Synthesis of furanone-based natural product analogues with quorum sensing antagonist activity

The synthesis of 5- and 3-(1'-hydroxyalkyl)-substituted 5H-furan-2-ones 4a-d and 8a-d as well as 5-alkylidene-5H-furan-2-ones 5a-d is described. A study of the structure-activity relationship of these furanone-based natural product analogues towards two different quorum sensing systems is reported. Although the synthesized compounds are not as potent quorum sensing inhibitors as some natural counterparts and a synthetic analogue hereof, interesting structure-activity relationships are seen.     

Nutritional requirements for boron, silicon, vanadium, nickel, and arsenic: current knowledge and speculation

Definition of specific biochemical functions in higher animals (including humans) for the ultratrace elements boron, silicon, vanadium, nickel, and arsenic still has not been achieved although all of these elements have been described as being essential nutrients. Recently, many new findings from studies using molecular biology techniques, sophisticated equipment, unusual organisms, and newly defined enzymes have revealed possible sites of essential action for these five elements. Based on these findings and the response of animals and/or humans to low intakes of these elements, the following speculations have been presented: 1) Boron has a role that affects cell membrane characteristics and transmembrane signaling. 2) Silicon is necessary for the association between cells and one or more macromolecules such as osteonectin, which affects cartilage composition and ultimately cartilage calcification. 3) Vanadium reacts with hydrogen peroxide to form a pervanadate that is required to catalyze the oxidation of halide ions and/or stimulate the phosphorylation of receptor proteins. 4) Nickel is needed for the CO2-fixation to propionyl-CoA to form D-methylmalonyl-CoA. 5) Arsenic has an important role in the conversion of methionine to its metabolites taurine, labile methyl, and the polyamines. If any of these speculations are found to be true, the element involved will be firmly established as having a nutritional requirement because the body obviously cannot synthesize it. Based on animal findings, the dietary requirement is likely to be small; that is, expressed in micrograms per day.     

The RBCC gene RFP2 (Leu5) encodes a novel transmembrane E3 ubiquitin ligase involved in ERAD

RFP2, a gene frequently lost in various malignancies, encodes a protein with RING finger, B-box, and coiled-coil domains that belongs to the RBCC/TRIM family of proteins. Here we demonstrate that Rfp2 is an unstable protein with auto-polyubiquitination activity in vivo and in vitro, implying that Rfp2 acts as a RING E3 ubiquitin ligase. Consequently, Rfp2 ubiquitin ligase activity is dependent on an intact RING domain, as RING deficient mutants fail to drive polyubiquitination in vitro and are stabilized in vivo. Immunopurification and tandem mass spectrometry enabled the identification of several putative Rfp2 interacting proteins localized to the endoplasmic reticulum (ER), including valosin-containing protein (VCP), a protein indispensable for ER-associated degradation (ERAD). Importantly, we also show that Rfp2 regulates the degradation of the known ER proteolytic substrate CD3-delta, but not the N-end rule substrate Ub-R-YFP (yellow fluorescent protein), establishing Rfp2 as a novel E3 ligase involved in ERAD. Finally, we show that Rfp2 contains a C-terminal transmembrane domain indispensable for its localization to the ER and that Rfp2 colocalizes with several ER-resident proteins as analyzed by high-resolution immunostaining. In summary, these data are all consistent with a function for Rfp2 as an ERAD E3 ubiquitin ligase.     

Nucleus-independent chemical shift criterion for aromaticity in π-extended tetraoxa[8]circulenes

Recently synthesized π-extended symmetrical tetraoxa[8]circulenes that exhibit electroluminescent properties were calculated at the density functional theory (DFT) level using the quantum theory of atoms in molecules (QTAIM) approach to electron density distribution analysis. Nucleus-independent chemical shift (NICS) indices were used to characterize the aromaticity of the studied molecules. The tetraoxa[8]circulene molecules were found to consist of two antiaromatic perimeters (according to the Hückel “4n” antiaromaticity rule) that include 8 and 24 π-electrons. Conversely, NICS calculations demonstrated the existence of a common π-extended system (distributed like a flat ribbon) in the studied tetraoxa[8]circulene molecules. Thus, these symmetrical tetraoxa[8]circulene molecules provide examples of diatropic systems characterized by the presence of induced diatropic ring currents.

Root traits as tools for creating phosphorus efficient crop varieties

This paper provides a brief assessment of the genetic variation in root properties (root morphology, including root hairs), mycorrhizal symbiosis, uptake kinetics parameters and root-induced changes (pH, organic acids and acid phosphatase) in the rhizosphere of various crop species and their genotypes and then briefly discusses the opportunities and challenges of using such knowledge for enhancing P efficiency of future crop genotypes by genetic means. Wide genotypic variation and heritability of root morphology, root hair length and density and thereby P acquisition provide opportunities for selection and breeding for root characteristics for increasing P acquisition. The progress is challenged by the concerns of high carbon cost of larger root systems and by the lack of cost effective methods to determine root length of a large number of genotypes under field conditions. The carbon cost of root hairs is low. Furthermore, low cost methods now exist to compare root hair formation of field grown genotypes. The development and application of sophisticated methods has advanced our knowledge on the role of mycorrhizal symbiosis in P acquisition and also on the molecular basis of fungi and plant interactions. However, extensive studies to explore genotypic variation in mycorrhizal responsiveness are rare, which makes it difficult to assess, how mycorrhizal symbiosis can be manipulated through breeding efforts. The promising variation found in P uptake kinetics parameters of crop genotypes in few studies indicates that more genotypes may be screened by relatively simple nutrient solution culture techniques. The genetic manipulation of the overall differences in cation-anion uptake, which is the main cause of rhizosphere pH change, may be difficult. For manipulation of rhizosphere pH, agronomic measures such as applications of ammonium or nitrate fertilisers may be more useful than breeding approaches. Also it seems difficult to assess what kind of genetic analysis should be performed to support the breeding efforts. Phosphorus mobilisation effect of pH depends on soil P compounds, therefore will differ with soil type. Both the enhanced release of organic acids and higher acid phosphatase activity in the rhizosphere may be useful for increasing P acquisition from inorganic and organic P pools, respectively. Modification of these traits by genetic means should be considered. For successful breeding programmes, the role of various root traits needs to be targeted in an integrated manner and then methods need to be developed for studying their importance under natural soil conditions, so that the genotypic variation can be explored and their ecological significance in P acquisition can be established.     

Cleavage of proteins of reproductive secretions by extracellular proteinases of Tritrichomonas foetus

Cleavage of host defense proteins from reproductive secretions was investigated as a potential virulence mechanism for Tritrichomonas foetus extracellular proteinases. Three categories of susceptibility to digestion were found among the defense proteins tested. Cleavage of fibrinogen, fibronectin, and albumin occurred rapidly with more than 50% of these digested within 30 min. Lactoferrin, immunoglobulin G1, and immunoglobulin G2 were more than 50% digested after 4 h. Transferrin, immunoglobulin M, and immunoglobulin A were the most resistant to the Tritrichomonas foetus extracellular proteinases, since 50% or more of the parent molecule remained after 24 h. The responsible proteinases were classified as cysteine (thiol) proteinases because cleavage was inhibited by the cysteine proteinase specific inhibitor, trans-epoxysuccinyl-L-leucylamido-(4-guanidino)butane and not by the serine proteinase specific inhibitor, phenylmethylsulfonyl fluoride. In addition, alpha 2-macroglobulin, but not alpha 1-antitrypsin, inhibits the action of the proteinases. The ratio of this naturally occurring inhibitor to the quantity of proteinases released may determine whether the above substrates are cleaved in vivo. Since these substrates are implicated in iron acquisition, cell adherence, and acquired immunity, Tritrichomonas foetus proteinases are likely to play a role in host-parasite interactions.     

Bovine virus diarrhea virus in free-living deer from Denmark

Free-living deer are suggested as a possible source of infection of cattle with bovine virus diarrhea (BVD) virus. To examine this hypothesis blood samples from 476 free-living deer were collected during two different periods and tested for BVD virus and antibody in Denmark. In 1995-96, 207 animals were tested. These included 149 roe deer (Capreolus capreolus), 29 fallow deer (Dama dama), 20 red deer (Cervus elaphus) and one sika deer (Cervus sika). For the remaining eight animals no species information was available. In 1998-99, 269 animals were tested including 212 roe deer and 57 red deer. The animals were selected from areas with a relatively high prevalence of cattle herds with a BVD persistent infection status in 1997 and 1998. All 207 samples from 1995-96 were found antibody-negative except two samples from red deer. Only 158 of the 207 samples were tested for virus and were all found negative. Of the 269 samples from 1998-99 all but one were antibody negative. The positive sample was from a red deer. All samples were virus-negative. It appears that BVD infection does not occur in roe deer in Denmark. The presence of antibody in a few red deer from various districts in Jutland probably results from cattle to deer transmission, rather than spread among deer. Hence, the possibility of free-living deer as a source of infection for cattle in Denmark seems to be remote.     

Characterization of water and wildlife strains as a subgroup of Campylobacter jejuni using DNA microarrays

Campylobacter jejuni is the leading cause of human bacterial gastroenteritis worldwide, but source attribution of the organism is difficult. Previously, DNA microarrays were used to investigate isolate source, which suggested a non‐livestock source of infection. In this study we analysed the genome content of 162 clinical, livestock and water and wildlife (WW) associated isolates combined with the previous study. Isolates were grouped by genotypes into nine clusters (C1 to C9). Multilocus sequence typing (MLST) data demonstrated that livestock associated clonal complexes dominated clusters C1–C6. The majority of WW isolates were present in the C9 cluster. Analysis of previously reported genomic variable regions demonstrated that these regions were linked to specific clusters. Two novel variable regions were identified. A six gene multiplex PCR (mPCR) assay, designed to effectively differentiated strains into clusters, was validated with 30 isolates. A further five WW isolates were tested by mPCR and were assigned to the C7‐C9 group of clusters. The predictive mPCR test could be used to indicate if a clinical case has come from domesticated or WW sources. Our findings provide further evidence that WW C. jejuni subtypes show niche adaptation and may be important in causing human infection.     

Differentiated inhibition of DNA, RNA and protein synthesis in L1210 cells by 8-methoxypsoralen

The synthesis of DNA, RNA and protein was measured in L1210 cells following treatment with 8-methoxypsoralen in combination with long wavelength ultraviolet irradiation. The results show that the DNA synthesis is strongly inhibited (approximately 95%) at 200 ng/ml reaching a minimum within 2 hours while RNA synthesis is only weakly affected at this concentration (approximately 40% inhibition). At 2 micrograms/ml the RNA synthesis is inhibited approximately 90%. Even at this concentration only a moderate effect is seen on the protein synthesis. These results strongly indicate that the phototoxic action of 8-methoxypsoralen is primarily due to inhibition of DNA synthesis.