Lectin-modified piezoelectric biosensors for bacteria recognition and quantification

The use of lectins for microorganism biosensors fabrication is proposed. Lectins are immobilised onto a gold-plated quartz crystal for direct piezoelectric label-free transduction of the bacteria–lectin binding event using an electrochemical quartz crystal microbalance (EQCM). Concanavalin A (Con A) and Escherichia coli were used for the evaluation of the lectin immobilisation method and the biosensor performance. Adsorption on nonpolarised and polarised (−0.200 V) gold-coated quartz crystals and immobilisation through avidin–biotin binding were checked for Con A surface attachment. Lectin–bacteria binding was evaluated in all cases. With a crystal modified with Con A via avidin–biotin immobilisation we obtained a linear calibration plot between 5.0 × 10⁶ and 2.0 × 10⁷ cfu mL⁻¹ by measuring frequency changes with E. coli concentration 1 h after bacteria addition. A remarkable increase in sensitivity was achieved when the analytical solution contained free biotinylated Con A, as a consequence of multiple lectin adhesion to Escherichia coli cell wall, which produced an accumulation of Con A–E. coli conjugates in the form of multilayers at the electrode surface. A detection limit of approximately 1.0 × 10⁴ cfu mL⁻¹ was achieved. Moreover nonspecific adsorptions were minimised. Using Con A and lectin from Arachis hypogaea, different response profiles were achieved for Escherichia coli, Staphylococcus aureus and Mycobacterium phlei, thus demonstrating the feasibility of bacteria discrimination. An approach involving filtering of free and lectin-bound bacteria and introduction of a filter in the measuring cell allowed a significant frequency change to be obtained for an E. coli concentration of 1.0 × 10³ cfu mL⁻¹ in order to further increase the sensitivity and discriminate between viable and nonviable cells; an approach using electrochemical measurements of bacterial catalase activity was also checked.     

Orientation of water molecules by the diamond surface

The properties of water in suspensions of diamond powders with particle sizes from 125–160 μm to 2–10 nm were studied. The dielectric constant of water in these suspensions changed from 1.3 × 10³ to 2.6 × 10⁶. The particle sizes correlated with the dielectric constants. The sound velocity of “diamond” water exceeded the initial velocity by 15–20 m/s. The crystals isolated from “diamond” water after prolonged storage had specific diffraction patterns and IR spectra. Their composition was not determined.     

Phase equilibria in binary subsystems of urea–biuret–water system

Joint results of the differential scanning calorimetry (DSC) and thermogravimetry (TG) experiments were the basis for the fusion enthalpy and temperature determination of the biuret (NH₂CO)₂NH (synthesis by-product of the urea fertilizer (NH₂)₂CO). Recommended values are Δ_m H = (26.1 ± 0.5) kJ mol⁻¹, T _m = (473.8 ± 0.4) K. The DSC method allowed for the phase diagrams of “water–biuret,” “water–urea,” “urea–biuret” binary systems to be studied; as a result, liquidus and solidus curves were precisely defined. Stoichiometry and decomposition temperature of the biuret hydrate identified, composition of the compound in “urea–biuret” system was suggested.     

A direct chemiluminescence method for the determination of nucleic acids using Ru(phen)32+–Ce(IV) system

A direct chemiluminescence method for the determination of nucleic acids has been developed based on the enhancement of nucleic acids on the chemiluminescence light emission of the reaction between Ru(phen)₃ ²⁺(phen = 1,10-phenanthroline) and Ce(IV). Under the optimum conditions, the calibration graphs are linear in the range of 5.0 × 10^–8–5.0 × 10^–5 g/mL for calf thymus DNA, 8.0 × 10^–8–5.0 × 10^–5 g/mL for fish sperm DNA and 1.0 × 10^–7–3.0 × 10^–5 g/mL for yeast RNA, respectively. The limits of detection are 1.0 × 10^–8 g/mL for calf thymus DNA, 3.1 × 10^–8 g/mL for fish sperm DNA and 5.2 × 10^–8 g/mL for yeast RNA, respectively. The final procedure allows the successful determination of calf thymus DNA, fish sperm DNA and yeast RNA in six synthetic samples. This method is simple, rapid and specific. Received: 22 January 1999 / Revised: 29 April 1999 / Accepted: 3 May 1999     

