Simple and Efficient Iridium(III)‐Catalyzed Water Oxidations

Abstract

BACKGROUND The Ku protein is a tightly associated heterodimer, comprised of 70‐kilodalton (kD) and 86‐kD subunits, that forms the DNA‐dependent protein kinase (DNA‐PK) complex together with the 470‐kD DNA‐PKcs catalytic subunit, and is involved mainly in DNA double‐strand breaks (DSBs) repair. The objective of the current study was to investigate the expression and DNA‐binding activity of the Ku protein in fresh tissues from patients with bladder carcinoma and to compare it with that in nontumor tissues obtained from the same organ. Moreover, the DNA‐binding activity of Ku was assessed after exposure of the tumor cells to 1 or 2 grays (Gy) of X‐rays. Furthermore, the level of phosphorylated Ku was analyzed in both the nuclear and cytoplasmic compartment of normal tissue after exposure to 2 Gy of X‐rays. METHODS The expression and DNA‐binding activity of Ku protein were assessed in tumor samples from patients who all were diagnosed with transitional cell carcinoma (TCC) of the bladder using Western blot analysis and the electrophoretic mobility shift assay, respectively. RESULTS Enhanced Ku activity and expression were found in tumor tissue compared with normal tissue for each patient. Moreover, variations in Ku activity were found in a dose‐dependent manner after the tumor cells were exposed to 1 or 2 Gy of X‐rays. A decrease in phosphorylated Ku in the cytoplasm and a parallel increase in the nucleus of normal tissue cells were observed after exposure to X‐rays. CONCLUSIONS The results of the current study suggest a possible role of Ku in regulating the DNA‐PK activity of DSBs repair in bladder tumors. Cancer 2001;92:2484–92. © 2001 American Cancer Society.

Water Oxidation with Molecularly Defined Iridium Complexes: Insights into Homogeneous versus Heterogeneous Catalysis

“…For IrCl 3 ·xH 2 O, the size distribution is between approximately 0.5 and 2 nm. [22] These results are in agreement with the observations of Grotjahn, who detected Ir-containing nanoparticles with sizes between 2 and 10 nm. [19] On the other hand, starting from 4 ( Figure 5 d and the Supporting Information SI4-4) no nanoparticles on the Ce matrix were detected, since these have obviously agglomerated to give bigger particles in the 10 mm range ( Figure 5 e and the Supporting Information SI4-4).…”

Untitled

“…On the nature of active species Soon after the first reports on the activity of Ir organometallic complexes (IrOMCs) in WO catalysis, ah ot controversy about the nature of actives pecies startedi nt he literature, stimulated by some publications [22,43,53,54] reporting evidenceo nt he transformation of some IrOMCs into IrO x NPs, which were known to be efficient WOCs. [55] In reality,t he formation of IrO x NPs was demonstrated only in af ew cases,m ostly when CAN is exploited as as acrificial oxidanta nd under conditions often far from those used in catalysis (millimolar concentration of catalyst and up to molar concentration of sacrificial oxidant).…”

“…[55] In reality,t he formation of IrO x NPs was demonstrated only in af ew cases,m ostly when CAN is exploited as as acrificial oxidanta nd under conditions often far from those used in catalysis (millimolar concentration of catalyst and up to molar concentration of sacrificial oxidant). [22,43,53] With NaIO 4 as sacrificial oxidant, DLS evidence for the formation of IrO x NPs was provided by Fujita and co-workers [56] when [Cp*Ir(6,6'-(OH) 2 -bpy)(H 2 O)] 2 + [56,57] (1 mm)w as used as pre-catalyst. Particularly,t hey found that at ransient species( A) responsible for most of the catalytic activity,w ere likely IrO x NPs, having dimensions in the range of 0.5-1.2 nm, thus con-taining4or 5I ra toms, as previously described by Harriman and co-workers.…”

“…fastest Ir WOC with both CAN [40] and NaIO 4 ; [41] [Cp*Ir{(-P(O)(OH) 2 } 3 ]Na (7), [17] which easily liberates up to three coordination sites by the oxidative expulsion of phosphate; mer-[IrCl 3 (pic)(HOMe)]K (8), [42] bearingt he pic ligand as 6,t husp otentially able to generate the same active species under the assumption thatC p* completely degrades; [24] IrCl 3 ·n H 2 O( 9) [43] and [Ir(OH) 6 ] 2À (10), [44][45][46] prepared according to the procedure reportedb yM allouk and co-workers. [44] The resultso ft his study,b eside reliably determining the relative activityo ft he differentc atalysts, allow also to obtain some clues concerning the active species, which appears to have am olecular nature.…”

Einkernige Katalysatoren zur Wasseroxidation

“…Die Bildung dieser blauen Schicht aus Iridiumoxid wird für [Cp*Ir]-Spezies beobachtet, die drei freie Bindungsstellen aufweisen. Die Tatsache, dass drei freie Positionen zur Produktion von Iridiumoxid erforderlich sind, bedeutet nicht, dass andere Komplexe definitionsgemäß molekular sind, da diese Nanopartikel bilden kçnnen, die sich nicht auf der Elektrode niederschlagen.Für einige weitere Iridiumvorstufen wie IrCl 3 ,[19,24] K 2 [IrCl 6 ][19] und [Ir(acac) 3 ][24] (acac = Acetylacetonato) ließ sich katalytische Aktivität für die Wasseroxidation nachweisen. Hçchstwahrscheinlich handelt es sich in diesen Fällen bei der eigentlichen katalytisch aktiven Spezies um Iridiumoxonanopartikel statt eines definierten molekularen Katalysators.…”