RESUMO
Adding to the versatile class of ionic liquids, we report the detailed structure and property analysis of a new class of asymmetrically substituted imidazolium salts, offering interesting thermal characteristics, such as liquid crystalline behavior, polymorphism or glass transitions. A scalable general synthetic procedure for N-polyaryl-N'-alkyl-functionalized imidazolium salts with para-substituted linker (L) moieties at the aryl chain, namely [LPhm ImH R]+ (L=Br, CN, SMe, CO2 Et, OH; m=2, 3; R=C12 , PEGn ; n=2, 3, 4), was developed. These imidazolium salts were studied by single-crystal X-ray diffraction (SC-XRD), NMR spectroscopy and thermochemical methods (DSC, TGA). Furthermore, these imidazolium salts were used as N-heterocyclic carbene (NHC) ligand precursors for mononuclear, first-row transition metal complexes (MnII , FeII , CoII , NiII , ZnII , CuI , AgI , AuI ) and for the dinuclear Ti-supported Fe-NHC complex [(OPy)2 Ti(OPh2 ImC12 )2 (FeI2 )] (OPy=pyridin-2-ylmethanolate). The complexes were studied concerning their structural and magnetic behavior via multi-nuclear NMR spectroscopy, SC-XRD analyses, variable temperature and field-dependent (VT-VF) SQUID magnetization methods, X-band EPR spectroscopy and, where appropriate, zero-field 57 Fe Mössbauer spectroscopy.
RESUMO
Lipid nanoparticles (LNPs) produced by antisolvent precipitation (ASP) are used in formulations for mRNA drug delivery. The mesoscopic structure of such complex multicomponent and polydisperse nanoparticulate systems is most relevant for their drug delivery properties, medical efficiency, shelf life, and possible side effects. However, the knowledge on the structural details of such formulations is very limited. Essentially no such information is publicly available for pharmaceutical dispersions approved by numerous medicine agencies for the use in humans and loaded with mRNA encoding a mimic of the spike protein of the severe acute respiratory syndrome coronavirus type 2 (SARS-CoV-2) as, e.g., the Comirnaty formulation (BioNTech/Pfizer). Here, we present a simple preparation method to mimic the Comirnaty drug-free LNPs including a comparison of their structural properties with those of Comirnaty. Strong evidence for the liquid state of the LNPs in both systems is found in contrast to the designation of the LNPs as solid lipid nanoparticles by BioNTech. An exceptionally detailed and reliable structural model for the LNPs i.a. revealing their unexpected narrow size distribution will be presented based on a combined small-angle X-ray scattering and photon correlation spectroscopy (SAXS/PCS) evaluation method. The results from this experimental approach are supported by light microscopy, 1H NMR spectroscopy, Raman spectroscopy, cryogenic electron microscopy (cryoTEM), and simultaneous SAXS/SANS studies. The presented results do not provide direct insights on particle formation or dispersion stability but should contribute significantly to better understanding the LNP drug delivery process, enhancing their medical benefit, and reducing side effects.
Assuntos
Vacina BNT162 , Nanopartículas , Humanos , Lipídeos/química , RNA Mensageiro/genética , Espalhamento a Baixo Ângulo , Difração de Raios X , Lipossomos , Nanopartículas/química , RNA Interferente Pequeno/genéticaRESUMO
Isolated active sites have great potential to be highly efficient and stable in heterogeneous catalysis, while enabling low costs due to the low transition metal content. Herein, we present results on the synthesis, first catalytic trials, and characterization of the Ga9Rh2 phase and the hitherto not-studied Ga3Rh phase. We used XRD and TEM for structural characterization, and with XPS, EDX we accessed the chemical composition and electronic structure of the intermetallic compounds. In combination with catalytic tests of these phases in the challenging propane dehydrogenation and by DFT calculations, we obtain a comprehensive picture of these novel catalyst materials. Their specific crystallographic structure leads to isolated Rhodium sites, which is proposed to be the decisive factor for the catalytic properties of the systems.
RESUMO
The activity of an yttrium alkoxide complex supported by a ferrocene-based ligand was controlled using redox reagents during the ring-opening polymerization of L-lactide. The oxidized complex was characterized by X-ray crystallography and (1)H NMR, XANES, and Mössbauer spectroscopy. Switching in situ between the oxidized and reduced yttrium complexes resulted in a change in the rate of polymerization of L-lactide. Synthesized polymers were analyzed by gel permeation chromatography. Polymerization of trimethylene carbonate was also performed with the reduced and oxidized forms of an indium alkoxide complex. The indium system showed the opposite behavior to that of yttrium, revealing a metal-based dependency on the rate of polymerization.
RESUMO
The four-coordinate iron(II) phosphoraniminato complex PhB(MesIm)(3)Fe-NâPPh(3) undergoes an S = 0 to S = 2 spin transition with T(C) = 81 K, as determined by variable-temperature magnetic measurements and Mössbauer spectroscopy. Variable-temperature single-crystal X-ray diffraction revealed that the S = 0 to S = 2 transition is associated with an increase in the Fe-C and Fe-N bond distances and a decrease in the N-P bond distance. These structural changes have been interpreted in terms of electronic structure theory.
