Apparent Specific Polarization and Dipole Moment of Some Poly(oxyethylene) Glycols in 1,4-Dioxane and Benzene Solutions at 298.15 K

Summary. The electrical permittivity of 1,4-dioxane and benzene solutions of some poly(oxyethylene) glycols up to the average molecular weight of 1590 were measured at 298.15 K. From the experimental data the limiting apparent specific polarization and partial molar polarization were calculated. The electrical dipole moment of the investigated solutes was estimated according to the Debye, Onsager, and Kirkwood theoretical approaches. The calculated dipole moments increase linearly with the square root of the number of monomeric units. The group dipole moment of the polar monomeric unit was calculated from the corresponding limiting partial molar volume, the refraction and polarization of the solute. The factor g, which takes into account the degree of flexibility of the chain, was estimated and found to be greater than 0.92, which means that the lower members of the poly(oxyethylene) glycols possess almost free rotation within the chain backbone of polymer.     

Apparent molar volumes and compressibilities of electrolytes and ions in γ-butyrolactone

The densities of tetraphenylphosphonium bromide, sodium tetraphenylborate, lithium perchlorate, sodium perchlorate and lithium bromide in γ-butyrolactone at (288.15, 293.15, 298.15, 303.15, 308.15 and 313.15) K and speed of sound at 298.15 K have been measured. From these data apparent molar volumes V_Φ at (288.15, 293.15, 298.15, 303.15, 308.15 and 313.15) K and the apparent molar isentropic compressibility K_S,Φ, at T = 298.15 K of the salts have been determined. The apparent molar volumes and the apparent molar isentropic compressibilities were fitted to the Redlich, Rosenfeld and Mayer equation as well as to the Pitzer and Masson equations yielding infinite dilution data. The obtained limiting values have been used to estimate the ionic data of the standard partial molar volume and the standard partial isentropic compressibility in γ-butyrolactone solutions.     

Apparent Molar Volumes and Viscosities of Dl-α-Alanine in Water-Ethanol Mixtures

Abstract

In this work we present a systematic study of the apparent molar volumes and the viscosities of DL-α-alanine in aqueous ethanol solutions at 25,00°C. The molar fractions of ethanol for the solvent mixtures were selected taking into account that thermodynamic properties such as partial molar volumes and heat capacities of these mixtures show a transition concentration around X _et = 0,1 at which its behavior suffers a deep change. Besides, this ethanol concentration is near to that required to produce 50% of protein denaturation.

The results were used to evaluate the limiting partial molar volume V0 of the solute the volume changes associated with its transfer from water to aqueous ethanol solutions and the viscosity B coefficients of DL-α-alanine. The values obtained for the transference molar volumes and the viscosity B coefficients of alanine in the aqueous mixtures show a minimum at X _et = 0,1000. The results are discussed in terms of changes in the solvent structure (Ref. [1])     

Thermokinetic Oscillation of a Two-step Reacting System Coupled with Thermal Conduction and Apparent

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Apparent Molar Volume and Apparent Molar Refraction of Mono-, Di-, Tri-, and Tetra(oxyethylene) Glycol in Aqueous, 1,4-Dioxane,and Benzene Solutions at 298.15 K

Summary. The density and refractive index of aqueous, 1,4-dioxane, and benzene solutions of poly (oxyethylene) glycols of the type HO–(CH₂CH₂O) _n –H (n varying from 1 to 4) were measured at 298.15K. From these experimental data the apparent molar volume and the apparent molar refraction at infinite dilution were calculated. The limiting apparent molar volume of the investigated compounds in a definite solvent depends linearly on the number of oxyethylene groups. From these data, the volume of the monomeric unit was evaluated and found to be greater in non-aqueous solvents than in water. The limiting apparent molar refraction of the solute for the investigated systems, within the experimental uncertainties, is equal to the molar refraction of the pure solute. The electronic polarizability of the solute molecule depends linearly on the number of monomeric units and the ratio of the electronic polarizability to the molecular van der Waals volume is constant and independent of the number of oxyethylene groups.Received February 24, 2003; accepted (revised) April 10, 2003 Published online August 18, 2003     

Apparent Molar Volume and Apparent Molar Refraction of Mono-, Di-, Tri-, and Tetra(oxyethylene) Glycol in Aqueous, 1,4-Dioxane, and Benzene Solutions at 298.15?K

The density and refractive index of aqueous, 1,4-dioxane, and benzene solutions of poly (oxyethylene) glycols of the type HO–(CH₂CH₂O) _n –H (n varying from 1 to 4) were measured at 298.15K. From these experimental data the apparent molar volume and the apparent molar refraction at infinite dilution were calculated. The limiting apparent molar volume of the investigated compounds in a definite solvent depends linearly on the number of oxyethylene groups. From these data, the volume of the monomeric unit was evaluated and found to be greater in non-aqueous solvents than in water. The limiting apparent molar refraction of the solute for the investigated systems, within the experimental uncertainties, is equal to the molar refraction of the pure solute. The electronic polarizability of the solute molecule depends linearly on the number of monomeric units and the ratio of the electronic polarizability to the molecular van der Waals volume is constant and independent of the number of oxyethylene groups.     

