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1.
Chemistry ; 2021 Mar 29.
Artigo em Inglês | MEDLINE | ID: mdl-33780048

RESUMO

The successive auration of p-tert -butyltetramercaptotetrathiacalix[4]arene, H 4 (MTC[4]), with gold(I) phosphine units was investigated. Through deprotonation with NaOMe, followed by salt metathesis reactions with (PR 3 )AuCl (R = Me, Ph) complexes with two and three [(PR 3 )Au] + moieties could be prepared and isolated, namely [(Ph 3 PAu) 2 H 2 (MTC[4])] and [(Me 3 PAu) 3 H(MTC[4])]. In [(Ph 3 PAu) 3 H(MTC[4])] two gold(I) ions already come close enough to undergo aurophilic interactions. To introduce a fourth  [(PR 3 )Au] + entity TlOEt had to be used for the deprotonation, which led to the finding that four gold(I) ions organised by the (MTC[4]) 4- coordination platform are able to bind and stabilize a monomeric TlCl species, yielding [(Me 3 PAu) 4 TlCl(MTC[4])]. As evidenced by structural and theoretical investigations the binding occurs through strong metallophilic interactions, which lead to photoluminescence at low temperatures.

2.
Angew Chem Int Ed Engl ; 59(17): 6735-6739, 2020 Apr 20.
Artigo em Inglês | MEDLINE | ID: mdl-32009289

RESUMO

Tetramercaptotetrathiacalix[4]arene (LH4 ) can be used as a coordination platform to bind four CuI ions at the thiolate and thioether S atoms. Donor ligands such as phosphanes can stabilize the resulting [LCu4 ] units, which then remain monomeric ([(Ph3 PCu)4 L]). In the absence of donor ligands, they aggregate, providing a hexamer ([LCu4 ]6 ) in high yields, with a hollow-sphere structure formed by an unprecedented Cu24 S48 cage that is surrounded by the organic framework of the calixarene chalices. Preliminary NMR experiments with regard to the host-guest chemistry in solution showed that the compound represents a polytopic host for acetonitrile and methane.

3.
Chemistry ; 23(49): 11797-11801, 2017 Sep 04.
Artigo em Inglês | MEDLINE | ID: mdl-28817213

RESUMO

A xanthene-based bismuthane/phosphane chelating ligand has been accessed that has enabled the synthesis of a palladium(0) bismuthane complex. The bismuthane donor proved to be hemilabile as it switched to a dangling position upon addition of O2 that gave a palladium(II) peroxide complex. Unlike the corresponding 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene (Xantphos) palladium peroxide, the bismuth analogue could be employed for catalytic phosphane oxidation and oxidative phenol coupling.

4.
Angew Chem Int Ed Engl ; 56(9): 2307-2311, 2017 02 20.
Artigo em Inglês | MEDLINE | ID: mdl-28111896

RESUMO

In metal-mediated O2 activation, nickel(II) compounds hardly play a role, but recently it has been shown that enzymes can use nickel(II) for O2 activation. Now a low-coordinate Lewis acidic nickel(II) complex has been synthesized that reacts with O2 to give a nickel(II) organoperoxide, as proposed for the enzymatic system. Its formation was studied further by UV/Vis absorption spectroscopy, leading to the observation of a short-lived intermediate that proved to be reactive in both oxygen atom transfer and hydrogen abstraction reactions, while the peroxide efficiently transfers O atoms. Both for the enzyme and for the functional model, the key to O2 activation is proposed to represent a concomitant electron shift from the substrate/co-ligand.

5.
Nat Neurosci ; 19(12): 1610-1618, 2016 12.
Artigo em Inglês | MEDLINE | ID: mdl-27723745

RESUMO

Intronic hexanucleotide expansions in C9ORF72 are common in amyotrophic lateral sclerosis (ALS) and frontotemporal dementia, but it is unknown whether loss of function, toxicity by the expanded RNA or dipeptides from non-ATG-initiated translation are responsible for the pathophysiology. We determined the interactome of C9ORF72 in motor neurons and found that C9ORF72 was present in a complex with cofilin and other actin binding proteins. Phosphorylation of cofilin was enhanced in C9ORF72-depleted motor neurons, in patient-derived lymphoblastoid cells, induced pluripotent stem cell-derived motor neurons and post-mortem brain samples from ALS patients. C9ORF72 modulates the activity of the small GTPases Arf6 and Rac1, resulting in enhanced activity of LIM-kinases 1 and 2 (LIMK1/2). This results in reduced axonal actin dynamics in C9ORF72-depleted motor neurons. Dominant negative Arf6 rescues this defect, suggesting that C9ORF72 acts as a modulator of small GTPases in a pathway that regulates axonal actin dynamics.


