Computational modeling of acrylodan-labeled cAMP dependent protein kinase catalytic subunit unfolding

Structure of the cAMP-dependent protein kinase catalytic subunit, where the asparagine residue 326 was replaced with acrylodan-cystein conjugate to implement this fluorescence reporter group into the enzyme, was modeled by molecular dynamics (MD) method and the positioning of the dye molecule in protein structure was characterized at temperatures 300 K, 500 K and 700 K. It was found that the acrylodan moiety, which fluorescence is very sensitive to solvating properties of its microenvironment, was located on the surface of the native protein at 300 K that enabled its partial solvation with water. At high temperatures the protein structure significantly changed, as the secondary and tertiary structure elements were unfolded and these changes were sensitively reflected in positioning of the dye molecule. At 700 K complete unfolding of the protein occurred and the reporter group was entirely expelled into water. However, at 500 K an intermediate of the protein unfolding process was formed, where the fluorescence reporter group was directed towards the protein interior and buried in the core of the formed molten globule state. This different positioning of the reporter group was in agreement with the two different shifts of emission spectrum of the covalently bound acrylodan, observed in the unfolding process of the protein.     

Preparation and study of photoswitchable fluorescence nanoparticles based on spirobenzopyran

The preparation and performance characterization of〈50 nm spirobenzopyran-based photochromic nanocomposites with photoswitchable fluorescence are presented.The nanocomposites were fabricated by means of a modifed miniemulsion polymerization process,in which the hydrophobic spirobenzopyran was covalently attached to the polymer chains and the matched fluorescent dyes were noncovalently embedded in the nanoscale cross-linked polymeric matrix,respectively.The obtained nanocomposites with a high relative fluorescence quantum yield（Q）exhibited superior fluorescent photoswitchable performance due to the effective photo-induced intermolecular energy transfer.The stability of photomerocyanine was also improved.     

Assessments of lifetimes and photoionization cross-sections at 10.6 μm of nd Rydberg states of Rb measured in a magneto-optical trap

By using IR laser photoionization in a magneto-optical trap, radiative lifetimes of rubidium Rydberg nd states (n = 16–20) have been measured. The measured lifetimes are: 4.63 μs for the 16d state, 5.39 μs (17d), 6.74 μs (18d), 8.06 μs (19d) and 8.99 μs (20d). The experimental values are in agreement with previous theoretical calculations. The reported method allows also for a measurement of the photoionization cross-sections of the specified Rydberg states at 10.6 μm. In this case the experimental values (ranging from 39 Mb for the 16d state to 30 Mb for the 20d state) look inconsistent with theoretical calculations.     

Binding of the bioflavonoid robinetin with model membranes and hemoglobin: Inhibition of lipid peroxidation and protein glycosylation

Recent years have witnessed burgeoning interest in plant flavonoids as novel therapeutic drugs targeting cellular membranes and proteins. Motivated by this scenario, we explored the binding of robinetin (3,7,3′,4′,5′-pentahydroxyflavone, a bioflavonoid with remarkable ‘two color’ intrinsic fluorescence properties), with egg yolk phosphatidylcholine (EYPC) liposomes and normal human hemoglobin (HbA), using steady state and time resolved fluorescence spectroscopy. Distinctive fluorescence signatures obtained for robinetin indicate its partitioning (K_p = 8.65 × 10⁴) into the hydrophobic core of the membrane lipid bilayer. HbA–robinetin interaction was examined using both robinetin fluorescence and flavonoid-induced quenching of the protein tryptophan fluorescence. Specific interaction with HbA was confirmed from three lines of evidence: (a) bimolecular quenching constant K_q ? diffusion controlled limit; (b) closely matched values of Stern–Volmer quenching constant and binding constant; (c) τ₀/τ = 1 (where τ₀ and τ are the unquenched and quenched tryptophan fluorescence lifetimes, respectively). Absorption spectrophotometric assays reveal that robinetin inhibits EYPC membrane lipid peroxidation and HbA glycosylation with high efficiency.     

Metal hydrides as bi-functional catalysts for hydrogen generation and oxidation in reversible MH-air fuel cells

Two kinds of metal hydride alloys as the bi-functional catalyst concept for hydrogen generation and oxidation in hydrogen-diffusion electrodes were investigated. The AB₅-type hydride electrode shows much higher catalytic activities than the Zr-based AB₂-type hydride electrode. However, the activity of Zr-based hydride electrodes can be improved only after removal of zirconium oxides on surface by a 1.0 M HF solution. The experiments demonstrated that the both metal-hydride hydrogen-diffusion electrodes for cycles of hydrogen generation (12 h) and oxidation (12 h) had good stability under the current densities of 100 and 50 mA/cm², respectively. The results also showed that small amounts of oxygen below 500 ppm and moisture up to 145,000 ppm in the hydrogen gas have little effect on the activity. It indicated that the hydride alloys as the non-noble-metal bi-functional catalysts in a reversible MH-air fuel cell have potential applications.     