The QSAR Research of Pyrrolobenzothiazepinones and Pyrrolobenzo-xazepinones-Novel and Specific Non-Nucleoside HIV-1 Reverse Transcriptase Inhibitors

IntroductionQSARisoneofthevaluablemeansindIugdedgne~allyfOrthoSesubStrateSwhicharenoknonclearly'ThetIadihonalQSARwasprDPagaIedbyHanschandFuitawhicheInPloyedmultiPlelinearregressiontechitiquestoobtalnqndtativerelationshiPs,ReCentiysome3DDSANmethodsareproposedwhichcantreastericandeleCtrnicproPertiessimultaneouslyinamorepraedcalmannr.TwoofthemoStsuccesthe3DQSARmdsodsareCoMFA[l],un-3D[2].AJthoughgreatPrOgresshasbenaCqulwttheSemethodshavehencrihdzedandshouldnillbeconsideredinthot…     

Specific C-H⋯N intramolecular interactions in the vinyloxy- and vinylthiopyridine series

A weak hydrogen bond with the participation of the vinyl group -hydrogen atom arises in 2-vinyloxypyridine and 2-vinylthiopyridine, which primarily exist in the s-trans-conformation, according to the ¹H and ¹³C NMR data. This interaction does not take place in 2-vinyloxymethyl- and 2-vinyloxyethylpyridines, which primarily exist in the s-cis-conformation. The C-H...N intramolecular interaction also does not occur in o-vinyloxyaniline due to the specific features of the stereoelectronic state of the amino group nitrogen atom.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1077–1081, August, 1991.     

Densities, Specific Heat Capacities, Apparent and Partial Molar Volumes and Heat Capacities of Glycine in?Aqueous Solutions of Formamide, Acetamide, and?N,N-Dimethylacetamide at T=298.15?K and?Ambient Pressure

Apparent molar volumes (V _2,φ ) and heat capacities (C _p2,φ ) of glycine in known concentrations (1.0, 2.0, 4.0, 6.0, and 8.0 mol⋅kg⁻¹) of aqueous formamide (FM), acetamide (AM), and N,N-dimethylacetamide (DMA) solutions at T=298.15 K have been calculated from relative density and specific heat capacity measurements. These measurements were completed using a vibrating-tube flow densimeter and a Picker flow microcalorimeter, respectively. The concentration dependences of the apparent molar data have been used to calculate standard partial molar properties. The latter values have been combined with previously published standard partial molar volumes and heat capacities for glycine in water to calculate volumes and heat capacities associated with the transfer of glycine from water to the investigated aqueous amide solutions, D[`(V)]<sub>2,tr</sub><sup>o</sup>\Delta\overline{V}_{\mathrm{2,tr}}^{\mathrm{o}} and D[`(C)]_p2,tr^o\Delta\overline{C}_{p\mathrm{2,tr}}^{\mathrm{o}} respectively. Calculated values for D[`(V)]<sub>2,tr</sub><sup>o</sup>\Delta\overline{V}_{\mathrm{2,tr}}^{\mathrm{o}} and D[`(C)]_p2,tr^o\Delta\overline{C}_{p\mathrm{2,tr}}^{\mathrm{o}} are positive for all investigated concentrations of aqueous FM and AM solutions. However, values for D[`(C)]_p2,tr^o\Delta\overline{C}_{p\mathrm{2,tr}}^{\mathrm{o}} associated with aqueous DMA solutions are found to be negative. The reported transfer properties increase with increasing co-solute (amide) concentration. This observation is discussed in terms of solute + co-solute interactions. The transfer properties have also been used to estimate interaction coefficients.     

Apparent Molar Volumes and Adiabatic Compressibilities of Crown Ethers and Glymes in H2O and D2O at 25°C

The apparent molar volumes and adiabatic compressibilities of 18-Crown-6, 15-Crown-5, 12-Crown-4, tetraglyme, and triglyme were measured at 25°C in H₂O and D₂O. The contribution of the -CH₂CH₂O- group to the limiting partial molar volumes and compressibilities of cyclic and open-chain ethers in both solvents are compared and solvent isotope effects calculated. It is concluded, based on the compressibility results, that there is a subtle difference between the hydration of the ethene oxde group in cyclic and open-chain ethers and that this difference persists in D₂O. These results indicate that the calculation of limiting apparent molar compressibilities using additivity schemes will have to account for whether the group is in a cyclic or open-chain compound.     

