Application of solid phase micro extraction for the rapid analysis of chlorinated organics in breast milk.

The method presented here allows the monitoring of persistent organochlorine compounds in breast milk using the solid phase microextraction technique (SPME) and gas chromatography with electron capture detection (GC-ECD). It describes the determination of hexachlorobenzene (HCB), alpha-, beta-, and gamma-hexachlorocyclohexane (HCH), dichlorodiphenyltrichloroethane (DDT) and its derivatives, and some important congeners of the polychlorinated biphenyls (PCB). Also included are more polar substances such as tri-, tetra- and penta-chlorophenols, which can be analyzed simultaneously with the afore-mentioned less polar compounds without the need of a derivatization for the determination of the phenolic compounds. The reproducibility of the results is very good down to the lower microg/L-region. The method is very fast and of low cost compared to the classic extraction and determination procedures.

New metal-binding ethyldiamino- and dicarboxy-products from Aspergillus niger industrial wastes.

The metal-binding ability of Aspergillus niger mycelial waste was improved by chemical modification. The latter was performed by introducing additional carboxy groups using oxidation methods or the introduction of the ethyldiamino group first by chlorination of A. niger using mesyl chloride and subsequent reaction of the product with ethylene diamine. Metal binding abilities of the products for Cd2+, Co2+, Ni2+ and Zn2+ were determined according to the Langmuir model, whereby pKD*-values of 3.88 up to 5.02 were revealed. Maximum capacities for the metals were found to be in the range 172 to 1064 mmol/kg.

Studies about the desorption of volatile halocarbons from activated carbon by application of static headspace gas chromatography.

The analysis of volatile halocarbons (VHCs) in air or ground air is often performed after their adsorption and enrichment on activated carbon. The current procedure for their subsequent determination is based on their extraction from the activated carbon with a volatile organic solvent such as n-pentane, followed by gaschromatographic (GC) analysis. In order to avoid extraction steps, the static headspace method in combination with GC analysis using diphenylmethane as a desorption agent has been applied. Satisfactory desorption rates for the chloromethanes, for 1,1,1-trichloroethane, trichloroethene and for tetrachloroethene have been obtained after a sample equilibration of 45 min at 120 degrees C in the presence of diphenylmethane. The results have shown a higher recovering rate especially of the unsaturated VHCs compared to the extraction with n-pentane, whereby a potential loss of analytes by the latter procedure has been avoided.

Activation of serine sulphydrase from baker's yeast (Saccharomyces cerevisiae) by vanadate.

Vanadate stimulates the liberation of H2S from cysteine in intact cells of baker's yeast (Saccharomyces cerevisiae) with a maximal increase of 60% at 10 microM NH4VO3. Protein separation from crude yeast extract yielded two active protein fractions which were found to catalyze the degradation of cysteine to H2S, pyruvate and ammonia or H2S and serine, respectively, thus characterizing them as cysteine desulphydrase and serine sulphydrase. Only the latter enzyme was found to be activated by vanadate, showing optimal enhancement of about 100% at 10 microM NH4VO3.

Characterization studies on cadmium-mycophosphatin from the mushroom Agaricus macrosporus.

A low molecular weight Cd-binding phosphoglycoprotein, cadmium-mycophosphatin, has been isolated from the mushroom Agaricus macrosporus. This protein has a molecular weight of 12,000 dalton and contains no sulfur but a high amount of acid amino acids (Glu, Asp), and carbohydrates (glucose, galactose). Cadmium-mycophosphatin has an isoelectric point less than pH 2, binds cadmium with a dissociation constant of KD = 1.59 X 10 M (pKD = 6.8) and is saturated with 13.5 mole Cd/mole, all Cd-binding sites being equivalent. It is suggested that Cd is bound by phosphoserine groups, similar relations being known from calcium-binding proteins in animals. From A. macrosporus four other low-molecular weight glycoproteins have been isolated which contain sulfur and bind cadmium and copper. The biological significance of these Cd-binding proteins is discussed.

Determination of 5-aminolevulinic acid in biological samples by high-performance liquid chromatography.

5-Aminolevulinic acid (ALA), the common precursor of all naturally occurring tetrapyrroles, forms a stable condensation product with 2-amino-3-hydroxynaphthalene which can be identified by its fluorescence. Separation of the compound by reversed-phase high-performance liquid chromatography on RPC-18 columns allows its detection down to the picomolar range and can be successfully applied for ALA analysis in small biological samples. The reaction product of ALA with 2-amino-3-hydroxynaphthalene has been synthesized and characterized.

Vanadium in photosynthesis of Chlorella fusca and higher plants.

The influence of vanadium compounds (vanadate, vanadyl citrate) on photosynthesis in Chlorella fusca and in algal and spinach chloroplasts has been investigated. It was found that: 1. At moderately high concentrations (at least 0.1 mM) both vanadate and vanadyl citrate enhance photosynthetic O2 production in intact C. fusca cells. At lower V concentration (about 2 microM) only vanadate stimulates photosynthesis. The increase is dependent on culture conditions and on light intensity. 2. Up to 1 mM V, neither vanadium compound influences PS II activity, either in intact cells or in algal or spinach chloroplasts. 3. The PS I reaction in algal and spinach chloroplasts is maximally enhanced (3-fold) in presence of vanadium (20 microM). The increase is independent of light intensity. 4. Cr(VI), Mo(VI), and W(VI) (1 mM) stimulate photosynthesis in intact C. fusca cells, but do not influence the photosystems of isolated chloroplasts. Vanadium is suggested to act as a redox catalyst in the electron transport from PS II to PS I.

