Search

Deuterium spin relaxation was used to examine the motion of enzyme-bound water on subtilisin Carlsberg colyophilized with inorganic salts for activation in different organic solvents. Spectral editing was used to ensure that the relaxation times were associated with relatively mobile deuterons, which were contributed almost entirely by [D.sub.2]O rather than hydrogen-deuteron exchange on the protein. The results indicate that the timescale of motion for residual water molecules on the biocatalyst, ([[tau].sub.c]) [D.sub.2]O, in hexane decreased from 65 ns (salt-free) to 0.58 ns (98% CsF) as [([k.sub.cat]/[K.sub.M]).sub.app] of the biocatalyst preparation increased from 0.092 [s.sup.-1]*[M.sup.-1] (saltfree) to 1,140 [s.sup.-1]*[M.sup.-1] (98% CsF). A similar effect was apparent in acetone; the timescale decreased from 24 ns (salt-free) to 2.87 ns (98% KF), with a corresponding increase in [([k.sub.cat]/ [K.sub.M]).sub.app] of 0.140 [s.sup.-1]*[M.sup.-1] (salt-free) to 12.8 [s.sup.-1]*[M.sup.-1] (98% KF). Although a global correlation between water mobility and enzyme activity was not evident, linear correlations between In[[([k.sub.cat]/[K.sub.M]).sub.app]] and ([[tau].sub.c])[D.sub.2]O were obtained for salt-activated enzyme preparations in both hexane and acetone. Furthermore, a direct correlation was evident between [([k.sub.cat]/[K.sub.M]).sub.app] and the total amount of mobile water per mass of enzyme. These results suggest that increases in enzymebound water mobility mediated by the presence of salt act as a molecular lubricant and enhance enzyme flexibility in a manner functionally similar to temperature. Greater flexibility may permit a larger degree of local transition-state mobility, reflected by a more positive entropy of activation, for the salt-activated enzyme compared with the salt-free enzyme. This increased mobility may contribute to the dramatic increases in biocatalyst activity. enzyme activation | organic solvents | salts | subtilisin Carlsberg

Mutnovskite, ideally [Pb.sub.2]As[S.sub.3](I,Cl,Br), is a new mineral from the high-temperature fumaroles of the Mutnovsky volcano, Kamchatka Peninsula, Russian Federation. It occurs as microscopic ruby-colored short-prismatic crystals up to 100 [micro]m across, closely associated with halogen-sulfosalts of Pb, Bi, and As, Cd-Pb-Bi sulfosalts, pyrite, anhydrite, and cristobalite. Mutnovskite is transparent in thin fragments with a dark-red to blue color. The crystals are soft and fragile. Cleavage and fracture were not observed and the Mohs hardness is approximately 2. In reflected light mutnovskite is silvery lead-grey in color with an iridescent tarnish. Pleochroism and anisotropy are not visible because of the strong orange internal reflections, especially in immersion. Reflectance percentages measured in air in the range 400-700 nm were tabulated. Reflectance percentages ([RM.sub.min], and [R.sub.max]) for the four COM wavelengths are 34.2, 34.6 (470 nm), 33.2, 33.5 (546 nm), 32.5, 32.7 (589 nm), and 31.4, 31.7 (650 nm), respectively. A mean of four electron microprobe analyses gave Pb 62.0(3), As 11.0(4), Bi 0.6(1), S 14.4(2), Se 0.2(3), I 8.9(3), CI 2.44(9), Br 1.1(7), Cu 0.03(2), Fe 0.01(1), total 100.7 wt%, corresponding, on the basis of a total of 7 atoms, to [Pb.sub.1.99][([As.sub.0.98][Bi.sub.0.02])).sub.[summation]1.00] [([S.sub.2.98][Se.sub.0.02]).sub.[summation]3.00][([I.sub.0.47][Cl.sub.0.46] [Br.sub.0.09]).sub.[summation1.02]. The nine strongest powder-diffraction lines [d in [Armstrong] (I/[I.sub.0])(hkl)] are: 4.69 (32) (002): 4.37 (67) (210): 3.34 (73) (020); 3.19 (100) (212); 2.715 (61) (022); 2.648 (66) (410); 2.539 (31) (213); 2.455 (29) (402); 1.894 (30) (232). Mutnovskite is orthorhombic, space group Pnma, with a = 11.543(1), b = 6.6764(7), and c = 9.359(1) [Armstrong], V = 721.3(1) [Armstrong], Z = 4. The crystal structure was solved and refined to R = 4.14%. It consists of three independent cation positions: Pb 1 and Pb2 have tricapped trigonal prismatic coordinations with S and I atoms (completed with one As atom in the case of Pb2), while As has threefold coordination with S atoms, which form the base of a trigonal pyramid with As at the apex. Pairs of Pb1-Pb2 prisms are connected in columns which extend along c. As[S.sub.3] coordinations are isolated from each other. S atoms and half of the Pb atoms form wavy close-packed layers. Two kinds of channels parallel to b occur between the layers. The smaller channels host As atoms close to the channel walls, with their lone-electron pairs occupying the median part, while the bigger ones accommodate rows of alternating halogen and Pb atoms. The new mineral is named after the type locality, the Mutnovsky volcano, Kamchatka Peninsula, Russian Federation. Keywords: Mutnovskite, chemical composition, new mineral, X-ray data, crystal struture, Kamchatka Peninsula, Mutnovsky volcano

