Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 70
Filtrar
Más filtros

Banco de datos
Tipo del documento
Intervalo de año de publicación
1.
Nucleic Acids Res ; 49(13): 7361-7374, 2021 07 21.
Artículo en Inglés | MEDLINE | ID: mdl-34181729

RESUMEN

N6-methyladenosine (m6A) is a common modification on endogenous RNA transcripts in mammalian cells. Technologies to precisely modify the RNA m6A levels at specific transcriptomic loci empower interrogation of biological functions of epitranscriptomic modifications. Here, we developed a bidirectional dCasRx epitranscriptome editing platform composed of a nuclear-localized dCasRx conjugated with either a methyltransferase, METTL3, or a demethylase, ALKBH5, to manipulate methylation events at targeted m6A sites. Leveraging this platform, we specifically and efficiently edited m6A modifications at targeted sites, reflected in gene expression and cell proliferation. We employed the dCasRx epitranscriptomic editor system to elucidate the molecular function of m6A-binding proteins YTHDF paralogs (YTHDF1, YTHDF2 and YTHDF3), revealing that YTHDFs promote m6A-mediated mRNA degradation. Collectively, our dCasRx epitranscriptome perturbation platform permits site-specific m6A editing for delineating of functional roles of individual m6A modifications in the mammalian epitranscriptome.


Asunto(s)
Adenosina/análogos & derivados , Desmetilasa de ARN, Homólogo 5 de AlkB/metabolismo , Metiltransferasas/metabolismo , ARN Mensajero/metabolismo , Adenosina/metabolismo , Desmetilasa de ARN, Homólogo 5 de AlkB/genética , Proteínas Asociadas a CRISPR/genética , Proliferación Celular , Células Cultivadas , Proteína Forkhead Box M1/genética , Proteína Forkhead Box M1/metabolismo , Glioblastoma/genética , Glioblastoma/metabolismo , Glioblastoma/patología , Humanos , Metiltransferasas/genética , Células Madre Neoplásicas/metabolismo , Proteínas Proto-Oncogénicas c-myc/genética , Proteínas Proto-Oncogénicas c-myc/metabolismo , Procesamiento Postranscripcional del ARN , ARN Mensajero/química , Proteínas de Unión al ARN/metabolismo , Proteínas Recombinantes de Fusión/metabolismo , Transcriptoma
2.
J Phys Chem A ; 126(43): 8021-8027, 2022 Nov 03.
Artículo en Inglés | MEDLINE | ID: mdl-36259764

RESUMEN

Calculations and experiments were conducted on ozonolysis of ethyl vinyl ether (EVE) and butyl vinyl ether to identify an unconventional diradical intermediate generated from the O-O bond cleavage of primary ozonide. The diradical can undergo a H atom shifting process that yields keto-hydroperoxide (KHP), the characteristic product that identifies the existence of a diradical intermediate. RRKM-ME calculation, based on the PES at the CCSD(T)/VTZ//M06-2X/6-311++G(2df,2p) level, disclosed branching ratios of ∼0.65% for KHP formation. Using synchrotron-generated vacuum-ultraviolet photoionization mass spectrometry measurements, the formation of KHPs (C4H8O4) in ozonolysis of EVE was confirmed by ion signals of C4H8O4+ (ionization of KHP) and C4H7O2+ (ion fragment from the loss of HO2 from KHP) by comparing their photoionization efficiency spectra with the calculated adiabatic ionization energies and appearance energies.