RESUMO
Two series of Schiff base metal complexes were investigated, where each series was supported by an ancillary ligand incorporating a ferrocene backbone and different N=X functionalities. One ligand is based on an imine, while the other is based on an iminophosphorane group. Cerium(IV), cerium(III), and yttrium(III) alkoxide complexes supported by the two ligands were synthesized. All metal complexes were characterized by cyclic voltammetry. Additionally, NMR, Mössbauer, X-ray absorption near-edge structure (XANES), and absorption spectroscopies were used. The experimental data indicate that iron remains in the +2 oxidation state and that cerium(IV) does not engage in a redox behavior with the ancillary ligand.
Assuntos
Cério/química , Quelantes/química , Compostos Ferrosos/química , Compostos Organometálicos/química , Óxidos/química , Ítrio/química , Cristalografia por Raios X , Ligantes , Metalocenos , Modelos Moleculares , Estrutura Molecular , Compostos Organometálicos/síntese química , EstereoisomerismoRESUMO
At-level and above-level hypersensitivity was assessed in patients with chronic complete thoracic spinal cord injury (SCI). Patients were classified using somatosensory mapping (brush, cold, pinprick) and assigned into 2 groups (ie, patients with at-level hypersensitivity [SCIHs, n = 8] and without at-level hypersensitivity [SCINHs, n = 7]). Gender and age-matched healthy subjects served as controls. Quantitative sensory testing (QST), electrically- and histamine-induced pain and itch, laser Doppler imaging, and laser-evoked potentials (LEP) were recorded at-level and above-level in SCI-patients. Six of 8 SCIHs, but 0 of 7 SCINHs patients suffered from neuropathic below-level pain. Clinical sensory mapping revealed spreading of hypersensitivity to more cranial areas (above-level) in 3 SCIHs. Cold pain threshold measures confirmed clinical hypersensitivity at-level in SCIHs. At-level and above-level hypersensitivity to electrical stimulation did not differ significantly between SCIHs and SCINHs. Mechanical allodynia, cold, and pin-prick hypersensitivity did not relate to impaired sensory function (QST), axon reflex flare, or LEPs. Clinically assessed at-level hypersensitivity was linked to below-level neuropathic pain, suggesting neuronal hyperexcitability contributes to the development of neuropathic pain. However, electrically evoked pain was not significantly different between SCI patients. Thus, SCI-induced enhanced excitability of nociceptive processing does not necessarily lead to neuropathic pain. QST and LEP revealed no crucial role of deafferentation for hypersensitivity development after SCI. PERSPECTIVE: At-level hypersensitivity after complete thoracic SCI is associated with neuropathic below-level pain if evoked by clinical sensory stimuli. QST, LEP, and electrically-induced axon reflex flare sizes did not indicate somatosensory deafferentation in SCIHs.
Assuntos
Potenciais Somatossensoriais Evocados/fisiologia , Hipersensibilidade/etiologia , Limiar da Dor/fisiologia , Traumatismos da Medula Espinal/complicações , Adulto , Estudos de Casos e Controles , Eletroencefalografia , Feminino , Histamina/farmacologia , Agonistas dos Receptores Histamínicos/farmacologia , Humanos , Fluxometria por Laser-Doppler , Masculino , Pessoa de Meia-Idade , Transtornos do Humor/etiologia , Condução Nervosa/fisiologia , Exame Neurológico , Medição da Dor , Percepção da Dor , Fatores de Tempo , Estimulação Elétrica Nervosa Transcutânea , Adulto JovemRESUMO
Antidepressants in the treatment of neuropathic pain are thought to partially exert their effect by inhibition of serotonin (5-HT) reuptake and thus activation of central antinociceptive pathways. Mice deficient for the 5-HT transporter (5-HTT-/- mice) are regarded as a model of lifelong treatment with a serotonin reuptake inhibitor. Here we investigated 5-HTT-/- mice and compared their pain-related behavior after a unilateral chronic constrictive sciatic nerve injury (CCI) with that of wild-type littermates. Wild-type mice reproducibly developed ipsilateral thermal hyperalgesia and mechanical allodynia after CCI. 5-HTT-/- mice did not develop thermal hyperalgesia, but showed bilateral mechanical allodynia after the nerve injury. 5-HT levels as measured with HPLC increased after CCI in the injured nerve in both genotypes and decreased in the lumbar spinal cord in wild-type mice. 5-HTT-/- mice had significantly lower 5-HT concentrations than wild-type mice in all tissues investigated. Thus, in 5-HTT-/- mice, reduced 5-HT levels in the injured peripheral nerves correlate with diminished behavioral signs of thermal hyperalgesia, a pain-related symptom caused by peripheral sensitization. In contrast, bilateral mechanical allodynia, a centrally mediated phenomenon, was associated with decreased spinal 5-HT concentrations in 5-HTT-/- mice and may possibly be caused by a lack of spinal inhibition.