The screening of the electrical potential at a charged solid surface in a molten salt is investigated in a computer simulation study. Despite pronounced oscillatory structure in the charge density, the structure and dynamics of the ions close to the interface are very similar to those in the bulk.

Research has been conducted on the virus adsorption to microporous filters. The effect of mono-, di- and trivalent salts on this adsorption has been investigated.

Research has been conducted on the generation of alpha-fluoromalonaldehyde sodium salt. The reaction of this salt with acid chlorides is described.

Research has been conducted on the addition of enolate to pyridinium salt. Results demonstrate that acid-induced cyclization of 1,4-dihydropyridine produces tetracyclic 3,7-methano[1,4]diazonino[1,2-a]indole.

A study concerning the formation of uracil salts has been carried out. Examination of intramolecular interactions of cross-conjugated uracilylbetaines is discussed.

The authors focus on the development of the cheaper reagents for the large-scale peptide couplings. Experiments have demonstrated that 2-mercaptopyridine 1-oxide compound is an appropriate material for the preparation of uronium salts.

A study of the onium transfer reaction of alkenyl(phenyl)iodonium tetrafluoroborates to prepare group 15 1-alkenyl(triphenyl)onium (P, As, Sb) tetrafluoroborates is presented. Results demonstrate that reaction involves base-induced reductive alpha-elimination of the iodonium salts.

A photopolymer for fabrication of volume-type transmission holograms, which are used primarily on the holographic reflector for reflective LCD's, is reported. This photopolymer consists of bisphenol-type epoxy resin and an acrylic monomer with diaryliodonium salt and 3-ketocoumarin as a complex initiator. The chemistry of the imaging formation is based on the radical polymerization of the monomer initiated by a holographic exposure, followed by the cationic polymerization of epoxy resin by UV exposure alder postexposure baking. The yellowish color of the hologram derivatives that resulted from the sensitizing dye and from the photospeed were improved to satisfy the specifications for the holographic reflector. The holographic reflector now gives brighter images.

A study concerning the effects of the casein kinase 2 (CK-2) absence on cell processes is presented. Results demonstrate that CK-2 does not regulate sodium influx or efflux.

Research has been conducted on the Escherichia coli melibiose carrier. Results indicate an uncoupling of proton cotransport and reduction in N (super)+-coupled transport.

Research has been conducted on the addition of Grignard reagents to quinolinium salts. Results indicate that this addition occurs at the 2- and 4-positions.

A study concerning the synthesis of bismuthonium salts and ylides is presented. Results indicate that they bear an ester group at alpha-position.

Research has been conducted on the generation of the organochromium(III) species. Iodonium salts reaction with anhydrous chromium dichloride is described.

Research has been conducted on the oxidation of nitroxyl radicals to N-oxo ammonium salts used for alcohols as oxidants. Prediction of the nitroxyl radicals redox potential is discussed.

Research was conducted to determine the one-component synthesis of pyrylium salts using electrophilic cyclization. The scope of a novel acid-induced cyclization of ortho-alkynylated aromatic carbonyl functionalities into the isobenzopyrylium salts was investigated. The efficient one- and/or two-pot preparations of the corresponding 3-arylisoquinolines, which can act as key intermediates in the synthesis of many isoquinolie alkaloids but have proven difficult to access through current methodology is described.

