The Effect of Dansyl-Modified β-Cyclodextrin on the Chaperone Activity of Heat Shock Proteins

The effect of dansyl modified -cyclodextrin (1)on the chaperone activity of heat shock proteins such as HSP70 and HSP90 hasbeen studied. The fluorescence intensity of 1 was decreased when HSP70 and HSP90 were added to the host solution. This phenomenon suggested that host–guest complexation was occuring. The binding constants of 1 were obtained using a 1:1 complex formation type equation by employing the guest-induced fluorescence variations. Host 1 exhibited a higher binding ability forHSP70 than for HSP90. The effects of 1 on the chaperone activity and degradation of HSP70 and HSP90 were studied by measuring the absorption of aggregation of citrate synthase (C.S.) and sodium dodecyl sulfate (SDS)polyacrylamide gel electrophoresis of trypsin degradation, respectively. Host1 can contribute to regulate C.S. aggregation andpromote trypsin degradation of HSP70 and HSP90.     

Effect of Temperature on The Solubility of α-Amino Acids and α,ω-Amino Acids in Water

The aqueous solubilities of glycine, dl-α-alanine (2-aminopropanoic acid), dl-α-aminobutyric acid (2-aminobutanoic acid), dl-α-norvaline (2-aminopentanoic acid), dl-α-norleucine (2-aminohexanoic acid), β-alanine (3-aminopropanoic acid), γ-aminobutyric acid (4-aminobutanoic acid), 5-aminovaleric acid (5-aminopentanoic acid), and 6-aminocaproic acid (6-aminohexanoic acid) were determined from 293.15 to 323.15 K at intervals of 5.00 K using the gravimetric method. The temperature dependence of the solubility of α-amino acids and α,ω-amino acids in water is well described by the van’t Hoff equation. Linear van’t Hoff plots were used to determine the differential enthalpy of solution. The results obtained are compared with reported values in literature and are discussed in terms of the position of the ionic groups in the hydrocarbon chain.     

Effect of Drying Methods on the Structure and Combustion Activity of Mn—Substituted Hexaaluminate Catalysts

Conventional oven drying (COD) and supercritical drying (SCD) methods were applied to the preparation of Mn-substituted hexaaluminate (BaMnA111O19-α) catalysts. The effect of drying methods on phase composition, specific surface area, pore structure, reduction behavior of Mn^3 ions, and combus-tion activity of the samples was investigated. The homogenous mixing of the components in the sol-gel process could be maintained by SCD, and the hexaaluminate phase was almost the only phase of the resulting materials after calcination. H2-TPR revealed that the Mn^3 ions in the sample obtained by SCD were easier to be reduced than that by COD. Moreover, the samples obtained by SCD have higher surface area, narrower pore size distribution, and higher combustion activity than those obtained by COD.     

The Effect of the Isocyanate–Hydroxyl Ratio on the Structure and Properties of Hard Polyurethanes

A comprehensive study has been carried out of the structure and rheological and physicomechanical properties of low-temperature curing polyurethane compositions based on polyisocyanate and a blend of hydroxyl-containing oligomers of different reactivity. The maximum curing rate and strength parameters (tensile strength and Young’s modulus) have been shown to be achieved at the ratio of the reacting groups NCO : OH = 1.1.     

The Effect of Rare Earth on the Activity of Methanol Synthesis Catalyst

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The Effect of a Covalent and a Noncovalent Small-Molecule Inhibitor on the Structure of Abg β-Glucosidase in the Gas-Phase

The effects of binding two small-molecule inhibitors to Agrobacterium sp. strain ATCC 21400 (Abg) β-glucosidase on the conformations and stability of gas-phase ions of Abg have been investigated. Biotin-iminosugar conjugate (BIC) binds noncovalently to Abg while 2,4-dinitro-2-deoxy-2-fluoro-β-d-glucopyranoside (2FG-DNP) binds covalently with loss of DNP. In solution, Abg is a dimer. Mass spectra show predominantly dimer ions, provided care is taken to avoid dissociation of dimers in solution and dimer ions in the ion sampling interface. When excess inhibitor, either covalent or noncovalent, is added to solutions of Abg, mass spectra show peaks almost entirely from 2:2 inhibitor-enzyme dimer complexes. Tandem mass spectrometry experiments show similar dissociation channels for the apo-enzyme and 2FG-enzyme dimers. The +21 dimer produces +10 and +11 monomers. The internal energy required to dissociate the +21 2FG-enzyme to its monomers (767?±?30 eV) is about 36 eV higher than that for the apo-enzyme dimer (731?±?6 eV), reflecting the stabilization of the free enzyme dimer by the 2FG inhibitor. The primary dissociation channels for the noncovalent BIC-enzyme dimer are loss of neutral and charged BIC. The internal energy required to induce loss of BIC is 482?±?8 eV, considerably less than that required to dissociate the dimers. For a given charge state, ions of the covalent and noncovalent complexes have about 15 % and 25 % lower cross sections, respectively, compared with the apo-enzyme. Thus, binding the inhibitors causes the gas-phase protein to adopt more compact conformations. Noncovalent binding surprisingly produces the greatest change in protein ion conformation, despite the weaker inhibitor binding.