Chemistry and biochemistry of vanadium.

The transition metal vanadium is considered to be essential for plants and animals. In order to understand its physiological function, some important chemical properties of V are reviewed, e.g. its redox activity and the tendency of V3+, VO2+, and VO3- ions to form chelates with numerous ligands. A survey of the occurrence and distribution of kV in geochemistry and in living organisms is followed by a consideration of the V influence on several metabolic events such as microbial nitrogen metabolism, chlorophyll biosynthesis, and activation or inhibition of regulatory enzymes.

The role of vanadium in green plants. IV. Influence on the formation of delta-aminolevulinic acid in Chlorella.

In a series of experiments, it is demonstrated that the trace element vanadium (4.10(-7) g-at/1 as NH4VO3) has a considerable positive influence on the synthesis of delta-aminolevulinic acid(delta-ALA) in the autotrophically growing green alga Chlorella pyrenoidosa, the effect being visible by an enhanced output of the amino acid into the culture medium in presence of levulinic acid (LA). The level of intracellularly accumulated delta-ALA, however, is not changed in presence of the metal. The V-effect on exogenous found delta-ALA is suppressed, when LA is added to the nutrient medium at low pH (pH5), although V-uptake into the algal cells is not disturbed by LA. As demonstrated in culture media with various nitrogen sources (urea, partially hydrolized urea, ammonium salts), the development of the pH during the cultivation time is important for the presentation of the V-effect on delta-ALA. It is suggested that vanadium acts as a catalyst in the conversion of 4,5-dioxovaleric acid to delta-ALA by transamination.

The role of vanadium in green plants. III. Influence on cell division of Chlorella.

Vanadium, although essential for growth and chlorophyll formation in unicellular green algae, reveals toxic influences on cell division of Chlorella pyrenoidosa, these disturbances arising in the same range of V-concentrations as the known positive effects of the trace metal. In permanent light, as documented by cell volume statistics, vanadium (4-10(-7) g-at/1 as NH4VO3) causes a significant shift of the distribution maxima to higher values of the algal cell volume, the shift having its optimum at 10(-5) g-at V/1. It is documented in pH-constant liquid culture that this effect is not due to a change of pH in the nutrient medium. Under synchronous conditions of algal cultivation (16:8h), vanadium causes a total arrest of cell division after 3 periods; this stop lasts for the next 3 cycles. Afterwards, asynchronous divisions newly occur and lead to generally larger autospores. Staining of algal cell nuclei revealed an inhibitory V-effect on nuclear division, yielding giant nuclei with multiple sets of chromosomes, and thereby limiting cell division. Under these conditions, Chlorella pyrenoidosa is not synchronizable in presence of vanadium.

The role of vanadium in gree plants. II. Vanadium in green algae--two sites of action.

Cells of Chlorella pyrenoidosa, derived from vanadium free agar slants, respond with great sensitivity to microamounts of vanadium, added as NH4VO3 to autotrophic liquid cultures. Between 0.01 and 1 microgram V per litre nutrient medium (2-10(-10)-2-10(-8) g-at/1), the algae respond with a continuous incrase in dry weight. At higher V-concentrations, further enhancement in biomass is accompanied by a additional increase in chlorophyll content. Maximum V-effect on both parameters was found to be at 500 microgram V/1 (10(-5) G-AT/1). Dry weight as well as chlorophyll content of Chlorella are decreased by concentrations above 25 mg V/1; 100 mg V/1 (2-10(-3) g-at/1) stop growth and cause death of the cells. The toxic threshold for the V-content in the algae was determined to be at 150-200 microgram V/g (3-4-10(-6) g-at/g) dry weight. Two different pH-optima for a positive vanadium action on dry weight and chlorophyll biosynthesis were established, the first at pH 7, the other in the range pH 7.5--8. Two sites of vanadium action in green algae are discussed.

Effect of vanadium on growth, chlorophyll formation and iron metabolism in unicellular green algae.

In the presence of vanadium, growth of Scenedesmus obliquus and Chlorella pyrenoidosa was increased five to sixfold as determined by dry weight, when cultured under autotrophic conditions for 7 days. The stimulation by vanadium decreased with increasing stability towards hydrolysis of the iron(III)-compounds added. Pentavalent vanadium (20 mug V/1 as NH4VO3) was able to overcome completely a limited iron-deficiency in the algae following growth in presence of 1.8 - 10(-5) m ferric chloride. Vanadium did not alter the iron uptake into the algal cells. 90% of offered 48V was taken up by Scenedesmus obliquus during 5 days of growth, and 21% thereof were found in the chloroplast fraction. In presence of vanadium, the chlorophyll formation was stimulated in Scenedesmus obliquus. This stimulation by vanadium was found to be light-dependent but occurred to a certain extent in the dark also. The main porphyrin of the yellow mutant 211-11h/20 of Chlorella vulgaris was identified as protoporphyrin-IX. The formation of this compound was stimulated by vanadium within 10 days up to 83%. The role of vanadium in the biosynthesis of chlorophylls is discussed.