3.
J Cardiovasc Pharmacol ; 78(5): e749-e760, 2021 11 01.
Artículo en Inglés | MEDLINE | ID: mdl-34321402

RESUMEN

ABSTRACT: Atherosclerosis (AS) is a major risk factor for cardiovascular disease, in which circular RNAs play important regulatory roles. This research aimed to explore the biological role of circular RNA Sterol Regulatory Element Binding Transcription Factor Chaperone (circSCAP) (hsa_circ_0001292) in AS development. Real-time PCR or Western blot assay was conducted to analyze RNA or protein expression. Cell proliferation and apoptosis were analyzed by CCK-8 assay and flow cytometry. The levels of lipid accumulation-associated indicators and oxidative stress factors were detected using commercial kits. The levels of inflammatory cytokines were examined using enzyme-linked immunosorbent assay. Intermolecular interaction was verified by dual-luciferase reporter analysis or RNA pull-down analysis. CircSCAP and phosphodiesterase 3B (PDE3B) levels were elevated, whereas the miR-221-5p level was decreased in patients with AS and oxidized low-density lipoprotein (ox-LDL)-induced THP-1 cells. CircSCAP absence suppressed lipid deposition, inflammation, and oxidative stress in ox-LDL-induced THP-1 cells. MiR-221-5p was a target of circSCAP, and anti-miR-221-5p largely reversed si-circSCAP-induced effects in ox-LDL-induced THP-1 cells. PDE3B was a target of miR-221-5p, and PDE3B overexpression largely counteracted miR-221-5p accumulation-mediated effects in ox-LDL-induced THP-1 cells. NF-κB signaling pathway was regulated by circSCAP/miR-221-5p/PDE3B axis in ox-LDL-induced THP-1 cells. In conclusion, circSCAP facilitated lipid accumulation, inflammation, and oxidative stress in ox-LDL-induced THP-1 macrophages by regulating miR-221-5p/PDE3B axis.


Asunto(s)
Aterosclerosis/enzimología , Fosfodiesterasas de Nucleótidos Cíclicos Tipo 3/biosíntesis , Lipoproteínas LDL/toxicidad , Macrófagos/efectos de los fármacos , MicroARNs/metabolismo , ARN Circular/metabolismo , Apoptosis/efectos de los fármacos , Aterosclerosis/genética , Aterosclerosis/patología , Estudios de Casos y Controles , Proliferación Celular/efectos de los fármacos , Fosfodiesterasas de Nucleótidos Cíclicos Tipo 3/genética , Citocinas/metabolismo , Inducción Enzimática , Femenino , Humanos , Mediadores de Inflamación/metabolismo , Macrófagos/enzimología , Macrófagos/patología , Masculino , MicroARNs/genética , Persona de Mediana Edad , Estrés Oxidativo/efectos de los fármacos , ARN Circular/genética , Transducción de Señal , Células THP-1
4.
Phys Chem Chem Phys ; 23(17): 10456-10467, 2021 May 05.
Artículo en Inglés | MEDLINE | ID: mdl-33890587

RESUMEN

2-Methyl-3-buten-2-ol (MBO232) is a biogenic volatile organic compound (BVOC), and has a large percentage of emission into the atmosphere. The vacuum ultraviolet (VUV) photochemistry of BVOCs is of great importance for atmospheric chemistry. Studies have been carried out on several BVOCs but have not extended to MBO232. In the present report, the photoionization and dissociation processes of MBO232 in the energy range of 8.0-15.0 eV have been studied by tunable VUV synchrotron radiation coupled with a time-of-flight mass spectrometer. By measuring the photoionization spectra, the adiabatic ionization energy (AIE) of MBO232 and the appearance energies (AEs) of the eight identified fragment ions (i.e., C4H7O+, C3H7O+, C5H9+, C3H6O+, CH3CO+, CH3O+, C4H5+, and C3H5+) were determined. High-level quantum chemistry calculations suggest that there are 3 direct channels and 5 indirect channels via transition states and intermediates accountable for these fragments. Among the reaction channels, the direct elimination of CH3 is the most dominant channel and produces the resonance-stabilized radical cation. Most interestingly, our results show that the CH3 selectively migrates towards the cation, which leads to the different indirect channels. The CH3 migration is a rare process in the dissociative photoionization of metal-free organic molecules. We explain the process by molecular orbital calculations and electron localization function analysis and explore the non-conventional dissociation channels via the CH3 roaming mechanism. We further perform kinetics analysis using RRKM theory for the channels of interest. The activation barrier, and rate constants are analyzed for the branching fractions of the products. These results provide important implications for the VUV photochemistry of BVOCs in the atmosphere.

