Dissimilar catalytic behavior of molecular or colloidal palladium systems with a new NHC ligand
Fernando Gómez-Villarraga, Jonathan De Tovar, Miguel Guerrero, Pau Nolis, Teodor Parella, Pierre Lecante, Nuria Romero, Lluís Escriche, Roger Bofill, Josep Ros, Xavier Sala, Karine Philippot and Jordi García-Antón
In this work, we describe the synthesis of a new N-heterocyclic carbene (NHC) ligand, derived from a hybrid pyrazole-imidazolium scaffold, namely 1-[2-(3,5-dimethylpyrazol-1-yl)ethyl]-3-((S)-1-phenylethyl)-3H-imidazol-2-ylidene (L). This ligand has been used as a stabilizer for the organometallic synthesis of palladium(0) nanoparticles (Pd NPs). L presents a better stabilizing effect than its pre-carbenic HLCl counterpart, allowing the formation of isolated Pd NPs while HLCl yields aggregated ones. Additionally, molecular Pd(II) coordination compounds of L and HLCl were synthesized and characterized to better understand the coordination modes of these ligands. Both molecular and colloidal Pd systems have been further tested in catalytic C–C coupling processes. Three different types of reactions have been observed depending on the catalytic system: (i) the Suzuki–Miyaura reaction takes place with Pd molecular complexes; (ii) a secondary reaction, the dehalogenation of the substrate, is always detected and (iii) the C–C homocoupling between two molecules of bromoarenes is observed with colloidal catalysts.
“Metronomic treatment in immunocompetent preclinical GL261 glioblastoma: effects of cyclophosphamide and temozolomide” by by L. Ferrer-Font, N. Arias-Ramos, S. Lope-Piedrafita, M. Julià-Sapé , M. Pumarola, C. Arús and A. P. Candiota. NMR Biomed. 2017. DOI: 10.1002/nbm.3748.
Glioblastoma (GBM) causes poor survival in patients even when applying aggressive treatment. In preceding years, efforts have focused in new therapeutic regimens with conventional drugs to activate immune responses that may enhance tumor regression and prevent regrowth, as for example the “metronomic” approaches.
We have evaluated whether metronomic CPA or TMZ administration could increase survival in orthotopic GL261 in C57BL/6 mice, an immunocompetent model. Longitudinal in vivo studies with CPA (140 mg/Kg) or TMZ (range 140-240 mg/Kg) metronomic administration (every 6 days) were performed in tumor-bearing mice. Tumor evolution was monitored at 7T with T2-weighted MRI, Diffusion weighted imaging and MRSI-based nosological images of response to therapy. Obtained results demonstrated that both treatments resulted in increased survival (38.6+21.0 days, n=30) compared to control (19.4+2.4 days, n=18). Also, it was found a clear edema appearance during chemotherapeutic treatment suggesting inflammatory associated processes. The necropsy performed in mice cured from GBM after high TMZ cumulative dosage (980-1400 mg/Kg) revealed lymphoma incidence.
“Metabolomics of Therapy Response in Preclinical Glioblastoma: A Multi-Slice MRSI-Based Volumetric Analysis for Noninvasive Assessment of Temozolomide Treatment” by N. Arias-Ramos, L. Ferrer-Font, S. Lope-Piedrafita, V. Mocioiu, M. Julià-Sapé , M. Pumarola, C. Arús and A. P. Candiota. Metabolites, 2017, 18;7(2). pii: E20. DOI: 10.3390/metabo7020020.
Glioblastoma (GBM) is the most common and aggressive glial primary tumor with a survival average of 14-15 months, even after application of standard treatment. Non-invasive surrogate biomarkers of therapy response may be relevant for improving patient survival. Nosological images of therapy response using a semi-supervised source extraction approach in preclinical GBM based on single slice Magnetic Resonance Spectroscopic Imaging (MRSI) was previously describe by our group. However, because of GBM heterogeneity, relevant response information could be missed just by studying one slice. Therefore, the goal of this work was to acquire 3D-like information from preclinical GBM under a longitudinal treatment protocol, using a multi-slice MRSI approach.
Nosological maps were obtained based on semi-supervised convex Non-negative Matrix Factorization and each voxel was colored according to the contribution to the spectral pattern of each one of the three sources or characteristic spectral patterns: Normal brain, actively proliferating tumour or responding tumour.
Heterogeneous response levels were observed and three arbitrary groups of treated animals were defined as: high response, intermediate response, and low response. Histopathological studies showed an inverse correlation between the responding pattern level and Ki67 proliferation rate.
“Long-term fertilization determines different metabolomic profiles and responses in saplings of three rainforest tree species with different adult canopy position” by A. Gargallo-Garriga, S. J. Wright, J. Sardans, M. Pérez-Trujillo, M. Oravec, K. Večeřová,O. Urban, M. Fernández-Martínez, T. Parella, J. Peñuelas.
