Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 10 de 10
Filtrar
Mais filtros










Base de dados
Intervalo de ano de publicação
1.
Mol Med Rep ; 20(3): 2294-2302, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31322186

RESUMO

All­trans retinoic acid (ATRA) can protect fibroblasts against ultraviolet (UV)­induced oxidative damage, however, its underlying molecular mechanism is still unclear. The present study aimed to investigate the role of 3­hydroxy­3­methylglutaryl reductase degradation (Hrd1) in the protective effect of ATRA on human skin fibroblasts exposed to UV. The expression of Hrd1 in human or mice skin was assessed by immunohistochemistry (IHC) staining and western blot analysis. Hrd1 siRNA (si­Hrd1) and Hrd1 recombinant adenoviruses (Ad­Hrd1) were used to downregulate and upregulate Hrd1 expression in fibroblasts, respectively. The interaction between Hrd1 and NF­E2­related factor 2 (Nrf2) was assessed by co­immunoprecipitation (co­IP) and immunofluorescence analysis. The results revealed that Hrd1 expression was increased but Nrf2 expression was decreased in UV­exposed human skin fibroblasts. In addition, ATRA could reverse the increase of Hrd1 expression induced by UV radiation in vivo and in vitro. ATRA or knockdown of Hrd1 could increase Nrf2 expression in fibroblasts exposed to UV radiation, and Hrd1 could directly interact with Nrf2 in skin fibroblasts. Notably, overexpression of Hrd1 abolished the protective effect of ATRA on the UV­induced decrease of Nrf2 expression, the production of reactive oxygen species (ROS) and the decrease of cell viability. In conclusion, the present data demonstrated that ATRA protected skin fibroblasts against UV­induced oxidative damage through inhibition of E3 ligase Hrd1.


Assuntos
Fibroblastos/efeitos dos fármacos , Protetores contra Radiação/farmacologia , Tretinoína/farmacologia , Ubiquitina-Proteína Ligases/genética , Raios Ultravioleta/efeitos adversos , Adulto , Animais , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos da radiação , Regulação para Baixo/efeitos dos fármacos , Regulação para Baixo/efeitos da radiação , Feminino , Fibroblastos/citologia , Fibroblastos/metabolismo , Fibroblastos/efeitos da radiação , Humanos , Masculino , Camundongos Endogâmicos BALB C , Pessoa de Meia-Idade , Estresse Oxidativo/efeitos dos fármacos , Estresse Oxidativo/efeitos da radiação , Espécies Reativas de Oxigênio/metabolismo , Pele/citologia , Pele/efeitos dos fármacos , Pele/metabolismo , Pele/efeitos da radiação , Ubiquitina-Proteína Ligases/análise , Ubiquitina-Proteína Ligases/metabolismo
2.
Chemosphere ; 150: 329-340, 2016 May.
Artigo em Inglês | MEDLINE | ID: mdl-26921586

RESUMO

Singlet and triplet potential energy surfaces for the atmospheric ozonation of trans-2-chlorovnyldichloroarsine (lewisite) are investigated theoretically. Optimizations of the reactants, products, intermediates and transition states are carried out at the BHandHLYP/6-311+G(d,p) level. Single point energy calculations are performed at the CCSD(T)/6-311+G(d,p) level based on the optimized structures. The detailed mechanism is presented and discussed. Various possible H (or Cl)-abstraction and C (or As)-addition/elimination pathways are considered. The results show that the As-addition/elimination is more energetically favorable than the other mechanisms. Rice-Ramsperger-Kassel-Marcus (RRKM) theory is used to compute the rate constants over the possible atmospheric temperature range of 200-3000 K and the pressure range of 10(-8)-10(9) Torr. The calculated rate constant is in good agreement with the available experimental data. The total rate coefficient shows positive temperature dependence and pressure independence. The modified three-parameter Arrhenius expressions for the total rate coefficient and individual rate coefficients are represented. Calculation results show that major product is CHClCHAs(OOO)Cl2 (s-IM3) at the temperature below 600 K and O2 + CHClCHAsOCl2 (s-P9) play an important role at the temperature between 600 and 3000 K. Time-dependent DFT (TD-DFT) calculations indicate that CHCl(OOO)CHAsCl2 (s-IM3) and CHOAsCl2 (s-P5) can take photolysis easily in the sunlight. Due to the absence of spectral information for arsenide, computational vibrational spectra of the important intermediates and products are also analyzed to provide valuable evidence for subsequent experimental identification.