5.
J Phys Chem A ; 125(16): 3316-3326, 2021 Apr 29.
Artículo en Inglés | MEDLINE | ID: mdl-33861064

RESUMEN

To clarify the contentions about dissociative photoionization mechanism of nitrogen dioxide via the a3B2 and b3A2 ionic states, a new threshold photoelectron-photoion coincidence (TPEPICO) velocity imaging has been conducted in the 12.8-14.0 eV energy range at the Hefei Light Source. The fine vibrational-resolved threshold photoelectron spectrum agrees well with the previous measurements. The ro-vibrational distributions of NO+, as the unique fragment ion in the dissociation of NO2+ in specific vibronic levels of a3B2 and b3A2 states, are derived from the recorded TPEPICO velocity images. A "cold" vibrational (v+ = 0) and "hot" rotational population is observed at the a3B2(0,3,0) and (0,4,0) vibronic levels, while the dissociation of NO2+ in b3A2(0,0,0) leads to the NO+ fragment with both hot vibrational and rotational populations. With the aid of the quantum chemical calculations at the time-dependent B3LYP level, minimum energy paths on the potential energy surfaces of the a3B2 and b3A2 states clarify their adiabatic dissociation mechanisms near the thresholds, and this study proposes reliable explanations for the observed internal energy distributions of fragment ions. Additionally, this study provides valuable insights into the application of the classical "impulsive" model on an overall slow dissociation process.

6.
Phys Chem Chem Phys ; 22(24): 13808-13817, 2020 Jun 24.
Artículo en Inglés | MEDLINE | ID: mdl-32538400

RESUMEN

Dissociative ionization of trifluoromethane (CHF3) is investigated in the 13.9-18.0 eV energy range using the threshold photoelectron-photoion coincidence (TPEPICO) technique coupled to a vacuum ultraviolet synchrotron radiation source. Four electronic states of CHF3+, i.e., the X2A1, A2A2, B2E, and C2E states, are populated upon ionization. In this energy range, the parent CHF3+ ions fully dissociate. For the CHF3+ ions in the ground state, the analysis of the time-of-flight profile of the unique CF3+ fragment ions suggests statistical dissociation. For the electronically excited CHF3+ ions, the C-F bond cleavage preferentially occurs to predominantly produce CHF2+ + F. Moreover, all TPEPICO images of the CHF2+ ions exhibit identical patterns, with a weak central spot revealing a previously unobserved statistical decomposition pathway, and the predominant ring in the images documents a fast nonstatistical dissociation channel. The unimolecular decomposition mechanisms of the CHF3+ ions are illuminated with the aid of the one-dimensional potential energy curves along the C-H and C-F coordinates calculated using the time-dependent density-functional theory. Moreover, a comparison of the dissociation dynamics of CHF3+ in these low-lying states with those of CF3Cl+ strongly suggests a substituent effect of chlorine atoms on the binding structure.

7.
Phys Chem Chem Phys ; 21(9): 4998-5005, 2019 Feb 27.
Artículo en Inglés | MEDLINE | ID: mdl-30762039

RESUMEN

The dissociative photoionization of CF3Cl was investigated using threshold photoelectron photoion coincidence (TPEPICO) imaging in the energy range of 12.30-18.50 eV. The coincident time-of-flight mass spectra and three-dimensional time-sliced images of the CF2Cl+ fragment were recorded at a few specific photon energies. Two fragmentation pathways were observed that led to the breakage of the C-Cl and C-F bonds, while the branching ratio elicited an energy-dependent relationship. The CF3+ fragment was dominant in the dissociation of the X2E, A2A' and B2A'' states, while CF2Cl+ became the predominant fragment and its branching ratio remained constant in the energy range associated with the C2E and D2E states. Based on the inflection point in the energy-dependent curve of the fragment branching ratios, the adiabatic ionization energy (IEa) of C2E is suggested to be 15.46 eV. Although the excess energy increased considerably from C2E to D2E, the kinetic energy release distributions (KERDs) of CF2Cl+ were similar. Moreover, the anisotropy parameters ß for the F-loss channel were positive and larger than those for the Cl-loss channel. The calculated F-loss potential energy curves of CF3Cl+ suggested that for the C2E and D2E states, the C-F bond rupture occurred via the internal conversion to the A2A' state followed by the dissociation attributed to the crossing of the barrier along the C-F coordinate. Based on the experimental and theoretical conclusions, the internal conversion is the rate-determining step in the dissociative photoionization of CF3Cl via the C2E and D2E ionic states, irrespective of whether the C-F and C-Cl bonds rupture.

