Decane Solution Research Articles

Effect of divalent and trivalent metal ions on artificial membrane permeation of fluoroquinolones.

The purpose of the present study was to evaluate the predictability of PAMPA for the effect of metal ions on the bioavailability of fluoroquinolones (FQ). Eleven FQs and seven metal ions were employed in this study. The PAMPA membrane consisted of a 10 % soybean lecithin (SL) - decane solution. A drug solution in MES buffer with or without a metal ion (added as a chloride salt) was added to the donor compartment. In the absence of metal ions, FQ showed relatively high permeability (> 5 × 10-6 cm/sec) in SL-PAMPA despite their hydrophilic and zwitterionic properties. As the PAMPA permeability ratio with/without metal ions became smaller, the urinary excretion and AUC ratios tended to be smaller, suggesting that SL-PAMPA is a suitable in vitro model to evaluate the potential effect of metal ions on the bioavailability of FQ. However, the reduction in AUC and urinary excretion was overestimated for low solubility metal ion formulations (dried aluminum hydroxide gel and La2(CO3)3・8H2O). In such cases, the dissolution of the metal ion formulations and the permeation of FQs should be simultaneously evaluated.

Thin ZIF-8 nanosheets synthesized in hydrophilic TRAPs.

The preparation method of nanosheets using hyperswollen lyotropic lamellar phases, the 'two-dimensional reactor in amphiphilic phases (TRAP) method', has successfully provided nanosheets of various non-layered materials. Previously reported examples started from a single hydrophobic or hydrophilic precursor and multiple hydrophobic precursors. Here, we propose a synthesis method of nanosheets of ZIF-8, zinc 2-methylimidazolate, with a sodalite-like framework. They grow up to a few nanometers of thickness and several hundred nanometers of width with neither aggregation nor impurities from multiple hydrophilic precursors in the stoichiometric ratio inside the hydrophilic TRAPs consisting of the amphiphile Brij L4. The thin nanosheets of ZIF-8 doped with Co2+ (Co-ZIF-8) synthesized by the same method maintained a high specific surface area after calcination. Therefore, the oxygen reduction reaction (ORR) activity of the calcined Co-ZIF-8 NSs for fuel cells becomes higher than that of the calcined conventional Co-ZIF-8 crystals.

Atom-planting synthesis of MCM-36 catalyst to investigate the influence of pore structure and titanium coordination state on epoxidation activity

Abstract The borosilicate ERB-1 was modified as titanosilicate with microporous and mesoporous composite MCM-36 structure accommodated as epoxidation catalyst for large size molecule of reactants in the aqueous solution. Ti-MCM-36 was synthesized by swelling and pillaring the MWW layer structure with SiO2 and atom-planting method with TiCl4. The 2D 1H double quantum NMR and in-situ infrared spectroscopy confirm that the swelling process with cetyltrimethylammonium bromide and tetrapropylammonium hydroxide for the MCM-36 synthesis causes the deboronation of the ERB-1 and formation of hydroxyl nest. During the atom-planting treatment, the TiCl4 reacts with the generated hydroxyl group and consumes the hydroxyl nest to form the tetrahedral titanium in the zeolite framework as Ti–O–Si. The UV–Vis spectra show that the incorporated titanium atoms are mainly existed in the form of tetracoordinated titanium. The titanosilicate pillared Si/Ti-MCM-36 with coexistence of tetrahedral and octahedral coordination titanium species were compared with Ti-MCM-36 to investigate the coordination state of Ti species for the liquid phase epoxidation of cyclohexene, cyclooctene with tert-butyl hydroperoxide aqueous solution, decane solution or H2O2 solution. Moreover, compared with the extra-framework octahedral coordination Ti species, the framework tetrahedral coordination titanium species are more efficient for epoxidation, especially with H2O2 as oxidant. By comparing with the performance of microporous Ti-ERB-1, the microporous and mesoporous composite Ti-MCM-36 is more efficient with the increase of the reactant molecule size from 1-hexene, cyclohexene, cyclooctene and soybean oil, which shows good epoxidation activity for soybean oil within H2O2 solution.

