Solid state electrochemical of the erbium hexacyanoferrate-modified carbon ceramic electrode and its electrocatalytic oxidation of <Emphasis Type="SmallCaps">l</Emphasis>-cysteine

A kind of erbium hexacyanoferrate (ErHCF)-modified carbon ceramic electrodes (CCEs) fabricated by mechanically attaching ErHCF samples to the surface of CCEs derived from sol–gel technique was proposed. The resulting modified electrodes exhibit well-defined redox responses with the formal potential of +0.215 V [vs saturated calomel electrode (SCE)] at a scan rate of 20 mV s⁻¹ in 0.5 M KCl (pH 7) solution. The voltammetric characteristics of the ErHCF-modified CCEs were investigated by voltammetry. Attractively, the ErHCF-modified CCEs presented good electrocatalytic activity with a marked decrease in the overvoltage about 400 mV for l-cysteine oxidation. The calibration plot for l-cysteine determination was linear at 5.0 × 10⁻⁶–1.3 × 10⁻⁴ M with a linear regression equation of I(A) = 0.558 + 0.148c (μM) (R ² = 0.9989, n = 20), and the detection limit was 2 × 10⁻⁶ M (S/N = 3). At last, the ErHCF-modified CCEs were used for amperometric detection of l-cysteine in real samples.     

Fluorescent sensing layer for the determination of<Emphasis Type="SmallCaps"> L</Emphasis>-malic acid in wine

An enzymatic method for determining L-malic acid in wine based on an L-malate sensing layer with nicotinamide adenine dinucleotide (NAD⁺), L-malate dehydrogenase (L-MDH) and diaphorase (DI), immobilized by sol-gel technology, was constructed and evaluated. The sol-gel glass was prepared with tetramethoxysilane (TMOS), water and HCl. L-MDH catalyzes the reaction between L-malate and NAD⁺, producing NADH, whose fluorescence (λ _exc = 340 nm, λ _em = 430 nm) could be directly related to the amount of L-malate. NADH is converted to NAD⁺ by applying hexacyanoferrate(III) as oxidant in the presence of DI. Some parameters affecting sol-gel encapsulation and the pH of the enzymatic reaction were studied. The sensing layer has a dynamic range of 0.1–1.0 g/L of L-malate and a long-term storage stability of 25 days. It exhibits acceptable reproducibility [s _r(%)≈10] and allows six regenerations. The content of L-malic acid was determined for different types of wine, and polyvinylpolypyrrolidone (PVPP) was used as a bleaching agent with red wine. The results obtained for the wine samples using the sensing layer are comparable to those obtained from a reference method based on UV-vis molecular absorption spectrometry, if the matrix effect is corrected for.     

Preparation of nanoparticle colloids of methoxy poly(ethylene glycol)-<Emphasis Type="Italic">b</Emphasis>-poly(<Emphasis Type="SmallCaps">D</Emphasis>,<Emphasis Type="SmallCaps">L</Emphasis>-lactide): effects of surfactant and organic solvent

Nanoparticle colloids of methoxy poly(ethylene glycol)-b-poly(D,L-lactide) (MPEG-b-PDLL) diblock copolymer were prepared by a modified spontaneous emulsification solvent diffusion method using acetone/ethanol as the mixture organic solvents. The MPEG-b-PDLL was synthesized by ring-opening polymerization of D,L-lactide using stannous octoate and MPEG with molecular weight of 5,000 g/mol as the initiating system. The MPEG-b-PDLL obtained was an amorphous polymer with molecular weight of 73,600 g/mol. Influences of acetone/ethanol (v/v) ratios and Tween 80 surfactant concentrations on characteristics of the colloidal nanoparticles were investigated and discussed. Light-scattering analysis showed that average diameters of the surfactant-free colloidal nanoparticles were in the range of 86–124 nm. The nanoparticle sizes decreased as the ethanol ratio increased. The Tween 80 did not show the significant effect on the nanoparticle sizes. Scanning electron micrographs of dried nanoparticles that demonstrated the aggregation of most particles suggested they were the soft nanoparticles. However, the dried nanoparticle morphology can be observed from scanning electron microscopy as having a spherical shape and smooth surfaces.     