Assuntos
Fatores de Despolimerização de Actina/metabolismo , Actinas/metabolismo , Fatores de Troca do Nucleotídeo Guanina/genética , Células-Tronco Pluripotentes Induzidas/metabolismo , Neurônios Motores/metabolismo , Proteínas/genética , Esclerose Amiotrófica Lateral/genética , Esclerose Amiotrófica Lateral/metabolismo , Animais , Encéfalo/metabolismo , Proteína C9orf72 , Expansão das Repetições de DNA/genética , Demência Frontotemporal/genética , Demência Frontotemporal/metabolismo , Humanos , Camundongos , Proteínas dos Microfilamentos/metabolismo
6.
Angew Chem Int Ed Engl ; 55(46): 14450-14454, 2016 11 07.
Artigo em Inglês | MEDLINE | ID: mdl-27739624

RESUMO

Stabilized borylenes (L2 BH:) with weakly π-accepting substituents L, such as phosphines, were previously believed to be unstable. In the current manuscript, we describe a series of complexes formally containing a phosphine-stabilized borylene or boryl anion. In contrast to common trivalent boron compounds, the boron-based ligands in this study act as electron-donating ligands. The reported iron hydride complexes exhibit a unique reactivity pattern, undergoing a reversible B-H reductive elimination concomitant with oxidation of the boron(I) center.

7.
Angew Chem Int Ed Engl ; 55(40): 12325-9, 2016 09 26.
Artigo em Inglês | MEDLINE | ID: mdl-27384019

RESUMO

To gain molecular level insights into the properties of certain functions and units of extended oxides/hydroxides, suitable molecular model compounds are needed. As an attractive route to access such compounds the trapping of early intermediates during the hydrolysis of suitable precursor compounds with the aid of stabilizing ligands is conceivable, which was tested for the aluminum(III)/water system. Indeed, trisilanols proved suitable trapping reagents: their presence during the hydrolysis of Al(i) Bu2 H in dependence on the amount of water used allowed for the isolation of tri- and octanuclear aluminum hydroxide cluster complexes [Al3 (µ2 -OH)3 (THF)3 (PhSi(OSiPh2 O)3 )2 ] (1) and [Al8 (µ3 -OH)2 (µ2 -OH)10 (THF)3 (p-anisylSi(OSiPh2 O)3 )4 ] (2). 1 can be regarded as the Al(OH)3 cyclic trimer, where six protons have been replaced by silyl residues. While 2 features a unique [Al8 (µ3 -OH)2 (µ2 -OH)10 ](12+) core. In contrast to most other known aggregates of this type, 1 and 2 can be readily prepared at reasonable scales, dissolve in common solvents, and retain an intact framework even in the presence of excessive amounts of water. This finding paves the way to future research addressing the reactivity of the individual functional groups.

8.
Inorg Chem ; 55(4): 1837-42, 2016 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-26845512

RESUMO

To investigate the effect of X in ambiphilic compounds BiX(o-PPh2-C6H4)2, PBiP-X, on metallophilic Pt-Bi interactions in its PtCl2 complexes two new derivatives PBiP-Me and PBiP-C6F5 were synthesized. Reaction with dichloro(1,5-cyclooctadiene)platinum(II) led to the platinum(II) complexes [PtCl2(PBiP-Me)], 3, and [PtCl2(PBiP-C6F5)], 4, which together with the halide [PtCl2(PBiP-Cl)], 2, reported previously, establish a series of related PBiP-X complexes differing only in X. This could be complemented by accessing [PtCl2(PBiP-OTf)], 5, through the reaction of 2 with AgOTf. Analysis of the geometrical and electronic structures of these complexes revealed that in all cases the platinum(II) centers act as donors (through their filled d(z(2)) orbitals) to the bismuth(III) centers (possessing σ*(Bi-X)/6p acceptor orbitals). The strength of these interactions increases with increasing electron-withdrawing character of X, which supports the conceptual approach in constructing this new class of compounds.

9.
Inorg Chem ; 53(20): 11335-43, 2014 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-25290535

RESUMO

The octahedral transition-metal complex [(dppa)Fe(Ph2P-N-PPh2)2] (1) [dppa = bis(diphenylphosphino)amine] with homofunctional bidentate ligands is described. The ligand exhibits hemilability due to its small bite angle and the steric repulsion of the coordinated donor groups. As the {Ph2P-N-PPh2}(-) ligand can act as an internal base, heterolytic cleavage of dihydrogen by complex 1 leads to the formation of the hydride complex [(dppa)(Ph2P-N-PPh2)Fe(H)(κ(1)-Ph2P-NH-PPh2)2] (2), representing an example of cooperative bond activation with a homofunctional hemilabile ligand. This study demonstrates that hemilability of homofunctionalized ligands can be affected by careful adjustment of geometric parameters.