Wettability Quantification in Mixed-Wet Rocks Using a New NMR-Based Method

Summary Nuclear magnetic resonance (NMR) measurements have been attractive options for wettability characterization of reservoir rocks as they are sensitive to the type of fluid in contact with the grain surface. Several NMR-based wettability indices are documented in previous publications. Most of these methods require extensive calibration or involve complex inversion algorithms, which makes them computationally expensive and complicates their applicability in mixed-wet multimodal rocks. In this paper, we introduce a new NMR-based wettability index and verify its reliability in pore-scale and core-scale domains using numerical simulations and experimental measurements, respectively. This new index requires calibration at fully water-saturated water-wet and fully hydrocarbon-saturated hydrocarbon-wet states and can be applied to mixed-wet rocks at any fluid saturation level. This new NMR-based wettability index is a function of the transverse magnetization (T2) of mixed-wet rocks, the bulk relaxivity and saturation of each fluid, and the T2 distributions for fully water-wet and hydrocarbon-wet samples of the same rock type. The reliability of the new index was first tested in the pore-scale domain. For this part, we selected several pore-scale microcomputed tomography (CT) images of carbonate and sandstone rocks. We used a previously developed finite volume simulator to model the T2 responses in these images at fully water-wet and fully hydrocarbon-wet wettability states. Then we generated synthetic partially saturated mixed-wet samples and simulated T2 responses in these synthetic images. We used the simulated T2 results for determining their NMR-based wettability index and verified its applicability in the pore-scale domain. Next, we tested the reliability of the new NMR-based wettability index in the core-scale domain using NMR measurements in four Texas Cream (TC) rock samples, obtained from the Edwards formation. We altered the wettability of the cores to be water-, hydrocarbon-, and mixed-wet by injecting brine, a naphthenic acid in decane solution, or an anionic surfactant solution. We quantified the wettability of these samples using the Amott-Harvey (AH) index and contact angle measurements. Next, we measured the T2 distribution of these samples at different fluid saturation levels. Finally, we quantified the wettability values of these core samples using the new NMR-based index and compared them to those obtained from the AH index and contact angle measurements. We documented successful verification of the proposed method on samples with wettability ranging from −0.90 to 0.98 and from −0.6 to 0.5 (independently quantified using the AH method) in the pore- and core-scale domains, respectively. Results demonstrated that the new NMR-based wettability index reliably estimates the wettability of mixed-wet rocks in a wide range of wettability states. The new wettability index can potentially improve the speed and reliability of NMR-based wettability characterization and is promising for log-scale wettability assessment in mixed-wet rocks.

Reversible Self-Assembled Monolayers (rSAMs) as Robust and Fluidic Lipid Bilayer Mimics

Lipid bilayers, forming the outer barrier of cells, display a wide array of proteins and carbohydrates for modulating interfacial biological interactions. Formed by the spontaneous self-assembly of lipid molecules, these bilayers feature liquid crystalline order, while retaining a high degree of lateral mobility. Studies of these dynamic phenomena have been hampered by the fragility and instability of corresponding biomimetic cell membrane models. Here, we present the construct of a series of oligoethylene glycol-terminated reversible self-assembled monolayers (rSAMs) featuring lipid-bilayer-like fluidity, while retaining air and protein stability and resistance. These robust and ordered layers were prepared by simply immersing a carboxylic acid-terminated self-assembled monolayer into 5-50 μM aqueous ω-(4-ethylene glycol-phenoxy)-α-(4-amidinophenoxy)decane solutions. It is anticipated that this new class of robust and fluidic two-dimensional biomimetic surfaces will impact the design of rugged cell surface mimics and high-performance biosensors.

