Production of <Emphasis Type="Italic">R</Emphasis>-Mandelic Acid Using Nitrilase from Recombinant <Emphasis Type="Italic">E. coli</Emphasis> Cells Immobilized with Tris(Hydroxymethyl)Phosphine

Recombinant Escherichia coli cells harboring nitrilase from Alcaligenes faecalis were immobilized using tris(hydroxymethyl)phosphine (THP) as the coupling agent. The optimal pH and temperature of the THP-immobilized cells were determined at pH 8.0 and 55 °C. The half-lives of THP-immobilized cells measured at 35, 40, and 50 °C were 1800, 965, and 163 h, respectively. The concentration of R-mandelic acid (R-MA) reached 358 mM after merely 1-h conversion by the immobilized cells with 500 mM R,S-mandelonitrile (R,S-MN), affording the highest productivity of 1307 g L^?1 day^?1 and the space-time productivity of 143.2 mmol L^?1 h^?1 g^?1. The immobilized cells with granular shape were successfully recycled for 60 batches using 100 mM R,S-MN as substrate at 40 °C with 64% of relative activity, suggesting that the immobilized E. coli cells obtained in this study are promising for the production of R-MA.     

Isothermal crystallization of polypropylene/surface modified silica nanocomposites

In the present work, 3-methacryloxypropyltrimethoxy-silane silanized silica(SiO_2-WD70) and 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide immobilized silica(SiO_2-WD70-DOPO) nanoparticles were prepared. Silica, SiO_2-WD70 and SiO_2-WD70-DOPO were incorporated into polypropylene(PP) by melt compounding. Differential scanning calorimetry(DSC), X-ray diffraction(XRD) and polarized optical microscopy(POM) were employed to investigate the isothermal crystallization behavior of PP and PP/silica composites. The kinetic constant(kn), and half crystallization time(t1/2) were calculated by Avrami equation,while the surface free energy of folding was calculated by Lauritzen-Hoffman theory. The increased kn, decreased t1/2 and the surface free energy(σe) in the order of PP, PP/SiO_2, PP/SiO_2-WD70 and PP/SiO_2-WD70-DOPO nanocomposites were attributed to the surface modification of silica. XRD indicated that SiO_2-WD70-DOPO addition had no effect on PP crystal structure but accelerated the crystallization rate. POM determined that SiO_2-WD70-DOPO addition promoted the nucleation of PP by inducing a higher nucleation density during isothermal conditions. The surface modified nanoparticle SiO_2-WD70-DOPO might find possible application as a new type of inorganic nano-sized nucleation agent for PP.     

Synthesis and spectral characteristics of phthalocyanines of unsymmetrical structure containing fragments of 3,6-didecyloxyphthalonitrile and 2-methyl-5,6-dicyanobenzimidazole

By alkylation of 3,6-dihydrooxyphthalonitrile with 1-bromodecane and by reaction of 4,5-diaminophthalodinitrile with acetic acid were synthesized respectively 3,6-didecyloxyphthalonitrile (A) and 2-methyl-5,6-dicyanobenzimidazole (B). The random condensation of the dinitriles obtained provided unsymmetrical phthalocyanines of A ₃ B, AABB, and AB ₃ type. Their spectral characteristics were investigated.     

Synthesis and Properties of Tetra(4-<Emphasis Type="Italic">tert</Emphasis>-butyl-5-phenylsulfanyl)phthalocyanines and Their Derivatives

The methods of synthesis of 4-tert-butyl-5-sulfanylphenyl-and 4-tert-butyl-5-(4'-carboxyphenylsulfanyl) phthalonitriles have been developed and on their basis the corresponding octa-substituted phthalocyanines have been prepared. The effect of the structure of the above phthalocyanine derivatives on their electronic absorption spectra and parameters of thermal degradation in the presence of air oxygen were studied.     