(Vapour + liquid) equilibria of the {carbon dioxide + pentafluoroethane (HFC-125)} system and the {carbon dioxide + dodecafluoro-2-methylpentan-3-one (NOVEC™1230)} system

Binary (vapour + liquid) equilibrium data were measured for the {carbon dioxide + pentafluoroethane (HFC-125)} system at temperatures from 313.15 K to 333.15 K and the {carbon dioxide + dodecafluoro-2-methylpentan-3-one (NOVEC™1230)} system at temperatures from 313.15 K to 343.15 K. These experiments were carried out with a circulating-type apparatus with on-line gas chromatography. The experimental data were correlated well by the Peng–Robinson equation of state using the Wong–Sandler mixing rules.     

The standard state thermodynamic properties for completely ionized hydrochloric acid and ionization of water up to 523 K

In this communication we report calorimetric data for the standard state enthalpies of solution of α-Ba(OH)₂ in high dilution (10^?3 m) hydrochloric acid obtained from integral heats of solution measurements from temperatures of (333.55 to 516.64) K and extrapolated to 298.15 K. From previous studies in this laboratory on BaCl₂(aq) and auxiliary literature data, the standard state thermodynamic functions for completely ionized HCl(aq) can be determined. These new data are in good agreement and confirm our previously reported results on HCl(aq) from ionic additivity. The enthalpy of formation of solid α-Ba(OH)₂ at temperature of 298.15 K of ?939.38 kJ · mol^?1 can also be calculated from the present results. Values of the standard state heat capacity change for the ionization of water up to temperature of 523.15 K and at p_sat were calculated from present results using the literature data for NaOH(aq) and NaCl(aq) obtained from high dilution calorimetric measurements.     

(Vapor + liquid) equilibria for the {water + poly(ethylene glycol diacetyl ether) (PEGDAE) and methanol + PEGDAE} systems

We measured binary (vapor + liquid) equilibrium data for the {water + poly(ethylene glycol diacetyl ether) (PEGDAE) and methanol + PEGDAE} systems at pressures up to 400 kPa and temperatures from 333 K to 393 K. A static apparatus was used in this study. The measured data were correlated by the Peng–Robinson equation of state using the Wong–Sandler mixing rules with NRTL as the excess Gibbs free energy model.     

Intramolecular allylation of the azo group of 2-(allylsilyl)azobenzenes and its photocontrol

Pentacoordinate allylsilanes bearing an azobenzene moiety were synthesized and their structures were elucidated. The reaction of allyldifluorosilane (E)-7a with BF₃ · OEt₂ did not proceed, but (E)-7a was allowed to react with a fluoride ion to give tetrafluorosilicate 8a via intramolecular allyl-migration from the silicon atom onto the azo group. Activation of both the nucleophilic and electrophilic parts by the Si⋯N interaction was found to be important for promotion of the allyl-migration reaction. The azobenzene moiety of the allylsilane was reversibly isomerized by photoirradiation. The (Z)-7a formed by photoirradiation of (E)-7a is in a tetracoordinate state in contrast to the (E)-7a, and it did not react with a fluoride ion at all under the conditions where (E)-7a reacted quantitatively. The reactivity was successfully controlled without changing any conditions other than the change of the coordination number of the silicon atom induced by photoirradiation.     

(Vapour + liquid) equilibria of the {1,1,1-trifluoroethane (HFC-143a) + isobutene} system

Isothermal (vapour + liquid) equilibrium data were measured for the {1,1,1-trifluoroethane (HFC-143a) + isobutene} as an alternative refrigerant in the temperature range from (273.15 to 348.15) K at 15 K intervals. A circulating-type apparatus with on-line gas chromatography was used in these experiments. The experimental data were correlated well by Peng–Robinson equation of state using the Wong–Sandler mixing rules.     

