Monovalent cation-dependent reversible phosphorylation of ribosomal protein S8 in growth arrested Tetrahymena: kinetics of formation, phosphoamino acids, and phosphopeptides of mono-, and diphosphorylated derivatives of protein S8.

The kinetics of formation of mono-, and diphosphorylated derivatives of ribosomal protein S8 in Tetrahymena starving in the presence of Na+ have been determined, and the phosphoamino acids present in these derivatives have been identified. The mono-phosphorylated product, S8', contains only phosphoserine, and behaves kinetically as the precursor of the diphosphorylated product S8" which contains phosphoserine, and phosphothreonine. Tryptic digestion release a single major phosphoserine containing peptide from both S8' and S8", and a single phosphothreonine containing peptide from S8".

[Medium-term Daphnia test. Evaluation of the toxicity of various trace metals in the presence of humic acids]. / Test Daphnie moyen terme. Evaluation de la toxicité de quelques métaux traces en présence d'acides humiques.

Toxicity of copper, cadmium and zinc complexed by the EDTA and HPO4(2)- ligands has recently been studied by the use of the short-term daphnia test. In order to detect the toxicity due to very small quantities of metals present in water in free ionic state or in complexed species formed with humic matters, a medium term test on Daphnia magna has been developed for a better appreciation of lethal and sublethal effects. Collected data are statistically analysed with the use, for instance, of "Lowest Rejected Concentration Tested" previously proposed by Skalski. The test defined in our laboratory allows to point out cadmium concentrations as small as 5 micrograms.l-1.