The effects on the stringent control of ribosomal ribonculeic acid synthesis of the removal of cell wall, cold-shock treatment of cells, LiCl treatment of toluene-treated cells, and hypotonic treatment of spheroplasts were examined using Escherichia coli rel+ cells. Neither the removal of cell wall with penicillin or lysozyme nor the cold-shock treatment of the cells had an effect on the stringent control. The control mechanism, however, disappeared after the LiCl treatment of the toluene-treated cells, with the release of some protein component(s), possibly from the cytoplasmic membrane. The hypotonic and other treatments of spheroplasts, which disrupt the cytoplasmic membrane, also led to the abolishment of the control mechanism. These results suggested that the operation of the stringent control of ribosomal ribonucleic acid synthesis requires the cytoplasmic membrane, in which some proteins labile with LiCl treatment are embedded.

No abstract

Glutathione synthetase of Escherichia coli B was modified with polyethylene glycol, and the properties of the resultant modified enzyme were investigated. The thermal stability of the modified enzyme and its resistance against several proteases increased compared with those of the native enzyme. The modified enzyme was injected intravenously via the rat tail vein, and the circulating life of the enzyme in plasma was monitored. The half-life of the native enzyme was 50 min, whereas that of the modified enzyme was approximately 24 h. The systemic anaphylaxis reaction was tested by using rats intravenously injected with the native and modified enzymes. For the native enzyme, strong reactions such as dyspnea and tumble were observed; however, no symptom or only a very weak reaction, such as scratching, was observed with the modified enzyme.

Ultra-fine particles of titanium dioxide (TiO 2 ) and Zinc oxides (ZnO) are very attractive as UV-protecting ingredients in cosmetic products. The UV-scattering behavior of single TiO 2 suspensions and complex ones in a silicone oil is studied in relation to rheological properties. To control the dispersion stability of suspensions, three polyoxyethylene(POE)-modified silicones of branch-type, (AB)n-type, and ABA-type are used as dispersants. Irrespective of molecular structure, the dispersants can stabilize the TiO 2 and ZnO particles and the flow of both single suspensions is Newtonian with low viscosity. However, the Newtonian flow profiles and high dispersion states are maintained only for complex suspensions prepared with ABA-type dispersant. Since the POE groups which are incorporated between terminal silicones groups attach to the particle surfaces, the steric stabilization is responsible for low viscosity and high dispersions. Because the UV scattering of suspensions is determined by the sizes of flocculated structures, the high transmittance in the visible ranges and low transmittance in the UVA and UVB ranges can be achieved in the presence of ABA-type dispersant.