Catalytic Activation of Small Molecules. Development and Characterisation of Ruthenium Complexes for Application in Catalysis

In this work, the synthesis, characterisation and catalytic application of ruthenium pincer complexes is presented. In this context, new synthetic strategies are discussed to obtain novel ruthenium pincer dihydrogen complexes. Furthermore, the reactivity of the complexes towards small molecules (e.g. alcohols, boranes, ammonia, amines, nitriles and hydrogen) was observed, delivering fundamental insights into catalytic applications. With the reactivity testing, new borylated B-H-σ-complexes were synthesised and characterised. Moreover, decarbonylation of alcohols were observed with these complexes, leading to a new strategy to functionalise ruthenium pincer complexes with CO ligands. In addition to standard analytic methods such as NMR and IR spectroscopy, for the first time LIFDI-MS analysis (liquid injection field desorption/ionisation-mass spectrometry) of the synthesised ruthenium pincer hydride complexes was carried out. This method is a mild approach to analyse reactive compounds such as ruthenium pincer complexes in mass spectrometry. The obtained ruthenium dihydrogen pincer complexes and the CO functionalised ruthenium pincer complexes were tested for their catalytic activity. In dehydrogenation reactions, one of the first homogeneously catalysed transformation of primary alcohols to carboxylic acid salts was achieved in aqueous medium without toxic, oxidative and/or aggressive additives required under mild reaction conditions (120 °C). Furthermore, effective hydrogenation of nitriles was successfully demonstrated, whereby the selectivity of the reaction equilibria can be controlled to obtain either secondary imines or primary amines with up to full conversion and high selectivity under low H2 pressure at 4 bar, low catalyst loading (0.5-1 mol%) and mild reaction temperatures (50-100 °C). Another catalytic application is the direct amination of alcohols with ammonia, which is a straight-forward approach to transform alcohols directly into the corresponding amines without any additional synthetic steps. Based on the results of investigative catalyst screenings, a new complex was synthesised, this is one of the most active catalyst for this reaction

Selective conversion of alcohols in water to carboxylic acids by in situ generated ruthenium trans dihydrido carbonyl PNP complexes

In this work, we present a mild method for direct conversion of primary alcohols into carboxylic acids with the use of water as an oxygen source. Applying a ruthenium dihydrogen based dehydrogenation catalyst for this cause, we investigated the effect of water on the catalytic dehydrogenation process of alcohols. Using 1 mol% of the catalyst we report up to high yields. Moreover, we isolated key intermediates which most likely play a role in the catalytic cycle. One of the intermediates was identified as a trans dihydrido carbonyl complex which is generated in situ in the catalytic process

Selective and mild hydrogen production using water and formaldehyde

With the increased efforts in finding new energy storage systems for mobile and stationary applications, an intensively studied fuel molecule is dihydrogen owing to its energy content, and the possibility to store it in the form of hydridic and protic hydrogen, for example, in liquid organic hydrogen carriers. Here we show that water in the presence of paraformaldehyde or formaldehyde is suitable for molecular hydrogen storage, as these molecules form stable methanediol, which can be easily and selectively dehydrogenated forming hydrogen and carbon dioxide. In this system, both molecules are hydrogen sources, yielding a theoretical weight efficiency of 8.4% assuming one equivalent of water and one equivalent of formaldehyde. Thus it is potentially higher than formic acid (4.4 wt%), as even when technical aqueous formaldehyde (37 wt%) is used, the diluted methanediol solution has an efficiency of 5.0 wt%. The hydrogen can be efficiently generated in the presence of air using a ruthenium catalyst at low temperature

Quantitation of BK Virus DNA for Diagnosis of BK Virus-Associated Nephropathy in Renal Transplant Recipients

Quantitative measurement of BK virus DNA (Q-BKDNA) has been used for the early diagnosis and monitoring of BK virus-associated nephropathy (BKVAN). This study was designed to determine the BKDNA cutoff for the diagnosis of BKVAN. Between June 2005 and February 2007, 64 renal transplant recipients taken renal biopsies due to renal impairment submitted plasma and urine for Q-BKDNA. Eight BKVAN patients (12.5%) had median viral loads of 6.0 log10 copies/mL in plasma and 7.3 log10 copies/mL in urine. Among 56 non-BKVAN patients, 45 were negative for Q-BKDNA; 4 were positive in plasma with a median viral load of 4.8 log10 copies/mL, and 10 were positive in urine with a median viral load of 4.8 log10 copies/mL. Receiver operating characteristic curve analysis showed that a cutoff of 4.5 log10 copies/mL in plasma and a cutoff of 5.9 log10 copies/mL in urine had a sensitivity of 100% and a specificity of 96.4%, respectively. A combined cutoffs of 4 log10 copies/mL in plasma and 6 log10 copies/mL in urine had better performance with a sensitivity of 100% and a specificity of 98.2% than each cutoff of urine or plasma. Q-BKDNA with the combined cutoffs could reliably diagnose BKVAN in renal transplant recipients

