Seasonal and geographical variations in levels of polychlorinated biphenyls (PCB) and polybrominated diphenyl ethers (PBDE) in Polish butter fat used as an indicator of environmental contamination.

The aim of this study was to evaluate the seasonal variation/geographical distribution of environmental concentration of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) across Poland using butter fat as an indicator of the contaminants. The average concentration of six indicator PCBs determined in the studied samples was 1500 pg g(-1) fat. The average concentration of 12 dioxin-like PCBs expressed as lower-bound dioxin-equivalent toxicity was 0.684 pg TEQ g(-1) fat. The average total concentration of 14 investigated PBDE congeners was 105 pg g(-1) fat. Statistically significant concentration differences between summer and winter samples were found. The results of this study indicate also a significant geographical diversification of butter contamination reflecting regional differences in environmental contamination. The seasonal variation of PBDE profiles evidences transformation of PBDE within the environment.

Structural studies of ROK fructokinase YdhR from Bacillus subtilis: insights into substrate binding and fructose specificity.

The main pathway of bacterial sugar phosphorylation utilizes specific phosphoenolpyruvate phosphotransferase system (PTS) enzymes. In addition to the classic PTS system, a PTS-independent secondary system has been described in which nucleotide-dependent sugar kinases are used for monosaccharide phosphorylation. Fructokinase (FK), which phosphorylates d-fructose with ATP as a cofactor, has been shown to be a member of this secondary system. Bioinformatic analysis has shown that FK is a member of the "ROK" (bacterial Repressors, uncharacterized Open reading frames, and sugar Kinases) sequence family. In this study, we report the crystal structures of ROK FK from Bacillus subtilis (YdhR) (a) apo and in the presence of (b) ADP and (c) ADP/d-fructose. All structures show that YdhR is a homodimer with a monomer composed of two similar α/ß domains forming a large cleft between domains that bind ADP and D-fructose. Enzymatic activity assays support YdhR function as an ATP-dependent fructose kinase.

Determination of total mercury in foods of plant origin in Poland by cold vapour atomic absorption spectrometry.

Total mercury concentrations were determined in 573 samples of agricultural crops and foods of plant origin which included cereals, fruit and vegetables and their products commercially available on the Polish market. The method of cold vapour atomic absorption spectrometry (CVAAS) after a wet-acid digestion in a closed-vessels and microwave oven was used and the reliability of the procedure demonstrated. Mercury concentrations in the agricultural crops and plant foods were generally below the maximum permissible limits in Poland and rarely exceeded 5 microg x kg(-1). Values ranged from <0.1 to 14 microg x kg(-1), mean 2.4 +/- 2.3 microg x kg(-1) in wheat and rye grains; from <0.1 to 2.4 microg x kg(-1), mean 0.5 +/- 0.4 microg x kg(-1) in nine varieties of vegetables; from <0.1 to 5.1 microg x kg(-1), mean 1.1 +/- 0.9 microg x kg(-1) in seven varieties of fruit; from <0.1 to 5.6 microg x kg(-1) in cereal products and jams; and from <0.1 to 3.0 microg x l(-1) in fruit and vegetable juices, nectars and beverages. The contribution of the mercury in the analysed agricultural crops and foods of plant origin to the weekly dietary intake of total mercury was 8 microg/person, which represents only 3% of the provisional tolerable weekly intake (PTWI) for this metal.

Amide and ester derivatives of N3-(4-methoxyfumaroyl)-(S)-2,3-diaminopropanoic acid: the selective inhibitor of glucosamine-6-phosphate synthase.

Several amide and ester derivatives of a glutamine analogue, N3-(4-methoxyfumaroyl)-(S)-2,3-diaminopropanoic acid (FMDP) (1-8), were synthesized and evaluated for the inhibitory activity in regard to glucosamine-6-phosphate synthase from Candida albicans. The syntheses were accomplished by the reaction of N2-tert-butoxycarbonyl-N3-(4-methoxyfumaroyl)-(S)-2,3-diaminopropanoic acid (BocFMDP) with the corresponding amines to give the FMDP amides (1-4) or with alkyl halides to give corresponding esters of FMDP (5-8). Among the synthesized compounds, the acetoxymethyl ester of FMDP was the most active inhibitor of the enzyme. Its IC50 value compared to that of FMDP (4 microM) was equal to 11.5 microM. The methyl and allyl esters and the N-hexyl-N-methyl-amide of FMDP exhibited a moderate enzyme inhibitory activity.

N3-oxoacyl derivatives of L-2,3-diaminopropanoic acid and their peptides; novel inhibitors of glucosamine-6-phosphate synthase.

Novel inhibitors 1-4 of glucosamine-6-phosphate synthase from Candida albicans have been designed based on acylation of the N3 amino group of L-2,3-diaminopropanoic acid with the corresponding ketoacids. These inhibitors have been shown to alkylate the fungal enzyme in a time-dependent manner. Compound 3 containing trans-beta-benzoyl acrylic acid as an acyl residue was found to be the most potent inhibitor in the series. Dipeptides composed of the active inhibitors and norvaline demonstrated potent antifungal activity against selected strains of Candida spp. and Saccharomyces cerevisiae. Their activity was reversed upon addition of N-acetylglucosamine to the medium.

