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A concise synthesis of (+)-pancratistatin and (+)-7-deoxypancratistatin from benzene using an enantioselective, dearomative carboamination strategy has been achieved. This approach, in combination with the judicious choice of subsequent olefin-type difunctionalization reactions, permits rapid and controlled access to a hexasubstituted core. Finally, minimal use of intermediary steps as well as direct, late stage C-7 hydroxylation provides both natural products in six and seven operations.

Screen-printed carbon electrodes (SPCEs) and carbon paste electrodes (CPEs) were prepared as "mercury-free" electrochemical sensors for the determination of trace metal ions in aqueous solutions. SPCEs were coated with conducting polymer layers of either polyaniline (PANI), or polyaniline-poly(2,2'-dithiodianiline) (PANI-PDTDA). Furthermore, CPEs containing electroactive compounds with reactivity towards metal ions were employed to obtain enhanced selectivity. Optimised experimental conditions for Hg(2+), Pb(2+), Ni(2+) and Cd(2+) determination included the supporting electrolyte concentration, deposition potential (E(d)) and accumulation time (t(acc)). For the modified carbon paste sensors (MCPEs) it was found that -400 mV is an adequate deposition potential and an accumulation time of 120 s was adequate for the determination using the different constructed electrodes. Initial results showed linearity in the examined concentration range between 1 × 10(-9) M and 1 × 10(-6) M using the SPCE/PANI-PDTDA sensor on laboratory prepared standard solutions, while good selectivity for the different metal ions were obtained. Furthermore, the limit of detection (LOD) was determined for each of the sensors and for the SPCE/PANI-PDTDA sensor it was found to be 2.2 × 10(-13) M, while for the SPCE/PANI sensor the LOD was determined to be 8.4 × 10(-11) M. The MCPE sensors also showed good linearity between the concentration range of 1 × 10(-3) to 1 × 10(-9) M. The LOD values for the various MCPE sensors, were found to be Hg(II) - 1.3 × 10(-7) M; Cd(II) - 2.9 × 10(-7) M; Ni(II) - 3.2 × 10(-7) M; and Pb(II) - 1.7 × 10(-7) M for the CPE/PANI-PDTDA sensor. For the CPE/PANI sensor the LOD values were Hg(II) - 1.5 × 10(-5) M; Cd(II) - 8.6 × 10(-7) M; Ni(II) - 9.5 × 10(-7) M; and Pb(II) - 1.3 × 10(-6) M. For the CPE/MBT sensor the LOD values were Hg(II) - 3.8 × 10(-5) M; Cd(II) - 1.4 × 10(-6) M; Ni(II) - 1 × 10(-6) M; and Pb(II) - 6.3 × 10(-5) M. Very low detection was obtained for the SPCE/PANI-PDTDA sensor in Hg(2+) determination, while the MCPE sensors delivered sensitive simultaneous detection for Hg(2+), Pb(2+), Ni(2+) and Cd(2+) metal ions.

An electrochemical protocol for real-time monitoring of drug release kinetics from therapeutic nanoparticles (NPs) is described. The method is illustrated for repetitive square-wave voltammetric measurements of the reduction of doxorubicin released from liposomes at a glassy-carbon electrode. Such operation couples high sensitivity down to 20 nM doxorubicin with high speed and stability. It can thus monitor in real time the drug release from NP carriers, including continuous measurements in diluted serum. Such direct and continuous monitoring of the drug release kinetics from therapeutic NPs holds great promise for designing new drug delivery NPs with optimal drug release properties. These NPs can potentially be used to deliver many novel compounds such as marine-life derived drugs and hydrophobic drugs with limited water solubility that are usually difficult to be characterized by traditional analytical tools.

Rhizobia are a group of bacteria that form nodules on the roots of legume host plants. The sequenced genomes of the rhizobia are characterized by the presence of many putative insertion sequences (IS) elements. However, it is unknown whether these IS elements are functional and it is therefore relevant to assess their transposition activity. In this work, several functional insertion sequences belonging to the IS1256, IS3, IS5, IS166, and IS21 families were captured from Rhizobium tropici, Rhizobium sp. NGR234 and Sinorhizobium meliloti, using pGBG1 as a trapping system. In silico analysis shows that homologs of rhizobia mobile elements are present in distantly related genomes, suggesting that Rhizobium IS elements are prone to genetic transfer.

Analysis of the 1,683,333-nt sequence of the pSymB megaplasmid from the symbiotic N(2)-fixing bacterium Sinorhizobium meliloti revealed that the replicon has a high gene density with a total of 1,570 protein-coding regions, with few insertion elements and regions duplicated elsewhere in the genome. The only copies of an essential arg-tRNA gene and the minCDE genes are located on pSymB. Almost 20% of the pSymB sequence carries genes encoding solute uptake systems, most of which were of the ATP-binding cassette family. Many previously unsuspected genes involved in polysaccharide biosynthesis were identified and these, together with the two known distinct exopolysaccharide synthesis gene clusters, show that 14% of the pSymB sequence is dedicated to polysaccharide synthesis. Other recognizable gene clusters include many involved in catabolic activities such as protocatechuate utilization and phosphonate degradation. The functions of these genes are consistent with the notion that pSymB plays a major role in the saprophytic competence of the bacteria in the soil environment.

The scarcity of usable nitrogen frequently limits plant growth. A tight metabolic association with rhizobial bacteria allows legumes to obtain nitrogen compounds by bacterial reduction of dinitrogen (N2) to ammonium (NH4+). We present here the annotated DNA sequence of the alpha-proteobacterium Sinorhizobium meliloti, the symbiont of alfalfa. The tripartite 6.7-megabase (Mb) genome comprises a 3.65-Mb chromosome, and 1.35-Mb pSymA and 1.68-Mb pSymB megaplasmids. Genome sequence analysis indicates that all three elements contribute, in varying degrees, to symbiosis and reveals how this genome may have emerged during evolution. The genome sequence will be useful in understanding the dynamics of interkingdom associations and of life in soil environments.

We have developed a procedure to directly clone large fragments from the genome of the soil bacterium Sinorhizobium meliloti. Specific regions to be cloned are first flanked by parallel copies of an origin of transfer (oriT) together with a plasmid replication origin capable of replicating large clones in Escherichia coli but not in the target organism. Supplying transfer genes in trans specifically transfers the oriT-flanked region, and in this process, site-specific recombination at the oriT sites results in a plasmid carrying the flanked region of interest that can replicate in E. coli from the inserted origin of replication (in this case, the F origin carried on a BAC cloning vector). We have used this procedure with the oriT of the plasmid RK2 to clone contiguous fragments of 50, 60, 115, 140, 240, and 200 kb from the S. meliloti pExo megaplasmid. Analysis of the 60-kb fragment allowed us to identify a 9-kb region capable of autonomous replication in the bacterium Agrobacterium tumefaciens. The nucleotide sequence of this fragment revealed a replicator region including homologs of the repA, repB, and repC genes from other Rhizobiaceae, which encode proteins involved in replication and segregation of plasmids in many organisms.

We determined the nucleotide sequences of 16S rRNA gene segments from five Rhizobium strains that have been isolated from tropical legume species. All share the capacity to nodulate Phaseolus vulgaris L., the common bean. Phylogenetic analysis confirmed that these strains are of two different chromosomal lineages. We defined the host ranges of two strains of Rhizobium etli and three strains of R. tropici, comparing them with those of the two most divergently related new strains. Twenty-two of the 43 tested legume species were nodulated by three or more of these strains. All seven strains have broad host ranges that include woody species such as Albizia lebbeck, Gliricidia maculata, and Leucaena leucocephala.