The pH-dependent inhibition of 22 metal salts was systematically examined for the yeast Saccharomyces cerevisiae. It was observed that the inhibition of growth by Cu, Co or Ni salts is substantially increased by histidine auxotrophy and by increasing the pH of the medium. Deletion of the high-affinity histidine permease Hip1p in His- strains caused greater sensitivity to Cu, Co and Ni and the requirement of a higher level of histidine to reverse the inhibition. It was concluded that intracellular histidine reduces the pH-dependent toxicity of Cu, Co and Ni.

Research was conducted to reexamine the salt effect to solve the problem of poor reproducibility. The synthesis of mesoporous silica molecular sieves was obtained in the presence of salts under different experimental conditions. A hydrothermal stability test in boiling water, X-ray diffraction, infrared spectroscopy and scanning electron microscopy were used to analyze the hydrothermal stability and structure of the silica materials. It was found that the time dependence was a very important factor for the improvement of the hydrothermal stability.

Research was conducted to extend the study of the rearrangement to indazoles of 1,3-diaryl-substituted fused (1,2,3)triazolo(1,5-alpha)benzimidazolium and benzthiazolium salts which were heated at 80 degrees C. The study was extended for novel related ring systems. Results indicate that the ring opening of fused (1,2,3)triazolium salts is a general phenomenon and is closely related to the well-known retro-electrocyclizations of neutral fused (1,2,3)triazoles and tetrazoles.

A study was conducted to investigate a density functional theory (DFT) approach to the polyelectrolyte system where the hard sphere contribution to the excess free energy is measured through a nonperturbative weighted density approximation and the electrical contribution is computed by perturbation with respect of the uniform fluid. The DFT was found to agree well with Monte Carlo simulations for the density distribution of monovalent, divalent and mixed salts around charged cylinders. Results also showed that the DFT is more accurate than the Poisson-Boltzmann and HNC theories for divalent and mixed salts.

A comparative study was conducted to investigate the reactivity of primary and quaternary allylic and homoallylic alkenylammonium salts with dimethyldioxirane and m-chloroperbenzoic acid. The study determined the stereochemical outcome of the epoxidation of the cyclic quaternary allylic salt (2-cyclohexenyl)trimethylammonium p-chlorobenzenesulfonate with dimethyldioxirane and m-chloroperbenzoic acid. It also determined the epoxidation rate constants for the reaction of select allylic and homoallylic primary and quaternary ammonium salts.

Research was conducted to examine the synthesis of a dehydro precursor, which when treated with tritium would yield (super 3)H(sub 2)-lobeline in one step. The process began with chiral pyridium salt which was reduced to oxazolidine, a dihydropyridine equivalent, followed by the removal of the phenylethanol auxiliary with concomitant introduction of the methyl group at nitrogen. Results provides strong evidence that the salts of (-)-lobeline exists in solution as a single stereoisomer and validated the synthesis of this natural product.

A study on lithium salt systems investigated two factors which contribute to the establishment of a high ambient temperature conductivity in an ionic liquid. These factors are, namely, a high fluidity and a high conductivity/viscosity decoupling index. One aim of the study was to discover factors that determine the decoupling index on one hand and the glass transition temperature and fragility on the other hand for liquid salt mixtures which do not crystallize at ambient temperature.

A study on room temperature molten salts presents the first report of low molecular weight ammonium cation salts being molten at room temperature. The new family of salts is based on the pyrrolidinium cation IV where the two alkyl substituents range from methyl up to butyl. These salts are shown to have melting points below room temperature in some instances and exhibit interesting conductive behavior in their crystalline state in other cases.

A study on lithium halides in water was conducted to carry out a simple comparison of the extremes of the liquid state for two common lithium salt systems where concentrated solutions approaching the dihydrate could be investigated in both molten and supercooled states. The experimental results suggest the types of systems where higher boiling points might be obtained without undue increase on the glass transition temperature and, therefore, the viscosity.

A study on molten nitrate salts was conducted to obtain insights into the dynamics of their glassy state by investigating the ion dynamics in the fragile glass-former 2Ca(NO3)2-3RbNO3 using 87Rb nuclear magnetic resonance techniques. The experiment covered a broad temperature range, namely 8 K less than T less than 500 K. The temperature dependent spin-lattice relaxation rate exhibits two maxima. The maximum observed near 390 K reveals that the ionic motion causing both the structural and conductivity relaxation occurs on roughly the same time scale.