Determination of serum <Emphasis Type="SmallCaps">d</Emphasis>-lactic and <Emphasis Type="SmallCaps">l</Emphasis>-lactic acids in normal subjects and diabetic patients by column-switching HPLC with pre-column fluorescence derivatization

d-Lactic and l-lactic acids were simultaneously determined by means of a column-switching high-performance liquid chromatography (HPLC) with fluorescence detection. As a fluorescence reagent, 4-nitro-7-piperazino-2,1,3-benzoxadiazole (NBD-PZ) was employed for the fluorescence derivatization of lactic acid. The proposed HPLC system adopted both octylsilica (Cadenza CD-C8) and amylose-based chiral columns (CHIRALPAK AD-RH), which proved to give a sufficient enantiomeric separation of the lactic acid derivatives with a separation factor () of 1.32 and a resolution (R_s) of 1.98. Moreover, the features of the first elution of d-lactic acid peak in the proposed HPLC were convenient for the determination of trace amount of serum d-lactic acid, which is known to increase under diabetes. Intra-day and inter-day accuracies were in the range of 90.5–101.2 and 89.0–100.7%, and the intra-day and inter-day precisions were 0.3–1.2 and 0.4–4.8%, respectively. The proposed method was applied to determine d-lactic and l-lactic acids in human serum of normal subjects and diabetic patients, showing that both d-lactic and l-lactic acid concentrations were significantly increased in the serum of diabetic patients (n=31) as compared with normal subjects (n=21). This fact was found for the first time owing to the development of the proposed HPLC method which is able to determine d-lactic and l-lactic acid simultaneously. Finally, serum d-lactic acid concentrations determined by the proposed HPLC method were compared with those from a reported enzymatic assay, and the smaller p value between normal subjects and diabetic patients was shown by the proposed HPLC method.     

Estimation of the specific content and nature of sorption sites of iron(<Emphasis Type="SmallCaps">III</Emphasis>) and zirconium(<Emphasis Type="SmallCaps">IV</Emphasis>) oxyhydroxides

The sorption of anions H₂PO₄ ⁻, HPO₄ ²⁻, PO₄ ³⁻, [Fe(CN)₆]³⁻, and [Fe(CN)₆]⁴⁻ from aqueous solutions on the surface of Fe^III and Zr^IV oxyhydroxide hydrogels freshly precipitated at pH 4–13 was studied. The region of sorbate concentrations was from 0.00025 to 0.06 mol L⁻¹. The plots of the anion uptakes vs. their equilibrium concentrations are represented by isotherms of the first type, which are well described by the Langmuir equation if the quantity of the amount adsorbed is expressed as mol-site g⁻¹. The maximum uptakes and constants of the Langmuir equation were calculated. The phosphate anions occupy the same number of sorption sites on the sorbents precipitated at different pH. The average specific content of sorption sites for the ferro- and zirconogels in the metastability period is independent of the pH of their precipitation, being 3.1·10⁻³ and 3.2·10⁻³ mol-site g⁻¹, respectively. The [Fe(CN)₆]³⁻ and [Fe(CN)₆]⁴⁻ anions are sorbed only on the positively charged sites of the hydrogels and occupy not more than 2·10 mol-site g⁻¹ in the studied interval of pH of precipitation. __________ Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1736—1741, August, 2005.     