Production of ethanol from waste paper using immobilized yeasts

This work is aimed at a selection of yeast strains suitable for simultaneous saccharification and fermentation of waste paper. The waste paper, as a lignocellulosic material, represents an unconventional source for the production of ethanol which is a promising alternative fuel. The yeast strains Saccharomyces cerevisiae and Pichia kudriavzevii produced the highest amounts of ethanol at 30 °C and were also resistant at 40 °C during the first 92 h of fermentation. These two strains were immobilized by entrapment into poly(vinyl alcohol) hydrogel lens-shaped particles LentiKats^®. The immobilized S. cerevisiae was a better ethanol producer and retained higher metabolic activity in repeated batch fermentations than P. kudriavzevii. The immobilized S. cerevisiae was also suitable for a long-term storage, with 23% decrease in the ethanol production ability after 1-year storage of yeast cells.     

Titanium tetra-<Emphasis Type="Italic">tert</Emphasis>-butoxide-<Emphasis Type="Italic">tert</Emphasis>-butyl hydroperoxide oxidizing system: Physicochemical and chemical aspects

The reaction of titanium tetra-tert-butoxide with tert-butyl hydroperoxide (1: 2) (C₆H₆, 20 C) involves the steps of formation of the titanium-containing peroxide (t-BuO)₃TiOOBu-t and peroxytrioxide (t-BuO)₃TiOOOBu-t. The latter decomposes with the release of oxygen, often in the singlet form, and also homolytically with cleavage of both peroxy bonds. The corresponding alkoxy and peroxy radicals were identified by ESR using spin traps. The title system oxidizes organic substrates under mild conditions. Depending on the substrate structure, the active oxidant species can be titanium-containing peroxide, peroxytrioxide, and oxygen generated by the system.     

Synthesis,characterization, and crystal structures of dioxomolybdenum(VI) complexes with O,N,N type tridentate hydrazone ligands as catalyst for oxidation of olefins

The preparation of Mo(VI) hydrazone complexes, cis-[MoO₂L¹(CH₃OH)] (I) and cis-[MoO₂L₂(CH₃OH)] (II), derived from N'-(3-bromo-2-hydroxybenzylidene)-2-chlorobenzohydrazide (H₂L¹) and N'-(3-bromo-2-hydroxybenzylidene)-4-bromobenzohydrazide (H₂L²), respectively, is reported. The complexes were characterized by elemental analyses, infrared and electronic spectroscopy, and single crystal structure analysis (CIF files ССDС nos. 1426875 (I), 1426871 (II)). The Mo atoms are coordinated by two cis terminal oxygen, ONO from the hydrazone ligand, and methanol oxygen. Even though the hydrazone ligands and the coordination sphere in both complexes are similar, the unit cell dimensions and the space groups are different. Complex I crystallized as orthorhombic space group Pca21 with unit cell dimensions a = 27.887(2), b = 8.0137(7), c = 15.544(1) Å, V = 3473.8(5) ų, Z = 8, R ₁ = 0.0450, wR ₂ = 0.0539. Complex II crystallized as triclinic space group P1, with unit cell dimensions a = 8.2124(4), b = 8.5807(5), c = 12.9845(8) Å, α = 83.366(2)°, β = 79.201(2)°, γ = 80.482(2)°, V = 883.03(9) Å3, Z = 2, R ₁ = 0.0278, wR ₂ = 0.0569. The complexes were tested as catalyst for the oxidation of olefins, and showed effective activity.     

Modeling the structure,absorption spectra,and cis-trans isomerization of thiacarbocyanine dyes

The relative stability of the trans-and cis-isomers of 3,3′-diethylthiacarbocyanine (Dye1) and 3,3′-diethyl-9-methylthiacarbocyanine (Dye2)¹, as well as sections of the potential energy surfaces along the internal coordinate of the isomerization reaction, were studied using the density functional theory. Calculation of the minimum energy pathway for the isomerization reaction showed that the barrier for rotation about the C₈–C₉ bond is higher for Dye1 than for Dye2. Local minimums were found for the singlet excited state of the 8,9-cis-and trans-isomers of the dyes. In the case of the trans-isomers, substantial changes in the dye structure do not occur and the local minimum of the excited state corresponds to the geometry of the starting trans-isomers, which favors efficient fluorescence. A search for the nearest local minimum of the singlet excited state of the 8,9-cis-isomers leads to structures, which differ significantly from the starting structures, and the intensity of the S₁ → S₀ transition in those structures appears to be practically zero. The results are in agreement with experimental data on the absorption, fluorescence, and fluorescence excitation spectra of the dyes.     

