Sequence specific 1H, 13C and 15N backbone resonance assignments of UVI31+ from Chlamydomonas reinhardtii.

The cDNA of UVI31+ was cloned from C. reinhardtii and expressed in E. coli from where the protein was purified to homogeneity. The purified protein exhibited beta-lactamase activity (Manuscript in preparation). However, UVI31+ has no homology with the known ß-lactamases. In order to understand the structural basis of the ability of UVI31+ to hydrolyze ß-lactam antibiotics, we in parallel, set out to structurally characterize it by NMR. Its ß-lactamase activity in relation to the solution structure by NMR is likely to provoke deeper understanding of its mechanism and facilitate the rationalization of other functions of the protein, if any. In this endeavor, we report almost complete sequence-specific backbone (1)H, (13)C and (15)N NMR assignments of UVI31+.

Postcoital contraception with levonorgestrel during the peri-ovulatory phase of the menstrual cycle. Task Force on Post-ovulatory Methods for Fertility Regulation.

The contraceptive efficacy and side effects of postcoital levonorgestrel used repeatedly during the peri-ovulatory period of one cycle was examined in 259 women. All subjects were of proven fertility in their present union and had ovulatory cycles as assessed from pre-treatment BBT charts. The mean number of coital acts during the treatment cycle was 7.5 (SD:2.6) and the mean number of 0.75 mg levonorgestrel tablets taken during the peri-ovulatory period was 4.0 (SD:1.2). Two pregnancies, both considered to be method failures, occurred, giving a failure rate of 0.8% per treated cycle. Although the overall effect of levonorgestrel on menstrual cycle length was small and insignificant, menstrual cycle disturbances were not uncommon. Intermenstrual bleeding or spotting occurred in 8.5% of the treated cycles and 12.5% of the cycles were less than 20 or more than 35 days. Other side effects, mainly nausea, headache and dizziness, were reported by about 20% of the subjects but the apparent incidence of these complaints varied markedly between the nine participating centres from 0% to just over 50%. The data suggest that repeated postcoital use of levonorgestrel is probably not a viable approach to fertility regulation for the majority of women who have regular intercourse and wish to limit the number of their pregnancies.

Preliminary crystallographic study of glucose-6-phosphate dehydrogenase from rat liver.

Crystals of D-glucose-6-phosphate: NADP+ oxidoreductase were obtained with the hanging drop, vapor diffusion and batch methods from ammonium sulfate-containing solutions. X-ray diffraction photographs indicate that the crystals belong to the orthorhombic space groups I222 or I2(1)2(1)2(1) with unit cell dimensions of a = 66.0 A, b = 140.8 A and c = 177.8 A. These data, together with results from sodium dodecyl sulfate/polyacrylamide gel electrophoresis and crystal density experiments, indicate that there is one 116,000 Mr dimer per asymmetric unit. The crystals diffract to at least 2.2 A and are suitable for X-ray crystallographic structure determination.

Role of Rec pathways on sensitivity of Escherichia coli to near-ultraviolet and visible light.

In Escherichia coli lack of the RecRC or RecF pathway is found to cause sensitivity to near-ultraviolet and visible light. Resistance to this light is restored in the RecBC-defective strain carrying either the sbcB (Rec+) or xonA (Rec-) mutation. The sensitivity, therefore, is not found to correlate with the degree of recombination proficiency as measured by genetic crosses.

Effect of near ultraviolet and visible light on amoeba.

The near ultraviolet and visible light (VL) impinging at an intensity of 2-5 x 10(2) J s-1 m-2 for 2-5 h kills the mitotic and the early S-phase (0- to 15-min-old) amoebae. At the mid- and late S-period only a fraction of cells are killed by VL and G2 phase cells are quite resistant. Amoebae of all cell cycle stages show a delay in the first mitotic division. DNA synthesis, as measured by [3H]thymidine incorporation, is depressed in the VL-exposed early-S amoebae. A concurrent but temporary inhibition in [3H]leucine incorporation also occurs in these cells. However, no significant change in [3H]uridine incorporation has been found. To localize the site of lethal damage, nuclear transplantation studies were undertaken between the control amoebae and the amoebae treated with VL. The nucleus of a VL-exposed early S-phase cell recovers when transplanted immediately after VL exposure into an enucleate G2 cytoplasm but dies if grafted into an enucleat S-phase cytoplasm. The therapeutic effect of the G2 cytoplasm, although at a lower level, is also evident even when the treated early S-phase nucleus is implanted 20 h later, but not after 48 h, into the G2 cytoplasm. The amoeba cytoplasm shows resistance to VL-irradiation, can accept a control nucleus from any cell cycle stage, and function normally. The G2 nucleus also remains apparently unaffected to VL exposure and can survive when it is transfered to the control cytoplasm of any cell-cycle phase. All these findings are discussed in the light of the possible existence of a repair system against VL-induced damage in the G2-phase amoeba.