Conformational transitions in polyelectrolyte adsorption

The mole fraction X of nucleic acid chromophores, adsorbed on cationic and anionic exchange chromatography paper disks, was calculated [O.L. H?rer and A. Grigorescu, Rev. Roum. Med. Virol., 43 (1992) 33] in terms of the standard Debye screening length D (in the 0.01 to 1.2 M ionic strength range), using data from MLSEA (multiple light scattering enhanced absorption) measurements. In contrast to the cases of mononucleotides or double-stranded and relatively rigid DNA structures, highly polymerized and single-stranded RNA shows sigmoidal-shaped X curves, suggesting that polymer adsorption may be regarded as a conformational transition from a three-dimensional statistical coil to a two-dimensional one.     

The effect of thermal treatment on antibacterial properties of nanostructured TiO<Subscript>2</Subscript>(N) films illuminated with visible light

This work focuses on the photocatalytic performances and antibacterial activity of nitrogen doped TiO₂ nanosystems with three and five layers obtained by a sol-gel route, followed by thermal treatment in oxygen or ammonia atmosphere at temperatures between 400 and 1000°C. Subsequently, the antibacterial activity of the obtained nanosystems on the Escherichia coli cells are determined and discussed. The obtained results show a significant dependence of the functional performances on the system’s composition. In particular, the antimicrobial activity of nitrogen-doped TiO₂ films is correlated with the temperature of thermal treatment and illumination time with visible artificial light.     

Effects of climate change and horticultural use on the spread of naturalized alien garden plants in Europe

Climate warming is supposed to enlarge the area climatically suitable to the naturalization of alien garden plants in temperate regions. However, the effects of a changing climate on the spread of naturalized ornamentals have not been evaluated by spatially and temporarily explicit range modelling at larger scales so far. Here, we assess how climate change and the frequency of cultivation interactively determine the spread of 15 ornamental plants over the 21st century in Europe. We coupled species distribution modelling with simulations of demography and dispersal to predict range dynamics of these species in annual steps across a 250 × 250 m raster of the study area. Models were run under four scenarios of climate warming and six levels of cultivation intensity. Cultivation frequency was implemented as size of the area used for planting a species. Although the area climatically suitable to the 15 species increases, on average, the area predicted to be occupied by them in 2090 shrinks under two of the three climate change scenarios. This contradiction obviously arises from dispersal limitations that were pronounced although we assumed that cultivation is spatially adapting to the changing climate. Cultivation frequency had a much stronger effect on species spread than climate change, and this effect was non‐linear. The area occupied increased sharply from low to moderate levels of cultivation intensity, but levelled off afterwards. Our simulations suggest that climate warming will not necessarily foster the spread of alien garden plants in Europe over the next decades. However, climatically suitable areas do increase and hence an invasion debt is likely accumulating. Restricting cultivation of species can be effective in preventing species spread, irrespective of how the climate develops. However, for being successful, they depend on high levels of compliance to keep propagule pressure at a low level.     

Testing for allelopathy in invasive plants: it all depends on the substrate!

Invasive plants can affect native plants through competition or allelopathy, and researchers often use pot experiments as a tool to measure the strength of these interactions. Recently, such pot experiments provided inconsistent estimates of the impact and allelopathic potential of invasive knotweed, one of the world’s most successful plant invaders. We suspected that the inconsistencies may be explained by the use of different substrates in different experiments. To test this, we conducted an experiment in which knotweed competed pairwise with five common native European species in several different substrates: two compost-based potting substrates and two natural soils, with or without extra fertilizer added. To test for allelopathy, we added activated carbon to half of the pots. We found that knotweed was generally much more successful, and there was much more evidence for its allelopathy, when tested in artificial potting substrates than in natural soils. Furthermore, addition of extra fertilizer decreased the dominance of knotweed and changed patterns of allelopathy. The physicochemical properties of potting soil, such as lower bulk density, higher pore space, permeability and nitrogen content may better allow rhizomes to penetrate and/or allelochemicals to be produced and diffused. If artificial substrates generally exaggerate dominance and allelopathy also in other invasive plants, then many previous studies may have overestimated the potential impact of invaders, and the results of these experiments should be interpreted with caution. To avoid misleading results, experiments that test the competitive or allelopathic impact of invasive plants should be done with natural soils, preferably from the targeted habitats.     

Pyranocoumarin, a novel anti-TB pharmacophore: synthesis and biological evaluation against Mycobacterium tuberculosis

Pyranocoumarin compounds were identified to embody a novel and unique pharmacophore for anti-TB activity. A systematic approach was taken to investigate the structural characteristics. Focused libraries of compounds were synthesized and evaluated for their anti-TB activity in primary screening assays. Compounds shown to be active were further determined for MIC and MBC values. Three of the four bactericidal compounds (16, 17c, and 18f) were amino derivatives, with MIC values of 16 microg/mL and respective MBC values of 32, 32, and 64 microg/mL.     

Synthesis and structural assignment of two major metabolites of the LTA4H inhibitor DG-051

The same two major CYP mediated metabolites of DG-051 were produced in the presence of rat, dog, monkey and human liver microsomes. Their respective structures were hypothesized based on mass spectrometry data correlated with the parent structure and confirmed by comparison with authentic synthetic samples. The number of regioisomers synthesized as candidates for metabolite M1 was narrowed down using a metabolic study of a selectively deuterated DG-051 analogue.     

Halophilic archaea isolated from man-made young (200 years) salt lakes in Slănic, Prahova, Romania

We isolated a number of extremely halophilic archaea from four salt lakes (Red Bath, Green Bath, Shepherd Bath and Bride Cave) located in Slanic Prahova, Romania. The characterization of 12 representative isolates by polyphasic approach revealed that 11 strains were members of the genus Haloferax and only one was a member of the genus Haloarcula. The 11 Haloferax isolates possessed sulfated diglycosylarchaeol-1 as the major membrane glycolipid, and G+C contents of total DNA were 63.4–65.8 mol%. The predominant isolation of Haloferax species from the lakes may suggest that the underground salt deposit possesses Haloferax species as the major biota of ancient origin. To the best of the authors’ knowledge, this is the first paper on the survey of halophilic archaea of man-made young salt lakes.