Plos One, 2017, 1-21. DOI: 10.1371/journal.pone.0177030
Tropical rainforests are frequently limited by soil nutrient availability. However, the response of the metabolic phenotypic plasticity of trees to an increase of soil nutrient availabilities is poorly understood. We expected that increases in the ability of a nutrient that limits some plant processes should be detected by corresponding changes in plant metabolome profile related to such processes. We studied the foliar metabolome of saplings of three abundant tree species in a 15 year field NPK fertilization experiment in a Panamanian rainforest. The largest differences were among species and explained 75% of overall metabolome variation.
“Chiral Recognition by Dissolution DNP NMR Spectroscopy of 13C-Labeled DL-Methionine” By Eva Monteagudo, Albert Virgili, Teodor Parella and Míriam Pérez-Trujillo.. Anal. Chem., 2017, 89 (9), pp 4939–4944 DOI: 10.1021/acs.analchem.7b00156
A method based on d-DNP NMR spectroscopy to study chiral recognition is described for the first time. The enantiodifferentiation of a racemic metabolite in a millimolar aqueous solution using a chiral solvating agent was performed. Hyperpolarized 13C-labeled DL-methionine enantiomers were differently observed with a single-scan 13C NMR experiment, while the chiral auxiliary at thermal equilibrium remained unobserved. The method developed entails a step forward in the chiral recognition of small molecules by NMR spectroscopy, opening new possibilities in situations where the sensitivity is limited, for example, when a low concentration of analyte is available or when the measurement of an insensitive nucleus, like 13C, is required. The advantages and current limitations of the method, as well as future perspectives, are discussed.
“Neonatal handling enduringly decreases anxiety and stress responses and reduces hippocampus and amygdala volume in agenetic model of differential anxiety: Behavioral-volumetric associations in the Roman rats trains” by C. Río-Álamos, I. Oliveras, M. A. Piludu, C. Gerbolés, T. Cañete, G. Blázquez, S. Lope-Piedrafita, E. Martínez-Membrives, R. Torrubia, A. Tobeña, and A. Fernández-Teruel. European Neuropsychopharmacology, 2017, 27: 146–158. DOI: 10.1016/j.euroneuro.2016.12.003
The hippocampus and amygdala have been proposed as key neural structures related to anxiety. A more active hippocampus/amygdala system has been related to greater anxious responses in situations involving conflict/novelty. The Roman Low- (RLA) and High-avoidance (RHA) rat strains constitute a genetic model of differential anxiety. Relative to RHA rats, RLA rats exhibit enhanced anxiety/fearfulness, augmented hippocampal/amygdala c-Fos expression following exposure to novelty/conflict, increased hippocampal neuronal density and higher endocrine responses to stress. Neonatal handling (NH) is an environmental treatment with long-lasting anxiety/stress-reducing effects in rodents. Since hippocampus and amygdala volume are supposed to be related to anxiety/fear, it was hypothesized a greater volume of both areas in RLA than in RHA rats, as well as that NH treatment would reduce anxiety and the volume of both structures. Adult untreated and NH-treated RHA and RLA rats were tested for anxiety, sensorimotor gating (PPI), stress-induced corticosterone and prolactin responses, two-way active avoidance acquisition and in vivo 7 T 1H-Magnetic resonance image.
As expected, untreated RLA rats showed higher anxiety and post-stress hormone responses, as well as greater hippocampus and amygdala volumes than untreated RHA rats. NH decreased anxiety/stress responses, especially in RLA rats, and significantly reduced hippocampus and amygdala volumes in this strain. Dorsal striatum volume was not different between the strains nor it was affected by NH. Finally, there were positive associations (as shown by correlations, factor analysis and multiple regression) between anxiety and PPI and hippocampus/amygdala volumes.
“Mutation of the 3-Phosphoinositide-Dependent Protein Kinase 1
(PDK1) Substrate-Docking Site in the Developing Brain Causes
Microcephaly with Abnormal Brain Morphogenesis Independently of
Akt, Leading to Impaired Cognition and Disruptive Behaviors” by Lluís Cordón-Barris, Sònia Pascual-Guiral, Shaobin Yang, Lydia Giménez-Llort, Silvia Lope-Piedrafita, Carlota Niemeyer, Enrique Claro, Jose M. Lizcano, and Jose R. Bayascas. Mol Cell Biol (2016), 36:2967–2982. DOI:10.1128/MCB.00230-16.
This report shows the involvement of PDK1 downstream effectors other than Akt in mouse neuropsychiatric-like disorders, with potential face and construct validity for negative and cognitive symptoms of schizophrenia. Results point to a prominent function for PIF pocket-dependent kinases as major effectors of this signaling hub downstream of Akt in the etiopathogenesis of schizophrenia that might provide construct validity to the PDK1 L155E mutants.
