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1.
Mol Carcinog ; 62(12): 1990-2004, 2023 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-37702006

RESUMO

Partitioning defective 3 (Par3) is a polarity protein critical in establishing epithelial cell polarity and tight junctions (TJs). Impaired intestinal epithelial barrier integrity is closely associated with colitis-associated colorectal cancer (CRC) progression. According to the GEO and TCGA database analyses, we first observed that the expression of Par3 was reduced in CRC patients. To understand how Par3 is related to CRC, we investigated the role of Par3 in the development of CRC using an in vivo genetic approach. Our results show that the intestinal epithelium-specific PAR3 deletion mice demonstrated a more severe CRC phenotype in the context of azoxymethane/dextran sodium sulfate (AOM/DSS) treatment, with a corresponding increase in tumor number and inflammatory cytokines profile. Mechanistically, loss of Par3 disrupts the TJs of the intestinal epithelium and increases mucosal barrier permeability. The interaction of Par3 with ZO-1 prevents intramolecular interactions within ZO-1 protein and facilitates the binding of occludin to ZO-1, hence preserving TJs integrity. Our results suggest that Par3 deficiency permits pathogenic bacteria and their endotoxins to penetrate the intestinal submucosa and activate TLR4/MyD88/NF-κB signaling, promoting inflammation-driven CRC development and that Par3 may be a novel potential molecular marker for the diagnosis of early-stage CRC.


Assuntos
Neoplasias Associadas a Colite , Colite , Humanos , Camundongos , Animais , Colite/induzido quimicamente , Colite/complicações , Colite/metabolismo , Neoplasias Associadas a Colite/complicações , Neoplasias Associadas a Colite/metabolismo , Neoplasias Associadas a Colite/patologia , Junções Íntimas/metabolismo , Inflamação/metabolismo , Mucosa Intestinal/metabolismo , Sulfato de Dextrana/toxicidade , Modelos Animais de Doenças , Camundongos Endogâmicos C57BL
2.
BMC Cancer ; 22(1): 628, 2022 Jun 08.
Artigo em Inglês | MEDLINE | ID: mdl-35672728

RESUMO

BACKGROUND: Eukaryotic translation elongation factors 1 δ (EEF1D), has garnered much attention with regards to their role in the drug resistance of cancers. In this paper, we investigated the effects and mechanisms of increasing the sensitivity of ovarian cancer cells to cisplatin or cis-dichlorodiammine platinum (DDP) by knockdown and knockout of EEF1D gene in cellular and animal models. METHODS: The EEF1D gene was knocked-down or -out by siRNA or CRISPR/Cas9 respectively in human ovarian cancer cell SKOV3, DDP-resistant subline SKOV3/DDP, and EEF1D gene in human primary ovarian cancer cell from 5 ovarian cancer patients with progressive disease/stable disease (PD/SD) was transiently knocked down by siRNA interference. The mice model bearing xenografted tumor was established with subcutaneous inoculation of SKOV3/DDP. RESULTS: The results show that reducing or removing EEF1D gene expression significantly increased the sensitivity of human ovarian cancer cells to DDP in inhibiting viability and inducing apoptosis in vitro and in vivo, and also boosted DDP to inhibit xenografted tumor growth. Interfering with EEF1D gene expression in mice xenografted tumor significantly affected the levels of OPTN, p-Akt, Bcl-2, Bax, cleaved caspase-3 and ERCC1 compared to DDP treated mice alone, and had less effect on PI3K, Akt and caspase-3. CONCLUSIONS: The knocking down or out EEF1D gene expression could enhance the sensitivity of ovarian cancer cells to DDP partially, which may be achieved via inactivating the PI3K/AKT signaling pathway, thus inducing cell apoptosis and decreasing repairment of DNA damage. Our study provides a novel therapeutic strategy for the treatment of ovarian cancer.