Ionic mobility in the antimony(<Emphasis Type="SmallCaps">iii</Emphasis>) fluorochloride complexes

Ionic mobility in the NaSbClF₃ · H₂O, KSbClF₃, and NH₄SbClF₃ fluorochloride complexes was studied by ¹H and ¹⁹F NMR spectroscopy in the temperature interval from 150 to 480 K. The types of ionic motions in the compounds were determined. Their physicochemical characteristics were compared with those of the earlier studied sodium, potassium, and ammonium tetrafluoroantimonates(iii). The replacement of one F atom by the Cl atom in MSbF₄ (M = Na, K, NH₄) changes both the structure of the Sb polyhedra forming the structure of the antimony(iii) fluorochloride complex and the character of ionic motions in the compounds. The ionic conductivity in the 324–436 K range was determined for NH₄SbClF₃: σ = 1.07 · 10⁻⁴ S cm⁻¹ at T = 423 K. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1353–1357, July, 2008.     

Poly(<Emphasis Type="SmallCaps">l</Emphasis>-lactide) networks with tailored water sorption

A poly(l-lactide) diol was obtained through ring opening polymerization of l-lactide, using 1,6 hexanediol and tin(II) 2 ethylhexanoate as a catalyst. In the second step, the poly(l-lactide) macromer (mLA) was obtained by the reaction of poly(l-lactide) diol with methacrylic anhydride. The effective incorporation of the polymerizable end groups was assessed by Fourier transform infrared spectroscopy and nuclear magnetic resonance (¹H NMR). Besides, poly(l-lactide) networks (pmLA) were prepared by photopolymerization of mLA. Further, the macromer was copolymerized with 2-hydroxyethyl acrylate seeking to tailor the hydrophilicity of the system. A set of hydrophilic copolymer networks were obtained. The phase microstructure of the new system and the network architecture was investigated by differential scanning calorimetry, infrared spectroscopy, dynamic mechanical spectroscopy, thermogravimetry, and water sorption studies.     

Association behavior of one-end hydrophobically modified poly[<Emphasis Type="Italic">N</Emphasis><Superscript>5</Superscript>-(2-hydroxyethyl) <Emphasis Type="SmallCaps">l</Emphasis>-glutamine] in water/ethylene glycol mixed solvent

Amphiphilic polymers Cn-PHEG consisting of water-soluble poly[N ⁵-2-(hydroxyethyl) l-glutamine] (PHEG) and hydrophobic alkyl chain (carbon number n = 12, 14, 16, or 18) attached at the PHEG terminal was prepared, and association behavior and structure of associate for Cn-PHEG in selective solvent (water/ethylene glycol mixed solvent) have been investigated. α-Helix content of PHEG block for all the polymers increased with weight fraction of ethylene glycol in the mixed solvent (W _EG). By light scattering measurements, formation of a small micelle was suggested for C14-, C16-, and C18-PHEG when W _EG = 0. With the increase in W _EG, appearance of a larger associate was revealed for C16- and C18-PHEG. Evaluated molecular weight and radius of gyration suggested that the micelle is star-like sphere when W _EG = 0 and worm-like cylinder when W _EG = 0.7. C12-PHEG did not demonstrate any distinct micellization behavior because of the weak hydrophobicity of C12 chain.     

Synthesis and studies of spectroscopic and electrochemical properties of dinuclear ruthenium(<Emphasis Type="SmallCaps">II</Emphasis>) and manganese(<Emphasis Type="SmallCaps">II</Emphasis>) complexes

New dinuclear ruthenium manganese complexes of general composition (bpy)₂Ru(L)MnCl_x(H₂O)₂ (L is 1,10-phenanthroline-5,6-dione, 3,3′-dicarboxy-2,2′-bipyridyl, or bis(pyrazolyl); x = 2 or 4) were synthesized by the reaction of (bpy)₂Ru(L) with MnCl₂ · 4H₂O. These compounds and the starting mononuclear ruthenium complexes were studied by spectrophotometric and electrochemical methods in MeCN. The position of the charge-transfer band Ru^II → L in the spectra depends on the donor-acceptor characteristics of the ligand L. For the dinuclear complex under study, the formal potentials of reversible one-electron oxidation of Ru^II are in the range of 0.9–1.2 V (vs. the standard hydrogen electrode), whereas oxidation of Mn^II occurs at more positive (by 0.1–0.2 V) potentials. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 2281–2285, October, 2005.     