Assuntos
Compostos de Anilina/química , Compostos Ferrosos/química , Hidrogênio/química , Fosfinas/química , Compostos Ferrosos/síntese química , Ligantes , Modelos Moleculares , Estrutura Molecular
10.
Inorg Chem ; 53(7): 3839-46, 2014 Apr 07.
Artigo em Inglês | MEDLINE | ID: mdl-24635355

RESUMO

Herein we report on the new NH-acid N-(2,3,4,5,6-pentafluorophenyl)-N-nonafluoro-tert-butylamine, HN(C6F5)(C(CF3)3), bearing two different sterically demanding and strongly electron-withdrawing perfluorinated amine substituents. The title compound and seven of its alkaline and alkaline earth metal salts were synthesized and investigated concerning their thermal, spectroscopic, and structural properties. The Li, Na, K, Cs, and Mg salts were investigated by single-crystal XRD analysis. The molecular structures reveal interesting motifs such as manifold fluorine metal secondary interactions. The lithium and magnesium compounds exhibit a remarkable thermal stability and an unexpectedly high volatility. We believe that this report will provoke investigations to apply the corresponding anion in ionic liquids, in lithium electrolytes, and as a weakly electron-donating ligand in the preparation of highly Lewis-acidic main group, rare earth, or transition metal complexes.

11.
Dalton Trans ; 42(31): 11252-61, 2013 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-23811820

RESUMO

A unique hydrido phosphine-borane iron(II) complex [(dppa)(Ph2P-N-P(BH3)Ph2)Fe(H)] (1) was obtained by the reaction of iron(II) chloride and two equivalents of bis(diphenylphosphino)amine (dppa) with an excess of sodium borohydride in acetonitrile-ethanol mixtures. Detailed investigations of the reaction revealed that a mixture of cis- and trans-[(dppa)2Fe(NCMe)2]²âº is formed prior to the reduction by sodium borohydride. Depending on the solvent, different products were obtained by the reduction: in acetonitrile-ethanol mixtures the hydrido phosphine-borane complex 1 is formed by formal insertion of BH3, while the reduction in pure acetonitrile results in the formation of the cationic complex trans-[(dppa)2Fe(H)(NCMe)](BH4) (4). Complex 4 is remarkably stable in ethanol and does not undergo phosphine-borane formation, even in the presence of excess sodium borohydride. This observation suggests that the phosphine-borane complex is generated by the reaction with the first equivalent of sodium borohydride with the participation of ethanol, followed by deprotonation or dihydrogen elimination. Experiments with similar diphosphine ligands, such as bis(diphenylphosphino)methane, did not yield a phosphine-borane complex, indicating the crucial role of the amine group in the observed reactivity.

12.
Inorg Chem ; 52(13): 7317-9, 2013 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-23763502

RESUMO

A new [Mn(III)9] complex was synthesized from a naphthoxime-based ligand. It was structurally and magnetically characterized, revealing a rare defect supertetrahedral topology and promising SMM properties with a large energy barrier of 67 K.

13.
J Cell Biol ; 199(3): 437-51, 2012 Oct 29.
Artigo em Inglês | MEDLINE | ID: mdl-23109669

RESUMO

Axonal maintenance, plasticity, and regeneration are influenced by signals from neighboring cells, in particular Schwann cells of the peripheral nervous system. Schwann cells produce neurotrophic factors, but the mechanisms by which ciliary neurotrophic factor (CNTF) and other neurotrophic molecules modify the axonal cytoskeleton are not well understood. In this paper, we show that activated signal transducer and activator of transcription-3 (STAT3), an intracellular mediator of the effects of CNTF and other neurotrophic cytokines, acts locally in axons of motoneurons to modify the tubulin cytoskeleton. Specifically, we show that activated STAT3 interacted with stathmin and inhibited its microtubule-destabilizing activity. Thus, ectopic CNTF-mediated activation of STAT3 restored axon elongation and maintenance in motoneurons from progressive motor neuronopathy mutant mice, a mouse model of motoneuron disease. This mechanism could also be relevant for other neurodegenerative diseases and provide a target for new therapies for axonal degeneration.