Assuntos
Antineoplásicos , Neoplasias Ovarianas , Animais , Antineoplásicos/farmacologia , Antineoplásicos/uso terapêutico , Apoptose , Carcinoma Epitelial do Ovário/tratamento farmacológico , Caspase 3/metabolismo , Linhagem Celular Tumoral , Proliferação de Células , Cisplatino/farmacologia , Cisplatino/uso terapêutico , Resistencia a Medicamentos Antineoplásicos/genética , Feminino , Humanos , Camundongos , Neoplasias Ovarianas/tratamento farmacológico , Neoplasias Ovarianas/genética , Neoplasias Ovarianas/patologia , Fator 1 de Elongação de Peptídeos/genética , Fator 1 de Elongação de Peptídeos/metabolismo , Fator 1 de Elongação de Peptídeos/farmacologia , Fosfatidilinositol 3-Quinases/metabolismo , Proteínas Proto-Oncogênicas c-akt/metabolismo , RNA Interferente Pequeno/genética
3.
Cancer Sci ; 112(7): 2625-2641, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-33931921

RESUMO

Bladder cancer (BLCA) remains the leading cause of cancer-related mortality among genitourinary malignancies worldwide. BLCA metastasis represents the primary reason for its poor prognosis. In this study, we report that decreased expression of partitioning defective 3 (Par3), a polarity protein (encoded by PARD3), is associated with tumor aggressive phenotypes and poor prognosis in BLCA patients. Consistently, ablation of Par3 promotes the metastasis and invasion of BLCA cells in vitro and in vivo. Further studies reveal that zinc finger protein Snail represses the expression of Par3 by binding to E2-box (CAGGTG) of PARD3 promoter-proximal. Inhibition of GSK-3ß promotes the expression and nuclear localization of Snail and then reduces the expression of Par3, resulting in the metastasis and invasion of BLCA cells. Moreover, we detected the interaction between Par3 (936-1356 aa) and ZO-1 (1372-1748 aa), which is involved in the maintenance of tight junction. Together, our results demonstrate that the GSK-3ß/Snail/Par3/ZO-1 axis regulates BLCA metastasis, and Snail is a major regulator for Par3 protein expression in BLCA.


Assuntos
Proteínas Adaptadoras de Transdução de Sinal/metabolismo , Proteínas de Ciclo Celular/metabolismo , Glicogênio Sintase Quinase 3 beta/antagonistas & inibidores , Neoplasias Pulmonares/secundário , Fatores de Transcrição da Família Snail/metabolismo , Neoplasias da Bexiga Urinária/metabolismo , Neoplasias da Bexiga Urinária/patologia , Proteínas Adaptadoras de Transdução de Sinal/deficiência , Proteínas Adaptadoras de Transdução de Sinal/genética , Animais , Proteínas de Ciclo Celular/deficiência , Proteínas de Ciclo Celular/genética , Núcleo Celular/metabolismo , Polaridade Celular/fisiologia , Técnicas de Silenciamento de Genes , Glicogênio Sintase Quinase 3 beta/metabolismo , Humanos , Camundongos , Camundongos Endogâmicos NOD , Camundongos SCID , Mutação , Invasividade Neoplásica , Metástase Neoplásica , Proteínas de Neoplasias/deficiência , Proteínas de Neoplasias/genética , Proteínas de Neoplasias/metabolismo , Fenótipo , Fosforilação , Prognóstico , Distribuição Aleatória , Fatores de Transcrição da Família Snail/genética , Junções Íntimas/fisiologia , Proteína da Zônula de Oclusão-1/metabolismo
4.
Phytomedicine ; 129: 155675, 2024 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-38678954