Assuntos
Poluentes Atmosféricos/análise , Arsenicais/análise , Substâncias para a Guerra Química/análise , Modelos Teóricos , Ozônio/química , Poluentes Atmosféricos/química , Poluentes Atmosféricos/efeitos da radiação , Arsenicais/química , Arsenicais/efeitos da radiação , Substâncias para a Guerra Química/química , Substâncias para a Guerra Química/efeitos da radiação , Cinética , Fotólise , Pressão , Temperatura Ambiente
3.
Int J Clin Exp Med ; 8(8): 14054-9, 2015.
Artigo em Inglês | MEDLINE | ID: mdl-26550367

RESUMO

BACKGROUND: To evaluate the impact of different hypoglycemic drugs on exercise-mediated blood glucose (BG) reduction. METHODS: One-hundred and five retirees who were diagnosed with type 2 diabetes mellitus (T2DM) within a two-year period were included in this study. The participants were instructed to walk for 20 to 30 minutes at a moderate-speed (4.0 to 4.5 km/h) after breakfast. Blood pressure and fingertip BG were measured before and after walking. RESULTS: The rate of BG reduction was significantly higher in all exercise groups when compared to that of non-exercised patients. Among all groups, BG declined the most in the un-medicated group, while the lowest BG reduction was observed in the acarbose group. Surprisingly, the BG reduction in acarbose group was significantly lower when compared with non-acarbose groups (P<0.0001). Interestingly, after further correcting for sex, age, BMI, diabetes history, walking time, walking speed and walking distance, only age was found to be an influencing factor (t=-3.304, P=0.001). Pearson correlation of age and BG reduction showed that correlation coefficient of age was only 0.183 and revealed no statistical significance. CONCLUSIONS: Walking at a moderate speed for 20 to30 minutes after breakfast provided a beneficial BG reduction effect in elderly T2DM patients. Among the medicated groups, the smallest BG reduction rate was observed in patients taking acarbose. We suggest that acarbose might influence hypoglycemic effects of exercise. The results of this study will be helpful for determining the best clinical usage of hypoglycemic medications in elderly T2DM patients.

4.
J Mol Graph Model ; 59: 31-9, 2015 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-25899446

RESUMO

The heterocyclic urea of deazapterin (DeAPa) and its protomeric conformers (b, c) with different substituents are selected as the building block for a series of dimers in different configurations. The stabilities of all dimers in various conditions have been investigated by density functional theory. Homodimer of b has more stability than other dimers. Topological analyses certify the coexistence of intermolecular with intramolecular H-bonds. Investigations into frequency demonstrate that all H-bonds show an evident red shift in their stretching vibrational frequencies. Electron donating substituents can provide favorable free energies of the dimer. Solvent effect computations suggest that the dimerization can be favored in weakly polar solvents, such as toluene and chloroform. UV-visible spectra exhibit obvious difference of maximum absorption wavelengths between monomers and dimers, thus may have potential applications for identifying intermolecular H-bonds and calculating association constant of DeAP equilibrium systems in experiments.


Assuntos
Hidrogênio/química , Polímeros/química , Simulação por Computador , Dimerização , Elétrons , Ligações de Hidrogênio , Modelos Moleculares , Teoria Quântica , Solventes/química , Vibração
5.
J Mol Model ; 19(12): 5579-86, 2013 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-24257902

RESUMO

The geometrical structures, energetics properties, and aromaticity of C(36-n) Si(n) (n ≤ 18) fullerene-based clusters were studied using density functional theory calculations. The geometries of C(36-n) Si(n) clusters undergo strong structural deformation with the increase of Si substitution. For the most energy favorable structures of C(36-n) Si(n) , the silicon and carbon atoms form two distinct homogeneous segregations. Subsequently, the binding energy, HOMO-LUMO energy gap, vertical ionization potential, vertical electron affinity, and chemical hardness for the energetic favorable C(36-n) Si(n) geometries were computed and analyzed. In addition, the aromatic property of C(36-n) Si(n) cagelike clusters was investigated, and the result demonstrate that these C(36-n) Si(n) cagelike structures possess strong aromaticity.

