An investigation of the interaction of cobra venom cytotoxins with liposomes by the fluorescent-probe method

The interaction of cytotoxins V_c1, V_c5, and V_c6 of the venom of the Central Asian cobra with liposomes having a negative surface charge prepared from a mixture of phosphatidylcholine and palmitic acid (1:1, molar) has been investigated with the aid of a pyrene fluorescent probe. It has been shown that on interacting with liposomes a cytotoxin increases the microviscosity of the hydrophobic region of membranes. This effect depends on the phase state of the lipids. Observations on the kinetics of the transfer of energy between pyrene probes and diphenylhexatriene have shown that on the addition of a cytotoxin to samples of liposomes with a negative surface charge an aggregation of the liposomes takes place without a disturbance of their integrity.Institute of Bioorganic Chemistry, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 6, pp. 755–759, November–December, 1986.     

A study of the interaction of the cytotoxin of the venom of the Central Asian cobra with liposomes by the spin probe method

It has been shown by the spin probe method that the action of the cytotoxin of the venom of the central asian cobra on artifical liposomes extends at least to the depth of localization of the iminoxyl head of stearic acid spin-labeled at C-16. The greatest effect of the cytotoxin is observed on liposomes with a negative surface charge.Institute of Bioorganic Chemistry, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Priorodnykh Soedinenii, No. 2, pp. 211–215, March–April, 1981.     

Boosting the Photoactivity of BiVO4 Photoanodes by a ZnCoFe-LDH Thin Layer for Water Oxidation

Monoclinic bismuth vanadate (BiVO₄) has been used as an efficient photoanode material for photoelectrochemical water oxidation owing to its suitable band gap and nontoxicity. Nevertheless, the practical application of BiVO₄ photoanode has been severely limited by the surface charge recombination and sluggish kinetic, which leads to the obtained photoactivity of BiVO₄ is much lower than its theoretical value. In this case, ZnCoFe-LDH thin layer is conformally decorated on the porous BiVO₄ photoanode through a simple electrodeposition process. The results show that a boosted photoactivity and a remarkably enhanced photocurrent density (3.43 mA cm⁻² at 1.23 V_RHE) are attained for BiVO₄/ZnCoFe-LDH. In addition, the optimized BiVO₄/ZnCoFe-LDH photoanode exhibits significant negative shift in the onset potential (0.51 V_RHE to 0.21 V_RHE), promotes charge separation efficiency (49.3% to 60.4% in the bulk, 29.6% to 61.9% on the surface at 1.23 V_RHE) and enhanced IPCE efficiency (25.5% to 54.7% at 425 nm) compared with that of bare BiVO₄ photoanode. It is demonstrated that the boosted photoactivity of BiVO₄/ZnCoFe-LDH photoanode is mainly ascribed to the synergy effects of the formation of p-n heterojunction between ZnCoFe-LDH and BiVO₄ to accelerate the photogenerated charge transfer and separation, broaden light absorption, as well as promote the surface water oxidation kinetics.     

Studies with inorganic precipitative membranes: XI. Membrane potential response,characterization and evaluation of effective fixed charge density

Membrane potentials arising across parchment supported nickel and cobalt phosphate membranes when they separete 1:1 electrolyte solutions of concentration c₁ and c₂ such that c₁=10 c₂, have been measured. The membranes in contactwith dilute solutions have been found to carry a negative charge whereas the charge reversal was observed when the membrane was separating concentrated solutions. The membrane potential data have been used according to the procedure prescribed by Teorell-Meyer-Sievers theory (the TMS theory) to derive the value of effective fixed charge density of membranes. The electrical double layer at the membrane-solution interface has been suggested to control the over all rate of diffusion.     

Correlation between flat-band potential position and oxygenated termination nature on boron-doped diamond electrodes

This paper deals with a study about the position of the flat-band potential and the surface chemistry of boron-doped diamond electrodes. Successive and mild anodic treatments have been performed on as-deposited electrodes, in H₂SO₄. From Mott–Schottky plots, flat-band potential (V_FB) evolution has been monitored, exhibiting successively negative then positive shifts during surface oxidation, depending on the anodic coulometric charge. Thanks to surface characterization by X-ray Photoelectron Spectroscopy (XPS), this particular evolution of V_FB has been related to the evolution of specific oxygen functionalities at the surface. While the general trends in the literature is to associate the V_FB displacement with the generation of oxygenated terminations, the results presented in this study exhibit the high sensitivity of V_FB to hydroxyl or ether groups.     