High-pressure phase equilibrium for the binary systems of {carbon dioxide (1) + dimethyl carbonate (2)} and {carbon dioxide (1) + diethyl carbonate (2)} at temperatures of 273 K, 283 K,and 293 K

Phase equilibrium data for the binary systems {carbon dioxide (CO₂) + dimethyl carbonate (DMC)} and {carbon dioxide (CO₂) + diethyl carbonate (DEC)} were measured at temperatures of 273 K, 283 K and 293 K in the pressure range of 0.5 MPa to 4.0 MPa. The measurements were carried out in a cylindrical autoclave with a moveable piston and an observation window. The experimental data were correlated with the Peng–Robison (PR) equation of state (EOS) and the Peng–Robinson–Stryjek–Vera (PRSV) equation of state with van der Waals-1 or Panagiotopoulos–Reid mixing rules. The correlations produced reasonable values for the interaction parameters. The comparisons between calculation results and experimental data indicate that the PRSV equation of state coupled with the Panagiotopoulos–Reid mixing rule produced the better correlated results.     

Dew points of binary carbon dioxide + water and ternary carbon dioxide + water + methanol mixtures: Measurement and modelling

Dew points for four carbon dioxide + water mixtures between 1.2×10⁵ and 41.1×10⁵ Pa in the temperature range from 251.9 to 288.2 K, and eight carbon dioxide + water + methanol mixtures between 1.2×10⁵ and 43.5×10⁵ Pa and temperatures from 246.0 to 289.0 K were experimentally determined. The experimental results obtained on the binary and ternary systems were analysed in terms of a predictive excess function–equation of state (EF–EOS) method, which reproduced the experimental dew point temperature data with absolute average deviation (AAD) between 0.8 and 1.8 K for the systems with water, and from 0.0 to 2.7 K for the systems with water and methanol. The experimental results obtained for carbon dioxide + water mixtures, with molar fraction of water lower than 0.00174, at pressure values higher than 5×10⁵ Pa were also compared to a predictive equation of state model. It reproduced experimental dew point temperature data with AAD between 0.2 and 0.6 K.     

Magnetic properties of nitronylnitroxide and iminonitroxide triradicals as model compounds for generalized ferrimagnets

A novel iminonitroxide triradical, p-triIN (1), has been synthesized, in which a π-conjugated biradical with a singlet ground state and a doublet monoradical are united by σ-bonds. The intramolecular exchange interaction within the para-phenylene-based biradical moiety has been found to be antiferromagnetic (2J(π)/k_B = −30.8 K) from magnetic susceptibility measurements on a parent biradical, p-bisIN (2). The magnetic properties of 1 have been examined by magnetic susceptibility χ_m. Upon cooling, the χ_mT value for 1 has decreased and passed across 0.38 emu mol⁻¹ K, which is expected for one mol of S = 1/2 spin with g = 2.0. The magnetic behavior of 1 indicates that the ground state of the molecular assemblage of 1 in the crystal is diamagnetic, which is attributable to one of the exotic spin states as predicted in a theoretical model of generalized ferrimagnetism. The possible occurrence of the generalized ferrimagnetic spin alignment is concluded in view of the magnetic properties of 1.     

(Vapour + liquid) equilibria of the {1,1-difluoroethane (HFC-152a) + n-butane (HC-600)} system

Binary (vapour + liquid) equilibrium data were obtained for the {1,1-difluoroethane (HFC-152a) + n-butane (HC-600)} system at temperatures from 313.15 K to 363.15 K. These experiments were carried out with a circulating-type apparatus with on-line gas chromatography. The experimental data were correlated well by Peng–Robinson equation of state using the Wong–Sandler mixing rules. This system shows positive azeotropic phase behaviour.     

Ultrafast ring opening reaction of a photochromic indolyl-fulgimide

The photo-induced ring-opening reaction C → E of a photochromic indolyl-fulgimide is investigated by sub-picosecond pump–probe spectroscopy in the visible and infrared spectral range. The thermally stable C-isomer shows a pronounced absorption in the visible spectral range without spectral overlap with the absorption of the E- and Z-isomer. The comparison of infrared and visible transient absorption data allows to assign the observed exponential 2.1 ps dynamics to the ring-opening reaction and the non-exponential 10–40 ps component to the cooling of the hot molecules. The transient absorption spectra taken 80 ps after photo-excitation are identical with the steady state difference spectra.     

The investigations on K and L X-ray fluorescence parameters of gold compounds

The study aimed to determine the chemical effects on the K and L X-ray intensity ratios and the K and L X-ray production cross sections for gold compounds. The K shell fluorescence yields and L shell average yields were also investigated. The samples were excited by 59.5 keV γ-rays from an ²⁴¹Am annular radioactive source and 123.6 keV γ-rays from a ⁵⁷Co annular radioactive source. K and L X-rays emitted from samples were counted by an Ultra-LEGe detector with a resolution of 0.150 keV at 5.9 keV. The experimental values were compared with theoretical, the semi-empirical and other experimental values.     