Purification to homogeneity of Candida albicans glucosamine-6-phosphate synthase overexpressed in Escherichia coli.

The Candida albicans GFA1 gene encoding glucosamine-6-phosphate synthase, an enzyme of cell wall biosynthesis pathway in fungi and bacteria, recently an object of interest as a target for the chemotherapy of systemic mycoses, was PCR amplified and cloned to an Escherichia coli expression vector pET23b. The activity of the enzyme in the lysates from the overproducing E. coli strain was approximately 50-100 times higher than in the lysates from the control E. coli strain. This abundant overproduction allows to purify milligram amounts of the enzyme to homogeneity.

Certified reference materials for quality control of mercury and selenium determination in food.

Several certified reference materials were used for quality control of mercury and selenium determination in food through different analytical procedures and techniques. The materials were selected with respect to different composition of matrix and levels of certified values. The results agreed well with the certified values for all analysed materials.

Oligomeric structure and regulation of Candida albicans glucosamine-6-phosphate synthase.

Candida albicans glucosamine-6-phosphate (GlcN-6-P) synthase was purified to apparent homogeneity with 52% yield from recombinant yeast YRSC-65 cells efficiently overexpressing the GFA1 gene. The pure enzyme exhibited Km(Gln) = 1.56 mM and Km(Fru-6-P) = 1.41 mM and catalyzed GlcN-6-P formation with kcat = 1150 min-1. The isoelectric point of 4.6 +/- 0.05 was estimated from isoelectric chromatofocusing. Gel filtration, native polyacrylamide gel electrophoresis, subunit cross-linking, and SDS-polyacrylamide gel electrophoresis showed that the native enzyme was a homotetramer of 79.5-kDa subunits, with an apparent molecular mass of 330-340 kDa. Results of chemical modification of the enzyme by group-specific reagents established an essential role of a cysteinyl residue at the glutamine-binding site and histidyl, lysyl, arginyl, and tyrosyl moieties at the Fru-6-P-binding site. GlcN-6-P synthase in crude extract was effectively inhibited by UDP-GlcNAc (IC50 = 0.67 mM). Purification of the enzyme markedly decreased the sensitivity to the inhibitor, but this could be restored by addition of another effector, glucose 6-phosphate. Binding of UDP-GlcNAc to the pure enzyme in the presence of Glc-6-P showed strong negative cooperativity, with nH = 0.54, whereas in the absence of this sugar phosphate no cooperative effect was observed. Pure enzyme was a substrate for cAMP-dependent protein kinase, the action of which led to the substantial increase of GlcN-6-P synthase activity, correlated with an extent of protein phosphorylation. The maximal level of activity was observed for the enzyme molecules containing 1. 21 +/- 0.08 mol of phosphate/mol of GlcN-6-P synthase. Monitoring of GlcN-6-P synthase activity and its sensitivity to UDP-GlcNAc during yeast --> mycelia transformation of C. albicans cells, under in situ conditions, revealed a marked increase of the former and a substantial fall of the latter.

[Mercury determination in food of plant origin by cole vapour atomic absorption spectrometry (CVAAS)]. / Oznaczanie rteci w zywnosci pochodzenia roslinnego technika ASA z generacja zimnych par (CVAAS).

The studies on the analytical procedure for mercury determination in food of plant origin on the level of 5 micrograms/kg, were carried out. For this reason, microwave digestion with HNO3 and cold vapour atomic absorption spectrometry (CVAAS) with tin (II) chloride reduction, were used. Both digestion and determination conditions were experimentally optimized. The procedure was checked using two real food samples: apple juice and preserved carrot with peas both spiked on two levels with mercury. On these results basic statistic parameters that characterized the method as standard deviation, relative standard deviation and recovery, were calculated. The precision was generally better than 10%, and recovery ranged from 96 to 100%. The detection limit of the entire procedure, defined as the mercury concentration corresponding to three times the standard deviation of ten consecutive determinations of blank measurement, was 0.012 microgram/l. Taking into account the amount of a sample and the factor of dilution the detection limit corresponds to 0.3 microgram/kg for 1.0 g, 1.0 microgram/kg for 0.3 g, and 0.15 microgram/l for 2 ml of a sample. Accuracy of the analytical procedure was tested by analysing five certified reference plant materials with the mercury contents ranged from 6 to 280 micrograms/kg. The obtained results were in a good agreement with their certified values. Both analyses of the spiked real samples and certified reference materials allow to suggest that this analytical procedure based on microwave digestion and cold vapour determination using Fully Automated Mercury System is suitable for mercury determination in food products of plant origin on the level of microgram/kg or microgram/l, with a good precision and accuracy.

[Codex foodstuffs committee FAO/WHO on methods of analysis and sampling]. / Komitet kodeksu zywnosciowego fao/who ds. metod analiz i pobierania próbek.