The Structure and Spectroscopy of α-Hydroxyphosphonates

Abstract

α-Hydroxyphosphonates are important intermediates in the preparation of various organophosphorus compounds. Methods for their preparation have been described.¹ We now report new aspects of their structure and spectroscopy. In the solid state, O,O-dimethyl α-hydroxy-α-phenyl-β-chloroethylphosphonate has been shown by X-ray diffraction studies to consist of hydrogen-bonded dimers with a hydrosen-bond length between the phosphoryl oxygen and hydroxyl hydrogen atom of 1.74 Å. The P=0 bond is relatively short (1.463).     

Structure–Activity Relationship of Iron Oxides for NO Reduction in the Presence of C3H6, CO,and O2

Spinel-type NiFe₂O₄ exhibited the highest NO reduction activity among base-metal oxides under simulated exhaust of a gasoline-powered vehicle. The structure–activity relationship of iron oxides has been investigated through both experimental and computational studies. Spinel iron oxide (γ-Fe₂O₃) exhibited a much higher NO reduction activity than that of iron oxide with other structures (α-Fe₂O₃ and LaFeO₃). Operando IR measurements clarified that the spinel structure facilitated the reaction between NO_x and adsorbed oxidized hydrocarbon or cyanide species. The high reactivity of the spinel structure was ascribed to the high adsorption energy of NO, as elucidated by DFT calculations. Furthermore, molecular orbital calculations demonstrated that the local coordination structure of the spinel iron oxide induced the involvement of not only σ but also π orbitals during NO adsorption on Fe atoms. This work clarified the origin of the structure-dependent activity of metal oxides, with a focus on their local coordination structures.     

Studies on the Relationship Between the Structure and Anticonvulsant Activity of Cinnamamides and Their Analogs

On the basis of systematic modification of the structure of componds of antiepilepsirine type, more than 200 cinnamamides were synthesized and tested by animal assay (maximal electroshock seizure, MES). Pharmacological evaluation showed that the configuration and the substituents on the phenyl ring and the nitrogen of amides, and substituents on the double bond displayed an important effect on the anticonvulsant activity.For studying the effect of the modification of structure to anticonvulsant activity, Hansch approach was employed to study the QSAR among 38 cinnamamides, and Hopfinger' s MSA was employed to study the MSA-QSAR among 26 cinnamamides.     

Cosolvent and Crowding Effects on the Temperature- and Pressure-Dependent Dissociation Process of the α/β-Tubulin Heterodimer

Tubulin is one of the main components of the cytoskeleton of eukaryotic cells. The formation of microtubules depends strongly on environmental and solution conditions, and has been found to be among the most pressure sensitive processes in vivo. We explored the effects of different types of cosolvents, such as trimethylamine-N-oxide (TMAO), sucrose and urea, and crowding agents to mimic cell-like conditions, on the temperature and pressure stability of the building block of microtubules, i. e. the α/β-tubulin heterodimer. To this end, fluorescence and FTIR spectroscopy, differential scanning and pressure perturbation calorimetry as well as fluorescence anisotropy and correlation spectroscopies were applied. The pressure and temperature of dissociation of α/β-tubulin as well as the underlying thermodynamic parameters upon dissociation, such as volume and enthalpy changes, have been determined for the different solution conditions. The temperature and pressure of dissociation of the α/β-tubulin heterodimer and hence its stability increases dramatically in the presence of TMAO and the nanocrowder sucrose. We show that by adjusting the levels of compatible cosolutes and crowders, cells are able to withstand deteriorating effects of pressure even up to the kbar-range.     