Chromatographic Separation of Bupivacaine Enantiomers by HPLC: Parameters Estimation of Equilibrium and Mass Transfer Under Linear Conditions

Bupivacaine is an amide type local anesthetic widely used in surgery and obstetrics because of its sustained peripheral and central nerve blockade. R-(+)-bupivacaine is more toxic to the central nervous and the cardiovascular systems than S-(?)-bupivacaine. To obtain S-(?)-bupivacaine with high degree of purity using a continuous simulated moving bed (SMB) unity, equilibrium and mass transfer parameters under dilute conditions were obtained by pulse experiments using 0,0′-bis[4-terc-butyl-benzoyl]-N,N′-diallyl-L-tartar diamide immobilized in silica (Kromasil^® CHI-TBB). The linear equilibrium constants were found to be 2.12 and 2.91 for R-(+)-and S-(?)-bupivacaine, respectively. Axial dispersion coefficients were found to be practically the same for both enantiomers. A fast kinetic of mass transfer was observed. The internal resistance to the mass transfer controls all the mass transfer process in this chiral column and the pore diffusion coefficients were of the order 10^?7cm²/s. The equilibrium and mass transfer parameters will be employed in future simulation and design of operating conditions of SMB unity.     

Synthesis, characterization and comparative studies on the photophysical and photochemical properties of metal-free and zinc(II) phthalocyanines with phenyloxyacetic acid functionalities

The synthesis and characterization of new peripherally and non-peripherally tetra-substituted metal-free and zinc(II) phthalocyanines with 2-, 3- and 4-phenyloxyacetic acid functionalities are described for the first time in this study. The new compounds have been characterized by elemental analysis, FT-IR, UV-Vis, MALDI-TOF and ¹H-NMR spectra. Photodegradation, singlet oxygen and fluorescence quantum yields, and fluorescence lifetimes of these compounds are studied in dimethylformamide (DMF). The influence of the substituent position on the phthalocyanine framework (non-peripherally or peripherally), central metal ion (metal-free or zinc) and the position of the COOH group (2-, 3- or 4-position on the phenyloxyacetic acid) on the spectroscopic, photophysical and photochemical properties have been investigated. Non-peripherally zinc(II) phthalocyanines (1b and 2b) and peripherally zinc(II) phthalocyanine (4b) gave good singlet oxygen quantum yields (Φ_Δ) (0.37, 0.39 and 0.38, respectively) which indicate the potential of the complexes as photosensitizers in applications of PDT.     

Computer Simulation of the Cathode Active Layer in Hydrogen–Oxygen Fuel Cell with Polymer Electrolyte: The Nature of the Overall Current Variations

Full computer simulation of the cathode structure in hydrogen–oxygen fuel cell with polymer electrolyte is performed. Both transport, support grains (agglomerates of carbon particles onto whose surface Pt-catalyst is deposited), and the current generation in active layer are simulated. The active layer operation in potentiostatic mode is studied. The effect of variations of the active layer and the fuel cell temperature (T_s and Т, respectively) on the cathode overall current I and the support grain flooding with water is calculated. The changes in the temperature difference T_s–Т was shown for the first time, experimentally and by the simulation, to generate variations of I and the degree of the support grain flooding with water. In particular, with the increasing of T_s–Т the current I increased, whereas the support grain flooding with water decreased; and vice versa, with the decreasing of T_s–Т the current I drops down, while, the support grain flooding with water grows. An explanation of the phenomena is presented, which takes account of structure of the support grains in which О₂ reduction and Н₂О generation occur. There exist intrinsic channels for protons and О₂ molecules transportation to the catalyst. Water releasing in the support grains is able to fill partially or even entirely the gas pores through which oxygen is supplied to the platinum. As a result, the current generated in the support grains can drop down significantly; at the same time, the value of I also drops down. The degree of the support grainfilling with water is determined by two processes, namely, the flooding and draining. The source of flooding is the current generation; that of draining, the water saturated vapor diffusion and water filtration in nanopores. The lower cathode potential, the higher the flooding rate, whereas the water removal rate grows or drops down with the increasing of decreasing of the temperature difference Т_s–Т, respectively. Thus, the temperature difference variations naturally lead to those of the quantity I.     