Thymine-substituted nitronyl nitroxide biradical as a triplet (S = 1) component for bio-inspired molecule-based magnets

As a novel crystal engineering approach to organic molecule-based magnets, we have proposed a strategy of bio-inspired molecular assemblage based on intermolecular hydrogen bonding. Complementary hydrogen bonding between nucleobases as found in DNA is a promising non-covalent interaction for controlling the molecular arrangement of open-shell building block molecules. The hydrogen bonding of complementary nucleobases substituted with radical entities of different spin quantum numbers S, e.g., S = 1 and S = 1/2, gives rise to a heteromolecular aggregation of the S = 1 and S = 1/2 entities, leading to organic ferrimagnetics. In this study, we have designed and synthesized a thymine-substituted nitronyl nitroxide biradical (1) as a triplet (S = 1) component for the bio-inspired ferrimagnetic system. The molecular ground state of 1 has been found to be triplet (S = 1) with a singlet–triplet energy gap of 2J/k_B = 21.4 K from magnetic susceptibility measurements. It has been found from X-ray structure analyses that the molecules form hydrogen-bonded aggregates in the crystalline solid state, in which the thymine moiety plays a primary role in the molecular packing. The ground-state triplet biradical serves as an S = 1 building block for bio-inspired molecule-based magnets with hydrogen-bonded nucleobase pairings.     

Preparation and properties of aminoxyl radicals having an aromatic core with long alkyl substituents

Series of monoradicals and biradicals having an aromatic core on one hand and long alkyl groups on the other hand have been prepared. It was found from their magnetic data that the biradical compounds having aromatic cores (azoxy, or azo) and long alkyl groups with TEMPO radicals at their ends showed fairly large antiferromagnetic interactions (J = −34, −39 K) being well expressed by ST model, while only weak antiferromagnetic interactions were observed in the corresponding PROXYL derivatives together with the corresponding monoradicals. The change of intermolecular magnetic interactions based on the structural change from trans- to cis-isomer by irradiation was found to be possible in a couple of azobenzene derivatives with an aminoxyl radical.     

Thermodynamic properties and equation of state of liquid di-isodecyl phthalate at temperature between (273 and 423) K and at pressures up to 140 MPa

We report measurements of the thermodynamic properties of liquid di-isodecyl phthalate (DIDP) and an equation of state determined therefrom. The speed of sound in DIDP was measured at temperatures between (293.15 and 413.15) K and a pressures between (0.1 and 140) MPa with a relative uncertainty of 0.1%. In addition, the isobaric specific heat capacity was measured at temperatures between (293.15 and 423.15) K at a pressure of 0.1 MPa with a relative uncertainty of 1%, and the density was measured at temperatures between (273.15 and 413.15) K at a pressure of 0.1 MPa with a relative uncertainty of 0.015%. The thermodynamic properties of DIDP were obtained from the measured speeds of sound by thermodynamic integration starting from the initial values of density and isobaric specific heat capacity obtained experimentally. The results have been represented by a new equation of state containing nine parameters with an uncertainty in density not worse than 0.025%. Comparisons with literature data are made.     

Phase equilibrium measurements of (methane + benzene) and (methane + methylbenzene) at temperatures from (188 to 348) K and pressures to 13 MPa

New isothermal pTxy data are reported for (methane + benzene) and (methane + methylbenzene (toluene)) at pressures up to 13 MPa over the temperature range (188 to 313) K using a custom-built (vapor + liquid) equilibrium (VLE) apparatus. The aim of this work was to investigate literature data inconsistencies and to extend the measurements to lower temperatures. For (methane (1) + benzene (2)), measurements were made along six isotherms from (233 to 348) K at pressures to 9.6 MPa. At temperatures below 279 K there was evidence of a solid phase, and thus only vapor phase samples were analyzed at these temperatures. For the (methane (1) + methylbenzene (3)) system, measurements were made along seven isotherms from T = (188 to 313) K at pressures up to 13 MPa. Along the 198 K isotherm, a significant change in the data’s p,x slope was observed indicating (liquid + liquid) equilibria at higher pressures. The data were compared with literature data and with calculations made using the Peng–Robinson (PR) equation of state (EOS). For both binary systems our data agree with much of the literature data that also deviate from the EOS in a similar manner. However, the data of Elbishlawi and Spencer (1951) for both binary systems, which appear to have received an equal weighting to other data in the EOS development, are inconsistent with the results of our measurements and data from other literature sources.