Assuntos
Axônios/fisiologia , Modelos Animais de Doenças , Doença dos Neurônios Motores/genética , Doença dos Neurônios Motores/patologia , Fator de Transcrição STAT3/fisiologia , Animais , Western Blotting , Fator Neurotrófico Derivado do Encéfalo/metabolismo , Núcleo Celular/genética , Proliferação de Células , Células Cultivadas , Fator Neurotrófico Ciliar/metabolismo , Feminino , Fator Neurotrófico Derivado de Linhagem de Célula Glial/metabolismo , Técnicas Imunoenzimáticas , Imunoprecipitação , Masculino , Camundongos , Camundongos Knockout , Camundongos Transgênicos , Doença dos Neurônios Motores/metabolismo , Neurônios Motores/citologia , Neurônios Motores/fisiologia , Mutação/genética , Estatmina/metabolismo
14.
Histochem Cell Biol ; 138(5): 737-48, 2012 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-22810847

RESUMO

Reduced levels of the SMN (survival of motoneuron) protein cause spinal muscular atrophy, the main form of motoneuron disease in children and young adults. In cultured motoneurons, reduced SMN levels lead to disturbed axon growth that correlates with reduced actin mRNA and protein in growth cones, indicating that anterograde transport and local translation of ß-actin mRNA are altered in this disease. However, it is not fully understood how local translation of the ß-actin mRNA is regulated in SMN-deficient motoneurons. Here, we established a lentiviral GFP-based reporter construct to monitor local translation of ß-actin mRNA. Time-lapse imaging of fluorescence recovery after photobleaching (FRAP) in living motoneurons revealed that ß-actin is locally translated in the growth cones of embryonic motoneurons. Interestingly, local translation of the ß-actin reporter construct was differentially regulated by various Laminin isoforms, indicating that Laminins provide extracellular cues for the regulation of local translation in growth cones. Notably, local translation of ß-actin mRNA was deregulated in motoneurons from a mouse model for the most severe form of SMA (Smn(-/-);SMN2). Taken together our findings suggest that local translation of ß-actin in growth cones of motoneurons is regulated by Laminin signalling and that this signalling is disturbed in SMA.


Assuntos
Actinas/biossíntese , Axônios/metabolismo , Laminina/metabolismo , Neurônios Motores/metabolismo , Proteína 1 de Sobrevivência do Neurônio Motor/metabolismo , Animais , Células Cultivadas , Modelos Animais de Doenças , Cones de Crescimento/metabolismo , Humanos , Camundongos , Camundongos Transgênicos , Fotodegradação , Biossíntese de Proteínas , RNA Mensageiro/metabolismo , Transdução de Sinais/genética , Atrofias Musculares Espinais da Infância/genética , Atrofias Musculares Espinais da Infância/metabolismo , Proteína 1 de Sobrevivência do Neurônio Motor/análise , Proteína 1 de Sobrevivência do Neurônio Motor/genética , Imagem com Lapso de Tempo
15.
J Neurosci ; 28(42): 10451-9, 2008 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-18923022

RESUMO

Although vascular endothelial growth factor-B (VEGF-B) is a homolog of the angiogenic factor VEGF, it has only minimal angiogenic activity, raising the question of whether this factor has other (more relevant) biological properties. Intrigued by the possibility that VEGF family members affect neuronal cells, we explored whether VEGF-B might have a role in the nervous system. Here, we document that the 60 kDa VEGF-B isoform, VEGF-B(186), is a neuroprotective factor. VEGF-B(186) protected cultured primary motor neurons against degeneration. Mice lacking VEGF-B also developed a more severe form of motor neuron degeneration when intercrossed with mutant SOD1 mice. The in vitro and in vivo effects of VEGF-B(186) were dependent on the tyrosine kinase activities of its receptor, Flt1, in motor neurons. When delivered intracerebroventricularly, VEGF-B(186) prolonged the survival of mutant SOD1 rats. Compared with a similar dose of VEGF, VEGF-B(186) was safer and did not cause vessel growth or blood-brain barrier leakiness. The neuroprotective activity of VEGF-B, in combination with its negligible angiogenic/permeability activity, offers attractive opportunities for the treatment of neurodegenerative diseases.


Assuntos
Neurônios Motores/metabolismo , Degeneração Neural/metabolismo , Fator B de Crescimento do Endotélio Vascular/fisiologia , Receptor 1 de Fatores de Crescimento do Endotélio Vascular/fisiologia , Esclerose Amiotrófica Lateral/genética , Esclerose Amiotrófica Lateral/metabolismo , Animais , Humanos , Ligantes , Camundongos , Camundongos Endogâmicos C57BL , Camundongos Knockout , Camundongos Transgênicos , Neurônios Motores/patologia , Degeneração Neural/genética , Degeneração Neural/patologia , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Isoformas de Proteínas/fisiologia , Ratos , Ratos Sprague-Dawley , Ratos Wistar , Superóxido Dismutase , Superóxido Dismutase-1 , Fator B de Crescimento do Endotélio Vascular/genética , Fator B de Crescimento do Endotélio Vascular/metabolismo , Receptor 1 de Fatores de Crescimento do Endotélio Vascular/biossíntese , Receptor 1 de Fatores de Crescimento do Endotélio Vascular/genética
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