Interaction of 1,3,2,4‐Benzodithiadiazines with Aromatic Phosphines and Phosphites

ABSTRACTAlthough an interaction between hydrocarbon and fluorocarbon 1,3,2,4‐benzodithiadiazines (1 ) and P(C6H5)3 continuously produces chiral 1,2,3‐benzodithiadiazol‐2‐yl iminophosporanes (2; in this work, 5,7‐difluoro derivative 2a ) via 1:1 condensation, an interaction between 1 and other PR3 reagents gives different products. With R  OC6H5 and both hydrocarbon and fluorocarbon 1, only X=P(OC6H5)3 (X = S, O) were identified in the complex reaction mixtures by 13С and 31Р NMR and GC‐MS. With R = C6F5, no interaction with the archetypal 1 was observed but catalytic addition of atmospheric water to the heterocycle afforded 2‐amino‐N‐sulfinylbenzenesulfenamide (4 ). With electrophilic B(C6F5)3 instead of nucleophilic P(C6F5)3, only adduct H3N→B(C6F5)3 and a new polymorph of C6F5B(OH)2 were isolated and identified by X‐ray diffraction (XRD). A molecular structure of 2a was confirmed by XRD, and the π‐stacked orientation of one of phenyl groups and heterocyclic moiety was observed. This structure is in general agreement with that calculated at the RI‐MP2 level of theory, as well as at three different levels of DFT theory with the PBE and B3LYP functionals. Mild thermolysis of 2a in a dilute decane solution gave persistent 5,7‐difluoro‐1,2,3‐benzodithiazolyl (3a ) identified by EPR in combination with DFT calculations.

Appropriate excitation wavelength removes obfuscations from pyrene excimer kinetics and mechanism studies

The experimental procedures of time-resolved laser photolysis studies of pyrene excimer formation in solution have been scrutinized and the appropriate modifications have been implemented. Contrary to the experimental methods applied in all related previous work, the selection of a suitable excitation wavelength (such that the corresponding pyrene absorbance is less than 0.5 absorbance units) utilized in our study results in simple homogeneous kinetics. Consequently, the rate parameters obtained and the mechanism proposed differ significantly from those published previously. The rate constant values of the unimolecular decay of the pyrene monomer, the unimolecular decay of the pyrene excimer, and the excimer formation in decane solution (η = 0.860 mPa s) at 25 °C are (2.38 ± 0.01) × 10(6) s(-1), (2.78 ± 0.02) × 10(7) s(-1), and (3.11 ± 0.06) × 10(9) M(-1) s(-1), respectively. The dissociation of the excimer to form a singlet excited state pyrene and a ground state pyrene was shown to be negligible. The energies of activation corresponding to the monomer and excimer unimolecular decays were found to be 2.51 ± 0.07 and 25.7 ± 0.7 kJ mol(-1), respectively. Also, our temperature resolved laser photolysis data revealed that the excimer formation has a negative energy of activation equal to -11.2 ± 0.5 kJ mol(-1). This unique phenomenon may be attributed to steric effects in the collision of the reactants. The current findings are important for the correct data analysis and interpretation in many applications of the pyrene excimer.

Densities and Excess Volumes of CO2 + Decane Solution from 12 to 18 MPa and 313.15 to 343.15 K