Synthesis,crystal structures,and catalytic oxidation of olefins of dioxomolybdenum(VI) complexes with aroylhydrazone ligands

Two Mo(VI) aroylhydrazone complexes, cis-[MoO₂(L¹)(CH₃OH)] (I) and cis-[MoO₂(L²)(CH₃OH)] (II), derived from 2-bromo-N'-(3,5-dibromo-2-hydroxybenzylidene)benzohydrazide (H₂L¹) and 2-bromo-N'-(2-hydroxy-4-methoxybenzylidene)benzohydrazide (H₂L²), respectively, are reported. The complexes were characterized by elemental analyses, infrared and electronic spectroscopy, and single crystal structure analysis (CIF files CCDC nos. 1443679 (I) and 1443678 (II)). The Mo atoms are coordinated by two cis terminal oxygen, ONO from the aroylhydrazone ligand, and methanol oxygen. Complex I crystallized as monoclinic space group P2₁/_c with unit cell dimensions a = 8.075(2), b = 13.905(1), c = 16.448(1) Å, β = 91.282(2)°, V = 1846.5(4) ų, Z = 4, R ₁ = 0.0859, wR ₂ = 0.2066. Complex II crystallized as triclinic space group P \(\overline 1 \), with unit cell dimensions a = 8.0824(6), b = 10.5919(8), c = 10.7697(8), α = 96.432(2)°, β = 97.438(2)°, γ = 103.119(2)°, V = 880.8(1) ų, Z = 2, R ₁ = 0.0271, wR ₂ = 0.0571. The complexes were tested as catalyst for the oxidation of olefins and showed effective activity.     

Theoretical modeling of the mechanism of aniline oxidation by singlet O<Subscript>2</Subscript>

The mechanism of aniline oxidation by singlet oxygen was studied by the DFT-PBE/L2 method. According to the calculations, aniline endoperoxide cannot participate in the reaction because of its energy instability. The addition of ¹O₂ to aniline proceeds with the simultaneous proton transfer to the oxygen molecule from the NH₂ group (for the syn-approach of oxygen) or from the aromatic ring (for the anti-approach). For the syn-approach of the ¹O₂ molecule, the HNC₆H₄(H)OOH intermediate is formed, whose decomposition leads to aniline p-hydroperoxide (predominantly) or p-iminoquinone. In the case of the anti-approach, the ¹O₂ molecule is inserted at the C–H bond to form aniline p-hydroperoxide (H₂NC₆H₄OOH). The decomposition of aniline p-hydroperoxide with the formation of p-aminophenol and H₂O₂ molecule proceeds via concerted mechanism.     

Inhibitory effect of 2,6-di-<Emphasis Type="Italic">tert</Emphasis>-butylphenol groups in iron and manganese porphyrins on the catalytic activity in the oxidation of hydrocarbons by hydrogen peroxide

Iron and manganese porphyrins containing 2,6-di-tert-butylphenyl groups (R₄PFeCl and R₄PMnCl) have been synthesized to be further immobilized on silica gels via various spacers. The activity of these porphyrins in the oxidation of alkanes and alkenes by hydrogen peroxide has been studied. 2,6-Di-tert-butylphenol groups decrease the catalytic activity of porphyrins in oxidation processes.     

Excited States of Weak Interacting Complexes of Formaldehyde and Alkali Metal Ions

The electronically excited states of formaldehyde and its complexes with alkali metal ions are investigated with the time-dependent density functional theory (TD DFT) method. Vertical transition energies for several singlet and triplet excited states, adiabatic transition energies for the first singlet and triplet excited states S₁ and T₁, the adiabatic geometries and vibrational frequencies of the ground state S₀ and the first singlet and triplet excited states S₁ and T₁ for formaldehyde and its complexes are calculated. Better agreement with the experiment than that of the CIS method is obtained for CH₂O at the TD DFT level. The nonlinear C=O?M⁺ interaction in the excited states S₁ and T₁ is weaker than the linear interaction in the ground state. In the S₀ and S₁ states, the C=O bond is elongated by cation complexation and its stretching frequency is red-shifted, but in the T₁ state the C=O bond is shortened and its frequency is blue-shifted.     