Assuntos
Hiperalgesia/fisiopatologia , Glicoproteínas de Membrana/deficiência , Proteínas de Membrana Transportadoras , Proteínas do Tecido Nervoso , Neuropatia Ciática/fisiopatologia , Glândulas Suprarrenais/metabolismo , Animais , Comportamento Animal , Proteínas de Transporte/genética , Modelos Animais de Doenças , Membro Posterior/fisiopatologia , Temperatura Alta , Ácido Hidroxi-Indolacético/metabolismo , Região Lombossacral , Glicoproteínas de Membrana/genética , Camundongos , Camundongos Knockout , Medição da Dor , Limiar da Dor , Tempo de Reação , Nervo Isquiático/fisiopatologia , Serotonina/metabolismo , Proteínas da Membrana Plasmática de Transporte de Serotonina , Temperatura Cutânea , Medula Espinal/fisiopatologiaRESUMO
Despite being implicated as important intermediates, iron(V) compounds have proven very challenging to isolate and characterize. Here, we report the preparation of the iron(V) nitrido complex, [PhB((t)BuIm)(3)Fe(V)≡N]BAr(F24) (PhB((t)BuIm)(3)(-) = phenyltris(3-tert-butylimidazol-2-ylidene)borato, BAr(F24) = B(3,5-(CF(3))(2)C(6)H(3))(4)(-)), by one electron oxidation of the iron(IV) nitrido precursor. Single-crystal x-ray diffraction of the iron(V) complex reveals a four-coordinate metal ion with a terminal nitrido ligand. Mößbauer and electron paramagnetic resonance spectroscopic characterization, supported by electronic structure calculations, provide evidence for a d(3) iron(V) metal center in a low spin (S = 1/2) electron configuration. Low-temperature reaction of the iron(V) nitrido complex with water under reducing conditions leads to high yields of ammonia with concomitant formation of an iron(II) species.
Assuntos
Compostos Férricos/química , Ferro/química , Fenômenos Químicos , Cristalização , Cristalografia por Raios X , Espectroscopia de Ressonância de Spin Eletrônica , Compostos Férricos/síntese química , Ligantes , Estrutura Molecular , Nitrogênio/química , Oxirredução , Espectroscopia de MossbauerRESUMO
The activity of cerium alkoxide complexes supported by a Schiff base ligand was controlled using redox reagents during the ring-opening polymerization of L-lactide. The rate of L-lactide polymerization was modified by switching in situ between the cerium(III) and cerium(IV) species.
RESUMO
The pro-inflammatory cytokine tumor necrosis factor (TNF)-alpha is an important mediator in hyperalgesia, nerve injury, and regeneration. Here, we used mice deficient of TNF receptor (TNFR) 1 or 2 to investigate the role of TNF signaling via receptor in each pain behavior and nerve de- and regeneration after chronic constriction injury (CCI) of the sciatic nerve. We found an absence of thermal hyperalgesia in mice deficient of TNFR1 and a reduction in mechanical and cold allodynia in mice deficient of TNFR1 or TNFR2 compared with wild-type mice. Nerve conduction studies and nerve pathology did not reveal major differences between genotypes in the temporal course of de- and regeneration of the nerve. We propose that the functional effects of the TNFRs on pain symptoms are independent of effects on nerve regeneration. Furthermore, the differential action of TNF via each of its receptors should be taken into account when considering clinical trials with TNF inhibitors for pain.
Assuntos
Regeneração Nervosa/fisiologia , Dor/fisiopatologia , Receptores Tipo II do Fator de Necrose Tumoral/deficiência , Receptores Tipo I de Fatores de Necrose Tumoral/deficiência , Nervo Isquiático/patologia , Animais , Comportamento Animal , Potenciais Somatossensoriais Evocados , Feminino , Hiperalgesia/fisiopatologia , Camundongos , Camundongos Endogâmicos C57BL , Medição da Dor , Limiar da Dor/fisiologia , Nervo Isquiático/lesõesRESUMO
Proinflammatory cytokines like tumor necrosis factor-alpha (TNF) contribute to Wallerian degeneration by enhancing the adhesion of leukocytes to the endothelium through increased expression of adhesion molecules. Here we studied the influence of TNF and TNF receptors (TNFR) on intercellular adhesion molecule-1 (ICAM-1) and macrophage influx following chronic constrictive injury (CCI) in mice by three different paradigms: (1) C57BL/Wld mice with delayed TNF up-regulation, (2) in vivo inhibition of TNFR1 and TNFR2 by neutralizing antibodies, and (3) three different types of mice with a genetic deficiency for TNFR. C57BL/Wld mice with a delayed macrophage influx had a delayed increase of ICAM-1 compared to control mice. In vivo inhibition of both TNFR significantly impaired macrophage recruitment; however, treatment with anti-TNFR1 antibodies increased endoneurial ICAM-1 expression. In TNFR1 and TNFR1+2, but not TNFR2-deficient mice, endoneurial ICAM-1 expression was significantly reduced, which correlated with prolonged Wallerian degeneration in TNFR1-deficient mice 2 weeks after CCI. Our data support the hypothesis that TNF regulates the expression of ICAM-1 predominantly through TNFR1.