8.
J Phys Chem A ; 123(1): 103-110, 2019 Jan 10.
Artículo en Inglés | MEDLINE | ID: mdl-30501195

RESUMEN

The thermal decomposition of furfural is investigated in a flow tube reactor at 30 Torr by synchrotron vacuum ultraviolet photoionization mass spectrometry (SVUV-PIMS) at temperatures from 1023 to 1273 K. Over 20 kinds of pyrolysis products, including short-lived radicals, stable oxygen-containing compounds, and hydrocarbons, are identified from the scanning photoionization efficiency (PIE) spectra. Vinylketene (CH2═CH-CH═C═O), which has been shown to be an important primary product, is also directly observed. The possible steps of hydrogen atom addition and hydrogen atom abstraction in the thermal decomposition of furfural are studied by theoretical calculations at the CBS-QB3 level. In addition to unimolecular decomposition, hydrogen atom addition followed by ring opening can lead to the production of vinylketene.

9.
J Phys Chem A ; 123(10): 1929-1936, 2019 Mar 14.
Artículo en Inglés | MEDLINE | ID: mdl-30811197

RESUMEN

Criegee intermediates have raised much attention in atmospheric chemistry because of their significance in ozonolysis mechanism. The simplest Criegee intermediate, CH2OO, and its reactions with acrylic acid including cycloadditions and insertions as main entrance channels have been investigated at CCSD(T)/cc-pVTZ//M06-2X/6-31G(d,p) level. Temperature- and pressure-dependent kinetics were predicted by solving the time-dependent master equations based on Rice-Ramsperger-Kassel-Marcus theory using MESS program, with temperatures from 200 to 500 K and pressures from 0.001 to 1000 atm. Variational transition state theory (VTST) was used for barrierless pathways and conventional transition state theory (CTST) for pathways with distinct barriers. Results indicate that hydroperoxymethyl acrylate is the dominant product under atmospheric conditions. The combination of two reactants will reduce the volatility and makes a possible factor that induces formation of secondary organic aerosols, which suggests CH2OO's entangled role in ever-increasing air pollution.

10.
J Neuroinflammation ; 15(1): 347, 2018 Dec 20.
Artículo en Inglés | MEDLINE | ID: mdl-30572907

RESUMEN

BACKGROUND: Neuroinflammation is closely associated with functional outcome in subarachnoid hemorrhage (SAH) patients. Our recent study demonstrated that fluoxetine inhibited NLRP3 inflammasome activation and attenuated necrotic cell death in early brain injury after SAH, while the effects and potential mechanisms of fluoxetine on neuroinflammation after SAH have not been well-studied yet. METHODS: One hundred and fifty-three male SD rats were subjected to the endovascular perforation model of SAH. Fluoxetine (10 mg/kg) was administered intravenously at 6 h after SAH induction. TAK-242 (1.5 mg/kg), an exogenous TLR4 antagonist, was injected intraperitoneally 1 h after SAH. SAH grade, neurological scores, brain water content, Evans blue extravasation, immunofluorescence/TUNEL staining, quantitative real-time polymerase chain reaction (qRT-PCR), and western blot were performed. RESULTS: Fluoxetine administration attenuated BBB disruption, brain edema, and improved neurological function after SAH. In addition, fluoxetine alleviated the number of Iba-1-positive microglia/macrophages, neutrophil infiltration, and cell death. Moreover, fluoxetine reduced the levels of pro-inflammatory cytokines, downregulated the expression of TLR4 and MyD88, and promoted the nuclear translocation of NF-κB p65, which were also found in rats with TAK-242 administration. Combined administration of fluoxetine and TAK-242 did not enhance the neuroprotective effects of fluoxetine. CONCLUSION: Fluoxetine attenuated neuroinflammation and improved neurological function in SAH rats. The potential mechanisms involved, at least in part, TLR4/MyD88/NF-κB signaling pathway.