Secondary structure of crystals

Published experimental data on the dependence of the properties of crystal substances on crystal size are discussed. The dependence is of the same form for different properties and different crystal substances. When the crystal diminishes in size, its properties remain constant until the size decreases to 10⁻⁵–10⁻⁶ cm; smaller crystals considerably change their properties. It is shown that the currently available experimental data are sufficient to substantiate the notion of an “elementary unit of a solid crystal” (“crystal quantum”). The elementary unit of a crystal is regarded as a basis for the secondary structure (macrostructure) of a solid and an elementary carrier of its “crystal” properties. Due to this notion, we can interpret the vast experimental material on the real structures and properties of solids from a single viewpoint. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 36, No. 4, pp. 724–730, July–August, 1995. Translated by L. Smolina     

Electrical conductivity of magnesium oxide as a catalyst for radical chain hydrocarbon pyrolysis reactions

The electrical conductivity of polycrystalline MgO between 350 and 750°C is determined by the transport of surface electronic and hole defects and depends on the applied voltage. Near 620°C at low applied voltages, the conductivity decreases by 1–2 orders of magnitude in a narrow temperature range (ΔT = 75°C), and this is accompanied by a change of the sign of the surface charge carriers. The “ignition” of the catalytic activity of magnesium oxide in free radical generation in radical chain hydrocarbon pyrolysis is observed in the same temperature range. It is assumed that the change of the sign of the charge carriers is due to the existence of an isoelectric temperature T _i and that, at T > T _i , O_O^· defects come out to the magnesium oxide surface.     

Plutonium and americium concentrations and vertical profiles in some Italian mosses used as bioindicators

We have examined the uptake of actinide elements Am and, Pu by different species of lichen and moss collected in two locations (Urbino, Central Italy; Alps region, North-east Italy). Plutonium and americium were separated and determined by extraction chromatography, electrodeposition and alpha-spectrometry. This paper summarizes our results with a special emphasis on the vertical profiles of these actinides in two different species of mosses. Several 1–2 cm depth sections were obtained and dated by²¹⁰Pb method. A typical peak for^239,240Pu and²⁴¹Am was found in the very old moss species (“Sphagnum Compactum”) at a depth corresponding to the period 1960–1970 which was the period characterized by the maximum nuclear weapon tests. In a younger moss species (“Neckeria Crispa”) no peak was observed and the regression curves showed that Am is more mobile than^239,240Pu and²³⁸Pu.     

A very thick film open-tubular trap for headspace capillary gas chromatography

Summary An open-tubular trap with a very thick film was studied for “full on-line” headspace capillary gas chromatography, and was used as an enrichment trap for headspace sampling. The preparation of the open-tubular column with up to an 80 μm thick film, by combining both static and dynamic coating, is described in detail. The break-through volume for the open-tubular trap of different film thickness, as the loading capacity for HS sampling, does not increase linearly in proportion to the film thickness. A study of the difference between a packed adsorbent trap and an open-tubular trap shows that HS capillary GC with open-tubular trap loses less of the retention capacity, has better resolution ability and higher recovery. By independently and rapidly heating the open-tubular trap, the GC peaks may have higher resolution. Examples of successful analyses, by the opentubular trap with “full on-line” HS capillary GC, include trace aromatic hydrocarbon (1 ppm-100 ppm) in polybutadiene-styrene rubber and trace alcohol and acrylic esters (10 ppm–1000 ppm) in polyacrylate hydrous emulsion.     

