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    ABSTRACT: Organometallic complexes have the potential to behave as catalytic drugs. We investigate here Rh(III) complexes of general formula [(Cpx)Rh(N,N′)(Cl)], where N,N′ is ethylenediamine (en), 2,2′-bipyridine (bpy), phenanthroline (phen) or N-(2-aminoethyl)-4-(trifluoromethyl)benzenesulfonamide (TfEn), and Cpx is pentamethylcyclopentadienyl (Cp*), 1-phenyl-2,3,4,5-tetramethylcyclopentadienyl (CpxPh) or 1-biphenyl-2,3,4,5-tetramethyl cyclopentadienyl (CpxPhPh). These complexes can reduce NAD+ to NADH using formate as an hydride source under biologically-relevant conditions. The catalytic activity decreased in the order of N,N-chelated ligand bpy>phen > en with Cp* as the η5-donor. The en complexes (1–3) became more active with extension to the CpX ring, whereas the activity of the phen (7–9) and bpy (4–6) compounds decreased. Cp*Rh(bpy)Cl]+ (4) showed the highest catalytic activity, with a TOF of 37.4±2h−1. Fast hydrolysis of the chlorido complexes 1–10 was observed by 1H NMR (< 10min at 310K). The pKa* values for the aqua adducts were determined to be ca. 8–10. Complexes 1–9 also catalysed the reduction of pyruvate to lactate using formate as the hydride donor. The efficiency of the transfer hydrogenation reactions was highly dependent on the nature of the chelating ligand and the Cpx ring. Competition reactions between NAD+ and pyruvate for reduction by formate catalysed by 4 showed a preference for reduction of NAD+. The antiproliferative activity of complex 3 towards A2780 human ovarian cancer cells increased by up to 50% when administered in combination with non-toxic doses of formate, suggesting that transfer hydrogenation can induce reductive stress in cancer cells.
    Full-text · Article · Oct 2015 · Journal of Inorganic Biochemistry
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    ABSTRACT: We report the direct deposition of indium antimonide, by molecular beam epitaxy (MBE) on gallium antimonide, resulting in the formation of quantum dots (QDs) with a maximum density of ~5.3×10^10 cm−2. Using reflection high energy electron diffraction (RHEED) and atomic force microscopy (AFM) for the analysis of samples with InSb depositions of 1–6 ML equivalent thickness, we observe an apparent value for the critical thickness for InSb/GaSb(001) deposition of 2.3±0.3 ML, for the growth temperatures of 275°C and 320°C.
    Full-text · Article · Mar 2015 · Journal of Crystal Growth
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    ABSTRACT: Which elements are essential for human life? Here we make an element-by-element journey through the periodic table and attempt to assess whether elements are essential or not, and if they are, whether there is a relevant code for them in the human genome. There are many difficulties such as the human biochemistry of several so-called essential elements is not well understood, and it is not clear how we should classify elements that are involved in the destruction of invading microorganisms, or elements which are essential for microorganisms with which we live in symbiosis. In general, genes do not code for the elements themselves, but for specific chemical species, i.e. for the element, its oxidation state, type and number of coordinated ligands, and the coordination geometry. Today, the biological periodic table is in a position somewhat similar to Mendeleev's chemical periodic table of 1869: there are gaps and we need to do more research to fill them. The periodic table also offers potential for novel therapeutic and diagnostic agents, based on not only essential elements, but also non-essential elements, and on radionuclides. Although the potential for inorganic chemistry in medicine was realized more than 2000 years ago, this area of research is still in its infancy. Future advances in the design of inorganic drugs require more knowledge of their mechanism of action, including target sites and metabolism. Temporal speciation of elements in their biological environments at the atomic level is a major challenge, for which new methods are urgently needed.
    Full-text · Article · Mar 2015 · Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences
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