Iridium is a relatively rare precious heavy metal, only slightly less dense than osmium. Researchers have long recognized the catalytic properties of square-planar IrI complexes, such as Crabtree’s ...hydrogenation catalyst, an organometallic complex with cyclooctadiene, phosphane, and pyridine ligands. More recently, chemists have developed half-sandwich pseudo-octahedral pentamethylcyclopentadienyl IrIII complexes containing diamine ligands that efficiently catalyze transfer hydrogenation reactions of ketones and aldehydes in water using H2 or formate as the hydrogen source. Although sometimes assumed to be chemically inert, the reactivity of low-spin 5d6 IrIII centers is highly dependent on the set of ligands. Cp* complexes with strong σ-donor C∧C-chelating ligands can even stabilize IrIV and catalyze the oxidation of water. In comparison with well developed Ir catalysts, Ir-based pharmaceuticals are still in their infancy. In this Account, we review recent developments in organoiridium complexes as both catalysts and anticancer agents. Initial studies of anticancer activity with organoiridium complexes focused on square-planar IrI complexes because of their structural and electronic similarity to PtII anticancer complexes such as cisplatin. Recently, researchers have studied half-sandwich IrIII anticancer complexes. These complexes with the formula (Cp x )Ir(L∧L′)Z0/n+ (with Cp* or extended Cp* and L∧L′ = chelated C∧N or N∧N ligands) have a much greater potency (nanomolar) toward a range of cancer cells (especially leukemia, colon cancer, breast cancer, prostate cancer, and melanoma) than cisplatin. Their mechanism of action may involve both an attack on DNA and a perturbation of the redox status of cells. Some of these complexes can form IrIII-hydride complexes using coenzyme NAD(P)H as a source of hydride to catalyze the generation of H2 or the reduction of quinones to semiquinones. Intriguingly, relatively unreactive organoiridium complexes containing an imine as a monodentate ligand have prooxidant activity, which appears to involve catalytic hydride transfer to oxygen and the generation of hydrogen peroxide in cells. In addition, researchers have designed inert IrIII complexes as potent kinase inhibitors. Octahedral cyclometalated IrIII complexes not only serve as cell imaging agents, but can also inhibit tumor necrosis factor α, promote DNA oxidation, generate singlet oxygen when photoactivated, and exhibit good anticancer activity. Although relatively unexplored, organoiridium chemistry offers unique features that researchers can exploit to generate novel diagnostic agents and drugs with new mechanisms of action.
The HIPASS catalogue – I. Data presentation Meyer, M. J.; Zwaan, M. A.; Webster, R. L. ...
Monthly notices of the Royal Astronomical Society,
June 2004, Volume:
350, Issue:
4
Journal Article
Peer reviewed
Open access
The H i Parkes All-Sky Survey (HIPASS) catalogue forms the largest uniform catalogue of H i sources compiled to date, with 4315 sources identified purely by their H i content. The catalogue data ...comprise the southern region δ < + 2° of HIPASS, the first blind H i survey to cover the entire southern sky. The rms noise for this survey is 13 mJy beam −1 and the velocity range is −1280 to 12 700 km s −1. Data search, verification and parametrization methods are discussed along with a description of measured quantities. Full catalogue data are made available to the astronomical community including positions, velocities, velocity widths, integrated fluxes and peak flux densities. Also available are on-sky moment maps, position–velocity moment maps and spectra of catalogue sources. A number of local large-scale features are observed in the space distribution of sources, including the super-Galactic plane and the Local Void. Notably, large-scale structure is seen at low Galactic latitudes, a region normally obscured at optical wavelengths.
Maturation promoting factor (MPF), a complex of cyclin-dependent kinase 1 and cyclin B, drives oocyte maturation in all animals. Mechanisms to block MPF activation in developing oocytes must exist to ...prevent precocious cell cycle progression prior to oocyte maturation and fertilization. This study sought to determine the developmental consequences of precociously activating MPF in oocytes prior to fertilization. Whereas depletion of Myt1 in Xenopus oocytes causes nuclear envelope breakdown in vitro, we found that depletion of the Myt1 ortholog WEE-1.3 in C. elegans hermaphrodites causes precocious oocyte maturation in vivo. Although such oocytes are ovulated, they are fertilization incompetent. We have also observed novel phenotypes in these precociously maturing oocytes, such as chromosome coalescence, aberrant meiotic spindle organization, and the expression of a meiosis II post-fertilization marker. Furthermore, co-depletion studies of CDK-1 and WEE-1.3 demonstrate that WEE-1.3 is dispensable in the absence of CDK-1, suggesting that CDK-1 is a major target of WEE-1.3 in C. elegans oocytes.
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