It has been widely considered that the global warming was induced by the increasing atmospheric concentrations of carbon dioxide, which has a significant impact on the sustainable development of the human society. Injecting carbon dioxide into depleted oil/gas reservoir has been developed to reduce carbon dioxide emission by the sequestration of CO2 underground, which is also considered as one promising approach to enhance oil recovery simultaneously. The evaluating of CO2 sequestration in oil reservoir needs highly accurate experimental data and models about the thermodynamic characters of CO2 + oil mixture. Density is one of key physical characters for simulating the diffusion and migration of carbon dioxide under the oil/gas reservoir. Research on volumetric behaviour is helpful to understand the expansion of the liquid phases in CO2 + oil mixture.In this paper, decane is investigated instead of petroleum because of the similar thermal physical property. The measurements have been performed at pressures from 12MPa to 18MPa and temperatures from 313.15K to 343.15K at four compositions x1 (x1 is the mole fraction of carbon dioxide) = 0.8690, 0.9135, 0.9430 and 0.9818 by a magnetic suspension balance (MSB). The accuracy of the experimental quantities presented in this work are T/K = ± 0.01, m/g = ± 10-5 respectively. One circulation pump (AKICO, Japan) is equipped to accelerate the dissolution of CO2 in decane. Some conclusions can be obtained from the experiment as follow: (1) the dissolution of CO2 increases the density of decane, the density of CO2 + decane solution increases with increasing pressure and decreases with increasing temperature. (2) the slope of density with respect to pressure increases with increasing CO2 mole fractions while the slope with respect to temperature decreases with increasing CO2 mole fractions. (3) the crossover phenomenon appears at different compositions and the crossover pressure increases with temperature. (4) the excess molar volumes of this binary mixture are negative and show negative increasing with temperature for the data reported in this work. The GERG - 2008 model is used to predict density of CO2 + decane solution, which takes temperature, pressure, and CO2 concentration into account. An empirical equation is also used to predict the density of this binary mixture. The predictions show that the empirical equation is in good agreement with the experimental data over the experimental range. The measurement and the model used in this work supplies the basic experimental data and theoretical analysis to CO2 sequestration and enhance oil recovery.

Self-assembled monolayer protective films for hybrid sliding contacts

Silicon nitride as an energy efficient material is replacing conventional steels for new generation engineering components such as bearings, cutting tools, electronics and engine parts in automotive, aerospace and wind industries. Compared with steel bearings, silicon nitride bearings can be operated at much higher temperatures and speeds with >60% weight reduction and up to 80% friction reduction. These are all due to its unique material properties, including high wear and corrosion resistance, low density and heat generation. Current lubrication solutions for hybrid contacts, where silicon nitride balls and steel races are used, are mostly relying on the protection film formed on the metal surfaces. Self-assembled monolayers (SAMs) have been found very useful in modifying surfaces, especially for microelectromechanical system and nanoscale applications, e.g. atomic force microscopy tips, etc. This study aims to investigate the feasibility of forming a SAM protection film on industrial grade bearing material silicon nitride to reduce the friction for the oil lubricated hybrid contacts. Four silanes with different functional head groups, including octadecyltrichlorosilane (OTS), octyltrichlorosilane, chlorodimethyloctadecylsilane and octadecyltrimethoxysilane, were initially investigated to form SAMs on industrial grade silicon nitride surfaces. The effects of concentration and immersion time of the silanes on the formation of SAMs on the silicon nitride surface were evaluated using contact angle measurements. The preliminary results show that the wetting properties of the silicon nitride surface can be effectively modified by the formation of SAMs from the silane solutions. OTS can form an order and compact SAM on the silicon nitride surfaces within 2 min at the concentration of 2··5 mM in decane solution, while the other three alkylsilanes can also effectively modify silicon nitride surfaces given sufficient immersion time, e.g. over 1 h. Tribological tests were subsequently carried out on a ball on disc rig where a steel ball and a silicon nitride disc were used. The effect of the formation of alkylsilane SAMs on the friction between the sliding contacts has been evaluated in two different methods. The first method was to test preformed SAM films under dry conditions, and the second was to premix one of the surfactants with Shell Vitrea ISO 32 mineral base oil and then spray the mixture to the contacts during the ball on disc testing. The test results show that an average of over 40 and 30% friction reduction was achieved for the hybrid contact when lubricated with the base oil mixed with OTS (>2··5 mM) and octadecyltrimethoxysilane (5 mM) respectively compared with that of the sliding contact lubricated by the base oil only. Since OTS may produce corrosive byproducts during SAM formation, octadecyltrimethoxysilane may be a more suitable additive for the hybrid contacts.