A capacitance manometer has been utilized to determine equilibrium water partial pressures and salt solubilities in aqueous NH4HSO4 over low temperature ranges. Measured pressures above the H2SO4 solution are consistent with values calculated using the procedure of Clegg et al, while results for the NH4HSO4 solutions also agree with calculated equilibrium water partial pressures. Solids form in the NH4HSO4 solutions at temperatures 258.0(sub 6) plus or minus 0.1 K, 246.4(sub 7) plus or minus 0.1 K and 261.0(sub 1) plus or minus 0.1 K.

The electrosynthetic approach has been found to be a convenient method in the reactions of two ketones and two alkenes leading to the formation monothianthrenium and bisthianthrenium salts. The selectivity to mono- or bisthianthrenium is proposed to be governed by the oxidation potential of the intermediate distonic radical cation. A single-crystal X-ray structure of the bisthianthrenium salt is also reported for the first time.

The monocarbonyl iodonium ylide is moderately nucleophilic in nature and undergoes stereoselective alkylidene transfer reaction to the C=N bond of the activated aldimines, affording 2-acylaziridines in good yields. This was gleaned from the results of an addition reaction of the monocarbonyl iodonium ylide to imines, which offers a stereoselective route for the synthesis of trans- and cis-2-acylaziridines. The stereochemical outcome of the aziridination was revealed to be dependent on both the activating groups of the imines and the reaction solvents.

Inorganic and organic salts of the cyanophosphonate dianion and the monoanion of ethyl cyanophosphonate have been synthesized through novel methods employing the deethylation of diethyl cyanophosphonate. The new procedures used iodotrimethylsilane instead of bromotrimethylsilane as the silyldealkylating reagent. The inorganic salts were easily prepared by the reaction of hydroxides such as NaOH and NH4OH. The organic salts were obtained by adding amines to solutions of cyanophosphonic acid or by reaction of a hydroxide of a quaternary ammonium cation with cyanophosphonic acid.

The tris(trifluoromethanesulfonyl)methide anion has been prepared through a two-step process. The anion has been synthesized as its cesium salt, using triflic anhydride as the electrophilic trifyl source. The corresponding ytterbium(III) and scandium(III) salts have also been synthesized and their use in the aromatic nitration of o-nitrotoluene with ytterbium(III) and scandium(III) triflates have been assessed. The triflide anion has been found to increase the activity of the triflide salts compared with the triflates in the aromatic nitration of the electron deficient arene o-nitrotoluene.

A study was conducted to analyze the translation encounter between ionic salts and nitroxide free radicals in aqueous solution. Relaxation time measurements were carried out as a function of magnetic field strength. The pH was adjusted based on the aliquots of dilute acid or base. Results indicated that magnetic relaxation data is not enough to generate a detailed characterization of local electrostatic fields between solutes.

The thermodynamic excess functions of solutions of strong electrolytes and their structure are described by an extension of the mean spherical approximation (MSA). Ionic association is also taken into account by means of Wertheim's formalism(super 18,19) in the MSA(super 20-24). Hydration effects are included using a concentration-dependent cation size and permittivity. The results show a very good representation for a number of mixed salts with a common cation. Cross parameters are introduced for salts without a common cation.

Research was conducted to examine the novel isomerization reaction of N,N-dimethyl-alpha-(methoxycarbonyl)-4-substituted-benzylammonium N-methylides with cesium fluoride. The reaction yielded two Stevens rearrangement products, namely methyl 3-(dimethylamino)-2-(4-substituted phenyl)propionates from N-methylides and methyl 3-(dimethylamino)-3-(4-substituted pphenyl)propionates from N-benzylides. When the cesium flouride used was not predried, additional Stevens rearrangement products were competitively formed from ylides.

The reactivities of a number of onium salts derived from 1-hydroxybenzotriazole and 1-hydroxy-7-azabenzotriazole were correlated with the structure of the reagents in question. Results verified that the aza derivatives are more reactive than the parent benzotriazole derivatives in both activation and coupling. Moreover, the activation step was determined by the structure of the carbon skeleton. The pyrrolidino derivatives were apparently preferred reagents compared to the piperidino analogues.

Research was conducted to examine the salt effects on binding and protein titration using a cavity-function theory for chemical association obtained with the exponential approximation. The coupling between the electrostatic interaction and hard-core interaction are investigated. Results indicate that the analytic theory more accurately predicts the electrostatic interaction factors measured in protein-titration experiments than the Debye-Huckel approximation theory.