Apparent and Transfer Molar Volumes for Aqueous Solution Containing Polyethylene Glycols and Amino Acid Ionic Liquids at 298.15 K

The densities of 1-n-butyl-3-methylimidazolium ([Bmim]) based amino acid ionic liquids (AAILs) prepared from glycine [Gly], alanine [Ala], and valine [Val], namely [Bmim][Gly], [Bmim][Ala] and [Bmim][Val], in aqueous?~?0.2 mol·kg^?1 polyethylene glycol (PEG400, PEG600 or PEG1000) and PEG400 solutions containing?~?(0.0946, 0.1891 and 0.3820) mol·kg^?1 of [Bmim][Gly], have been determined at 298.15 K. The experimental densities were used to evaluate the apparent molar volumes in the mixed solvent system and further used to obtain transfer molar volumes of AAILs for their transfer from water to aqueous PEG solutions and of PEG400 for its transfer from water to aqueous solutions containing (0.0946, 0.1891 and 0.3820) mol·kg^?1 of [Bmim][Gly]. The transfer molar volumes of AAILs and of PEG400 are found to be negative. The effects of alkyl chain-length variation on the anion of AAILs as well as the chain-length of PEG on transfer molar volumes are investigated and discussed in terms of hydrophobic–hydrophilic, hydrophobic–hydrophobic, and ion–hydrophobic interactions.     

Aβ28-Induced Specific and Effective Serum Antibodies Against Aβ42

Though phase I clinical trial of immunotherapy for Alzheimer's disease(AD) with inoculated Aβ42 in humans had been proven to be effective,phase II immunotherapy trial was discontinued in 2002 because a few patients developed significant inflammatory reactions caused by C-terminal domain of Aβ42.The aim of the study was to investigate the levels and the abilities of antibodies induced by C-terminal truncated Aβ species to inhibit Aβ42 aggregation and cytotoxity in vitro.46-week-old male BALB/c mice,Aβ42 and Aβ28/Aβ35/Aβ42 with a C-terminal eight-histidine tag(Aβ28H8,Aβ35H8,and Aβ42H8) were applied in the present study.The mice were randomly divided into 5 groups(n=8),control mice immunized with the normal saline,Aβ42-immunized mice and Aβ42H-/Aβ35H-/Aβ28H-immunized mice.All the serum antibodies were evaluated by measuring their abilities to inhibit Aβ42 aggregation and cytotoxity in vitro.Each mouse was vaccinated with purified Aβ peptide emulsified with Freund's adjuvant(volume ratio 1:1).Titers,concentrations and isotypes of serum antibodies against Aβ42 were measured by indirect ELISA.Effects of serum antibodies on Aβ42 aggregation and disassembly of Aβ42 fibrils in vitro were observed by electron microscopy.Effects of serum antibodies on Aβ42 cytotoxicity were determined by MTT assay.Aβ42 or Aβ28 could induce higher anti-Aβ42 antibody titer(1:6400) than Aβ35(1:3200).Significantly,Aβ28 induced more IgG1 and IgG2b isotype antibodies and less IgG2b isotype antibody than other Aβ species though all the induced serum antibodies could inhibit Aβ42 aggregation or fibrillogenesis,could induce the disassembly of Aβ42 aggregates,and neutralized or inhibited the cytotoxicity of Aβ42 in vitro.C-Terminal truncated Aβ28 could induce the same effective but safer serum antibodies against Aβ42 than full length Aβ42 by eliciting more Th2-type immune responses.     

Specific features of the reaction of l-cysteine with pyridoxal and N-pyridoxylidene-β-alanine

The mechanisms of condensation of l-cysteine, l-methionine, and l-serine with pyridoxal and of transaldimination of N-pyridoxylidene-??-alanine with l-cysteine were studied by the kinetic method. Unlike methionine and serine, the condensation of cysteine with pyridoxal and transaldimination with Npyridoxylidene-??-alanine involves intermediate formation of stable product having a thiazolidine ring. Its structure was determined by elemental analysis, UV, and IR spectroscopy, and quantum-chemical calculations. The thiazolidine fragment in the pyridoxal condensation product with l-cysteine is turned through an angle of ??90° with respect to the pyridine ring plane due to mutual repulsion of the negatively charged oxygen atom in the ortho position of the pyridine ring and sulfur and nitrogen atoms in the thiazolidine ring.     