Contact Angle Measurement for Oil–Mineral–Water System on a Micro Scale

Enhanced Oil Recovery (EOR) is used to increase the production of oil from geological reservoirs. EOR technology often involves injecting water into rock formations to recover oil remaining in rock pores. Therefore, an evaluation of the wettability of the oil–mineral–water 3-phase interfacial system is needed. In particular, the contact angle of water on the mineral surface in the presence of oil is the essential parameter governing wettability. In this study, the contact angles in the decane–muscovite–water interfaces were measured using an Atomic Force Microscope (AFM). The topologies of small water droplets (mostly less than 15 μm) in a liquid decane solution on muscovite plates were acquired with an AFM. The height and contact width obtained from the profiles of small droplets provide the contact angles between decane–muscovite–water interfaces. To correct for the effect of scanning pressure on topologies, contact angle measurements were carried out at different scanning pressures and force curves were measured on the decane–water interface. The corrected contact angles of water droplets showed around 20 degrees over a contact width of about 6 μm, which were in agreement with macroscopic contact angle data, while they decreased to about 15 degrees at a smaller contact width than about 2 μm. The relationship between corrected contact angles and droplet sizes is explained well by the modified Young's equation with a line-tension force of -2.1 × 10-9 N. The results indicate that the wettability of oil–mineral–water interfaces differs between nano/micro scale and macro scale. Therefore, microscopic wettability should be considered when evaluating EOR in real rock systems.

Compensation and cooperative effects in H-bond thermodynamics of hydroperoxides

Abstract Self-association of cumyl (CUH), tertiary butyl and 3-phenylmethyl hydroperoxides in various solvents and hetero-association of CUH with acetone and acetophenone in n -decane solutions were studied by FTIR spectroscopy. The obtained results were analyzed in combination with DFT data on linear and cyclic CUH self-associates. The analysis of the complexation enthalpies and entropies revealed compensation and cooperative effects, which were for the first time observed for H-bonding of hydroperoxides.

Influence of Cationic Composition and pH on the Formation of Metal Stearates at Oil–Water Interfaces

We study the formation of layers of metal stearates at the interface between a decane solution of stearic acid and aqueous salt solutions of variable composition and pH by monitoring the evolution of their mechanical, optical, and chemical properties as a function of time after formation of the interface. For values of the pH below the pK(a) of stearic acid hardly any interfacial activity is observed. For pH > pK(a), stearic acid deprotonates at the interface and forms metal stearates, eventually leading to the formation of macroscopic solid layers. Dynamic interfacial tension measurements reveal that the process takes place in several stages, which we attribute to the successive formation of dilute and dense monolayers followed by three-dimensional growth. In the presence of divalent ions, the solid layers display a significant increase in the dilatational storage modulus. Experiments performed with an aqueous phase containing multiple cation species (artificial seawater) give rise to particularly pronounced growth of solid layers, which preferentially incorporate Ca(2+) as revealed by X-ray photoelectron and infrared spectroscopy. Our results highlight in particular the importance of the complex synergistic effects of simultaneously present monovalent and divalent cation species on the interfacial adsorption.

Microstructure and morphology of self-assembling multiblock poly(ethylene-1-butene)-n copolymers in solution studied by wide-Q small-angle neutron scattering and microscopy

Multiblock ethylene-1-butene copolymers (PEB-n) with graded ethylene content (where n is the number of ethyl branches per 100 backbone carbons) represent efficient cold filter plugging point (CFPP) depressants for crude oils and middle distillates. The aggregation behavior and the interaction with wax molecules of a tetrablock PEB-2.6/PEB-6.0/PEB-10.9/ PEB-13.2 and triblock PEB-6.5/PEB-8.9/PEB-10.1 copolymers in decane solutions were investigated over a wide temperature range by combining different small-angle neutron scattering techniques and optical microscopy. The experimental results revealed in the decrease of temperature formation and evolution of multisized structural levels showing a hierarchical organization on the length scale from 1 nm up to 10 μm. One-dimensional polymer aggregates arising as initial structures associate and branch that lead to the occurrence of complex macroaggregates with diffusive interfaces and sizes of several microns. The one-dimensional copolymer structure shows longitudinal density modulation and micellar-like substructures in neat polymer solutions. When wax is added, this structure becomes more homogeneous in decrease of temperature as a consequence of the cocrystallization of wax and copolymer. The wax crystallization in board-like objects of much smaller size than required by the CFPP criterion of oil and refinery industry (filter mesh size of 45 μm) is templated and controlled by the assembling features of the crystalline-amorphous PEB-n multiblock copolymers.

