DNA cleavage and antitumour activity of platinum(II) and copper(II) compounds derived from 4-methyl-2-N-(2-pyridylmethyl)aminophenol: spectroscopic, electrochemical and biological investigation

The reaction of the redox-active ligand, Hpyramol (4-methyl-2-N-(2-pyridylmethyl)aminophenol) with K2PtCl4 yields monofunctional square-planar [Pt(pyrimol)Cl], PtL-Cl, which was structurally characterised by single-crystal X-ray diffraction and NMR spectroscopy. This compound unexpectedly cleaves supercoiled double-stranded DNA stoichiometrically and oxidatively, in a non-specific manner without any external reductant added, under physiological conditions. Spectro-electrochemical investigations of PtL-Cl were carried out in comparison with the analogue CuL-Cl as a reference compound. The results support a phenolate oxidation, generating a phenoxyl radical responsible for the ligand-based DNA cleavage property of the title compounds. Time-dependent in vitro cytotoxicity assays were performed with both PtL-Cl and CuL-Cl in various cancer cell lines. The compound CuL-Cl overcomes cisplatin-resistance in ovarian carcinoma and mouse leukaemia cell lines, with additional activity in some other cells. The platinum analogue, PtL-Cl also inhibits cell-proliferation selectively. Additionally, cellular-uptake studies performed for both compounds in ovarian carcinoma cell lines showed that significant amounts of Pt and Cu were accumulated in the A2780 and A2780R cancer cells. The conformational and structural changes induced by PtL-Cl and CuL-Cl on calf thymus DNA and phi X174 supercoiled phage DNA at ambient conditions were followed by electrophoretic mobility assay and circular dichroism spectroscopy. The compounds induce extensive DNA degradation and unwinding, along with formation of a monoadduct at the DNA minor groove. Thus, hybrid effects of metal-centre variation, multiple DNA-binding modes and ligand-based redox activity towards cancer cell-growth inhibition have been demonstrated. Finally, reactions of PtL-Cl with DNA model bases (9-Ethylguanine and 5'-GMP) followed by NMR and MS showed slow binding at Guanine-N7 and for the double stranded self complimentary oligonucleotide d(GTCGAC)(2) in the minor groove

Imaging of Streptomyces coelicolor A3(2) with Reduced Autofluorescence Reveals a Novel Stage of FtsZ Localization

Imaging of low abundance proteins in time and space by fluorescence microscopy is typically hampered by host-cell autofluorescence. Streptomycetes are an important model system for the study of bacterial development, and undergo multiple synchronous cell division during the sporulation stage. To analyse this phenomenon in detail, fluorescence microscopy, and in particular also the recently published novel live imaging techniques, require optimal signal to noise ratios. Here we describe the development of a novel derivative of Streptomyces coelicolor A3(2) with strongly reduced autofluorescence, allowing the imaging of fluorescently labelled proteins at significantly higher resolution. The enhanced image detail provided novel localization information for the cell division protein FtsZ, demonstrating a new developmental stage where multiple FtsZ foci accumulate at the septal plane. This suggests that multiple foci are sequentially produced, ultimately connecting to form the complete Z ring. The enhanced imaging properties are an important step forward for the confocal and live imaging of less abundant proteins and for the use of lower intensity fluorophores in streptomycetes

Regulation of antibiotic production in Actinobacteria: new perspectives from the post-genomic era

The antimicrobial activity of many of their natural products has brought prominence to the Streptomycetaceae, a family of Gram-positive bacteria that inhabit both soil and aquatic sediments. In the natural environment, antimicrobial compounds are likely to limit the growth of competitors, thereby offering a selective advantage to the producer, in particular when nutrients become limited and the developmental programme leading to spores commences. The study of the control of this secondary metabolism continues to offer insights into its integration with a complex lifecycle that takes multiple cues from the environment and primary metabolism. Such information can then be harnessed to devise laboratory screening conditions to discover compounds with new or improved clinical value. Here we provide an update of the review we published in NPR in 2011. Besides providing the essential background, we focus on recent developments in our understanding of the underlying regulatory networks, ecological triggers of natural product biosynthesis, contributions from comparative genomics and approaches to awaken the biosynthesis of otherwise silent or cryptic natural products. In addition, we highlight recent discoveries on the control of antibiotic production in other Actinobacteria, which have gained considerable attention since the start of the genomics revolution. New technologies that have the potential to produce a step change in our understanding of the regulation of secondary metabolism are also described