Extended detection range for an optical enzymatic glucose sensor coupling with a novel data-processing method

A new data-processing method was established and applied for optical enzymatic glucose sensing, in which oxygen and glucose were simultaneously consumed. The oxygen level remaining in the detection system, which was equal to the difference between the initial and consumed oxygen concentrations, could be measured using fluorescent oxygen indicators immobilized in the sensing layer. It was deduced that the ratio of I ₀ and I was inversely proportional to glucose concentration, where I ₀ is the maximum fluorescence intensity in various glucose solutions, and I is the fluorescence intensity at various concentrations of glucose. Using the new data-processing method, the detection range of the calibration curve method was extended from 0 to 1.2 mmol L^?1, which was enlarged about 2–3 folds over that in ordinary approaches. The prepared glucose sensor could be directly applied to detect high concentrations of glucose.     

XPS,UPS, and STM studies of nanostructured CuO films

A Cu₁O_1.7 oxide film containing a large amout of superstoichiometric oxygen was obtained by low-temperature oxidation of metallic copper in the oxygen plasma. An STM study of the film structure showed that ～10 nm planar copper oxide nanocrystallites with particles packed parallel to the starting metal surface. In an XPS study, the spectral characteristics of the Cu2p and O1s lines indicated that particles with a CuO lattice formed (E _bnd(Cu2p _3/2) = 933.3 eV and a shake-up satellite, E _bnd(O1s) = 529.3 eV). The additional superstoichiometric oxygen is localized at the sites of contact of nanoparticles in the interunit space and is characterized by a state with the binding energy E _bnd(O1s) = 531.2 eV. Due to the formation of a nanostructure in the films during low-temperature plasma oxidation, the resulting copper oxide has a much lower thermal stability than crystalline oxide CuO.     

System vanadium alkoxy compound-<Emphasis Type="Italic">tert</Emphasis>-butyl hydroperoxide-oxidant of hydrocarbon C-H bonds

Vanadium alkoxy compounds [(t-BuO)₄V, (t-BuO)₃VO] react with tert-butyl hydroperoxide (C₆H₆, 20°C) to liberate oxygen, partly in the singlet form, and to form alkoxyl and peroxyl radicals via the intermediacy of vanadium peroxides and trioxide. These systems are capable of oxidizing hydrocarbon C-H bonds. The process is radical in nature and involves formation of carbon-centered radicals and their reaction with oxygen generated in the systems. Vanadium-containing peroxides, too, take part in the oxidation reaction.     

Nucleophilic Substitution in 4-Bromo-5-nitrophthalodinitrile: XVI.<Superscript>1</Superscript> 4-(1<Emphasis Type="Italic">H</Emphasis>-Benzotriazol-1-yl)-5-[(4-carboxyphenyl)oxy/sulfanyl]- phthalonitriles and Cobalt Phthalocyanines Thereof

A method of synthesis of 4-(1H-benzotriazol-1-yl)-5-[(4-carboxyphenyl)oxy]- and -5-[(4-carboxyphenyl) sulfanyl]phthalonitriles starting with 4-bromo-5-nitrophthalonitriles was developed. The synthesized phthalonitriles were used to prepare cobalt tetra-4-(1H-benzotriazol-1-yl)-tetra-5-[(4-carboxyphenyl)oxy/sulfanyl]phthalocyanines. The spectral and catalytic properties of the resulting octasubstituted phthalocyanines were studied.     

Modification of silica nanoparticles with stereisomers of <Emphasis Type="Italic">p</Emphasis>-<Emphasis Type="Italic">tert</Emphasis>-butylthiacalix[4]arene containing four 2-oxo-2-{[3-(triethoxysilyl)prop-1-yl]amino}ethoxy substituents at the lower rim

Three stereoisomers (cone, partial cone, and 1,3-alternate) of p-tert-butylthiacalix[4]arene bearing four anchor propyltriethoxysilane substituents at the lower rim were synthesized for the first time. Surface modification of silica nanoparticles (d = 12 nm) with the synthesized macrocycles gave novel hybride thiacalix [4]arene?SiO₂ particles. The obtained nanostructured adsorbents were found to efficiently extract nitroaromatic compounds from aqueous solutions. The partial cone and 1,3-alternate thiacalix[4]arene–SiO₂ hybrid particles showed affinity to nitrophenols.