Synthesis of Novel L-Series 2′, 3′-Dideoxy-3′-Hydroxy-Methyl-Nucleosides and a Convenient Method for the Separation of Nucleosede Anomers

Abstract

Photoinduced addition of methanol to 5(R)-(tert-butyldimethylsilyloxymethyl)-2(5H)-furan-2-one (derived from L-gulono-1, 4-lactone) provided the photoadduct 5(R)-(tert-butyldimethylsiloxymethyl)-4(S)-hydroxymethyl-tetrahydrofuran-2-one, which was converted into two L-series-2′, 3′-dideoxy-3′-hydroxymethyl-nucleosides. In addition, we describe a new method for the chromatographic separation of cytidine anomers using a N-2-(4-nitrophenyl)ethyl carbamate derivative.     

Activation of Ran GTPase by a Legionella Effector Promotes Microtubule Polymerization,Pathogen Vacuole Motility and Infection

The causative agent of Legionnaires'' disease, Legionella pneumophila, uses the Icm/Dot type IV secretion system (T4SS) to form in phagocytes a distinct “Legionella-containing vacuole” (LCV), which intercepts endosomal and secretory vesicle trafficking. Proteomics revealed the presence of the small GTPase Ran and its effector RanBP1 on purified LCVs. Here we validate that Ran and RanBP1 localize to LCVs and promote intracellular growth of L. pneumophila. Moreover, the L. pneumophila protein LegG1, which contains putative RCC1 Ran guanine nucleotide exchange factor (GEF) domains, accumulates on LCVs in an Icm/Dot-dependent manner. L. pneumophila wild-type bacteria, but not strains lacking LegG1 or a functional Icm/Dot T4SS, activate Ran on LCVs, while purified LegG1 produces active Ran(GTP) in cell lysates. L. pneumophila lacking legG1 is compromised for intracellular growth in macrophages and amoebae, yet is as cytotoxic as the wild-type strain. A downstream effect of LegG1 is to stabilize microtubules, as revealed by conventional and stimulated emission depletion (STED) fluorescence microscopy, subcellular fractionation and Western blot, or by microbial microinjection through the T3SS of a Yersinia strain lacking endogenous effectors. Real-time fluorescence imaging indicates that LCVs harboring wild-type L. pneumophila rapidly move along microtubules, while LCVs harboring ΔlegG1 mutant bacteria are stalled. Together, our results demonstrate that Ran activation and RanBP1 promote LCV formation, and the Icm/Dot substrate LegG1 functions as a bacterial Ran activator, which localizes to LCVs and promotes microtubule stabilization, LCV motility as well as intracellular replication of L. pneumophila.     

Global change effects on Bromus tectorum L. (Poaceae) at its high‐elevation range margin

Global change is likely to affect invasive species distribution, especially at range margins. In the eastern Sierra Nevada, California, USA, the invasive annual grass, Bromus tectorum, is patchily distributed and its impacts have been minimal compared with other areas of the Intermountain West. We used a series of in situ field manipulations to determine how B. tectorum might respond to changing climatic conditions and increased nitrogen deposition at the high‐elevation edge of its invaded range. Over 3 years, we used snow fences to simulate changes in snowpack, irrigation to simulate increased frequency and magnitude of springtime precipitation, and added nitrogen (N) at three levels (0, 5, and 10 g m^?2) to natural patches of B. tectorum growing under the two dominant shrubs, Artemisia tridentata and Purshia tridentata, and in intershrub spaces (INTR). We found that B. tectorum seedling density in April was lower following deeper snowpack possibly due to delayed emergence, yet there was no change in spikelet production or biomass accumulation at the time of harvest. Additional spring rain events increased B. tectorum biomass and spikelet production in INTR plots only. Plants were primarily limited by water in 2009, but colimited by N and water in 2011, possibly due to differences in antecedent moisture conditions at the time of treatments. The threshold at which N had an effect varied with magnitude of water additions. Frequency of rain events was more influential than magnitude in driving B. tectorum growth and fecundity responses. Our results suggest that predicted shifts from snow to rain could facilitate expansion of B. tectorum at high elevation depending on timing of rain events and level of N deposition. We found evidence for P‐limitation at this site and an increase in P‐availability with N additions, suggesting that stoichiometric relationships may also influence B. tectorum spread.     

Role of emergent and submerged vegetation and algal communities on nutrient retention and management in a subtropical urban stormwater treatment wetland

A 4.6-ha urban stormwater treatment wetland complex in southwest Florida has been investigated for several years to understand its nutrient retention dynamics. This study investigates the role of aquatic vegetation, both submerged vegetation (such as benthic macrophytic and algal communities) and emergent plant communities, on changes in nutrient fluxes through the wetlands. Gross and net primary productivity of water column communities and net primary productivity of emergent macrophytes were used to estimate nutrient fluxes through vegetation in these wetlands using biannual biomass, nutrient concentrations of plant material, and areal coverage data. Emergent macrophyte net primary productivity was estimated as the difference between the increase of productivity during the wet season and the loss during the dry season which, in turn, suggested approximately 0.11g-N m^??2 y^??1 and 0.09g-P m^??2 yr^??2 being removed, primarily from the soil, by emergent vegetation. Water column primary productivity accounted for a much larger flux of nutrients with approximately 39.6g-N m^??2 yr^??1 and 2.4g-P m^??2 yr^??1 retained in algal communities. These fluxes, combined with measurements in parallel studies, allowed us to develop preliminary nutrient budgets for these wetlands and identify gaps, or missing fluxes, in our models for these wetlands. The results further validated previous findings that suggested that there are large inputs of nitrogen (up to 62.3g-N m^??2 yr^??1) that are not accounted for by the pumped inflow. Additionally, management suggestions are provided to improve water quality by identifying vegetative species that are most effective at retaining nutrients.