Overproduction of Glucoamylase by a Deregulated Mutant of a Thermophilic Mould <Emphasis Type="Italic">Thermomucor indicae-seudaticae</Emphasis>

Thermomucor indicae-seudaticae, a glucoamylase-producing thermophilic mould, was mutagenised using nitrous acid and gamma (⁶⁰Co) irradiation in a sequential manner to isolate deregulated mutants for enhanced production of glucoamylase. The mutants were isolated on Emerson YpSs agar containing a non-metabolisable glucose analogue 2-deoxy-d-glucose (2-DG) for selection. The preliminary screening for glucoamylase production using starch–iodine plate assay followed by quantitative confirmation in submerged fermentation permitted the isolation of several variants showing varying levels of derepression and glucoamylase secretion. The mutant strain T. indicae-seudaticae CR19 was able to grow in the presence of 0.5 g l⁻¹ 2-DG and produced 1.8-fold higher glucoamylase. As with the parent strain, glucoamylase production by T. indicae-seudaticae CR19 in 250-ml Erlenmeyer flasks attained a peak in 48 h of fermentation, showing higher glucoamylase productivity (0.67 U ml⁻¹ h⁻¹) than the former (0.375 U ml⁻¹ h⁻¹). A large-scale cultivation in 5-l laboratory bioreactor confirmed similar fermentation profiles, though the glucoamylase production peak was attained within 36 h attributable to the better control of process parameters. Although the mutant grew slightly slow in the presence of 2-DG and exhibited less sporulation, it showed faster growth on normal Emerson medium with a higher specific growth rate (0.138 h⁻¹) compared to the parent strain (0.123 h⁻¹). The glucoamylase produced by both strains was optimally active at 60 °C and pH 7.0 and displayed broad substrate specificity by cleaving α-1,4- and α-1,6-glycosidic linkages in starch, amylopectin, amylose and pullulan. Improved productivity and higher specific growth rate make T. indicae-seudaticae CR19 a useful strain for glucoamylase production.     

Determination of <Emphasis Type="SmallCaps">D</Emphasis>- and <Emphasis Type="SmallCaps">L</Emphasis>-amino acids produced by cyanobacteria using gas chromatography on Chirasil-Val after derivatization with pentafluoropropyl chloroformate

A rapid and simple method was developed for the determination of free amino acids (AAs) released from cyanobacteria. The procedure involves trapping of AAs from the centrifuged cyanobacterial culture fluid on a cation-exchange resin, their release together with the resin by direct treatment with the reaction medium, followed by immediate derivatization with a corresponding chloroformate. The extractive alkylation transfers the analytes into an organic phase, an aliquot of which is subjected to GC analysis. Identification and quantification of AAs was performed by GC/MS and GC/FID, respectively, using propyl chloroformate (PCF) as the derivatization reagent. For chiral analysis, the cyanobacteria extracts were treated with 2,2,3,3,3-pentafluoropropyl chloroformate (PFPCF) to create more volatile analytes. Separation of the AA enantiomers was accomplished on a Chirasil-Val capillary column and the D/L enantiomeric ratios were determined. AAs of cyanobacteria are considered to be important for the assessment of energy flow in an aquatic food web, nutrition value of cyanobacteria in a food web and for cell–cell communication within cyanobacteria. The highest levels of AAs were found in the summer period at the beginning of the season (July). In the September and October samples, the amount of AAs was lower, the number of D-AAs decreased and the D/L ratio was higher than in the July sample. Based on the obtained results it can be assumed that young populations excrete AAs in higher concentrations and a different composition compared to actively growing populations. Figure PFPCF derivatization scheme     

Temperature- and pressure-responsive properties of <Emphasis Type="SmallCaps">l</Emphasis>- and<Emphasis Type="SmallCaps"> dl</Emphasis>-forms of poly(<Emphasis Type="Italic">N</Emphasis>-(1-hydroxymethyl)propylmethacrylamide) in aqueous solutions

The structural transition of the l- and dl forms of poly(N-(1- hydroxymethyl)propylmethacrylamide (PHMPMA) in aqueous solution was studied by measuring the pressure dependence of the apparent scattering intensity, differential scanning calorimetry (DSC), and circular dichroism (CD). The thermodynamic implications of the results are discussed in relation to the chiral structure of the side chain, and differences in the thermal and barometric transitions. T-P diagrams of the transition showed characteristic ellipsoid features. Antagonism of the temperature and pressure effects was observed only for P(dl-HMPMA). For P(l-HMPMA), the transition temperature (T _tr) decreased with increasing pressure, and the highest T _tr was observed at atmospheric pressure (0.1 MPa). For both polymers, the highest P _trs were observed at the lowest temperatures. The l polymer showed a specific negative peak in its CD spectrum at around 220 nm in the lower temperature region and the temperature dependence was reproduced by a single-step transition, with the midpoint corresponding to the T _tr obtained from the scattering measurements. Coupled with the results from the DSC, the different behavior between the P(l-HMPMA) and P(dl-HMPMA) could be explained in terms of the chain states before and after the transition. The cooperative factors derived from the DSC measurement revealed that about 4 to 5 polymers of the present size were necessary to perform a thermal transition for P(l-HMPMA), and that P(dl-HMPMA) underwent its transition as an almost single molecular event.This revised version was published online in June 2005 with correction to the article category.     

Spacered dinuclear copper(<Emphasis Type="SmallCaps">II</Emphasis>) complexes with acyldihydrazones of aliphatic dicarboxylic acids and 2-hydroxy-5-nitroacetophenone

Dinuclear copper(II) complexes with acyldihydrazones of 2-hydroxy-5-nitroacetophenone (H₄L) of the composition Cu₂(Py)_xL·mEtOH were synthesized and characterized. In these complexes, the coordination polyhedra of the copper atoms are linked to each other by a polymethylene chain of different lengths, from one to five monomer units. The structure of the [Cu₂L·4Mrf] complex (Mrf is morpholine) based on acyldihydrazone of malonic acid was established by X-ray diffraction. The copper(II) atoms in this complex are [4+1]-coordinated and are spaced by 6.94 Å. At room temperature, the signal in the ESR spectra of solutions of the complexes based on acyldihydrazones of malonic, succinic, glutaric, and adipic acids has a seven-line hyperfine structure with the constant of (35.3–38.8)·10⁻⁴ cm⁻¹ (g = 2.109–2.112) due to exchange interactions between unpaired electrons and two equivalent copper nuclei. An increase in the length of the polymethylene chain to five monomer units hinders exchange interactions, and the ESR signal of the complex based on acyldihydrazone of pimelic acid has a four-line hyperfine structure with a _Cu = 72.7·10⁻⁴ cm⁻¹ typical of mononuclear copper(II) complexes. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 229–234, February, 2007.     

High Soluble Expression of <Emphasis Type="SmallCaps">d</Emphasis>-Amino Acid Oxidase in <Emphasis Type="Italic">Escherichia coli</Emphasis> Regulated by a Native Promoter

To express high-active soluble d-amino acid oxidase (DAAO), a constitutive plasmid that is regulated by a native hydantoinase promoter (P_Hase), was constructed. A d-amino acid oxidase gene (dao) was ligated with the P_Hase and cloned into pGEMKT to constitutively express protein of DAAO without the use of any inducer such as isopropyl β-d-1-thiogalactopyranoside which is poisonous to the cells and environment. The ribosome binding site region, host strain, and fermentation conditions were optimized to increase the expression level. When cultivated in a 5-m³ fermenter, the enzyme activity of JM105/pGEMKT-R-DAAO grown at 37 °C was found to be 32 U/mL and increase 16-fold over cells of BL21(DE3)/pET-DAAO grown at 28 °C. These results indicate the success of our approaches to overproducing DAAO in soluble form in Escherichia coli.     

Octacyanomolybdate-doped-poly(4-vinylpyridine) ionomer film electrode for the electrocatalytic oxidation of <Emphasis Type="SmallCaps">l</Emphasis>-ascorbic acid

Poly(4-vinylpyridine) (PVP)-based anion exchange polymers are not studied as much as cation exchange polymers Nafion and Eastman Kodak AQ for electroanalytical applications. Similarly, octacyanomolybdate [Mo(CN)₈ ⁴⁻] has not been studied much as a redox mediator. This communication presents results from examinations of the behaviour of Mo(CN)₈ ⁴⁻-doped PVP ionomer film electrode to highlight the opportunities for realization of the application of this composite electrode for l-ascorbic acid (AH₂) estimation via electrocatalytic mediation in acidic medium. The modified electrodes were characterized by cyclic voltammetry and rotating disc electrode voltammetry. PVP coatings possess strong anion-binding capacity for Mo(CN)₈ ⁴⁻ mediator with an extraction coefficient of 990, and electrostatically cross-linked PVP films offer insignificant resistance to permeation of AH₂, facilitating a cross-exchange reaction between the substrate and the mediator in the entire film volume. They show effective electrocatalytic oxidation of AH₂, with the oxidation potential of AH₂ decreased by ∼200 mV in overpotential compared to that at bare electrode. Mo(CN)₈ ⁴⁻/PVP composite electrode does not respond to the more common interferents of l-ascorbic acid estimation even at high positive potentials. These and several other attractive potentialities of the modified electrode are demonstrated by direct determination of AH₂ in a commercial vitamin C tablet without any special treatment, with the value closely agreeing (±0.75%) with the reference method.     

EPR spectra and structures of dinuclear copper(<Emphasis Type="SmallCaps">II</Emphasis>) complexes with acyldihydrazones of benzenedicarboxylic acids

Spacer-armed dinuclear copper(II) complexes with condensation products of isophthalic and terephthalic acid dihydrazides with salicylaldehyde and 2-hydroxyacetophenone were synthesized and studied by EPR and X-ray diffraction. The compositions and structures of most of the complexes were determined by elemental analysis, thermogravimetric analysis, and IR spectroscopy. The structure of the copper(II) complex with acyldihydrazone of salicylaldehyde and 1,3-benzenedicarboxylic acid (H₄L) with the composition [Cu₂L¹·2morph·MeOH] (morph is morpholine) was established by X-ray diffraction. The Cu^II atoms are spaced by 10.29 Å and are structurally nonequivalent. One copper cation has a square-planar coordination formed by donor atoms (2 N + O) of the doubly deprotonated acylhydrazine fragment and the N atom of the morpholine molecule. The second copper atom is additionally coordinated by a methanol molecule through the oxygen atom, so that this copper atom is in a tetragonal-pyramidal coordination with the oxygen atom in the axial position. The EPR spectra of liquid solutions of the complexes based on 1,4-benzenedicarboxylic acid acyldihydrazones and 1,3-benzenedicarboxylic acid bis(salicylidene)hydrazone at room temperature show a four-line hyperfine structure with the constant a _Cu = 54.4–67.0·10⁻⁴ cm⁻¹ (g = 2.105–2.147), which is indicative of the independent behavior of the paramagnetic centers. The EPR spectrum of a solution of the complex based on isophthalic acid and 2-hydroxyacetophenone shows the seven-line hyperfine structure corresponding to two equivalent copper nuclei (g = 2.11, a _Cu = 36.5·10⁻⁴ cm⁻¹). Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1898–1905, October, 2007.     