Photostimulated exoemission from the surface of magnesia

Photostimulated exoemission (PSE) from magnesia was studied along with the effect of the adsorption of active gases (H₂, O₂, CO₂, and water vapors) on the intensity and kinetics of the emission decay. Based on the literature data, it was shown that PSE was excited from the local surface centers including a pair of low-coordinated ions Mg_1c²⁺-O_1c²⁻ and V_s hole centers, which were also active centers of photosorption and photocatalytic oxidation of methane and some other hydrocarbons.     

Salt catalyzed heterogeneous dilute acid hydrolysis of the difficultly accessible portion of cellulose: Effect of nature of metal co-ion

The effect of nature of metal co-ion on the rate of hydrolysis, V_c, of the difficulty accessible portion of cellulose was investigated for Li⁺, Na⁺, K⁺, and Ca²⁺. For the univalent ions V_c decreases exponentially with an increase in ionic radius for a given concentration of co-ion. For Ca²⁺, V_c is lower than would be predicted on the basis of ionic radius. This is attributed to the increased charge and/or increased degree of hydration. For the univalent ions the data presented suggest V_c increases sharply with concentration up to 0.25M, while for Ca²⁺, V_c increases more gradually up to 2.25M, before V_c begins to drop.     

Understanding the Roles of Oxygen Vacancies in Hematite‐Based Photoelectrochemical Processes

Oxygen vacancy (V_O) engineering is an effective method to tune the photoelectrochemical (PEC) performance, but the influence of V_O on photoelectrodes is not well understood. Using hematite as a prototype, we herein report that V_O functions in a more complicated way in PEC process than previously reported. Through a comprehensive analysis of the key charge transfer and surface reaction steps in PEC processes on a hematite photoanode, we clarify that V_O can facilitate surface electrocatalytic processes while leading to severe interfacial recombination at the semiconductor/electrolyte (S‐E) interface, in addition to the well‐reported improvements in bulk conductivity. The improved bulk conductivity and surface catalysis are beneficial for bulk charge transfer and surface charge consumption while interfacial charge transfer deteriorates because of recombination through V_O‐induced trap states at the S‐E interface.     

Comparative study of the cytotoxins of the venom of the central asian cobraNaja naja oxiana by the intrinsic-fluorescence method

The intrinsic fluorescence of cytotoxin V_C1 and V_C5 from the venom of the Central Asian cobra due to the tyrosine residues and differing with respect to quantum yield for these two polypeptides because of the nonidentity of the microenvironments of the tyrosyl residues has been measured and characterized. The dependence of the quantum yield on the pH and the temperature also indicate this nonidentity.Institute of Bioorganic Chemistry, Academy of Sciences of the Uzbek SSR, Tashkent. Institute of Biochemistry, Academy of Sciences of the Uzbek SSR, Tashkent. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 226–228, March–April, 1986.     

Structural aspects of the metal-insulator transition in V4O7

V₄O₇ has a transition with decreasing temperature at 250 K and the structure has been refined at 298 and 200 K. The triclinic structure (A$\text{1}$) consists of rutile-like layers of VO₆ octahedra extending indefinitely in the a-b plane and four octahedra thick along the c-axis. The average VO distances for the four independent V atoms are 1.967, 1.980, 1.969, and 1.984 Å at 298K and 1.948, 1.992. 1.961, and 2.009 Å at 200K. At 200K there is a clear separation into strings of V³⁺ or V⁴⁺ ions running parallel to the pseudorutile c-axis. In addition, all of the 3+ and half of the 4+ sites are paired to form short VV bonds. The remaining V⁴⁺ atom is displaced toward one oxygen so as to balance its electrostatic charge. The distortion at the metal-insulator transitions in V₄O₇, Ti₄O₇, VO₂ + Cr, and NbO₂ are compared.     

Ba3V2S4O3: A Mott Insulating Frustrated Quasi‐One‐Dimensional S=1 Magnet

Through a solid‐state reaction, a practically phase pure powder of Ba₃V₂S₄O₃ was obtained. The crystal structure was confirmed by X‐ray single‐crystal and synchrotron X‐ray powder diffraction (P6₃, a=10.1620(2), c=5.93212(1) Å). X‐ray absorption spectroscopy, in conjunction with multiplet calculations, clearly describes the vanadium in charge‐disproportionated V^IIIS₆ and V^VSO₃ coordinations. The compound is shown to be a strongly correlated Mott insulator, which contradicts previous predictions. Magnetic and specific heat measurements suggest dominant antiferromagnetic spin interactions concomitant with a weak residual ferromagnetic component, and that intrinsic geometric frustration prevents long‐range order from evolving.     