The Effect of Preliminary Treatment on the Catalytic Activity of Cobalt–Silica Gel Catalysts in the Complete Oxidation of Methane

The effect of temperature in multiple oxidative–reductive treatments on the activity of cobalt–silica gel catalysts in the complete oxidation of methane is studied. A decrease in the temperature of oxidative–reductive treatments from 500°C to 300°C results in an irreversible decrease in the activity of samples prepared by the impregnation of SiO₂with cobalt nitrate. A sample prepared from cobalt acetate and calcined at 500°C shows a lower activity, which was close to the activity of samples prepared from nitrates and calcined at 300°C.     

Synthesis and Study of Thermophysical Properties of Polystyrenes Prepared in the Presence of Conjugated α-Dinitrones Based on Glyoxal

Doklady Chemistry - A one-step convergent method was proposed for the synthesis of branched macromolecules in the presence of conjugated dinitrones (N,N-dimethylglyoxal dinitrone,...     

Effect of temperature on the dilution enthalpies of α,ω-amino acids in aqueous solutions

Dilution enthalpies of aqueous solutions of 3-amino propanoic acid, 4-amino butanoic acid, 5-amino pentanoic acid, and 6-amino hexanoic acid were determined at T = (293.15, 298.15, 303.15, and 308.15) K using an LKB flow microcalorimeter. The homotactic interaction coefficients were obtained according to the McMillan–Mayer theory from the experimental data. For all the systems studied, the dilution of α,ω-amino acids in water is an exothermic process; the pair coefficients have positive values which increases with chain length. The obtained values of the interaction coefficients are interpreted in terms of solute–solvent and solute–solute interactions and are used as indicative of hydrophobic behavior of the amino acid studied.     

Oligomerization of α-Methylstyrene in the Presence of Mordenite Type Zeolite

The activity and selectivity of coarse-porous H-mordenite in synthesis of cyclic and linear dimers of -methylstyrene were studied.     

The Reactions Between Halides and Alcohols in the Presence of Phase Transfer

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A Study on the Simultaneous Determination of Copper and Tin in the Presence of Lead

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Steric Exclusion Liquid Chromatography Studies in Urea on the Denaturation of the Bovine Eye Lens Protein α-Crystallin

Abstract

Steric exclusion liquid chromatography in the presence of intermediate urea concentrations with lowangle laser light scattering detection was used to investigate the stepwise dissociation of the multimeric bovine eye lens protein α-crystallin. The change in the quaternary structure of α-crystallin as a function of increasing urea concentration clearly resembled dissociation by increasing alkaline pH, urea or guanidine-HC1 concentrations when studied by sedimentation velocity analysis. Next to native and native-like threelayer aggregates (M_r 6.5 ? 7.5 × 10⁵), the first dissociation products (two-layer molecules M_r 4 ? 5.5 × 10⁵), the second dissociation products (core molecules M_r 2.5 ? 3 × 10⁵), and monomeric subunits (M_r 20 000) could be characterized. In the range from 2.6 to 4.4 M urea, we found a gradual decrease in the proportion of the remaining three-layer aggregates and an increase in that of monomeric subunits. The fluorescence emission maxima showed increasing solvent exposure of the tryptophan residues going from three-layer aggregates to monomeric subunits. The subunit compositions for most dissosiation products did not significantly differ from that of native α-crystallin. The interpretation of earlier results on Sephacryl-S200 steric exclusion chromatography in 3.8 M urea appeared to be an oversimplification.     

The Effect of α-Branched Side Chains on the Structural and Opto-Electronic Properties of Poly(Diketopyrrolopyrrole-alt-Terthiophene)

Introducing solubilizing α-branched alkyl chains on a poly(diketopyrrolopyrrole-alt-terthiophene) results in a dramatic change of the structural, optical, and electronic properties compared to the isomeric polymer carrying β-branched alkyl side chains. When branched at the α-position the alkyl substituent creates a steric hindrance that reduces the tendency of the polymer to π–π stack and endows the material with a much higher solubility in common organic solvents. The wider π–π stacking and reduced tendency to crystallize, evidenced from grazing-incidence wide-angle X-ray scattering, result in a wider optical band gap in the solid state. In solar cells with a fullerene acceptor, the α-branched isomer affords a higher open-circuit voltage, but an overall lower power conversion efficiency as a result of a too well-mixed nanomorphology. Due its reduced π–π stacking, the α-branched isomer fluoresces and affords near-infrared light-emitting diodes emitting at 820 nm.