Comparison between Matched Related and Alternative Donors of Allogeneic Hematopoietic Stem Cells Transplanted into Adult Patients with Acquired Aplastic Anemia: Multivariate and Propensity Score-Matched Analysis

We retrospectively compared the outcomes of 225 patients with adult acquired aplastic anemia (AA) who underwent allogeneic hematopoietic stem cell transplantation (alloHSCT) from matched related donors (MRDs), and those treated by alloHSCT from alternative donors (ADs). Univariate and multivariate analyses of factors associated with survival were performed. Multivariate analysis showed that age at alloHSCT of ≤31 years, MRD, successful engraftment, absence of acute graft-versus-host disease (aGVHD), and platelet engraftment at ≤21 days, were independent predictors of longer survival. In addition, time to aGVHD and cumulative nonrelapse mortality (NRM) were better in MRD than in AD recipients. Using propensity score matching (PSM), we performed a case-control study comparing 25 patients in each group who underwent alloHSCT from MRDs and ADs. Pretransplantation clinical factors were well balanced in either group. Median survival time was similar, and no statistically significant difference in transplantation outcomes was apparent when MRD and AD recipients were compared. In conclusion, our results suggest that alloHSCT from an AD should be considered earlier in adult patients with AA who do not have an MRD

NHERF2 specifically interacts with LPA(2) receptor and defines the specificity and efficiency of receptor-mediated phospholipase C-beta 3 activation

Lysophosphatidic acid (LPA) activates a family of cognate G protein-coupled receptors and is involved in various pathophysiological processes. However, it is not clearly understood how these LPA receptors are specifically coupled to their downstream signaling molecules. This study found that LPA, but not the other LPA receptor isoforms, specifically interacts with Na+/H+ exchanger regulatory factor2 (NHERF2). In addition, the interaction between them requires the C-terminal PDZ domain-binding motif of LPA(2) and the second PDZ domain of NHERF2. Moreover, the stable expression of NHERF2 potentiated LPA-induced phospholipase C-beta (PLC-beta) activation, which was markedly attenuated by either a mutation in the PDZ-binding motif of LPA(2) or by the gene silencing of NHERF2. Using its second PDZ domain, NHERF2 was found to indirectly link LPA(2) to PLC-beta3 to form a complex, and the other PLC-beta isozymes were not included in the protein complex. Consistently, LPA(2)-mediated PLC-beta activation was specifically inhibited by the gene silencing of PLC-beta3. In addition, NHERF2 increases LPA-induced ERK activation, which is followed by cyclooxygenase-2 induction via a PLC-dependent pathway. Overall, the results suggest that a ternary complex composed of LPA(2), NHERF2, and PLC-beta3 may play a key role in the LPA2-mediated PLC-beta signaling pathwayclose606

Dynamic relocalization of NHERF1 mediates chemotactic migration of ovarian cancer cells toward lysophosphatidic acid stimulation

NHERF1/EBP50 (Na+/H+ exchanger regulating factor 1; Ezrin-binding phosphoprotein of 50 kDa) organizes stable protein complexes beneath the apical membrane of polar epithelial cells. By contrast, in cancer cells without any fixed polarity, NHERF1 often localizes in the cytoplasm. The regulation of cytoplasmic NHERF1 and its role in cancer progression remain unclear. In this study, we found that, upon lysophosphatidic acid (LPA) stimulation, cytoplasmic NHERF1 rapidly translocated to the plasma membrane, and subsequently to cortical protrusion structures, of ovarian cancer cells. This movement depended on direct binding of NHERF1 to C-terminally phosphorylated ERM proteins (cpERMs). Moreover, NHERF1 depletion downregulated cpERMs and further impaired cpERM-dependent remodeling of the cell cortex, suggesting reciprocal regulation between these proteins. The LPA-induced protein complex was highly enriched in migratory pseudopodia, whose formation was impaired by overexpression of NHERF1 truncation mutants. Consistent with this, NHERF1 depletion in various types of cancer cells abolished chemotactic cell migration toward a LPA gradient. Taken together, our findings suggest that the high dynamics of cytosolic NHERF1 provide cancer cells with a means of controlling chemotactic migration. This capacity is likely to be essential for ovarian cancer progression in tumor microenvironments containing LPA

Tuneable Hydrogenation of Nitriles into Imines or Amines with a Ruthenium Pincer Complex under Mild Conditions

The selective hydrogenation of aromatic and aliphatic nitriles into amines and imines is described. Using a ruthenium pincer complex, the selectivity towards amines or imines can be controlled by simple parameter changes. The reactions are conducted under very mild conditions between 50-100 degrees C at 0.4MPa H-2 pressure without any additives at low catalytic loadings of 0.5-1mol%, which results in quantitative conversions and high selectivity