Hemes destined for cytosolic hemoproteins must originate in one of the cellular compartments which have the capacity for heme synthesis, namely the chloroplast or the mitochondria. Since developing chloroplasts from greening cucumber (Cucumis sativus, cv. Sumter) cotyledons are known to contain complete heme and chlorophyll biosynthetic pathways, they were tested for their capacity export hemes. Picomole quantities of heme were measured by reconstitution of the heme with apo-peroxidase and subsequent determination of peroxidase activity. The assay method was sensitive (as little as 0.7 picomole of heme could be detected in a volume of 100 microliters) and was linear with heme concentration. When intact plastids were incubated with apo-peroxidase, a steady-state rate of efflux between 0.12 and 0.45 picomole heme/minute/milligram plastid protein was measured. The efflux rate was not due to plastid breakage and could be enhanced by incubating with the heme precursor, baminolevulinic acid. Cold acetone extraction removed 47 ± 17 picomoles heme/milligram plastid protein from the total b-type heme pool in the chloroplasts (166 ± 9 picomoles heme/milligram protein, by acid-acetone extraction). The reconstitution technique provided a similar estimate of readily exchangeable heme in the plastid, 37 ± 8 picomoles heme/milligram protein (or 6 micromolar in the plastids). These values may be indicative of a 'free heme pool' which exists in the chloroplast.

In one step, 8 octahedral metal 'corners' and 12 ligand 'edges' come together to form a supramolecular cube.

No abstract

A detailed study on the uptake and antimicrobial activity of a RuII theranostic complex with wild-type S. aureus, MRSA, and other mutants has identified the specific resistance mechanisms that Gram-positive bacteria display against this lead.

The synthesis of two new luminescent dinuclear Ir(III)-Ru(II) complexes containing tetrapyrido[3,2-a:2',3'-c:3'',2''-h:2''',3'''-j]phenazine (tpphz) as the bridging ligand is reported. Unlike many other complexes incorporating cyclometalated Ir(III) moieties, these complexes display good water solubility, allowing the first cell-based study on Ir(III)-Ru(II) bioprobes to be carried out. Photophysical studies indicate that emission from each complex is from a Ru(II) excited state and both complexes display significant in vitro DNA-binding affinities. Cellular studies show that each complex is rapidly internalised by HeLa cells, in which they function as luminescent nuclear DNA-imaging agents for confocal microscopy. Furthermore, the uptake and nuclear targeting properties of the complex incorporating cyclometalating 2-(4-fluorophenyl)pyridine ligands around its Ir(III) centre is enhanced in comparison to the non-fluorinated analogue, indicating that fluorination may provide a route to promote cell uptake of transition-metal bioprobes.