Investigating the Role of Adducts in Protein Supercharging with Sulfolane

The supercharging effect of sulfolane on cytochrome c (cyt c) during electrospray ionization mass spectrometry (ESI-MS) in the absence of conformational effects was investigated. The addition of sulfolane on the order of 1 mM or greater to denaturing solutions of cyt c results in supercharging independent of protein concentration over the range of 0.1 to 10 μM. While supercharging was observed in the positive mode, no change in the charge state distribution was observed in the negative mode, ruling out polarity-independent factors such as conformational changes or surface tension effects. A series of sulfolane adducts observed with increasing intensity concurrent with increasing charge state suggests that a direct interaction between sulfolane and the charged sites of cyt c plays an important role in supercharging. We propose that charge delocalization occurring through large-scale dipole reordering of the highly polar supercharging reagent reduces the electrostatic barrier for proximal charging along the cyt c amino acid chain. Supporting this claim, supercharging was shown to increase with increasing dipole moment for several supercharging reagents structurally related to sulfolane.     

Enhancement of immune response and protection in BALB/c mice immunized with liposomal recombinant major surface glycoprotein of Leishmania (rgp63): The role of bilayer composition

Development of new generation vaccines requires adjuvants to elicit the type and intensity of immune response needed for protection. Liposomes have been shown to be an effective adjuvant formulation. In this study, the role of liposome bilayer composition with different phase transition temperature (T_c) to induce a T helper 1 (Th1) type of immune response and protection against leishmaniasis in BALB/c mice was assessed. Liposome formulations with different bilayer compositions consisting of egg phosphatidylcholine (EPC, T_c < 0 °C), dipalmitoylphosphatidylcholine (DPPC, T_c 41 °C), or distearoylphosphatidylcholine (DSPC, T_c 54 °C) were prepared. All liposomes were contained rgp63 as a recombinant antigen and used to immunize mice subcutaneously 3 times in 3-week intervals. Evaluation of lesion development and splenic parasite burden after challenge with L. major, evaluation of Th1 cytokine (IFN-γ) and Th2 cytokine (IL-4), and titration of IgG isotypes were carried out to assess the type of generated immune response and extent of protection. The results indicated the generated immune response in mice was influenced by the bilayer composition of liposomes, so that mice immunized with liposomes consisting of EPC induced a Th2 type of immune response while liposome consisting of DPPC or DSPC induced Th1 type of immune response. It seems that liposomes prepared with higher Tm phospholipids are suitable formulation to induce Th1 type of immune response and protection, and so might be used for further investigations to develop an effective vaccine against leishmaniasis.     

Tautomerism of Aza cycles: IV. Tautomeric structure of 4,5-dihydropyrazol-5-one annelated on bond C3-C4 with piperidine cycle,and its three hydrochlorides

5-Methyl-2-phenyl-3,3a,4,5,6,7-hexahydro-2H-pyrazolo[4,3-c]pyridin-3-one has been synthesized and shown to exist in crystal as zwitterionic structure with the proton localized on the nitrogen atom in the piperidine ring and negative charge delocalized over the pyrazololate fragment. The structure of 2: 1, 1: 2, and 2: 3 hydrochlorides derived from the title compound has been determined by X-ray analysis.     

Ab-initio SCF study of the nature of bonding in neutral and cationic silicon hydrides and analogous carbon compounds

The nature of bonding in a number of neutral and cationic silicon hydrides has been studied on the basis of atomic charge (q_A), valency (V_A), molecular valency (V_M) and localised molecular orbitals (LMO). Several structural isomers of each species have been considered. It is found that the most stable isomer is generally associated with maximum q_si and minimum V_si and V_M. Protonation of the neutral hydrides leads to an increase in the positive charge of Si, and in molecular valency. The bonding characteristics of the most stable isomers of the silicon hydrides have been compared with that of analogous hydrocarbons. It has been observed that the difference in bonding stems mainly from the highly electro-positive nature of the Si atom which prefers to form three-centre rather than multiple bonds. The molecular hardness parameters (η) have also been calculated. The most stable isomers of silicon hydrides are generally associated with maximum η. The HSAB principle has been tested by considering some hydrogenation and proton transfer reactions. It is qualitatively satisfied in both cases.     

