Antimicrobial properties of highly fluorinated tris(pyrazolyl)borates

Highly fluorinated tris(pyrazolyl)borates were tested for their antimicrobial activity against various bacterial species. Both the silver(I) tris(pyrazolyl)borate [HB(3,5-(CF(3))(2)Pz)(3)]Ag(THF) (THF=tetrahydrofuran) and the sodium analog [HB(3,5-(CF(3))(2)Pz)(3)]Na(THF) appeared highly effective at inhibiting the growth of two different species of Gram-positive bacteria (i.e. being 12 and 21 fold more effective, respectively, (on a molar basis, based on the minimum inhibitory concentrations) against Staphylococcus aureus than silver sulfadiazine, a currently used silver antimicrobial). This suggests that the ligand portion of these molecules is responsible for the observed high effectiveness against the Gram-positive species. Furthermore, it appeared that the fluorinated substituents on the tris(pyrazolyl)borate were important for this high level of growth inhibition. Against two species of Gram-negative bacteria, including Pseudomonas aeruginosa, the fluorinated silver(I) tris(pyrazolyl)borate exhibited a moderate level of growth inhibition (similar to that of silver sulfadiazine), while the sodium analog showed very little ability to inhibit growth, indicating that for the Gram-negative species, the apparent responsible antimicrobial portion is the silver ion.     

The response regulator RpaB binds the high light regulatory 1 sequence upstream of the high-light-inducible <Emphasis Type="Italic">hliB</Emphasis> gene from the cyanobacterium <Emphasis Type="Italic">Synechocystis</Emphasis> PCC 6803

Cyanobacteria, like other photosynthetic organisms, respond to the potentially damaging effects of high-intensity light by regulating the expression of a variety of stress-responsive genes through regulatory mechanisms that remain poorly understood. The high light regulatory 1 (HLR1) sequence can be found upstream of many genes regulated by high-light (HL) stress in cyanobacteria. In this study, we identify the factor that binds the HLR1 upstream of the HL-inducible hliB gene in the cyanobacterium Synechocystis PCC 6803 as the RpaB (Slr0947) response regulator.     

Shifts of community composition and population density substantially affect ecosystem function despite invariant richness

There has been considerable focus on the impacts of environmental change on ecosystem function arising from changes in species richness. However, environmental change may affect ecosystem function without affecting richness, most notably by affecting population densities and community composition. Using a theoretical model, we find that, despite invariant richness, (1) small environmental effects may already lead to a collapse of function; (2) competitive strength may be a less important determinant of ecosystem function change than the selectivity of the environmental change driver and (3) effects on ecosystem function increase when effects on composition are larger. We also present a complementary statistical analysis of 13 data sets of phytoplankton and periphyton communities exposed to chemical stressors and show that effects on primary production under invariant richness ranged from ?75% to +10%. We conclude that environmental protection goals relying on measures of richness could underestimate ecological impacts of environmental change.     

Scraggly, a new hair loss mutation on mouse Chromosome 19

By use of chlorambucil, we have generated a mouse mutation called scraggly (sgl) that exhibits skin and hair defects. Homozygous mutant mice exhibit hair loss, skin defects, and abnormalities in sebaceous lipid composition. We have constructed a high-resolution genetic map of mouse Chromosome (Chr) 19 that links this mutation to the anonymous DNA marker D19Umi1. An additional cross, (BALB/c × CAST/Ei) F₁× BALB/c, was used to map markers around this mutation as well as to map the potential candidate genes, Fgf8 and Cyp17. Allelism tests between sgl and asebia (ab), another hair loss mutation on mouse Chr 19, showed that these genes were separate and distinct. Received: 8 December 1998 / Accepted: 10 May 1999     

Novel monosaccharides as potent inhibitors of cell proliferation

The effects of several novel monosaccharides upon thymidine incorporation into both normal and tumour cells were investigated. The monosaccharide 2-deoxy-3-[1-(R)-(ethoxycarbonyl)ethyl]-α-D -allo-pyranose had the most inhibitory effect on proliferation, with the (S)-enantiomer having less inhibitory effects. The chiral centre at carbon-7 was found to be an important part of the molecule, as 2-deoxy-3-[methoxycarbonyl methyl]-α-D -allo-pyranose had greatly decreased anti-proliferative properties in comparison with the parent compound. In addition, the 2-deoxy structure at carbon-2 was also found to be important, as 3-[1-(S)-(ethoxycarbonyl)ethyl]-α-D -allo-hexopyranose had greatly decreased inhibitory properties in comparison with the parent compound. The results indicate that these novel monosaccharides possess potent anti-proliferative properties, related to their chiral carbon-7 and 2-deoxy carbon-2 structure and suggest that further substitutions of the functional group at carbon-7 may improve these properties and possibly produce inhibitor selectivity for tumour cells in preference to normal cells. © 1997 John Wiley & Sons, Ltd.     

Silent chromatin in yeast: an orchestrated medley featuring Sir3p

The title for the review article published in BioEssays 20:30–40 should read ‘Silent chromatin in yeast: an orchestrated medley featuring Sir3p’. Please note corrections for Figure 3 as follows The publisher regrets these errors. © 1998 John Wiley & Sons, Inc.