Hydrogenases, accessory genes and the regulation of [NiFe] hydrogenase biosynthesis in Thiocapsa roseopersicina

The purple (Sulphur) phototrophic bacterium, Thiocapsa roseopersicina BBS contains several [NiFe] hydrogenases, of which two are membrane bound. Mutant T. roseopersicina cells, carrying deletions in both gene clusters showed hydrogenase activity. This activity was located in the cytoplasm. The structural gene cluster hoxEFUYH was identified and sequenced. In addition, genes homologous to hupUV/hoxBC, the hydrogen sensing hydrogenase have been identified and sequenced.Regulation of hydrogenase biosynthesis was studied in detail for HydSL (renamed HynSL). A random mutagenesis system was optimised for T. roseopersicina. One of the mutations was in a gene similar to that coding for the HypF proteins in other organisms. Inactivation of the hypF gene resulted in a 60-fold increase in hydrogen evolution under nitrogen fixing conditions. In addition to hypF, the following accessory genes were identified: hydD, hupK, hypC1, hypC2, hypDE. Characterisation of the corresponding gene products and search for additional accessory genes are in progress.     

The Pupal Parasitoid Trichopria drosophilae Is Attracted to the Same Yeast Volatiles as Its Adult Host

Journal of Chemical Ecology - There is increasing evidence that microorganisms, particularly fungi and bacteria, emit volatile compounds that mediate the foraging behaviour of insects and therefore...     

Mid-IR real-time monitoring of the carbocationic polymerization of isobutylene and styrene

The in-situ monitoring of the living carbocationic polymerization of isobutylene (IB) and styrene (St) with a fiber optic Attenuated Total Reflection (ATR) probe in the mid-IR "fingerprint" range is reported here for the first time. Monomer consumption was followed by the disappearance of the C=C stretching for both IB and St, and the C−H bending of the CH₃-group in IB. The formation of polyisobutylene (PIB) was also monitored by tracing the asymmetrical doublet characteristic of C−H bending of the t-butyl groups of the PIB. Conversion measurements by conventional off-line gravimetry correlated well with the new technique. Received: 27 August 1997/Revised version: 2 November 1997/Accepted: 20 November 1997     

Journal report card

The impact factor is one of the most used scientometric indicators. Its proper and improper uses have been discussed extensively before. It has been criticized extensively, yet it is still here. In this paper I propose the journal report card, which is a set of measures, each with an easily comprehensible meaning that provides a fuller picture of the journals?? standing. The set of measures in the report card include the impact factor, the h-index, number of citations at different points on the ranked list of citations, extent of uncitedness and coverage of the h-core. The report card is computed for two sets of journals, the top-20 journals in JCR 2010 and the top-20 journals in JCR 2010 for the category Information and Library Science.     

Rejoinder to “Multiple versions of the h-index: cautionary use for formal academic purposes”

Scientometrics - In a Letter to the Editor, the authors of this paper show, to highlight the practical risks of using the h-index, how academics’ data and bibliometric information can be...     

Luster Pottery from the Thirteenth Century to the Sixteenth Century: A Nanostructured Thin Metallic Film

Luster is a decorative metallic film that was applied on the surface of medieval glazed pottery. It can be obtained via the low-temperature (∼650°C), controlled reduction of copper and silver compounds. In this paper, we show that luster is a thin layered film (200–500 nm thick) that contains metallic spherical nanocrystals dispersed in a silicon-rich matrix and has a metal-free outermost glassy layer that is 10–20 nm thick. Silver nanocrystals seem to be separated from those of copper, forming aggregates 5–100 μm in diameter. This composite structure exhibits optical properties that are dependent on both the particle size and the matrix. Luster is indeed the first reproducible nanostructured thin metallic film that was made by humans.     

Investigation of the Antiproliferative Properties of Natural Sesquiterpenes from Artemisia asiatica and Onopordum acanthium on HL-60 Cells in Vitro

Plants and plant extracts play a crucial role in the research into novel antineoplastic agents. Four sesquiterpene lactones, artecanin (1), 3β-chloro-4α,10α-dihydroxy-1α,2α-epoxy-5α,7αH-guaia-11(13)-en-12,6α-olide (2), iso-seco-tanapartholide 3-O-methyl ether (3) and 4β,15-dihydro-3-dehydrozaluzanin C (4), were isolated from two traditionally used Asteraceae species (Onopordum acanthium and Artemisia asiatica). When tested for antiproliferative action on HL-60 leukemia cells, these compounds exhibited reasonable IC₅₀ values in the range 3.6–13.5 μM. Treatment with the tested compounds resulted in a cell cycle disturbance characterized by increases in the G1 and G2/M populations, while there was a decrease in the S phase. Additionally, 1–3 elicited increases in the hypodiploid (subG1) population. The compounds elicited concentration-dependent chromatin condensation and disruption of the membrane integrity, as revealed by Hoechst 33258–propidium staining. Treatment for 24 h resulted in significant increases in activity of caspases-3 and -9, indicating that the tested sesquiterpenes induced the mitochondrial pathway of apoptosis. The proapoptotic properties of the sesquiterpene lactones were additionally demonstrated withannexin V staining. Compounds 1 and 2 increased the Bax/Bcl-2 expression and decreased the expressions of CDK1 and cyclin B2, as determined at the mRNA level by means of RT-PCR. These experimental results indicate that sesquiterpene lactones may be regarded as potential starting structures for the development of novel anticancer agents.     

One-pot synthesis of gelatin-based,slow-release polymer microparticles containing silver nanoparticles and their application in anti-fouling paint

Gelatinous polymer matrix microparticles containing silver nanoparticles (AgNPs) were prepared by a novel method to obtain quasi non-swelling anti-fouling paint additives with slow-release characteristics. A w/o type dispersion were elaborated with the aqueous phase of gelatin, urea, silver-nitrate and formaldehyde dispersed in linseed oil. Gelatin was cross-linked by formaldehyde, together with urea for limiting the swelling of the product. Silver-nitrate was reduced with the assistance of gelatin and formaldehyde into homogenously dispersed AgNPs. The microparticles and embedded AgNPs were visualized by scanning and transmission electronmicroscopy. Encapsulated AgNPs with ∼18 nm crystallite size were identified by X-ray powder diffraction. Characterization of gelatin–urea–formaldehyde polymer matrices was carried out by attenuated total reflectance FTIR spectroscopy. Silver dissolution from microparticles and paints with AgNP-containing microparticles was measured by inductively coupled plasma spectrometer and resulted in highly sustained release, compared to unmodified gelatin microparticles and paints containing uncapsulated silver salts. A 7-month-long fouling experiment run in natural sweetwater media showed that solvent-based acrylic paint with AgNPs-containing gelatinous microparticles as additives offered resistance against biofouling at low Ag-release ratio.