     

Escaped bait: Bull shark Carcharhinus leucas with an intentionally attached harness rig

A 193 cm total length female bull shark Carcharhinus leucas was captured in Florida bearing intentionally attached materials which resembled a harness. Harness-type live bait rigs are commonly used for small baitfish; some anglers use such devices with small sharks when targeting large sharks and bony fish. Biofouling on the apparatus and the extent of the injuries indicated the material had likely been on the shark for several years. This case highlights the dangers of using these types of devices on juveniles of long-lived species that attain a large body size.     

Expression and characterization of cell-signalling molecules in Campylobacter jejuni

Aims: This study investigated the production and effects of cell‐signalling compounds on selected survival and virulence mechanisms of Campylobacter jejuni. Methods and Results: The production of Autoinducer 1 (AI‐1) compounds by Camp. jejuni was investigated in‐vitro using a variety of available AI‐1 bioassays. We further examined the role of a range of commercially available homoserine lactones (HSL) and a novel compound (cjA) isolated from Camp. jejuni. The selected attributes included the transformation to a viable but nonculturable (VBNC) state, biofilm formation, interleukin 8 (IL‐8) stimulation in INT‐407 cells and virulence gene expression as determined by qRT‐PCR. This study is the first to report an HSL or HSL mimic produced by Camp. jejuni. Short chained HSLs and the novel compound cjA prolonged the delay to a VBNC state as well as inhibiting biofilm formation and the majority of HSLs examined and the HSL mimic cjA significantly affected virulence gene expression as well as increasing the production of IL‐8 in challenged INT‐407 cells. Conclusions: Despite the lack of a homologous HSL kinase or sensor, Camp. jejuni appears to produce, as well as detect, exogenous signalling molecules and respond accordingly to aid in the survival and virulence capabilities of this micro‐organism. Significance and Impact of the Study: This study suggests that Camp. jejuni is able to detect and utilize as well as possibly produce cell‐signalling molecules that enhance both survival and virulence attributes. This possibility opens a new field in the search for Camp. jejuni reduction and elimination strategies.     

xtalPiMS: a PiMS-based web application for the management and monitoring of crystallization trials

A major advance in protein structure determination has been the advent of nanolitre-scale crystallization and (in a high-throughput environment) the development of robotic systems for storing and imaging crystallization trials. Most of these trials are carried out in 96-well (or higher density) plates and managing them is a significant information management challenge. We describe xtalPiMS, a web-based application for the management and monitoring of crystallization trials. xtalPiMS has a user-interface layer based on the standards of the Protein Information Management System (PiMS) and a database layer which links the crystallization trial images to the meta-data associated with a particular crystallization trial. The user interface has been optimized for the efficient monitoring of high-throughput environments with three different automated imagers and work to support a fourth imager is in progress, but it can even be of use without robotics. The database can either be a PiMS database or a legacy database for which a suitable mapping layer has been developed.     

Cathelicidin is involved in the intracellular killing of mycobacteria in macrophages

Macrophages have been shown to kill Mycobacterium tuberculosis through the action of the antimicrobial peptide cathelicidin (CAMP), whose expression was shown to be induced by 1,25-dihydroxyvitamin D3 (1,25D3). Here, we investigated in detail the antimycobacterial effect of murine and human cathelicidin against Mycobacterium smegmatis and M. bovis BCG infections. We have synthesized novel LL-37 peptide variants that exhibited potent in vitro bactericidal activity against M. smegmatis, M. bovis BCG and M. tuberculosis H37Rv, as compared with parental peptide. We show that the exogenous addition of LL-37 or endogenous overexpression of cathelicidin in macrophages significantly reduced the intracellular survival of mycobacteria relative to control cells. An upregulation of cathelicidin mRNA expression was observed that correlated with known M. smegmatis killing phases in J774 macrophages. Moreover, RNAi-based Camp knock-down macrophages and Camp(-/-) bone marrow derived mouse macrophages were significantly impaired in their ability to kill mycobacteria. M. smegmatis killing in Camp(-/-) macrophages was less extensive than in Camp(+/+) cells following activation with FSL-1, an inducer of cathelicidin expression. Finally we show that LL-37 and 1,25D3 treatment results in increase in colocalization of BCG-containing phagosomes with lysosomes. Altogether, these data demonstrate that cathelicidin plays an important role in controlling intracellular survival of mycobacteria.