6.
Phys Chem Chem Phys ; 14(47): 16476-85, 2012 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-23131708

RESUMO

Stimulated by the preparation and characterization of the isolated pentagon rule (IPR) violating chlorofullerene: C(60)Cl(8) (Nat. Mater. 2008, 7, 790-794), we have performed a systematic investigation on the structural stabilities, electronic and optical properties of the IPR-violating C(60)X(8) (X = H, F, and Cl) fullerene compounds via density functional theory. The large energy gaps between the highest occupied and the lowest unoccupied molecular orbitals provide a clear indication of high chemical stabilities of C(60)X(8) derivatives, and moreover, the C(60)X(8) molecules present great aromatic character with the negative nucleus independent chemical shift values. In the addition reactions of C(60) (C(2v)) + 4X(2) → C(60)X(8), a series of exothermic processes are involved, with high reaction energies ranging from -71.97 to -233.16 kcal mol(-1). An investigation on the electronic property shows that C(60)F(8) and C(60)Cl(8) could be excellent electron acceptors as a consequence of large vertical electron affinities. The density of state analysis suggests that the frontier molecular orbitals of C(60)X(8) are mainly from the carbon orbitals of two separate annulene subunits, and the influence from X atoms is secondary. In addition, the ultraviolet-visible spectra and second-order hyperpolarizabilities of C(60)X(8) are calculated by means of time-dependent density functional theory and a finite field approach, respectively. Both the average static linear polarizability <α> and second-order hyperpolarizability <γ> of C(60)X(8) increase greatly compared to those of C(60).

7.
J Comput Chem ; 32(4): 658-67, 2011 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-20845421

RESUMO

Stimulated by the recent isolation and characterization of C56Cl10 chlorofullerene (Tan et al., J Am Chem Soc 2008, 130, 15240), we perform a systematic study on the geometrical structures, thermochemistry, and electronic and optical properties of C56X10 (X = H, F, and Cl) on the basis of density functional theory (DFT). Compared with pristine C56, the equatorial carbon atoms in C56X10 are saturated by X atoms and change to sp³ hybridization to release the large local strains. The addition reactions C56 + 5X2 --> C56X10 are highly exothermic, and the optimal temperature for synthesizing C56X10 should be ranged between 500 and 1000 K. By combining 10 X atoms at the abutting pentagon vertexes and active sites, C56Cl10 molecules exhibit large energy gaps between the highest occupied and lowest unoccupied molecular orbitals (from 2.84 to 3.00 eV), showing high chemical stabilities. The C56F10 and C56Cl10 could be excellent electron acceptors for potential photonic/photovoltaic applications in consequence of their large vertical electron affinities. The density of states is also calculated, which suggest that the frontier molecular orbitals of C56X10 are mainly from the carbon orbitals of two separate annulene subunits, and the contributions derived from X atoms are secondary. In addition, the ultraviolet-visible spectra and second-order hyperpolarizabilities of C56X10 are calculated by means of time-dependent DFT and finite field approach, respectively. Both the average static linear polarizability <α> and second-order hyperpolarizability <γ> of these compounds are larger than those of C60 due to lower symmetric structures and high delocalization of π electron density on the two separate annulene subunits.