Fibrous Monolith Wear Resistant Components for the Mining Industry Progress Report

During the reporting period, work continued on development of formulations using the materials down-selected from the initially identified contenders for the fibrous monolith wear resistant components. In the previous reporting period, a two-stage binder removal process was developed that resulted in prototype parts free of voids and other internal defects. During the current reporting period, work was performed to characterize the two-stage binder removal process for WC-Co based FM material systems. Use of this process has resulted in the fabrication of defect free sintered WC-Co FM bodies, with minimal free carbon porosity and densities approaching 100% theoretical. With the elimination of free carbon porosity and other binder removal process related defects, development work focused on optimizing the densification and eliminating defects observed in WC-Co based FM consolidated by pressureless sintering. Shrinkage of the monolithic core and shell materials used in the WC-Co based FM system was measured, and differences in material shrinkage were identified as a potential cause of cell boundary cracking observed in sintered parts. Re-formulation of material blends for this system was begun, with the goal of eliminating mechanical stresses during sintering by matching the volumetric shrinkage of the core and shell materials. Thirty-three 7/8 inch drill bit inserts (WC-Co(6%)/WC-Co(16%) FM) were hot pressed during the reporting period. Six of these inserts were delivered for field-testing by Superior Rock Bit during the upcoming reporting period. In addition, Al{sub 2}O{sub 3}/Al{sub 2}O{sub 3}-TiCN FM cutting tool inserts were fabricated, and cutting tests performed

Tracking the Subtle Mutations Driving Host Sensing by the Plant Pathogen Streptomyces scabies

The acquisition of genetic material conferring the arsenal necessary for host virulence is a prerequisite on the path to becoming a plant pathogen. More subtle mutations are also required for the perception of cues signifying the presence of the target host and optimal conditions for colonization. The decision to activate the pathogenic lifestyle is not “taken lightly” and involves efficient systems monitoring environmental conditions. But how can a pathogen trigger the expression of virulence genes in a timely manner if the main signal inducing its pathogenic behavior originates from cellulose, the most abundant polysaccharide on earth? This situation is encountered by Streptomyces scabies, which is responsible for common scab disease on tuber and root crops. We propose here a series of hypotheses of how S. scabies could optimally distinguish whether cello-oligosaccharides originate from decomposing lignocellulose (nutrient sources, saprophyte) or, instead, emanate from living and expanding plant tissue (virulence signals, pathogen) and accordingly adapt its physiological response

Fibrous Monolith Wear Resistant Components for the Mining Industry Progress Report

During the reporting period, work continued on development of formulations using the materials down-selected from the initially identified contenders for the fibrous monolith wear resistant components. The FM systems studied were: WC-Co/WC-Co, WC-Co/Co, diamond/WC-Co, and Al{sub 2}O{sub 3}/Al{sub 2}O{sub 3}-TiCN. Extrudable formulations for the materials listed were developed during the first twelve months of this effort, and work during the reporting period was focused on the development of optimized binder removal processes. A two stage binder removal process was developed that resulted in prototype parts free of voids and other internal defects. In addition, changes in the binder removal atmosphere resulted in the apparent elimination of residual carbon, an important consideration when consolidating WC-Co containing systems. Using the improved binder removal processes, parts were consolidated by both sintering and hot pressing to >99% theoretical density. Samples of these materials were sent to Kyocera for mechanical evaluations. Fabrication of drill bit inserts was begun, and binder removal begun during the reporting period. A total of 24 green inserts were fabricated, and will be consolidated and delivered for field testing during the upcoming reporting period