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  • 1995-1999  (4)
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  • 1
    Electronic Resource
    Electronic Resource
    The ‘petite-negative’ yeast Kluyveromyces lactis has a single gene expressing pyruvate decarboxylase activity (1996)
    Oxford, UK : Blackwell Publishing Ltd
    Molecular microbiology 19 (1996), S. 0 
    Details
    ISSN: 1365-2958
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: We cloned and sequenced the pyruvate decarboxylase (PDC; EC 4.1.1.1) structural gene KIPDCA in the yeast Kluyveromyces lactis and found it to be allelic to the previously isolated rag6 mutation. The putative amino acid sequence of the KIPdcAp appeared to be highly homologous to those of the yeast Pdc proteins identified so far. The disruption of KIPDCA indicated that it is the only PDC structural gene in K. lactis, as evidenced by the lack of PDC activity and ethanol production in the pdcAΔ strains and by the absence of growth on glucose in the presence of respiratory inhibitors. It was observed that expression of the KIPDCA gene is induced by glucose at the transcriptional level. Transcription of the gene was reduced in the rag1, rag2, rag5 and rag8 mutants, which are defective for the low-affinity glucose permease, phosphoglucose isomerase, hexokinase, and a positive regulator of RAG1 expression, respectively.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2958.1996.346875.x
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Preparation and homogeneity study of a mussel candidate reference material for certification of organotin compounds (1995)
    Springer
    Microchimica acta 120 (1995), S. 281-287 
    Details
    ISSN: 1436-5073
    Keywords: certified reference material ; mussel ; organotin ; homogeneity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Organotin compounds are currently determined in various environmental matrices (in particular water, sediment and shellfish) to form the basis of control measures for the levels of contamination, as required in some EC Directives. Accurate measurements are a prerequisite for the enforcement of this legislation, which implies that good quality control of determinations should be ensured. One of the tools for achieving accuracy is to use certified reference materials (CRMs). With regard to tin species, however, CRMs are rather scarce and mainly concern sediment and fish matrices certified for their butyltin content. The present study deals with the preparation of a mussel candidate reference material and the verification of its homogeneity prior to the certification of the contents of butyl- and phenyl-tin compounds. 100kg of mussels (Mytilus edulis) were collected, carefully washed with fresh water in order to eliminate matrix salts and immediately frozen by immersion in liquid nitrogen. The mussels were shelled (in the frozen state) and the edible part was stored in thermally sealed polyethylene bags which were stored at −25 °C. The frozen material was ground in a Teflon-coated grinding mill, spread on sterilized flat trays and freeze-dried. The freeze-dried material was then ground for 15 days in a zirconia ball mill and sieved on a titanium sieve to separate the fibrous part. Successively, the material was mixed for 15 days under argon atmosphere in a special polyethylene-lined mixing drum and bottled in brown Pyrex-glass bottles. 21 bottles were selected during the course of the bottling procedure to verify the within- and between-bottle homogeneity of the overall batch. The within-bottle homogeneity was verified by determining the organotin (butyl- and phenyltins) content for subsamples of 500 mg in ten replicates from one bottle, whereas the between-bottle homogeneity was controlled by one organotin measurement from each of 20 bottles. The analyses were performed by GC-MS. The results showed that the homogeneity of the material makes it suitable as a candidate reference material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01244438
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Interlaboratory exercises to compare analytical method performances (1996)
    Springer
    Microchimica acta 123 (1996), S. 95-102 
    Details
    ISSN: 1436-5073
    Keywords: intercomparison ; analytical methods ; rainwater
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Three intercomparison exercises on simulated rainwater were held in the period 1991–93 involving 72 to 99 laboratories in Europe and South America. The exercises required the analysis of pH, conductivity, main anions (Cl−, NO 3 − and SO 4 2− ) and main cations (Ca2+, K+, Mg2+, Na+ and NH 4 + ). The concentrations of the single ions ranged between 5 and 150 μmoll−1. Results were used to evaluate and compare the precision of the analytical methods. A general improvement in precision was observed in the course of the exercises.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01244382
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  • 4
    Electronic Resource
    Electronic Resource
    TUNA FISH (T-30) – A new proficiency testing material for the determination of As and Hg in seafood (1997)
    Springer
    Fresenius' journal of analytical chemistry 358 (1997), S. 441-445 
    Details
    ISSN: 1432-1130
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The quality of the aquatic and marine environment can be monitored by the determination of pollutants in organisms living in this environment. Certified reference materials and well-organised proficiency tests are powerful means of ensuring a constant level of quality and verifying the correct application of standardised methods. The preparation of a tuna fish proficiency testing material for the evaluation of quality of As and Hg monitoring in seafood is described. Preparation and characterisation of the material as well as studies on its homogeneity and stability are described. Concentrations of 3.4 ± 0.2 mg/kg total arsenic and 2.91 ± 0.09 mg/kg total mercury have been determined as target values. Moreover indicative values for some trace elements (Cd, Cu, Ni, Pb, Sr) and some major constituents (Al, Br, C, Ca, Cl, Fe, H, K, Mg, N, Na, P, S, Si, Zn) have also been measured.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002160050443
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    Paper (German National Licenses)
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