Asunto(s)
Lesiones Encefálicas/tratamiento farmacológico , Proteínas de Unión al Calcio/metabolismo , Fluoxetina/uso terapéutico , Proteínas de Microfilamentos/metabolismo , Fármacos Neuroprotectores/uso terapéutico , Transducción de Señal/efectos de los fármacos , Receptor Toll-Like 4/metabolismo , Animales , Barrera Hematoencefálica/efectos de los fármacos , Barrera Hematoencefálica/fisiopatología , Edema Encefálico/tratamiento farmacológico , Edema Encefálico/etiología , Lesiones Encefálicas/etiología , Lesiones Encefálicas/mortalidad , Lesiones Encefálicas/patología , Citocinas/genética , Citocinas/metabolismo , Modelos Animales de Enfermedad , Regulación de la Expresión Génica/efectos de los fármacos , Factor Estimulante de Colonias de Granulocitos/metabolismo , Interleucina-3/metabolismo , Masculino , Factor 88 de Diferenciación Mieloide/metabolismo , FN-kappa B/metabolismo , Ratas , Ratas Sprague-Dawley , Proteínas Recombinantes de Fusión/metabolismo , Hemorragia Subaracnoidea/complicaciones , Hemorragia Subaracnoidea/mortalidad , Sulfonamidas/uso terapéutico
11.
Phys Chem Chem Phys ; 20(10): 7351-7360, 2018 Mar 07.
Artículo en Inglés | MEDLINE | ID: mdl-29485656

RESUMEN

Water molecules, which serve as both hydrogen bond donors and acceptors, have been found to influence the conformational landscape of gas-phase phenyl-ß-d-glucopyranoside. Herein, tetrahydrofurfuryl alcohol (THFA), a sugar-like molecule without chromophores (e.g. phenyl-substitution), was used as the model sugar molecule for exploring the behaviour of water molecules on the conformational landscape of a pentose sugar such as deoxyribose. We used mass selected infrared-vacuum ultraviolet (IR-VUV) (118 nm) spectroscopy to investigate the hydrated neutral THFA and its complex cation in a supersonic jet. High level density functional theory (DFT) calculations were performed to ascertain the experimental results. The results revealed that the water molecule tends to insert into the twisted conformer at a position where two stronger intermolecular hydrogen bonds were formed by breaking the weak intramolecular interactions. We found that the twisted conformer of the hydrated neutral THFA complex is more stable than the envelope conformation, while the latter is more stable for the THFA molecule. However, the conformational landscape of the hydrated THFA complex cation did not significantly change on microsolvation with water molecules. These results indicated that the dominant structural landscape of the hydrated cationic complex is the twisted configuration with a trans-hydroxymethyl group. This finding provides valuable insight into the microsolvation of gas-phase sugar molecules.

12.
Phys Chem Chem Phys ; 20(7): 4917-4925, 2018 Feb 14.
Artículo en Inglés | MEDLINE | ID: mdl-29384156

RESUMEN

The dissociative photoionization of CF3Cl was investigated in the photon energy range of 12.30-18.50 eV. The low-lying electronic states of CF3Cl+ cations were prepared by the method of threshold photoelectron-photoion coincidence (TPEPICO). The threshold photoelectron spectrum and the coincident time-of-flight mass spectra at the specific photon energies were recorded. Only a CF3+ fragment was observed at lower energy, while a CF2Cl+ fragment appeared for C2E and D2E states. As Cl-loss from the ground ionic state is statistical, the total kinetic energy release distribution (KERD) is represented as a Boltzmann profile, and a 0 K appearance energy of AP0 =12.79 ± 0.02 eV is derived from the statistical modelling of the breakdown diagram from 12.60 to 12.85 eV without taking into account the kinetic shift. For the A2A1 and B2A2 states of CF3Cl+ cations, the total KERDs are bimodal, where a parallel faster dissociation appears together with the statistical distribution. At higher energies like the C2E and D2E ionic states, a bimodal distribution similar to that of the A2A1 and B2A2 states is also observed for the KERD. With the aid of the calculated Cl-loss potential energy curves, the dissociative mechanisms of internal energy-selected CF3Cl+ cations are proposed.

13.
J Phys Chem A ; 121(25): 4743-4753, 2017 Jun 29.
Artículo en Inglés | MEDLINE | ID: mdl-28581756

RESUMEN

The dissociative photoionization of vinyl chloride (C2H3Cl) in the 11.0-14.2 eV photon energy range was investigated using threshold photoelectron photoion coincidence (TPEPICO) velocity map imaging. Three electronic states, namely, A2A', B2A″, and C2A', of the C2H3Cl+ cation were prepared, and their dissociation dynamics were investigated. A unique fragment ion, C2H3+, was observed within the excitation energy range. TPEPICO three-dimensional time-sliced velocity map images of C2H3+ provided the kinetic energy release distributions (KERD) and anisotropy parameters in dissociation of internal-energy-selected C2H3Cl+ cations. At 13.14 eV, the total KERD showed a bimodal distribution consisting of Boltzmann- and Gaussian-type components, indicating a competition between statistical and non-statistical dissociation mechanisms. An additional Gaussian-type component was found in the KERD at 13.65 eV, a center of which was located at a lower kinetic energy. The overall dissociative photoionization mechanisms of C2H3Cl+ in the B2A″ and C2A' states are proposed based on time-dependent density functional theory calculations of the Cl-loss potential energy curves. Our results highlight the inconsistency of previous conclusions on the dissociation mechanism of C2H3Cl+.