Influence of Drop Growth Rate and Size on the Interfacial Tension of Triton X-100 Solutions as a Function of Pressure and Temperature

The interfacial tension (IFT) between decane and aqueous solutions of Triton X-100 was determined by the pendant-drop technique, and the effects of the temperature, pressure, surfactant concentration, droplet growth rate, and size were studied. Three aqueous solutions of surfactant were used (0.48 × 10−4 mol · L−1, 0.96 × 10−4 mol · L−1, 1.43 × 10−4 mol · L−1), and the experiments were performed at (2, 3, and 4) MPa and at (30, 40, and 50) °C. As expected, the alkane drop changed its shape, and the IFT of the system decreased as the surfactant adsorbed onto the interface, until the drop finally separates from the capillary, in a maximum time of 2120 s. According to the results, the influence of temperature on the IFT is inversely proportional to the surfactant concentration, because when the concentration increases, the temperature has little effect on it. It was also noticed that the effect of pressure on the IFT at lower surfactant concentrations is less significant than at higher concentrations. When the temperature decreases, the pressure reduces its effect on the IFT, as occurs with systems at 30 °C. The droplet growth rate does not significantly affect the IFT value, while its size does; therefore, when transient studies are carried out, it is required to control the drop size.

Hierarchical structures formed by partially crystalline polymers in solution: from fundamentals to applications – a combined conventional, focusing and ultra-small-angle neutron scattering study

Multilevel aggregates with characteristic sizes covering four orders of magnitude, from 1 nm to 10 µm, are formed upon cooling decane solutions of poly(ethylene-butene) random copolymers (designated as PEB-n, where n is the number of ethyl side branches per 100 backbone C atoms) and wax-containing mixed solutions. The partially crystalline PEB-7.5 copolymers form two distinct morphologies that evolve on a range of length scales. When these polymers are mixed with wax molecules having a crystallization point lower than the polymer aggregation temperature, a hierarchy of morphologies evolves on decreasing the temperature. The multilevel structures were elucidated by combining conventional small-angle neutron scattering, focusing small-angle neutron scattering and ultra-small-angle neutron scattering investigations with microscopy. Contrast-matching analysis of the wax and copolymer components within the common morphologies revealed the wax-crystal modification capacity of the PEB-7.5 copolymers. Since the copolymers limit the growth of wax crystals, they are potential pour-point depressants for the fuel industry.

Fibrillar structure of self‐assemblies formed from heterocomplementary monomers linked through sextuple hydrogen‐bonding arrays

AbstractThe nanostructure of the fibrillar supramolecular aggregates generated in decane solutions of homoditopic heterocomplementary monomers forming sextuple hydrogen‐bond‐mediated self‐assemblies was investigated by small‐angle neutron scattering and cryogenic‐temperature transmission electron microscopy. The persistence length (Lp) of the fibrillar aggregates was found to be ∼18 nm, as inferred from combined measurements of the radius of gyration and of the contour length. The values of both the weight‐average molecular weight and the mass per unit length of the fibers suggest that the latter consist of few aggregated monomolecular wires. At T = 25 °C, the formation of branched aggregates occurs around the crossover concentration, C*, between the dilute and semidilute regimes, whereas the classical behavior of equilibrium polymers is observed at T = 65 °C. © 2006 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 103–115, 2007

Structure and Properties of Supramolecular Polymers Generated from Heterocomplementary Monomers Linked through Sextuple Hydrogen-Bonding Arrays

The synthesis of homoditopic heterocomplementary monomers forming sextuple hydrogen-bond-mediated self-assemblies in apolar solvents is described. The nanostructures of the fibrillar aggregates formed in decane solutions of such monomers were investigated by small-angle neutron scattering. The fibers were found to be rigid, with an average length that increases upon increasing concentration and/or decreasing temperature. The cross section and the mass per unit length of the fibrillar aggregates are constant in the explored concentration range spanning both the dilute and semidilute regimes. These parameters are also insensitive to a temperature change. From the values of the cross section and of the mass per unit length, it can be inferred that the fibers contain on the average several monomolecular wires.