RESUMO

BACKGROUND: Gemcitabine (GEM) resistance is the primary reason why combination chemotherapy is limited in triple-negative breast cancer (TNBC). Ganoderic acid D (GAD), a natural triterpenoid compound obtained from Ganoderma lucidum, has been shown to have antitumor activities. However, whether GAD can reverse GEM resistance in TNBC requires further investigation. PURPOSE: This study investigated whether and how GAD could reverse GEM resistance in TNBC as an antitumor adjuvant. METHODS: The effects of GAD on cell proliferation, cell cycle, and glycolysis were studied in vitro using a GEM-resistant (GEM-R) TNBC cell model. We enriched key pathways affected by GAD using proteomics techniques. Western blotting and qPCR were used to detect the expression of glycolysis-related genes after GAD treatment. A mouse resistance model was established using GEM-R TNBC cells, and hematoxylin-eosin staining and immunohistochemistry were used to assess the role of GAD in reversing resistance in vivo. RESULTS: Cellular functional assays showed that GAD significantly inhibited proliferation and glucose uptake in GEM-R TNBC cells. GAD reduces HIF-1α accumulation in TNBC cells under hypoxic conditions through the ubiquitinated protease degradation pathway. Mechanistically, GAD activates the p53/MDM2 pathway, promoting HIF-1α ubiquitination and proteasomal degradation and downregulating HIF-1α-dependent glycolysis genes like GLUT1, HK2, and PKM2. Notably, GAD combined with gemcitabine significantly reduced the growth of GEM-R TNBC cells in a subcutaneous tumor model. CONCLUSIONS: This study reveals a novel antitumor function of GAD, which inhibits glycolysis by promoting HIF-1α degradation in GEM-R TNBC cells, offering a promising therapeutic strategy for TNBC patients with GEM resistance.


Assuntos
Proliferação de Células , Desoxicitidina , Resistencia a Medicamentos Antineoplásicos , Gencitabina , Glicólise , Subunidade alfa do Fator 1 Induzível por Hipóxia , Neoplasias de Mama Triplo Negativas , Neoplasias de Mama Triplo Negativas/tratamento farmacológico , Desoxicitidina/análogos & derivados , Desoxicitidina/farmacologia , Humanos , Resistencia a Medicamentos Antineoplásicos/efeitos dos fármacos , Subunidade alfa do Fator 1 Induzível por Hipóxia/metabolismo , Animais , Glicólise/efeitos dos fármacos , Feminino , Linhagem Celular Tumoral , Camundongos , Proliferação de Células/efeitos dos fármacos , Camundongos Nus , Camundongos Endogâmicos BALB C , Lanosterol/farmacologia , Lanosterol/análogos & derivados , Triterpenos/farmacologia , Reishi/química
5.
Front Plant Sci ; 14: 1116300, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-36909420

RESUMO

Introduction: Phylogenomics have been widely used to resolve ambiguous and controversial evolutionary relationships among plant species and genera, and the identification of unique indels in plastomes may even help to understand the evolution of some plant families. Menispermum L. (Menispermaceae) consists of three species, M. dauricum DC., M. canadense L., and M. mexicanum Rose, which are disjuncly distributed among East Asia, Eastern North America and Mexico. Taxonomists continue to debate whether M. mexicanum is a distinct species, a variety of M. dauricum, or simply a synonym of M. canadense. To date, no molecular systematics studies have included this doubtful species in phylogenetic analyses. Methods: In this study, we examined phylogenomics and phylogeography of Menispermum across its entire range using 29 whole plastomes of Menispermaceae and 18 ITS1&ITS2 sequences of Menispermeae. We reconstructed interspecific relationships of Menispermum and explored plastome evolution in Menispermaceae, revealing several genomic hotspot regions for the family. Results and discussion: Phylogenetic and network analyses based on whole plastome and ITS1&ITS2 sequences show that Menispermum clusters into two clades with high support values, Clade A (M. dauricum) and Clade B (M. canadense + M. mexicanum). However, M. mexicanum is nested within M. canadense and, as a result, we support that M. mexicanum is a synonym of M. canadense. We also identified important molecular variations in the plastomes of Menispermaceae. Several indels and consequently premature terminations of genes occur in Menispermaceae. A total of 54 regions were identified as the most highly variable plastome regions, with nucleotide diversity (Pi) values > 0.05, including two coding genes (matK, ycf1), four introns (trnK intron, rpl16 intron, rps16 intron, ndhA intron), and 48 intergenic spacer (IGS) regions. Of these, four informative hotspot regions (trnH-psbA, ndhF-rpl32, trnK-rps16, and trnP-psaJ) should be especially useful for future studies of phylogeny, phylogeography and conservation genetics of Menispermaceae.