14.
Phys Chem Chem Phys ; 18(19): 13554-63, 2016 05 11.
Artículo en Inglés | MEDLINE | ID: mdl-27141555

RESUMEN

Photoionization and dissociation of the 1-propanol dimer and subsequent fragmentations have been investigated by synchrotron vacuum ultraviolet (VUV) photoionization mass spectrometry and theoretical calculations. Besides the protonated monomer cation (C3H7OH)·H(+) (m/z = 61) and Cα-Cß bond cleavage fragment CH2O·(C3H7OH)H(+) (m/z = 91), the measured mass spectrum at an incident photon energy of 13 eV suggests a new dissociation channel resulting in the formation of the (C3H7OH)·H(+)·(C2H5OH) (m/z = 107) fragment. The appearance energies of the fragments (C3H7OH)·H(+), CH2O·(C3H7OH)H(+) and (C3H7OH)·H(+)·(C2H5OH) are measured at 10.05 ± 0.05 eV, 9.48 ± 0.05 eV, and 12.8 ± 0.1 eV, respectively, by scanning photoionization efficiency (PIE) spectra. The 1-propanol ion fragments as a function of VUV photon energy were interpreted with the aid of theoretical calculations. In addition to O-H and Cα-Cß bond cleavage, a new dissociation channel related to Cß-Cγ bond cleavage opens. In this channel, molecular rearrangement (proton transfer and hydrogen transfer after surmounting an energy barrier) gives rise to the generated complex, which then dissociates to produce the mixed propanol/ethanol proton bound cation (C3H7OH)·H(+)·(C2H5OH). This new dissociation channel has not been reported in previous studies of ethanol and acetic acid dimers. The photoionization and dissociation processes of the 1-propanol dimer are described in the photon energy range of 9-15 eV.

15.
J Chem Phys ; 142(2): 024306, 2015 Jan 14.
Artículo en Inglés | MEDLINE | ID: mdl-25591352

RESUMEN

While methyl transfer is well known to occur in the enzyme- and metal-catalyzed reactions, the methyl transfer in the metal-free organic molecules induced by the photon ionization has been less concerned. Herein, vacuum ultraviolet single photon ionization and dissociation of ethanol dimer are investigated with synchrotron radiation photoionization mass spectroscopy and theoretical methods. Besides the protonated clusters cation (C2H5OH)⋅H(+) (m/z = 47) and the ß-carbon-carbon bond cleavage fragment CH2O⋅(C2H5OH)H(+) (m/z = 77), the measured mass spectra revealed that a new fragment (C2H5OH)⋅(CH3)(+) (m/z = 61) appeared at the photon energy of 12.1 and 15.0 eV, where the neutral dimer could be vertically ionized to higher ionic state. Thereafter, the generated carbonium ions are followed by a Wagner-Meerwein rearrangement and then dissociate to produce this new fragment, which is considered to generate after surmounting a few barriers including intra- and inter-molecular methyl migrations by the aid of theoretical calculations. The appearance energy of this new fragment is measured as 11.55 ± 0.05 eV by scanning photoionization efficiency curve. While the signal intensity of fragment m/z = 61 starts to increase, the fragments m/z = 47 and 77 tend to slowly incline around 11.55 eV photon energy. This suggests that the additional fragment channels other than (C2H5OH)⋅H(+) and CH2O⋅(C2H5OH)H(+) have also been opened, which consume some dimer cations. The present report provides a clear description of the photoionization and dissociation processes of the ethanol dimer in the range of the photon energy 12-15 eV.