The phosphoinositide (PI) 3-kinase/Akt signaling pathway plays essential roles during neuronal development. 3-Phosphoinositide-dependent protein kinase 1 (PDK1) coordinates the PI 3-kinase signals by activating 23 kinases of the AGC family, includingAkt. Phosphorylation of a conserved docking site in the substrate is a requisite for PDK1 to recognize, phosphorylate, and activate most of these kinases, with the exception of Akt. This differential mechanism of regulation it has been exploited by generating neuron-specific conditional knock-in mice expressing a mutant form of PDK1, L155E, in which the substrate-docking site binding motif, termed the PIF pocket, was disrupted. As a consequence, activation of all the PDK1 substrates tested except Akt was abolished. The mice exhibited microcephaly, altered cortical layering, and reduced circuitry, leading to cognitive deficits and exacerbated disruptive behavior combined with diminished motivation. The abnormal patterning of the adult brain arises from the reduced ability of the embryonic neurons to polarize and extend their axons, highlighting the essential roles that the PDK1 signaling beyond Akt plays in mediating the neuronal responses that regulate brain development.
Mononuclear ruthenium compounds bearing N-donor and N-heterocyclic carbene ligands: structure and oxidative catalysis
Dalton Trans., 2017, Accepted Manuscript
ABSTRACT A new CNNC carbene-phthalazine tetradentate ligand has been synthesised, which under reaction with [Ru(T)Cl3] (T = trpy, tpm, bpea; trpy = 2,2′;6′,2″-terpyridine; tpm = tris(pyrazol-1-yl)methane; bpea = N,N-bis(pyridin-2-ylmethyl)ethanamine) in MeOH or iPrOH undergoes a C-N bond scission due to the nucleophilic attack of a solvent molecule, with the subsequent formation of the mononuclear complexes cis-[Ru(PhthaPz-OR)(trpy)X]n+, [Ru(PhthaPz-OMe)(tpm)X]n+ and trans,fac-[Ru(PhthaPz-OMe)(bpea)X]n+ (X = Cl, n = 1; X = H2O, n = 2; PhthaPz-OR = 1-(4-alkoxyphthalazin-1-yl)-3-methyl-1H-imidazol-3-ium), named 1a+/2a2+ (R = Me), 1b+/2b2+ (R = iPr), 3+/42+ and 5+/62+, respectively. Interestingly, regulation of the stability regions of the different Ru oxidation states is obtained by the different ligand combinations, going from 62+, where Ru(III) is clearly stable and mono-electronic transfers are favoured, to 2a2+/2b2+, where Ru(III) is almost unstable with regards to its disproportion. The catalytic performance of the Ru-OH2 complexes in chemical water oxidation at pH 1.0 points to poor stability (ligand oxidation), with subsequent evolution of CO2 together with O2, especially for 42+ and 62+. In electrochemically driven water oxidation, the highest TOF values are obtained for 2a2+ at pH 1.0. In alkene epoxidation, complexes favouring bi-electronic transfer processes show better performances and selectivities than those favouring mono-electronic transfers, while alkenes containing electron-donor groups promote better performances than those bearing electron-withdrawers. Finally, when cis-β-methylstyrene is employed as substrate, no cis/trans isomerization takes place, thus indicating the existence of a stereospecific process.
“Structural discrimination from in-situ measurement of 1DCH and 2DHH RDCs” by Núria Marcó, R. R. Gil and Teodor Parella. Magnetic Resonance in Chemistry 2017, DOI:
A fast RDC-assisted strategy involving the simultaneous determination of scalar and total coupling constants from a single 1JCH/2JHH-resolved NMR spectrum is reported. It is shown that the concerted use of the directly measured 1DCH (for all CHn multiplicities) and 2DHH residual dipolar couplings allows an on-the-fly assignment of diastereotopic CH2 protons, as well as of an efficient discrimination between all eight possible diastereoisomeric structures of strychnine, which contains six stereocenters.
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“Perfect 1JCH-resolved HSQC: Efficient measurement of one-bond proton-carbon coupling constants along the indirect dimension” by Núria Marcó, A.A. Souza, Pau Nolis, R. R. Gil and Teodor Parella. Journal of Magnetic resonance 2017, 276, 37-42. DOI: 10.1016/j.jmr.2017.01.002
A versatile 1JCH-resolved HSQC pulse scheme for the speedy, accurate and automated determination of one-bond proton-carbon coupling constants is reported. The implementation of a perfectBIRD element allows a straightforward measurement from the clean doublets obtained along the highly resolved F1 dimension, even for each individual 1JCHa and 1JCHb in diastereotopic HaCHb methylene groups. Real-time homodecoupling during acquisition and other alternatives to minimize accidental signal overlapping in overcrowded spectra are also discussed.
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