6.
J Affect Disord ; 301: 400-425, 2022 03 15.
Artigo em Inglês | MEDLINE | ID: mdl-35032510

RESUMO

BACKGROUND: To study the safety and patients' tolerance of transcranial magnetic stimulation (TMS), we conducted a systematic review and meta-analysis of the major depressive disorder population. METHODS: Our study followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. We searched the literature published before April 30th, 2021 and performed a random-effects meta-analyses which included drop-out due to adverse events, serious adverse events and other non-serious adverse events as primary and secondary outcomes. RESULTS: A total of 53 randomized sham-controlled trials with 3,273 participants were included. There was no increased risk of drop-out due to an adverse event (active TMS intervention group=3.3%, sham TMS intervention group=2.3%, odds ratio = 1.30, 95% CI= 0.78-2.16, P = 0.31) or a serious adverse event (active TMS intervention group=0.9%, sham TMS intervention group=1.5%, odds ratio = 0.67, 95% CI= 0.29-1.55, P = 0.35). Our findings suggest that TMS intervention may significantly increase the risk of non-serious adverse events including: headaches (active TMS intervention group=22.6%, sham TMS intervention group=16.2%, odds ratio = 1.48, 95% CI= 1.15-1.91, P = 0.002), discomfort (active TMS intervention group=10.9%, sham TMS intervention group=5.0%, odds ratio 1.98, 95% CI= 1.22-3.21, P = 0.006) and pain (active TMS intervention group=23.8%, sham TMS intervention group=5.2%, odds ratio= 8.09, 95% CI= 4.71-13.90, P < 0.001) at the stimulation site, but these non-serious events were mostly mild and transient after TMS treatment. CONCLUSIONS: These findings provide evidence for the safety and patients' tolerance of transcranial magnetic stimulation technique as an alternative monotherapy or as an add-on treatment for major depressive disorder.


Assuntos
Transtorno Depressivo Maior , Estimulação Magnética Transcraniana , Transtorno Depressivo Maior/etiologia , Transtorno Depressivo Maior/terapia , Cefaleia , Humanos , Ensaios Clínicos Controlados Aleatórios como Assunto , Estimulação Magnética Transcraniana/efeitos adversos , Estimulação Magnética Transcraniana/métodos , Resultado do Tratamento
7.
Front Genet ; 11: 380, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32457795

RESUMO

The moonseed genus Menispermum L. (Menispermaceae) is disjunctly distributed in East Asia and eastern North America. Although Menispermum has important medicinal value, genetic and genomic information is scarce, with very few available molecular markers. In the current study, we used Illumina transcriptome sequencing and de novo assembly of the two Menispermum species to obtain in-depth genetic knowledge. From de novo assembly, 53,712 and 78,921 unigenes were generated for M. canadense and M. dauricum, with 37,527 (69.87%) and 55,211 (69.96%) showing significant similarities against the six functional databases, respectively. Moreover, 521 polymorphic EST-SSRs were identified. Of them, 23 polymorphic EST-SSR markers were selected to investigate the population genetic diversity within the genus. The newly developed EST-SSR markers also revealed high transferability among the three examined Menispermaceae species. Overall, we provide the very first transcriptomic analyses of this important medicinal genus. In addition, the novel microsatellite markers developed here will aid future studies on the population genetics and phylogeographic patterns of Menispermum at the intercontinental geographical scale.

8.
Front Plant Sci ; 11: 361, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32391025

RESUMO

Saxifragaceae, a family of over 600 species and approximately 30 genera of herbaceous perennials, is well-known for intergeneric hybridization. Of the main lineages in this family, the Heuchera group represents a valuable model for the analysis of plastid capture and its impact on phylogeny reconstruction. In this study, we investigated plastome evolution across the family, reconstructed the phylogeny of the Heuchera group and examined putative plastid capture between Heuchera and Tiarella. Seven species (11 individuals) representing Tiarella, as well as Mitella and Heuchera, were selected for genome skimming. We assembled the plastomes, and then compared these to six others published for Saxifragaceae; the plastomes were found to be highly similar in overall size, structure, gene order and content. Moreover, ycf15 was lost due to pseudogenization and rpl2 lost its only intron for all the analyzed plastomes. Comparative plastome analysis revealed that size variations of the plastomes are purely ascribed to the length differences of LSC, SSC, and IRs regions. Using nuclear ITS + ETS and the complete plastome, we fully resolved the species relationships of Tiarella, finding that the genus is monophyletic and the Asian species is most closely related to the western North American species. However, the position of the Heuchera species was highly incongruent between nuclear and plastid data. Comparisons of nuclear and plastid phylogenies revealed that multiple plastid capture events have occurred between Heuchera and Tiarella, through putative ancient hybridization. Moreover, we developed numerous molecular markers for Tiarella (e.g., plastid hotspot and polymorphic nuclear SSRs), which will be useful for future studies on the population genetics and phylogeography of this disjunct genus.

