium-ennea-isopropoxy) copper(II), [Cu{Zr₂(OPr-i)₉}-(RCOCHCOR)] and [Cu{Zr₂(OPr-i)₉}(-OAr)], have been prepared by the interaction of K(RCOCHCOR) or KOAr (1 mol) [R = R = Me (1a); R = R = CF₃ (1b); R = Me, R = CF₃ (1c); OAr = 2,6-Me₂C₆H₃O (2a), 3,5-Me₂C₆H₃O (2b), p-ClC₆H₄O (2c)] with [Cu{Zr₂-(OPr-i) ₉}(-Cl)] (1 mol) in PhH. Alcohol interchanges of the derivative [Cu{Zr₂(OPr-i)₉}(-Cl)] have also been studied. These new compounds have been characterized by elemental analyses, i.r., electronic and e.s.r. spectra, and magnetic susceptibility measurements. The studies indicate a distorted octahedral geometry around Cu^II.     

Chemistry of natural compounds and bioorganic chemistry Synthesis of (±)-furodizinin and (±)-furodizin

The racemic forms of natural Omnoterpenoids, (±)-furodizinin and (±)-furodizin, were synthesized by cationic cyclization of the or -furylmethyl derivatives of linalool, geraniol and nerol.A. M. Moiseenkov (1936–1992), an outstanding Russian organic chemist, would have been sixty on July 6, 1996, He contributed significantly to the chemistry of terpenoids. The scientific heritage of A, M. Moiseenkov is rich and diversified. This work is devoted to the walizWon of one of his ideas. For the preliminary communication see Ref. 1.DeceasedTranslated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1842–1847, July, 1996.     

Application of nucleic acid–lipid conjugates for the programmable organisation of liposomal modules

We present a critical review of recent work related to the assembly of multicompartment liposome clusters using nucleic acids as a specific recognition unit to link liposomal modules. The asymmetry in nucleic acid binding to its non-self complementary strand allows the controlled association of different compartmental modules into composite systems. These biomimetic multicompartment architectures could have future applications in chemical process control, drug delivery and synthetic biology. We assess the different methods of anchoring DNA to lipid membrane surfaces and discuss how lipid and DNA properties can be tuned to control the morphology and properties of liposome superstructures. We consider different methods for chemical communication between the contents of liposomal compartments within these clusters and assess the progress towards making this chemical mixing efficient, switchable and chemically specific. Finally, given the current state of the art, we assess the outlook for future developments towards functional modular networks of liposomes.     

DNA-binding and photocleavage studies of metallofluorescein–porphyrin complexes of zinc(II) and copper(II)

The DNA-binding behaviors of the fluorescein?Cporphyrinatozinc(II) complex Zn(Fl-PPTPP) (Fl-PPTPP?=?5-(4-fluoresceinpropyloxy)phenyl-10,15,20-triphenylporphyrin) and fluorescein?Cporphyrinatocopper(II) complex Cu(Fl-PPTPP) with calf thymus DNA (CT-DNA) were investigated by UV?CVis absorption titrations, fluorescence spectra, viscosity measurements, thermal denaturation and circular dichroism. The results suggest that both complexes interact with CT-DNA by intercalation. In addition, their photocleavage reactions with pBR322 supercoiled plasmid DNA were investigated. Both complexes exhibit significant DNA cleavage activity, and singlet oxygen may play an important role in these reactions.     

Synthesis and Magnetic Properties of Fe(II) and Nd(III) Complexes of Poly(N-2-thiazolylacrylamide)

In recent years,the organic ferromagnets have drawn growing attention due to their characteristics of structural diversities,low density,and readily processing1-3.Design and synthesis of magnetic polymers are one of great challenges in today′s magnetic material research,and some significant achievements have been made in this field4,5.In this article,we describe the synthesis of acrylamide-type polymer with pendent thiazolyl groups(Scheme1).The as-prepared polymer exhibited better solubility …     

Synthesis and characterization of sterically encumbered β-ketoiminate complexes of iron(II) and zinc(II)

The synthesis, structure, and spectroscopic signatures of a series of four-coordinate iron(II) complexes of β-ketoiminates and their zinc(II) analogues are presented. An unusual five-coordinate iron(II) triflate with three oxygen bound protonated β-ketoimines is also synthesized and structurally characterized. Single-crystal X-ray crystallographic analysis reveals that the deprotonated bis(chelate)metal complexes are four-coordinate with various degrees of distortion depending on the degree of steric bulk and the electronics of the metal center. Each of the high-spin iron(II) centers exhibits multiple electronic transitions including ligand π to π*, metal-to-ligand charge transfer, and spin-forbidden d-d bands. The (1)H NMR spectra of the paramagnetic high-spin iron(II) centers are assigned on the basis of chemical shifts, longitudinal relaxation times (T(1)), relative integrations, and substitution of the ligands. The electrochemical studies support variations in the ligand strength. Parallel mode EPR measurements for the isopropyl substituted ligand complex of iron(II) show low-field resonances (g > 9.5) indicative of complex aggregation or crystallite formation. No suitable solvent system or glassing mixture was found to remedy this phenomenon. However, the bulkier diisopropylphenyl substituted ligand exhibits an integer spin signal consistent with an isolated iron(ii) center [S = 2; D = -7.1 ± 0.8 cm(-1); E/D = 0.1]. A tentative molecular orbital diagram is assembled.