Asunto(s)
Dimerización , Etanol/química , Procesos Fotoquímicos , Sincrotrones , Rayos Ultravioleta , Modelos Moleculares , Conformación Molecular
16.
J Phys Chem A ; 118(34): 7096-103, 2014 Aug 28.
Artículo en Inglés | MEDLINE | ID: mdl-25080068

RESUMEN

In present report, we explored hyperconjugation effects on the site- and bond-selective dissociation processes of cationic ethanol conformers by the use of theoretical methods (including configuration optimizations, natural bond orbital (NBO) analysis, and density of states (DOS) calculations, etc.) and the tunable synchrotron vacuum ultraviolet (SVUV) photoionization mass spectrometry. The dissociative mechanism of ethanol cations, in which hyperconjugative interactions and charge-transfer processes were involved, was proposed. The results reveal Cα-H and C-C bonds are selectively weakened, which arise as a result of the hyperconjugative interactions σCα-H → p in the trans-conformer and σC-C → p in gauche-conformer after being ionized. As a result, the selective bond cleavages would occur and different fragments were observed.


Asunto(s)
Cationes/química , Etanol/química , Electrones , Espectrometría de Masas , Modelos Químicos
17.
J Chem Phys ; 140(4): 044312, 2014 Jan 28.
Artículo en Inglés | MEDLINE | ID: mdl-25669528

RESUMEN

Dissociative photoionization of methyl bromide (CH3Br) in an excitation energy range of 10.45-16.90 eV has been investigated by using threshold photoelectron-photoion coincidence (TPEPICO) velocity imaging. The coincident time-of-flight mass spectra indicate that the ground state X(2)E of CH3Br(+) is stable, and both A(2)A1 and B(2)E ionic excited states are fully dissociative to produce the unique fragment ion of CH3 (+). From TPEPICO 3D time-sliced velocity images of CH3 (+) dissociated from specific state-selected CH3Br(+) ion, kinetic energy release distribution (KERD) and angular distribution of CH3 (+) fragment ion are directly obtained. Both spin-orbit states of Br((2)P) atom can be clearly observed in fast dissociation of CH3Br(+)(A(2)A1) ion along C-Br rupture, while a KERD of Maxwell-Boltzmann profile is obtained in dissociation of CH3Br(+)(B(2)E) ion. With the aid of the re-calculated potential energy curves of CH3Br(+) including spin-orbit coupling, dissociation mechanisms of CH3Br(+) ion in A(2)A1 and B(2)E states along C-Br rupture are revealed. For CH3Br(+)(A(2)A1) ion, the CH3 (+) + Br((2)P1/2) channel is occurred via an adiabatic dissociation by vibration, while the Br((2)P3/2) formation is through vibronic coupling to the high vibrational level of X(2)E state followed by rapid dissociation. C-Br bond breaking of CH3Br(+)(B(2)E) ion can occur via slow internal conversion to the excited vibrational level of the lower electronic states and then dissociation.

18.
Eur J Mass Spectrom (Chichester) ; 20(6): 419-28, 2014.
Artículo en Inglés | MEDLINE | ID: mdl-25905866

RESUMEN

We investigated the photoionization and dissociation photoionization of the ß-pinene molecular using time-of-flight mass spectrometry with a tunable vacuum ultraviolet source in the region from 8.00eV to 15.50eV. The experimental ionization energy (IE) value is 8.60eV using electron impact as the ionization source which is not in good agreement with theoretical value (8.41 eV) with a G3MP2 method. We obtained the accurate IE of ß-pinene (8.45 ± 0.03eV) derived from the efficiency spectrum which is in good agreement with the theoretical value (8.38eV) of the CBS-QB3 method. We elucidated the dissociation pathways of primary fragment ions from the ß-pinene cation on the basis of experimental observations in combination with theoretical calculations. Most of the dissociation pathways occur via a rearrangement reaction prior to dissociation. We also determined the structures of the transition states and intermediates for those isomerization processes.