A Green Chemistry Approach to a More Efficient Asymmetric Catalyst: Solvent-Free and Highly Concentrated Alkyl Additions to Ketones

There is a great demand for development of catalyst systems that are not only efficient and highly enantioselective but are also environmentally benign. Herein we report investigations into the catalytic asymmetric addition of alkyl and functionalized alkyl groups to ketones under highly concentrated and solvent-free conditions. In comparison with standard reaction conditions employing toluene and hexanes, the solvent-free and highly concentrated conditions permit reduction in catalyst loading by a factor of 2- to 40-fold. These new conditions are general and applicable to a variety of ketones and dialkylzinc reagents to provide diverse tertiary alcohols with high enantioselectivities. Using cyclic conjugated enones, we have performed a tandem asymmetric addition/diastereoselective epoxidation using the solvent-free addition conditions followed by introduction of a 5.5 M decane solution of tert-butyl hydroperoxide (TBHP) to generate epoxy alcohols. This one-pot procedure allows access to syn epoxy alcohols with three contiguous stereocenters with excellent enantio- and diastereoselectivities and high yields. Both the solvent-free asymmetric additions and asymmetric addition/diastereoselective epoxidation reactions have been conducted on larger scale (5 g substrate) with 0.5 mol % catalyst loadings. In these procedures, enantioselectivities equal to or better than 92% were obtained with isolated yields of 90%. The solvent-free and highly concentrated conditions are a significant improvement over previous solvent-based protocols. Further, this chemistry represents a rare example of a catalytic asymmetric reaction that is highly enantioselective under more environmentally friendly solvent-free conditions.

Reconstitution of biological molecular generators of electric current. Transhydrogenase.

Direct measurement of the electrogenic activity of purified mitochondrial transhydrogenase has been carried out. To this end, beef-heart transhydrogenase was isolated and reconstituted with phospholipids to form proteoliposomes. The transhydrogenase proteoliposomes were incorporated into a membrane filter impregnated with a decane solution of phospholipids. It is shown that addition of substrates of either the forward (NADPH and NAD+) or the reverse (NADH and NADP+) transhydrogenase reaction gives rise to an electric potential difference across the proteoliposome-treated membrane filter. The electric vector depends upon the direction of the reaction. The proteoliposome-supplemented compartment charges negatively in the case of the forward reaction and positively in the case of the reverse one. Addition of the reaction products after substrates equalizes the potentials. The transhydrogenase-treated membrane filter retains the ability to perform transhydrogenase-linked electrogenesis after removal of excess non-incorporated proteoliposomes. The electric potential difference reaching 20 mV immediately after the transhydrogenase substrate addition, slowly decreases due to accumulation of the reaction products. Such decay is prevented when the mixture is supplemented with the substrate-regenerating and product-utilizing enzymic systems. Under these conditions, a steady continuous electric current of about 10 pA can be observed.

Crystallization of F 1F 0-ATP synthase from Chloroflexus aurantiacus

Crystallization of F 1F 0-ATP synthase from thermophilic bacterium Chloroflexus aurantiacus was carried out in the present work. A new crystallization method based on slow detergent removal in a two-phase system, consisting of decane and protein solution, was developed. Three-dimensional protein crystals were grown by this method. Two-dimensional molecular lattice with unit cell parameters of a=28 nm, b=23 nm and φ =104° was observed by atomic force microscopy on their surface. Thickness of protein surface layer of the crystals was determined also. Model of the protein molecular packing of the crystals is suggested basing on the experimental data.