The topics of the XIX Session of the Codex Alimentarius Committee held in Budapest are reviewed. In the report on the Session the main stress was laid on the matters connected with guidelines on sampling, endorsement of methods of analysis for codex standards and the matters concerning quality assurance systems in laboratories.

[Aluminum in infant food]. / Glin w odzywkach dla niemowlat.

The potential risk for health because of aluminium content of infant formulas has been taken into consideration. Results of aluminium determination of milk and milk-cereal products and others, from different countries, have been discussed. Primary study on the aluminium content of Polish commercially available infant formulas were performed. The obtained levels were comparable to those reported by other authors.

[Cadmium and lead levels in milk, milk-cereal and cereal formulas for infants and children up to 3 years of age]. / Wystepowanie kadmu i olowiu w odzywkach mlecznych, mleczno-zbozowych i zbozowych przeznaczonych dla niemowlat i dzieci do lat 3.

Cd and Pb contents were determined in milk formulae, milk-cereal formulae and cereal formulae produced by Okregowe Zaklady Koncentratów Spozywczych (OZKS) (Regional Food Concentrates Processing Plants) for infants and children up to 3 years of age. The major parts of the assortments were found to contain products whose cadmium and/or lead contents exceeded the admissible norms. These contents were as follows: in milk formulae: from less than 2 to 8 micrograms Cd/kg and from less than 20 to 180 micrograms Pb/kg; in milk-cereal formulae: from less than 2 to 20 micrograms Cd/kg and from less than 20 to 180 micrograms Pb/kg; in cereal formulae from less than 2 to 70 micrograms Cd/kg and from less than 20 to 400 micrograms Pb/kg. Contents of Cd and Pb were the highest in cereal formulae mainly in those produced of wheat flour and buckwheat-rice flour. Determinations of Cd and Pb contents in raw materials and in some cereal intermediate products revealed that the occurrence of excessively high Cd and Pb contents in the cereal-containing formulae was due to contamination of the cereal raw materials with these metals.

On the content of arsenic, lead, copper, zinc, tin and iron in bottled fruit, strained fruit pulp and bottled jam produced in Poland.

One hundred and fifty-three samples of bottled fruit, strained fruit pulps and jams contained in glass jars were analysed for heavy metals. All arsenic concentrations were less than the limit of detection of 0.04 mg/kg as were all tin concentrations for which the limit of detection was 8 mg/kg. The concentrations of the lead were all below 0.2 mg/kg for bottled fruit and 0.3 mg/kg for stained pulps and jams. In bottled fruit 98% of samples contained less than 3 mg/kg of copper, 98% less than 5 mg/kg of zinc and 97% less than 10 mg/kg of iron. In strained pulps all samples contained less than 2 mg/kg of copper and less than 5 mg/kg of zinc, 41% of samples contained less than 20 mg/kg of iron. In jams all samples contained less than 2 mg/kg of copper and less than 5 mg/kg of zinc, 96% samples contained less than 20 mg/kg of iron.

[A method of atomic absorption spectrophotometry (AAS) for analysis of cadmium and lead levels in the plant material]. / Metoda absorpcyjnej spektrometrii atomowej (ASA) oznaczania zawartosci kadmu i olowiu w materiale roslinnym.

The conditions were evolved and checked for simultaneous determination of cadmium and lead levels in plant material using the flame technique of ASA. For decomposition of the organic substances in plant material wet mineralization was used with a mixture of nitric acid, perchloric acid and sulpuric acid in volume proportions 6:2:0.25. The levels of cadmium and lead were determined in the organic phase after extraction with n-butyl acetate of the previously produced complexes with NaDDTK. The obtained limits of cadmium and lead detectability were 0.002 and 0.02 mg/kg respectively. The recovery rate of the method ranged from 96 to 98%, while the variability index was from 2.6 to 10.2%. The correctness of the evolved analytical procedure was confirmed by determination of the content of both elements in the NBS-SRM 1571 standard (orchard leaves) and by participation in the international interlaboratory investigation of the Polish standard (dried cabbage leaves).

[Content of cadmium and lead in berries and seed fruits]. / Zawartosc kadmu i olowiu w owocach jagodowych i ziarnkowych.

By the method of atomic absorption spectrometry (AAS) the content of cadmium and lead was determined in 217 samples of various fruits from an agricultural region. The purpose of the work was a preliminary trial for establishing whether under similar conditions of cultivation environment it would be possible to demonstrate differences in the ability of accumulating cadmium and lead in relation to the type and species of fruit-bearing plants. Berries were found to contain higher amounts of both elements than grain fruits. The mean values of these elements were for berries from 0.012 to 0.077 mg Cd/kg and from 0.04 to 0.15 mg Pb/kg, and in grain fruits these values were from 0.007 to 0.008 mg Cd/kg and from below 0.02 to 0.02 mg Pb/kg. The greater ability of Cd and Pb cumulation by berries may be due to the well known ability of this type of fruit to accumulate also other mineral components, such as Ca, Fe, P, Mg, K, and among these Ca and Fe are known to reduce the toxicity of Cd and Pb.