Assuntos
Fulerenos/química , Elétrons , Modelos Moleculares , Fenômenos Ópticos , Teoria Quântica , Espectrofotometria
8.
J Comput Chem ; 31(14): 2650-7, 2010 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-20740565

RESUMO

Electronic structures and nonlinear optical properties of two highly deformed halofullerenes C(3v) C(60)F(18) and D(3d) C(60)Cl(30) have been systematically studied by means of density functional theory. The large energy gaps (3.62 and 2.61 eV) between the highest occupied and lowest unoccupied molecular orbitals (HOMOs and LUMOs) and the strong aromatic character (with nucleus-independent chemical shifts varying from -15.08 to -23.71 ppm) of C(60)F(18) and C(60)Cl(30) indicate their high stabilities. Further investigations of electronic property show that C(60)F(18) and C(60)Cl(30) could be excellent electron acceptors for potential photonic/photovoltaic applications in consequence of their large vertical electron affinities. The density of states and frontier molecular orbitals are also calculated, which present that HOMOs and LUMOs are mainly distributed in the tortoise shell subunit of C(60)F(18) and the aromatic [18] trannulene ring of C(60)Cl(30), and the influence from halogen atoms is secondary. In addition, the static linear polarizability and second-order hyperpolarizability of C(60)F(18) and C(60)Cl(30) are calculated using finite-field approach. The values of and for C(60)F(18) and C(60)Cl(30) molecules are significantly larger than those of C(60) because of their lower symmetric structures and high delocalization of pi electrons.


Assuntos
Elétrons , Fulerenos/química , Óptica e Fotônica , Simulação de Dinâmica Molecular , Teoria Quântica
9.
Phys Chem Chem Phys ; 12(36): 10846-56, 2010 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-20657941

RESUMO

Singlet and triplet potential energy surfaces for the reactions of oxygen atoms ((3)P and (1)D) with CF(3)CN have been studied computationally to evaluate the reaction mechanisms, possible products, and rate constants. On the triplet surface, six kinds of pathway are revealed, namely: direct fluorine abstraction, C-addition/elimination, N-addition/elimination, substitution, insertion and F-migration. The results show that the reaction should occur mainly through the C-addition/elimination mechanism involving the chemically activated CF(3)C(O)N* intermediate, and the major products are CF(3) and NCO. The rate constants for C-addition/elimination channel of the reaction of O((3)P) with CF(3)CN have been determined by using RRKM statistical rate theory and compared with the experimental data. On the singlet surface, the atomic oxygen can easily insert into the C-F or C-C bond of CF(3)CN, forming the insertion intermediates FOCF(2)CN and CF(3)OCN, and O((1)D) can add to the carbon or nitrogen atom of the CN group in CF(3)CN, forming the addition intermediates CF(3)C(O)N and CF(3)CNO; both approaches are found to be barrierless. The decomposition and isomerization of some intermediates were also modeled at the QCISD(T)/6-311+G(2df)//B3LYP/6-311+G(d) level for the better understanding of the O((1)D) with CF(3)CN chemistry. The decomposition products CF(3) and NCO arising from CF(3)OCN and CF(3)NCO are the dominant species. Further comparison with similar reactions is also summarized.

10.
J Mol Graph Model ; 28(8): 891-8, 2010 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-20430661

RESUMO

A systematic study on the geometrical structures and electronic properties of C(68)X(4) (X=H, F, and Cl) fullerene compounds has been carried out on the basis of density functional theory. In all classical C(68)X(4) isomers with two adjacent pentagons and one quasifullerene isomer [C(s):C(68)(f)] containing a heptagon in the framework, the C(s):0064 isomers are most favorable in energy. The addition reaction energies of C(68)X(4) (C(s):0064) are high exothermic, and C(68)F(4) is more thermodynamically accessible. The C(68)X(4) (C(s):0064) possess strong aromatic character, with nucleus independent chemical shifts ranging from -22.0 to -26.1 ppm. Further investigations on electronic properties indicate that C(68)F(4) and C(68)Cl(4) could be excellent electron-acceptors for potential photonic/photovoltaic applications in consequence of their large vertical electron affinities (3.29 and 3.15 eV, respectively). The Mulliken charge populations and partial density of states are also calculated, which show that decorating C(68) fullerene with various X atoms will cause remarkably different charge distributions in C(68)X(4) (C(s):0064) and affect their electronic properties distinctly. Finally, the infrared spectra of the most stable C(68)X(4) (C(s):0064) molecules are simulated to assist further experimental characterization.


Assuntos
Fulerenos/química , Modelos Moleculares , Algoritmos , Eletroquímica , Estrutura Molecular , Termodinâmica
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA