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1.
Front Microbiol ; 15: 1374406, 2024.
Artigo em Inglês | MEDLINE | ID: mdl-38362499

RESUMO

[This corrects the article DOI: 10.3389/fmicb.2023.1284864.].

2.
Front Microbiol ; 14: 1284864, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-38029206

RESUMO

Introduction: Biodiversity maintenance and its underlying mechanisms are central issues of ecology. However, predicting the composition turnovers of microbial communities at multiple spatial scales remains greatly challenging because they are obscured by the inconsistent impacts of climatic and local edaphic conditions on the assembly process. Methods: Based on the Illumina MeSeq 16S/18S rRNA sequencing technology, we investigated soil bacterial and eukaryotic communities in biocrusts with different successional levels at a subcontinental scale of Northern China. Results: Results showed that irrespective of spatial scale, bacterial α diversity increased but eukaryotic diversity decreased with the primary succession, whereas both ß diversities decreased at the subcontinental scale compared with smaller scales, indicating that the biogeographic pattern of soil microorganisms was balanced by successional convergence and distance decay effect. We found that the convergence of bacterial and eukaryotic communities was attributed to the turnovers of generalist and specialist species, respectively. In this process, edaphic and climatic factors showed unique roles in the changes of diversity at local/subcontinental scales. Moreover, the taxonomic diversity tended to be more susceptible to climatic and edaphic conditions, while biotic factors (photosynthesis and pigments) were more important to phylogenetic diversity. Conclusion: Taken together, our study provided comprehensive insights into understanding the pattern of microbial diversity at multiple spatial scales of drylands.

3.
Front Public Health ; 11: 1089764, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37711249

RESUMO

Aim: Breastfeeding generates short-term and long-term benefits for both mother and child. Exclusive breastfeeding (EBF) is promoted in China for years, but its practice still lags far behind the international average, even among low- and middle- income countries. This study aimed to investigate factors associated with EBF during postpartum. Methods: This study was conducted in a tertiary referral hospital in Gansu Province, Northwest China from October 2019 to April 2020. 3,738 postnatal women were finally included and each of them completed an elaborately designed questionnaire. Infant feeding patterns (EBF or not) and reasons for NEBF (non-exclusive breastfeeding) were collected. The feeding knowledge score was based on 17 questions in relation to breastfeeding. The total score ranges from 0 to 17. Higher score means better understanding about breastfeeding knowledge. Multivariate logistic regression models were used to determine associated factors of EBF during postpartum. A subgroup analysis was conducted to investigate the association between feeding knowledge score and exclusive breastfeeding. Results: Six weeks after childbirth, 1891 mothers (50.6%) maintained EBF. Among the NEBF mothers, 57.01% (n = 1,053) of them stopped exclusive breastfeeding due to self-perceived lack of breast milk production. Factors associated with NEBF were higher maternal age, ethnic minorities and cesarean section. Protective factors of EBF included multipara, positive feeding attitude and high breastfeeding knowledge score. In subgroup analysis, we found the breastfeeding knowledge score had a significant impact on the mothers of Han nationality, underwent cesarean or natural delivery, both primiparous and multiparous, and those with positive attitude towards breastfeeding (p < 0.05). Conclusion: We need a comprehensive and individualized framework of strategies to support children, mothers and their families. During puerperium, improving maternal knowledge of breastfeeding is beneficial to EBF practice. However, for ethnic minorities and those with less active breastfeeding attitudes, breastfeeding knowledge is of limited use, more researches are needed to explore the uncovered reasons, so that more personalized interventions could be developed for them.


Assuntos
Aleitamento Materno , Cesárea , Gravidez , Criança , Lactente , Humanos , Feminino , Estudos Transversais , Período Pós-Parto , China/epidemiologia , Mães
4.
Front Oncol ; 13: 1166373, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-37404751

RESUMO

Background: Recent discoveries uncovered the complex cancer-nerve interactions in several cancer types including skin cutaneous melanoma (SKCM). However, the genetic characterization of neural regulation in SKCM is unclear. Methods: Transcriptomic expression data were collected from the TCGA and GTEx portal, and the differences in cancer-nerve crosstalk-associated gene expressions between normal skin and SKCM tissues were analyzed. The cBioPortal dataset was utilized to implement the gene mutation analysis. PPI analysis was performed using the STRING database. Functional enrichment analysis was analyzed by the R package clusterProfiler. K-M plotter, univariate, multivariate, and LASSO regression were used for prognostic analysis and verification. The GEPIA dataset was performed to analyze the association of gene expression with SKCM clinical stage. ssGSEA and GSCA datasets were used for immune cell infiltration analysis. GSEA was used to elucidate the significant function and pathway differences. Results: A total of 66 cancer-nerve crosstalk-associated genes were identified, 60 of which were up- or downregulated in SKCM and KEGG analysis suggested that they are mainly enriched in the calcium signaling pathway, Ras signaling pathway, PI3K-Akt signaling pathway, and so on. A gene prognostic model including eight genes (GRIN3A, CCR2, CHRNA4, CSF1, NTN1, ADRB1, CHRNB4, and CHRNG) was built and verified by independent cohorts GSE59455 and GSE19234. A nomogram was constructed containing clinical characteristics and the above eight genes, and the AUCs of the 1-, 3-, and 5-year ROC were 0.850, 0.811, and 0.792, respectively. Expression of CCR2, GRIN3A, and CSF1 was associated with SKCM clinical stages. There existed broad and strong correlations of the prognostic gene set with immune infiltration and immune checkpoint genes. CHRNA4 and CHRNG were independent poor prognostic genes, and multiple metabolic pathways were enriched in high CHRNA4 expression cells. Conclusion: Comprehensive bioinformatics analysis of cancer-nerve crosstalk-associated genes in SKCM was performed, and an effective prognostic model was constructed based on clinical characteristics and eight genes (GRIN3A, CCR2, CHRNA4, CSF1, NTN1, ADRB1, CHRNB4, and CHRNG), which were widely related to clinical stages and immunological features. Our work may be helpful for further investigation in the molecular mechanisms correlated with neural regulation in SKCM, and in searching new therapeutic targets.

5.
Front Nutr ; 10: 1259777, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-38239842

RESUMO

Introduction: Monochorionic, diamniotic (MCDA) monozygotic twins share nearly all genetic variation and a common placenta in utero. Despite this, MCDA twins are often discordant for a range of common phenotypes, including early growth and birth weight. As such, MCDA twins represent a unique model to explore variation in early growth attributable primarily to in utero environmental factors. Methods: MCDA twins with a range of within-pair birth weight discordance were sampled from the peri/postnatal epigenetic twin study (PETS, Melbourne; n = 26 pairs), Beijing twin study (BTS, Beijing; n = 25), and the Chongqing longitudinal twin study (LoTiS, Chongqing; n = 22). All PETS participants were of European-Australian ancestry, while all Chinese participants had Han ancestry. The average of the birth weight difference between the larger and smaller co-twins for all twin pairs was determined and metabolomic profiles of amino acids, TCA cycle intermediates, fatty acids, organic acids, and their derivatives generated from cord blood plasma by gas chromatograph mass spectrometry. Within and between co-twin pair analyses were performed to identify metabolites specifically associated with discordance in birth weight. Multivariable regression and pathway enrichment analyses between different regions were performed to evaluate the geographical effects on the metabolism of MCDA twin pairs. Results: PETS twins showed a markedly different metabolic profile at birth compared to the two Chinese samples. Within-pair analysis revealed an association of glutathione, creatinine, and levulinic acid with birth weight discordance. Caffeine, phenylalanine, and several saturated fatty acid levels were uniquely elevated in PETS twins and were associated with maternal BMI and average within pair birth weight, in addition to birth weight discordance. LoTiS twins had higher levels of glutathione, tyrosine, and gamma-linolenic acid relative to PETS and BTS twins, potentially associated with eating habits. Conclusion: This study highlights the potential role of underlying genetic variation (shared by MZ twins), in utero (non-shared by MZ twins) and location-specific (shared by MZ twins) environmental factors, in regulating the cord blood metabolome of uncomplicated MCDA twins. Future research is needed to unravel these complex relationships that may play a key role in phenotypic metabolic alterations of twins independent of genetic diversity.