Apparent and standard molar volumes and heat capacities of aqueous Ni(ClO4)2 from 25 to 85°C

Apparent molar heat capacities and volumes of aqueous Ni(C10₄)₂ were measured from 25 to 85°C over a concentration range of 0.02 to 0.8 mol-kg^-1 using a Picker flow microcalorimeter and a Picker vibrating-tube densimeter. An extended Debye-Hückel equation was fitted to the experimental data to obtain expressions for the apparent molar properties as functions of ionic strength for Ni(ClO₄)₂(aq). The standard-state partial molar properties for Ni(C10₄)₂(aq) in the temperature range 25 to 85°C were obtained and can be expressed by empirical equations as 97787 and withT in K. The standard partial molar heat capacities and volumes for Ni²⁺ (aq) from 25 to 86°C were obtained by using the additivity rule and data for ClO^- ₄(aq) in the literature. These values were extrapolated to 300°C by employing the Helgeson-Kirkham-Flower (HKF) equations, amended to include a standard-state correction term.     

α-Acrylaldehyde 3-Pyrrolyl BODIPY as a Specific Optical Sensor for Cysteine and Homocysteine

A new fluorophore, α-acrylaldehyde 3-pyrrolyl BODIPY was synthesized by treating 3-pyrrolyl BODIPY with a mixture of 3-(dimethylamino) acrolein and POCl₃ under Vilsmeier–Haack reaction conditions. The X-ray structure revealed that the fluorophore was almost planar, and the appended pyrrole was in the same plane with a small deviation from the mean plane. We investigated the potential use of α-acrylaldehyde 3-pyrrolyl BODIPY for sensing thiol containing amino acids such as cysteine/homocysteine (Cys/Hcy). Our studies showed that the α-acrylaldehyde- 3-pyrrolyl BODIPY was found to be useful for exclusive sensing of Cys/Hcy and to exhibit different optical signaling responses to Cys and Hcy at physiological pH in aq. CH₃CN (1 : 1 v/v, PBS) medium. The enhancement in optical properties for Cys and quenching in same properties for Hcy was attributed to different binding modes of Cys/Hcy with α-acrylaldehyde 3-pyrrolyl BODIPY.     

Specific Photographic and Luminescent Properties of Sulfur + Gold–Sensitized Silver Halide Emulsions

It was found that the introduction of univalent gold ions at the initial step of sulfur sensitization could lead to a dramatic fall in the light sensitivity (S) and a considerable increase in the intensity of low-temperature ( = 77 K) luminescence (I) of silver sulfide clusters produced by sensitization. An increase in the hold time was accompanied by an increase in S and a decrease in I. The fall in S is associated with the oxidation of the silver moiety in (Ag₂S)_pAg⁺ _k or (Ag₂S)_qAg⁰ _n (q > p) clusters, which are light sensitivity centers. AgBr(I) emulsions subjected to sulfur + gold-sensitization exhibited a flash of IR-excited green luminescence from paired iodine centers. The appearance of this flash is due to the generation of deep electron traps by sulfur–gold sensitization.     

Specific features of the behavior of α- and β-glycosylfluoride tetraacetates during chemical ionization in isobutane and tetramethylsilane

Reactions of - and -glycosylfluoride tetraacetates with trimethylsilicenium ion in the gas phase during chemical ionization have been studied. The [M+SiMe₃]⁺ ions formed from the glycosylfluorides are more stable than the corresponding [M+H]⁺ ions. The cleavage of the weakest glycosidic bond leading to the generation of glycosidic ions is not dominant for the trimethylsilylated ions, as it has been observed in the corresponding protolytic reactions. The ratio of the intensities of the [M+SiMe₃]⁺ and [M–F]⁺ ions characterizes the probability of the initial localization of the trimethylsilyl ion at the glycosidic center; the equatorial orientation of fluorine at C(1) makes it possible for the electrophile to bond with this substituent. Generation of the glycosidic ions is rather weakly affected by increasing temperature, whereas [M-AcO]⁺ formation is significantly intensified.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 629–633, April, 1994.This work was carried out with financial support from the Russian Foundation for Basic Research.     

Apparent molar and partial molar volumes of aqueous ceric ammonium nitrate solutions at 20, 25, 30, and 35°C

Present paper reports the measured densities (ρ) and refractive indices (n _D) of aqueous solutions of ceric ammonium nitrate (CAN) at 20, 25, 30, and 35°C in different concentrations of solution. Apparent molar volumes (φ_v) have been calculated from the density data at different temperatures and fitted to Massons relation to get limiting partial molar volumes (? _v ⁰ ) of CAN. Refractive index data were fitted to linear dependence over concentration of solutions and values of constant K and n _D ⁰ for different temperatures were evaluated. Specific refractions (R _D) of solutions were calculated from the refractive index and density data. Concentration and temperature effects on experimental and derived properties have been discussed in terms of structural interactions.