Evaluation of EC Comparison on the Determination of 226Ra, 228Ra, 234U and 238U in Mineral Waters

This report describes all details of the comparison for the determination of 226Ra, 228Ra, 234U and 238U in mineral waters among 45 European laboratories monitoring radioactivity in food and the environment. Three commercially available mineral waters were provided as comparison samples. Reference values of the four radionuclides under study in this comparison were determined in collaborative work of IRMM and the Bundesamt für Strahlenschutz (BfS), using tracer techniques and standardised radionuclide solutions. The reference values are thus traceable to the SI units. The sample preparation and measurement processes applied in the participating laboratories are described and the results of the comparison are presented and discussed in detail. Whereas, in general, the measurement results for the uranium isotopes show a relatively favourable agreement with the reference value, the results of this comparison point at severe problems of 226Ra and 228Ra determination in about one fourth and more than one third of the laboratories, respectively. For radium, 19 results corresponding to 14 % of all are even off by a factor of two or more. By comparison, for uranium, this number amounts to 6 % (9 results out of 150). Nevertheless, also for the determination of uranium, 14 % to 23 % of the laboratories report results not compliant with the En evaluation criterion. The corresponding participants are urgently requested to investigate and revise their analytical methods.JRC.D.4-Nuclear physic

表紙、執筆者紹介、奥付、裏表紙

Treatment with dimethyl suberimidate, a cross-linking bifunctional agent, showed that Sm1 and Sm2 nucleases of Serratia marcescens B10M1 are polydisperse in solution and consist of monomers and dimers at the level of pH optimal for the enzyme activity. The data suggest that nucleases from the strain B10M1 and any other strain are polydisperse at pH optimum if their amino acid sequences are identical

Polydispersity of Serratia marcescens Nuclease at Optimum pH

Treatment with dimethyl suberimidate, a cross-linking bifunctional agent, showed that Sm1 and Sm2 nucleases of Serratia marcescens B10M1 are polydisperse in solution and consist of monomers and dimers at the level of pH optimal for the enzyme activity. The data suggest that nucleases from the strain B10M1 and any other strain are polydisperse at pH optimum if their amino acid sequences are identical

Polydispersity of Serratia marcescens nuclease at optimal pH values | Polidispersnost' nukleazy Serratia marcescens pri optimal'nom znachenii pH.

Treatment with dimethyl suberimidate, a cross-linking bifunctional agent, showed that Sm1 and Sm2 nucleases of Serratia marcescens B10M1 are polydisperse in solution and consist of monomers and dimers at the level of pH optimal for the enzyme activity. The data suggest that nucleases from the strain B10M1 and any other strain are polydisperse at pH optimum if their amino acid sequences are identical

Polydispersity of Serratia marcescens nuclease at optimum pH

Treatment with dimethyl suberimidate, a cross-linking bifunctional agent, showed that Sm1 and Sm2 nucleases of Serratia marcescens B10M1 are polydisperse in solution and consist of monomers and dimers at the level of pH optimal for the enzyme activity. The data suggest that nucleases from the strain B10M1 and any other strain are polydisperse at pH optimum if their amino acid sequences are identical

Study of the mechanism of action of p-chloromercuribenzoate on endonuclease from the bacterium Serratia marcescens

The mechanism of action of p-chloromercuribenzoate (PCMB) on Serratia marcescens nuclease was investigated. The analysis showed that PCMB forms complexes with DNA. Binding of C7H5O2Hg+ to DNA changes the secondary structure of the DNA. These changes alter the enzymatic activity of S. marcescens nuclease, which was previously found to be sensitive to the secondary structure of the substrates. The nuclease activity was either suppressed or stimulated in the presence of PCMB depending on the C7H5O2Hg+ to nucleotide equivalent ratio. Binding of C7H5O2Hg+ to DNA did not form an abortive enzyme-substrate complex. Binding of Mg2+ to the C7H5O2Hg-DNA complex caused appropriate changes in secondary structure of the substrate. Since Mg2+ and C7H5O2Hg+, though differing in the type of metal cation, are similar in their mechanisms of influence on enzymatic activity of S. marcescens nuclease, the identity of other metal-containing effectors in their mechanism of action on Serratia marcescens nuclease is assumed

Study of the mechanism of action of p-chloromercuribenzoate on endonuclease from the bacterium Serratia marcescens

The mechanism of action of p-chloromercuribenzoate (PCMB) on Serratia marcescens nuclease was investigated. The analysis showed that PCMB forms complexes with DNA. Binding of C7H5O2Hg+ to DNA changes the secondary structure of the DNA. These changes alter the enzymatic activity of S. marcescens nuclease, which was previously found to be sensitive to the secondary structure of the substrates. The nuclease activity was either suppressed or stimulated in the presence of PCMB depending on the C7H5O2Hg+ to nucleotide equivalent ratio. Binding of C7H5O2Hg+ to DNA did not form an abortive enzyme-substrate complex. Binding of Mg2+ to the C7H5O2Hg-DNA complex caused appropriate changes in secondary structure of the substrate. Since Mg2+and C7H5O2Hg+, though differing in the type of metal cation, are similar in their mechanisms of influence on enzymatic activity of S. marcescens nuclease, the identity of other metal-containing effectors in their mechanism of action on Serratia marcescens nuclease is assumed