A study was conducted to analyze the interaction between uncharged polymers and ionic surfactants in dilute aqueous solution using isothermal titration microcalorimetry. The 2277 TAM Thermal Activity Monitory system was utilized to carry out calorimetric measurements in a high-precision thermostatic bath. Experimental results indicated that the presence of extra salt and polarity of counterions influenced the interaction between polymers and surfactants.

A study was conducted to analyze the influence of salt and nonelectrolyte stress on the growth of Lactobacillus plantarum. The R 3010 quadrupole mass spectrometer was utilized to record electrospray mass spectra while L. plantartum cells were determined on cellulose actetate filters. Results indicated that severe growth inhibition correlated with the inability of cells to accommodate K+ to levels needed to restore turgor.

Research was conducted to examine procedures for the enantioselective synthesis of functionalized aminocyclopentenes and their application to the preparation of biomedically relevant cyclic and acyclic targets. The procedure developed for the synthesis of (+)-mannostatin A was modestly concise and economical in addition to its ability to highlighting the preparative utility of pyridinium salt photochemistry. It was also observed to have the flexibility necessary for the preparation of various regiochemical and stereochemical analogues of the natural product.

Research was conducted to examine the role of neopentyl 3-triflyloxypropanesulfonate, a reactive sulfopropylation reagent for the preparation of chemiluminescent labels. Neopentyl 3-triflyloxypropanesulfonate was easily prepared and was observed to be much more reactive than 1,3-propane sultone in the preparation of sterically hindered sulfopropylated acridinium chemiluminescent labels. It is also expected that this reactive sulfopropylating reagent will be of use in the functionalization of heterocyclic bases.

The synthesis of tripolar bis(hetarenio)pyrimidin-4-olates and some of their alkylated dicationic derivatives were investigated. Chlorine displacement reactions between tetrachloropyrimidine and nucleophilic heteroaromatics proceeded smoothly and yielded (5-chloropyrimidin-2,4,6-triyl)trishetarenium salts. Computations were performed on a representative compound to assess the classification of the pyrimidin-4-olates as hybrids between cross-conjugated mesomeric betaines and hetarenium salts.

The mean spherical approximation (MSA) model was used to study the osmotic and activity coefficients for aqueous solutions of pure associating electrolytes. The binding MSA was used to examine the association of ions of opposite charges for a variety of solutions of pure salts. Results showed that good fits can be obtained in some solutions of very high concentrations. A description for sulphuric acid was also obtained at low concentration.

The dependence of stability effect of protein salt-bridges on variations in the atomic parameters and the treatment of the dielectric change at the molecular boundary was investigated using continuum calculations. Results showed that the largest desolvation penalties were produced by approximation of the molecular surface, while smallest was produced by the smoothed boundary. The various parameter sets wee also found to produce relatively similar energetics, which is partly due to compensating effects.

The synthesis, properties, and reactivity of N,N'-difluorobipyridinium and related salts are presented. Synthesization was conducted using direct fluorination in a step-by-step manner of a mixture of a bipyridyl and a Lewis acid, a Bronsted acid or the alkali metal salt of an acid. results indicate that N,N'-difluoro-2,2'-bipyridinium bis(tetrafluoroborate) is a highly reactive electrophilic fluorinating agent with high effective fluorine content.

A study was conducted to examine the use of iminium salts to determine the catalytic asymmetric epoxidation of alkenes by Oxone. Bromine was added through a reflux condenser for vigorous reaction subsides while amine was dissolved in an ethanol solution. Results indicated that the catalytic procedure is very easy to use and does not need the support of chromatography and double bond stereochemistry.

Research was conducted to study the photochemical reactions of hydrocarbons by nitropyridinium salts. A mixture of pyridine derivatives and trimethyl or triethyloxonium tetrafluoroborate was stirred at room temperature while photochemical reactions were performed in a reactor equipped with a high pressure Hg lamp. Results indicated that hydrocarbon chains with different types of substituents can be oxidized by photoactivated nitropyridinium salts.

The heterogeneous reactions of nitryl halides with aqueous salt solutions as a model substrate for atmospheric sea salt aerosol were investigated. The reaction of Br2 with nitrite solution was found to be a convenient approach to the synthesis of BrNO2. The heterogeneous reactions result in the formation and loss of BrNO2 on salt solutions. The temperature-dependent lifetime of BrNO2 in a quartz cell was measured and the activation energy for the unimolecular decay at atmospheric pressure was obtained.