6.
Transl Cancer Res ; 11(10): 3698-3710, 2022 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-36388018

RESUMO

Background: Transforming growth factor-ß1 (TGF-ß1) is the predominant form of TGF-ß and induces epithelial-to-mesenchymal transition (EMT) in melanoma. Tumor cell-intrinsic programmed death ligand-1 (PD-L1) plays a crucial role in maintenance of the EMT in melanoma. However, the relationship among tumor cell-intrinsic PD-L1, TGF-ß1 and EMT is very complicated. Methods: We investigated the bidirectional regulation between cell-intrinsic PD-L1 and TGF-ß1 in melanoma, and explored the role of PD-L1 in TGF-ß1-induced EMT and tumor progression. Results: We found that TGF-ß1 upregulated PD-L1 expression in B16-F0 and B16-F10 melanoma cells. Interestingly, PD-L1 also enhanced the intracellular TGF-ß1 mRNA levels and induced the secretion of TGF-ß1. Immunohistochemical staining revealed that PD-L1 protein expression was co-localized with α-smooth muscle actin (SMA) protein expression in melanoma, suggesting that PD-L1 was associated with EMT. By using shRNA lentivirus to knockdown PD-L1 (PD-L1-shRNA) in melanoma cell lines, we showed that TGF-ß1-induced EMT was significantly inhibited in PD-L1-shRNA melanoma cells, which was characterized by the lower fibronectin (FN1) mRNA and higher E-cadherin (CDH1) mRNA levels (both are EMT markers) than that in control. TGF-ß1-induced melanoma cell proliferation and migration were also markedly inhibited in PD-L1-shRNA cells. Consistent with the observation in vitro, PD-L1 knockdown inhibited tumor growth and repressed TGF-ß1-induced EMT characterized by reduction of FN1 and increase of CDH1 in mouse model. Conclusions: The present study demonstrated a bidirectional regulation between cell-intrinsic PD-L1 and TGF-ß1 in melanoma, which may help in designing promising combinations which include targeting TGF-ß1 signaling along with PD-L1.

7.
Clin Immunol ; 241: 109078, 2022 08.
Artigo em Inglês | MEDLINE | ID: mdl-35840054

RESUMO

Stem cell like memory T (TSCM) cells have emerged as the apex of memory T cell differentiation for their properties of self-renewal and replenishing progenies. With potent long-term persistence, proliferative capacity and antitumor activity, TSCM cells were thought to be the ideal candidate for cancer immunotherapies. Several strategies have been proposed, such as manipulations of cytokines, metabolic factors, signal pathways, and T cell receptor signal intensity, to induce more TSCM cells in vitro, in the hope that they could reach a clinical order of magnitude to provide more long-lasting and effective anti-tumor effects in vivo. In this review, we summarized the differentiation characteristics of TSCM cells and strategies to generate more TSCM cells. We focused on their roles and application in the cancer immunotherapy especially in adoptive cell transfer therapy and cancer therapeutic vaccines, and hopefully provided clues for future understanding and researches.


Assuntos
Vacinas Anticâncer , Neoplasias , Linfócitos T CD8-Positivos , Humanos , Memória Imunológica , Imunoterapia Adotiva , Células T de Memória , Neoplasias/terapia , Células-Tronco
8.
Aging (Albany NY) ; 12(21): 21273-21289, 2020 11 09.
Artigo em Inglês | MEDLINE | ID: mdl-33168784

RESUMO

The purpose of the present study was to evaluate the role of Hrd1 in the ultraviolet (UV) radiation induced photoaging and explore its potential mechanism. The nude mice were exposed to the UVA/UVB irradiation for 10 weeks. The animals were subcutaneously injected with AAV5-NC, Hrd1-shRNA-AAV5, or Hrd1-overexpression-AAV5. The HSF cells were also transfected with Ad-NC, Ad-shRNA-Hrd1, or Ad-Hrd1, and irradiated by UVA/UVB stimulation. The clinical skin samples were harvested for detecting Hrd1 and IGF-1R expressions. As a result, the knockdown of Hrd1 attenuated the histopathological alteration and collagen degradation in UV-induced nude mice. The inhibition of Hrd1 by Hrd1-shRNA-AAV5 and Ad-shRNA-Hrd1 inhibited the Hrd1 expression and promoted IGF-1R, Type I collagen and type III collagen in mice and HSF cells. The overexpression of Hrd1 exerted the reverse effect. The Co-IP assay also indicated the interaction between Hrd1 and IGF-1R. Hrd1-mediated IGF-1R downregulation and collagen degradation were also observed in clinical skin samples. In conclusion, the present results demonstrated that Hrd1 degraded IGF-1R and collagen formation in UV-induced photoaging.


Assuntos
Envelhecimento da Pele/patologia , Envelhecimento da Pele/efeitos da radiação , Ubiquitina-Proteína Ligases/metabolismo , Raios Ultravioleta , Animais , Colágeno Tipo I/metabolismo , Colágeno Tipo III/metabolismo , Regulação para Baixo , Feminino , Masculino , Camundongos Nus , RNA Mensageiro/metabolismo , Receptor IGF Tipo 1/metabolismo
9.
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
10.
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
11.
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.

12.
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 , Ligação de Hidrogênio , Modelos Moleculares , Teoria Quântica , Solventes/química , Vibração
13.
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.

14.
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).

15.
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
16.
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
17.
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.

18.
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
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