Synthesis and aromatizational rearrangements of new imino-, hydrazono-, and azino-2,5-cyclohexadienylidene systems as ligands for cascade type metallocomplexes

Three approaches to the synthesis ofN-substituted imino-, hydrazono-, and azino-2,5-cyclohexadienylidene systems based on reactions of 4-methyl-4-trichloromethylcyclohexa-2,5-dienone with aminophenols and hydrazones and condensation of hydrazones ofpara-semiquinoid ketones with carbonyl compounds, including that of the ferrocene series, were realized. The latter reaction, when applied to 3,6-dibromophenanthrene-9, 10-quinone, was accompanied by quantitative aromatizational molecular rearrangement with the elimination of the CCl₃ group. Using Rh¹ complexes as an example, it was shown that the heteroorganic ligands obtained can be used for the synthesis of mixed-ligand metallocomplexes with triple coordination of the metal atom including simultaneous metal-ligand interactions of the n-, π-, and σ-types. The principle of metal-ligand “cascade” appeared as a result of the generalization of two new phenomena of organometallic sereodynamics, which we have found recently^2,3 and have called oxidative and reductive redox-rotation. In the “cascade”, type1 (“metal-ligand-metal”) or type2 (“ligand-metal-ligand”) metallocomplexes, one or several coordinated metal ligand”) metallocomplexes, one or several coordinated metal atoms capable of concertedly and reversibly changing their valence in the course of intramolecular conformational transformation are in positions of mutual conjugation. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 363–367, February, 1997.     

Nucleophilic reactivity of the peroxide anion in microemulsions of the “oil-in-water” type in the decomposition of phosphate and toluenesulfonate esters

The kinetics of the reaction of the 4-nitrophenyl esters of diethylphosphoric and 4-toluenesulfonic acids with HO^– and HOO^– anions in microemulsions of the “oil-in-water” type was studied. It was shown that the reactivity of the HOO^– anion depends on the nature of the detergent forming the microemulsion and decreases in the order cetyltrimethylammonium bromide > Triton X-100 > sodium dodecyl sulfate. It was established that concentration of the reagents on the surface of the microdrops leads to an increase of 2–3 orders of magnitude in the rate during the transition from aqueous solutions to the microemulsion.     

Packing of complex anions and effect of mutual ordering of heavy cations in structures with the paratungstate ion [H2W12O42]10−

The packing of [H ₂W₁₂O₄₂]¹⁰⁻ polyanions in seven known crystal structures is analyzed. The centers of the polyanions are arranged according to the law of the F- cell (3 cases) or I- cell (2 cases) or according to a more complex law. “Coherence” in the arrangement of heavy W atoms belonging to different polyanions is established: there are crystallographic planes with high concentrations of these atoms;this is an effect of superstructural ordering up to formation of the cation sublattice with light “filler” atoms (K, Mg, Na, N) partly addressed to the sites of the sublattice. Translated fromZhumal Strukturnoi Khimii, Vol. 38, No. 4, pp. 732–738, July–August, 1997.     

<Superscript>3</Superscript>H and <Superscript>90</Superscript>Sr in urine radiobioassay intercomparison results from the intercomparison studies program at Oak Ridge National Laboratory: statistical analysis of laboratory performance

The Intercomparison Studies Program (ISP) at the Oak Ridge National Laboratory (ORNL, Oak Ridge, TN USA) provides natural-matrix human urine quality-assurance/quality-control (QA/QC) samples to radiobioassay analysis laboratories. Samples are provided to these laboratories as “single-blind” or “double-blind” unknowns, spiked with radioactive-solution standards at “low” levels (e.g., 0.7–7 Bq g⁻¹ for ³H and 0.7–7 Bq kg⁻¹ for ⁹⁰Sr). Participants use the results as a tool for self-evaluation and a measure of performance. In this paper, sample preparation and the results of testing during the years 2001–2005 for ³H and ⁹⁰Sr are presented and discussed.     

Standardization of pH measurements based on the ion interaction approach

The Pitzer method was used to calculate the pH values on the conventional and “true” scales for the TRIS—TRIS·HCl−NaCl−H₂O buffer system in the 0–40 °C temperature region and 0–4 NaCl molality interval. This buffer can be used as a standard for pH measurements in a wide range of ionic strengths. The conventional scale is used in cells without a salt bridge. The “true” scale is recommended for pH measurements using cells with a salt bridge. At the same concentrations of the buffer solution, the “true” scale is essentially transformed into the scale of the National Bureau of Standards (NBS) of the USA. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 676–680, April, 2000.     

Selenomethionine content of candidate reference materials

Selenium has been identified as an antioxidant of importance in the diet. Accurate determination of its chemical forms depends on the availability of suitable reference materials (RMs). Two candidate reference materials for determination of selenomethionine (Semet) in food-related materials, a standard wheat gluten sample (NIST RM 8418 Wheat Gluten) and a commercial selenium enriched yeast, have been examined by use of a gas chromatography–isotope dilution mass spectrometry (IDMS) procedure, after treatment of the matrix with 0.1 mol L^–1 hydrochloric acid containing stannous chloride, addition of CNBr, and extraction with chloroform. This procedure results in cleavage of the CH₃Se group to form volatile CH₃SeCN. Addition of isotopically enriched ⁷⁴Semet to an analytical sample enables estimation of the naturally occurring protein-bound ⁸⁰Semet by IDMS without a protein-digestion process. We found that the Wheat Gluten RM contains a significant amount of Semet as a portion of its assigned value of 2.58 μg Se_total g^–1. Commercial selenium yeast tablets are labeled as containing an elevated level of “organic selenium”, usually as Semet. The sample we investigated contained 210 μg Se_total g^–1 sample as determined separately by IDMS, measuring elemental selenium after digestion. 73% of this total (153±21 μg Se_Semet g^–1; n = 23) was present as Semet. Thus, these two materials contain significant amounts of their total selenium content as Semet and would be good candidates for further study and characterization as reference materials for determining this important food component. The CNBr reaction used will also enable the determination of Se-(methyl)selenocysteine, the biological role of which is of recent interest. In addition to matrix RMs for Semet, it is important to have standard materials of the pure substance. We have examined a sample of a candidate standard material of selenomethionine being prepared by the USP. It was confirmed that this material is pure selenomethionine. Received: 13 December 2000 / Revised: 5 March 2001 / Accepted: 12 March 2001     

Analysis of the arrangements of two atomic varieties and an algorithm for deriving planar centered cells for 36 nets

An algorithm for obtaining and calculating the arrangements of two atomic varieties in a one-dimensional periodic row is suggested. An algorithm for deriving planar centered cells on a regular trigonal 3⁶ net that reduces two-dimensional cells to one-dimensional rows is developed. In most cases, centered three-dimensional cells may be reduced to two-dimensional cells; this facilitates analysis and comparison of structures. Variants of periodicity “degeneration” for one-, two-, and three-dimensional cases are analyzed. Reduced planar centered cells for n=2–12 (n is the number of sites in the cell) are described. Institute of Inorganic Chemistry, Siberian Branch, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 37, No. 3, pp. 520–527, May–June, 1996.     

Contamination assessment of heavy metal in surface sediments of the Wuding River, northern China

The heavy metal contents and the contamination levels of the surface sediments of the Wuding River, northern China, were investigated. Heavy metal concentration ranged in μg g⁻¹: 50.15–71.91 for Cr, 408.1–442.9 for Mn, 20.11–43.59 for Ni, 17.51–20.1 for Cu, 68.32–89.57 for Zn, 0.2–0.38 for Cd and 15.08–16.14 for Pb in the Wuding River sediments. The enrichment factor (EF) and the geo-accumulation index (Igeo) demonstrated that the sediments of the Wuding River had been polluted by Cd, Cr and Ni, which mainly originated from anthropogenic sources, whereas the sediments had not been polluted by Zn, Pb, Cu and Mn, which were derived from the crust. In addition, the assessment results of EF and Igeo suggested that the sediments of the Wuding River was “moderately” polluted by Cd and “unpolluted to moderately” polluted by Cr and Ni. The elevated urban sewage discharges and agriculture fertilizers usage in river basin are the anthropogenic sources of these heavy metals in river.     

Determination of biogenic amines in fermented beverages and vinegars by pre-column derivatization withpara-nitrobenzyloxycarbonyl chloride (PNZ-Cl) and reversed-phase LC

Summary The reagentp-nitrobenzyloxycarbonyl chloride (PNZ-CI) was used for pre-column derivatization of biogenic amines (BAs) at ambient temperature followed by reversed-phase, liquid-chromatographic separation of the derivatives. Optimized derivatization of samples was achieved within 10 min in borate buffer by adding PNZ-Cl in acetonitrile (MeCN). Excess reagent was scavenged by subsequent addition of glycine in water. For LC a Superspher^? RP-18e column and gradient elution using a ternary gradient system containing sodium acetabe buffer (pH 6.1), sodium acetate buffer (pH 4.3) and MeCN, were used. The PNZ-derivatives were quantified by their UV-absorption at 265 nm. Detection limits of BAs were approximately 62–1000 μg L⁻¹ (injected amounts: 53–850 pg) at a signal-to-noise ratio of 3:1. The coefficients of determination were 0.9906–0.9992. Diaminohexane was used as internal standard. Recoveries of BAs ranged from 78–93% depending on the food matrix. This method was applied to the quantitative determination of 2-phenylethylamine, tryptamine, serotonin, putrescine, histamine, cadaverine, tyramine, spermidine, and spermine, in beer, wine, vinegars, and lactic fermented cabbage juice. Parts of the results were presented at the 35th Congress of the “Deutsche Gesellschaft für Ern?hrung”, Kiel, 19^th–20^th March 1998, and the “Regionaltagung der Lebensmittelchemiker”, Giessen, 9^th–10^th March 1998     

Bacteriophage SPZ7 endolysin: The influence of effectors on the lytic activity of the enzyme on the lysis of gram-negative microorganisms

The possibilities of bacteriophage SPZ7 endolysin functioning in the lysis of gram-negative bacteria “from without” were studied. A significant 1.5–3-fold increase in bacteriophage SPZ7 endolysin activity during the lysis of S. enteritidis N60 and E. coli TG1 cells in the presence of high-molecular surfactants, pluronics with a large hydrophobic block, hen’s egg lysozyme, and low concentrations of a peptide antibiotic (colistin), was shown. The developed approach may be promising for improving the efficiency of pharmaceutical bacteriophage enzyme-based antibacterials working against gram-negative microorganisms.     

Effect of food: Microorganism ratio in activated sludge foam control

Foaming is a common operational problem in activated sludge processes that often adversely affects the quality of the treated effluent. Overgrowth of the filamentous Nocardia spp. in the microbial ecosystem was previously identified as the cause of foaming. In the present study, the specific growth rate of Nocardia amarae was found to be much higher than that of nonfilamentous bacteria under food:microorganism (F:M) ratios lower than 0.5 mg of biological oxygen demand (BOD)/(mg of mixed liquor suspended solids [MLor]·d). This indicated that filamentous overgrowth may occur in normal activated sludge processes that are continually operated under the usual F:M range of 0.2–0.6 mg of BOD/(mg of MLSS·d). A novel two-component feast-fast operation (FFO) that capitalized on the sensitivity of filamentous bacteria to F:M ratio was designed to prevent and control foaming problems. The F:M ratio in the “feasting” aeration unit was 0.8 mg of BOD/(mg of MLSS·d) whereas that in the “fasting” aeration unit was 0.2 mg of BOD/(mg of MLSS·d). The FFO resulted in an overall process F:M ratio that still remained within the normal range, while avoiding prolonged exposure of the activated sludge ecosystem to an F:M ratio below 0.5 mg of BOD/(mg of MLSS·d). The FFO suppressed the over growth of filamentous bacteria without adversely affecting the organic treatment efficiency of the modified process.     

Effect of ligand coordination type on the relative stability of linear mercury clusters

The problem of stabilization of linear mercury clusters with acceptor ligands coordinated along the symmetry axis of the cluster is discussed in terms of the MNDO method. It is shown that stable four-membered rings Hg₂Cl₂ may be formed. It is proposed that the structure of linear mercury clusters with side coordination of ligands be described as the result of “polymerization” of short stable linear molecules XHg_nX (n=1, 2) and HgX ₂ ¹⁻ , HgX ₃ ¹⁻ ions with accepting terminal groups. Mordovia State University. Institute of Organoelement Compounds, Russian Academy of Sciences. Translated fromZhurnal Strukturnoi Khimii, Vol. 39, No. 1, pp. 26–34, January–February, 1998. This work was performed in the framework if the interindustry scientific and technical program “Fullerenes and Atomic Clusters.”