Investigation of the relationship betweenT c and the Coulomb interaction of copper cations from the neighboring CuO2 layers

Sixty known high-temperature cuprates from different systems are analyzed. It is shown that the temperature of the transition to the superconducting state (T_c) correlates with the Coulomb interaction V_ij between the Cu cations from the neighboring CuO₂ layers. The dependence T_c(V_ij) is plotted as two families of parabolic curves resembling an orthogonal system of confocal parabolas. It follows from this relationship that the optimal doping of CuO₂ layers depends on the Cu-Cu distances between the neighboring CuO₂ layers. Methods of varying the charges on and the distances between the copper atoms are demonstrated. The potential applications of this relationship for developing the compositions of new high-temperature materials and choosing methods to raise T_c of known high-temperature cuprates are discussed.     

Space charge influenced photocurrent transients in fluid solution

The dependence of space charge influenced current transients on the spatial distribution of photogenerated carriers in the bulk of a conductivity cell was investigated with the aim of correlating the observed time evolution of the currents with carrier properties such as mobilities and recombination constant. Approximate analytical solutions for the limiting cases of sheet and full interelectrode illumination show how experimental transients result from the competition between the dynamically interdependent processes: interionic recombination, charge carrier migration and discharge at the electrodes, and space charge buil-up. The voltage dependence of the time at which the secondary photocurrent maxima are observed yield mobilities of 2.0 × 10^?4 and 2.8 × 10^?3 cm² V^?1 s^?1 respectively for the pyrene cation and the solvated electron in tetrahydrofuran at room temperature. A bimolecular recombination rate constant of 2.3 × 10^?9 cm³ s^?1 is shown to be consistent with the space charge densities present after total separation of the positive and negative carriers for various periods of charge carrier recombination.     

The phase behaviour ofl-α-phosphatidylcholine in the presence of chlorpromazine under different experimental conditions

The phase behaviour ofl-α-phosphatidylcholine liposomes has been studied as a function of temperature, pH, ionic strength, etc., in the presence and absence of chlorpromazine by a polarization method using 1,6-diphenyl-1,3,5-hexatriene as a fluorescence probe. The gel crystalline to liquid crystalline (T_c), liquid crystalline to cubic (T_II), and cubic to hexagonal (H_II) transition temperatures in multilayer liposomes have been detected, and are found to be affected by chlorpromazine under different experimental conditions.     

长链双烷基次膦酸作为共吸附剂修饰TiO_2光阳极

对TiO2/染料/电解质界面进行修饰是提高染料敏化太阳电池(DSC)性能的有效手段,其中引入共吸附剂有机小分子和染料共同吸附在TiO2表面是一种简单有效提高DSC性能的方法.本文合成了长链的双正十二烷基次膦酸(DDdPA)作为染料的共吸附剂应用于染料敏化太阳电池.通过红外光谱(FT-IR)表征DDdPA在TiO2表面的吸附;借助电化学阻抗谱(EIS)及强度调制光电流谱(IMPS)/强度调制光电压谱(IMVS)等技术表征了电子的传输与复合动力学过程.研究发现,DDdPA可以很好地与染料共同吸附在TiO2表面;与二(3,3-二甲基丁基)次膦酸(DINHOP)相比,DDdPA的引入可以更好地抑制TiO2/染料/电解质界面处的电子复合;在优化浓度配比下,DDdPA的引入有效提高了器件的电子寿命,使TiO2导带边负移约30 mV,最终使器件的开路电压提高了47 mV,光电转换效率提升约10%.     

Prediction of surface tension and surface concentration of binary refrigerant system (R290/R600a) at various temperatures and pressures

The surface tension of a binary refrigerant mixture of R290(propane: C₃H₈) and R600a(isobutane:i-C₄H₁₀) has been calculated by using critical constants (P_c, V_c and T_c) and acentric factor (ω) at three isotherms of 278 K, 300 K and 320 K over the pressure range from 187.7 to 1540.2 kPa. In this paper, new formalism has been made by using simple mixing rule for modifying the predictive models: Brock–Bird, Pitzer, Hakim et al., Bolotin, Sastri–Rao and Zuo–Stenby. On comparing the computed values of surface tension with experimental data, satisfactory results have been observed. The average absolute deviation (AAD) obtained from the comparison of experimental and calculated surface tension values for six models is less than 1.9%. Finally, in a new approach, the extended Langmuir model (EL) was used to finding more information about the surface structure and surface concentration of binary refrigerant mixtures.