Fabrication of modified TiO2 nanoparticle carbon paste electrode for simultaneous determination of dopamine, uric acid, and l-cysteine

A carbon paste electrode, modified with 2, 2′-[1,7-hepthandiylbis(nitriloethylidyne)]-bis-hydroquinone and TiO₂ nanoparticles, was used for the simultaneous determination of dopamine (DA), uric acid (UA), and l-cysteine. The study was carried out by using cyclic voltammetry, chronoamperometry, and square wave voltammetry (SWV) techniques. Some kinetic parameters such as the electron transfer coefficient (α) and heterogeneous rate constant (k_s) were also determined for the DA oxidation. A dynamic range of 8.0–1400 μM, with the detection limit of 8.4 × 10⁻⁷ M for DA, was obtained using SWV (pH = 7.0). The prepared electrode was successfully applied for the determination of DA, UA, and l-cysteine in real samples.     

Theoretical study of structure and properties of hexuronic acid and <Emphasis Type="SmallCaps">d</Emphasis>-glucosamine structural units of glycosaminoglycans

The Becke3LYP functional of DFT theory was used to investigate molecular structure and sodium affinity of the systems CH₃CO₂Na (1), CH₃–O–SO₃Na (2), CH₃–NH–SO₃Na (3), saccharide_1Na₂ (4), saccharide_2Na (5), saccharide_3Na₃ (6), saccharide_4Na₂ (7), and saccharide_5Na₂ (8), respectively, which are models of N- and O-sulfate glycosaminoglycans. Interaction enthalpies, entropies and Gibbs energies of the sodium-coordinated systems in the gas phase were determined with the B3LYP/6-311+G(d,p) and B3LYP/6-31+G(d) methods. The computed Gibbs energies, ΔG ^o , of model systems 1–3 are negative and span a rather broad energy interval (from −500 to −1,500 kJ mol⁻¹). Gibbs interaction energies for sodium acetate, sodium sulfate and sodium sulfamate functions of the five saccharides, systems 4–8 are always lower than those values found for the model compounds 1–3. The ionization of sodium salts of saccharides studied in gas phase is in most cases connected with considerable conformational rearrangement of the ionic species. This rearrangement causes an additional energetic stabilization of anionic species and is connected with the substantial release of entropy.     

Rapid Determination of <Emphasis Type="SmallCaps">l</Emphasis>-Glutamine using Engineered <Emphasis Type="Italic">Escherichia coli</Emphasis> Overexpressing Glutamine Synthetase

A genetically engineered Escherichia coli was developed as the source of enzyme for rapidly quantifying glutamine. E. coli BL21 (DE3) cells overexpressing a glutamine synthetase from Bacillus subtilis were prepared as tube aliquots and used in a small volume of nontoxic mixture. The current method was compared to high performance liquid chromatography analysis, Sigma kit (GLN-1) and Mecke method. The method is applicable to a wide range of glutamine concentrations (0.05–2.5 mM) and correlates well to the detection results obtained from high performance liquid chromatography (Pearson correlation is 0.978 at the 0.01 level). Moreover, the whole assay procedure takes less than 15 min and uses nontoxic reagents, so it can be applied to monitor glutamine production and utilization conveniently.     

Palladium(<Emphasis Type="SmallCaps">I</Emphasis>) and palladium(0) carbonyl bromide complexes

New Pd^I and Pd⁰ carbonyl bromide complexes co-existing in the same crystal were synthesized and studied by X-ray diffraction analysis. The crystals consist of dimeric complex anions composed of the central Pd(μ-CO)₂Pd fragment and four partially disordered terminal ligands (CO and Br⁻). The complexes were characterized by IR, ESR, and X-ray photoelectron spectroscopy. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1349–1355, June, 2005.