RNA Polymerase-Binding and Transcription Initiation Sites Upstream of the Methyl Reductase Operon of Methanococcus vannielii

RNA Polymerase, purified from Methanococcus vannielii, was shown by exonuclease III footprinting to bind to a 49-base-pair (bp) region of DNA in the intergenic region upstream of mcrB. Sl nuclease protection experiments demonstrated that transcription Initiation in vivo occurs within this region at 32 or 33 bp 5' to the A T G translation initiation codon of mcrB and 19 or 20 bp 3' to a T A T A box

Aspects of the coordination chemistry of phosphorus(V) chloro-compounds

Acceptor properties of several phosphorus(v) chloro compounds have been studied by solution and solid state (^31)P n.m.r. techniques, using pyridine, 1,10-phenanthroline, 2,2'-dipyridyl and chloride ions as ligands. Six co-ordinate adduct formation has been detected in most systems. As reported previously(^1), phosphorus pentachloride forms a molecular 1:1 adduct with pyridine. Bidentate pyridines produce PC1(_4)(L-L)(^+) PC1(_6)(^-) (L-L = 2,2'-dipyridyl or 1,10-phenanthroline). Non-stoichiometric adducts PC1(_4)phen(+)(PC1(_6)(^-))(_1-x)C1(^-)(_x) (x<l) disproportionate on dissolution to the 2:1 complex. PC1(_4)(^+) SbC1(_6)(^-) reacts with pyridine in nitrobenzene to give the equilibrium PC1(_4) (pyridine)(_2)(^+) SbC1(_6)(^-) = PC1(_5).pyridine + SbC1(_5).pyridine Solid PC1(_4)(pyridine)(_2)(^+) SbC1(_6)(^-) has been successfully isolated, however. Solution-stable adducts PC1(_4)(L-L)(^+) SbC1(_6)(^-) are formed with bidentate pyridines. Phenyltetrachlorophosphorane PhPC1(_4), catechyl phosphorus trichloride (C(_6)H(_4)0(_2))PC1(_3) and bis-catechyl phosphorus monochloride (C(_6)H(_4)0(_2))(_2) PC1 yield chloride ion adducts which are partially dissociated in solution. Each has been isolated as a solid. These phosphoranes also form molecular 1:1 adducts with pyridine, of which only PhPC1(_4) pyridine dissociates in solution. In the presence of excess pyridine, (C(_6)H(_4)0(_2))PCl(_2) (pyridine)(_2)(^+)C1(^-) and (C(_6)H(_4)0(_2))(_2)P (pyridine)(_2)(^+)C1(^-) equilibrate with the 1:1 adducts. The acceptors slowly produce cationic adducts with bidentate pyridines viz. PhPC1(_3)(L_L)(^+) C1(^-), (C(_6)H(_4)0(_2))PC1(_2)(L-L)(^+) (C(_6)H(_4)0(_2))PC1(_4)(^-) and (C(_6)H(_4)0(_2))(_2)P(dipyridyl)(^+) C1(^-). Similar cationic adducts Z(_4)P(L-L)(^+) MC1(_6)(^-) are rapidly formed by addition of bidentate ligands to PhPC1(_3)(^+) SbC1(_6)(^-), PhPC1(_3)(^+) PC1(_6_(^-), (C(_6)H(_4)0(_2))PC1(_2) (^+) SbC1(_6)(^-) and (C(_6)H(_4)0(_2))(_2)P(^+) SbC1(_6)(^-). The solid hexachloroantimonate adducts possess unexpected stability to water and moist air. Pyridine adducts Z(_4)P(pyridine)(_2)(^+)SbC1(_6)(^-) are formed with (C(_6)H(_4)0(_2))PC1(_2)(^+) SbC1(_6)(^-) and (C(_6)H(_4)0(_2))(_2)P(^+) SbC1(_6)(^-) but not with PhPC1(_3)(^+) SbC1(_6)(^-). Preliminary experiments with methyltetrachlorophosphorane (MePC1(_4)) show the formation of MePC1(_5)(^-) on addition of chloride ions. The addition of substituted pyridines to PCl(_5) and PCl(_4)(^+) SbC1(_6)(^-) has been investigated. 3- and 4-substituted non- methylated pyridines yield complexes, but 2-substituted pyridines show a much lower tendency to co-ordinate. Methyl pyridines are attacked by the phosphorus species in solution. Reactions of the type R(_3)P + PC1(_5) → R(_3)PC1(-2) + PC1(_3) R(_3)PC1(_2) + PC1(_5) → R(_3)PC1(^+) PC1(_6)(^-) have also been studied. By variation of the reaction stoichiometry, either R(_3)PC1(_2) or R3PC1(^+) PC1(_6)(^-) may be prepared. With PhPC1(_2), however, only PhPC1(_3)(+)PC1(_6)(^-) has been isolated

On some non-conformal fractals

This paper presents a simple method of calculating the Hausdorff dimension for a class of non-conformal fractals

Use of a restriction enzyme-digested PCR product as substrate for helicase assays

DNA helicases play essential roles in many cellular processes. The currently available techniques to generate substrates for helicase assays are fairly complicated and need some expertise not available in all laboratories. Here, a PCR-based method to generate a substrate for a helicase assay is described, and its application for several archaeal, bacterial and viral enzymes is demonstrated

The effects of an experimental programme to support students’ autonomy on the overt behaviours of physical education teachers

Although the benefits of autonomy supportive behaviours are now well established in the literature, very few studies have attempted to train teachers to offer a greater autonomy support to their students. In fact, none of these studies has been carried out in physical education (PE). The purpose of this study is to test the effects of an autonomy-supportive training on overt behaviours of teaching among PE teachers. The experimental group included two PE teachers who were first educated on the benefits of an autonomy supportive style and then followed an individualised guidance programme during the 8 lessons of a teaching cycle. Their behaviours were observed and rated along 3 categories (i.e., autonomy supportive, neutral and controlling) and were subsequently compared to those of three teachers who formed the control condition. The results showed that teachers in the experimental group used more autonomy supportive and neutral behaviours than those in the control group, but no difference emerged in relation to controlling behaviours. We discuss the implications for schools of our findings

The Impacts of a Subglacial Discharge Plume on Calving, Submarine Melting, and Mélange Mass Loss at Helheim Glacier, South East Greenland

Almost half of the Greenland ice sheet’s mass loss occurs through iceberg calving at marine terminating glaciers. The presence of buoyant subglacial discharge plumes at these marine termini are thought to increase mass loss both through submarine melting and by undercutting that consequently increases calving rates. Plume models are used to predict submarine melting and undercutting. However, there are few observations that allow these relationships to be tested. Here we use airborne lidar from the terminus of Helheim Glacier, SE Greenland to measure the bulge induced at the surface by the upwelling plume. We use these measurements to estimate plume discharge rates using a high‐resolution, three‐dimensional plume model. Multi‐year observations of the plume are compared to a record of calving from camera and icequake data. We find no evidence to suggest that the presence of a plume, determined by its visibility at the surface, increases the frequency of major calving events and also show that mass loss at the terminus driven directly by plume discharge is significantly less than mass loss from major calving events. The results suggest that the contribution of direct plume‐driven mass loss at deep marine‐terminating glaciers may be less than at shallower termini