19.
J Craniofac Surg ; 25(4): 1441-7, 2014 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-24911608

RESUMEN

BACKGROUND: The choice of carotid artery endarterectomy (CEA) or carotid artery stenting (CAS), as surgical and interventional treatment of atherosclerotic carotid stenosis, respectively, has been controversial in decades, especially for asymptomatic patients with carotid stenosis. Age and the diameter of impaired carotid artery might be 2 important factors to decide whether CEA or CAS should be performed. Besides, contrast-enhanced ultrasound (CEUS) has been confirmed as an effective method to predict the risk of stroke by classifying the carotid plaque into 4 grades. The role of CEUS in the choice of CEA or CAS still remains unclear. METHODS: A retrospective analysis of 38 patients who underwent CEA with primary closure and 36 patients who underwent CAS in our hospital from October 2008 to January 2013 is conducted. Preoperative CEUS was performed to all patients, and data were collected and analyzed. All CEAs were performed with transverse incision. RESULTS: The hospital stay was longer for the endarterectomy group than the stenting group (15.39 versus 10.91 d, P < 0.001), with an approximately two-third reduction of hospital costs (¥23686.21 versus ¥60855.34, P < 0.001). The overall incidence of perioperative complications in the endarterectomy group was 7.9%, with no statistically significant difference in the group with internal carotid artery greater than or equal to 5 mm and in the group with internal carotid artery less than 5 mm (9.1% versus 6.3%, P = 0.75). No restenosis occurred in either of the subgroups during the follow-up. In patients older than 70 years, the perioperative complications were 0% in CEA and 10.53% in CAS (P = 0.42); the long-term restenosis was 0% in CEA and 5.26% in CAS (P = 0.67). In patients younger than 70 years, the perioperative complications were 11.5% in CEA and 23.53% in CAS (P = 0.31); the long-term restenosis was 0% in CEA and 0% in CAS (P > 0.01). For patients with grade 4 plaque in CEUS, the incidence of adverse events in the CAS group was significantly higher than that in the CEA group (7.14% versus 55.56%, P < 0.05). CONCLUSIONS: There were no significant differences in perioperative complications or restenosis rate between the CAS group and the CEA group in this study. Neither the diameter of impaired carotid artery or age could be considered as an indication of applying CEA or CAS. However, CEUS might be used as a perioperative assessment method to decide whether CEA or CAS should be performed to different patients. The higher the grade of plaque enhancement, the higher the risk of adverse events and restenosis for CAS might occur.


Asunto(s)
Estenosis Carotídea/terapia , Endarterectomía Carotidea/métodos , Stents , Anciano , Estenosis Carotídea/economía , Análisis Costo-Beneficio , Endarterectomía Carotidea/economía , Femenino , Humanos , Tiempo de Internación/economía , Masculino , Persona de Mediana Edad , Complicaciones Posoperatorias/economía , Complicaciones Posoperatorias/etiología , Estudios Retrospectivos , Stents/economía
20.
Cancer Immunol Res ; 12(2): 232-246, 2024 02 02.
Artículo en Inglés | MEDLINE | ID: mdl-38091354

RESUMEN

Isocitrate dehydrogenase (IDH)-wild-type (WT) high-grade gliomas, especially glioblastomas, are highly aggressive and have an immunosuppressive tumor microenvironment. Although tumor-infiltrating immune cells are known to play a critical role in glioma genesis, their heterogeneity and intercellular interactions remain poorly understood. In this study, we constructed a single-cell transcriptome landscape of immune cells from tumor tissue and matching peripheral blood mononuclear cells (PBMC) from IDH-WT high-grade glioma patients. Our analysis identified two subsets of tumor-associated macrophages (TAM) in tumors with the highest protumorigenesis signatures, highlighting their potential role in glioma progression. We also investigated the T-cell trajectory and identified the aryl hydrocarbon receptor (AHR) as a regulator of T-cell dysfunction, providing a potential target for glioma immunotherapy. We further demonstrated that knockout of AHR decreased chimeric antigen receptor (CAR) T-cell exhaustion and improved CAR T-cell antitumor efficacy both in vitro and in vivo. Finally, we explored intercellular communication mediated by ligand-receptor interactions within the tumor microenvironment and PBMCs and revealed the unique cellular interactions present in the tumor microenvironment. Taken together, our study provides a comprehensive immune landscape of IDH-WT high-grade gliomas and offers potential drug targets for glioma immunotherapy.


Asunto(s)
Neoplasias Encefálicas , Glioma , Humanos , Isocitrato Deshidrogenasa/genética , Leucocitos Mononucleares/patología , Perfilación de la Expresión Génica , Mutación , Microambiente Tumoral/genética
SELECCIÓN DE REFERENCIAS
DETALLE DE LA BÚSQUEDA