9.
Oncotarget ; 8(50): 88079-88093, 2017 Oct 20.
Artigo em Inglês | MEDLINE | ID: mdl-29152143

RESUMO

PGPIPN is a therapeutic hexapeptide derived from bovine ß-casein. Here we investigated the role and mechanism of this peptide on alcoholic fatty liver disease (AFLD). We took human hepatic cell line LO2 and hepatocellular carcinoma cell line HepG2 to establish the models of steatosis hepatocyte induced by alcohol, taken PGPIPN as pharmacological intervention. And we also established the model of AFLD mice, taken PGPIPN as therapeutic drug and glutathione (GSH) as positive control. We assayed the biochemical materials related to liver injury, lipid metabolism and oxidation, and observed morphology change and fat accumulation of hepatocyte. The gene expressions and/or activities related to liver injury, lipid metabolism and oxidation, such as ACC, PPAR-γ, CHOP and Caspase-3, were assessed by real time PCR and western blot. Our results showed PGPIPN alleviated hepatic steatosis in both model cells and AFLD model mice. PGPIPN can effectively reduce the lipid accumulation and oxidative stress of hepatocyte in a dose-dependent manner. PGPIPN alleviated alcohol-induced cell steatosis and injuries by regulating the gene expressions and/or activities of ACC, PPAR-γ, CHOP and Caspase-3. Our results demonstrated PGPIPN had the protective and therapeutic effect on AFLD, which may serve as a potential therapeutic agent for AFLD.

10.
Asia Pac J Clin Oncol ; 12(1): e65-74, 2016 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-23910020

RESUMO

AIM: To investigate the association between plasma visfatin levels and risk of early and advanced colorectal cancer (CRC). METHODS: In total, 358 CRC patients and 286 controls were enrolled. According to the T factor of the TNM system. cancer patients were divided into two subgroups: early and advanced cancer. Levels of visfatin, anthropometric and metabolic parameters, which were classified as low, medium, and high, based on the tertile distributions in the control group, were determined. RESULTS: The visfatin levels in patients with advanced and early cancer were higher than in controls (least significant difference test, P = 0.004 and 0.013, respectively). The patients in the highest tertile of visfatin concentration presented significantly higher odds for early and advanced CRC, adjusted for potential confounding factors (odds ratio 3.37; 95% CI, 1.93-8.37; P = 0.011; odds ratio 2.38; 95% CI: 1.82-8.35; P = 0.015, respectively). The visfatin level correlated significantly with waist:hip ratio (P < 0.05 for all) among case and control participants. Plasma visfatin levels in early and advanced CRC yielded a receiver operating characteristic curve area of 72 and 86%, respectively. The optimal sensitivity and specificity were 73% and 57% in discriminating between early CRC and normal controls while they were 76% and 68% in discriminating between advanced CRC and normal controls. CONCLUSION: An increased level of visfatin was a strong risk factor for both early and advanced CRC in Chinese patients. Plasma visfatin levels might be a potential biomarker for CRC detection.


Assuntos
Biomarcadores Tumorais/sangue , Neoplasias Colorretais/sangue , Neoplasias Colorretais/patologia , Citocinas/sangue , Nicotinamida Fosforribosiltransferase/sangue , Adulto , Idoso , Povo Asiático , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Razão de Chances , Curva ROC , Fatores de Risco
11.
Med Oncol ; 29(5): 3129-35, 2012 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-22752603

RESUMO

The research is to investigate the association between plasma concentrations of total and high-molecular-weight (HMW) adiponectin and risk of early and advanced colorectal cancer. One hundred and sixty-five male colorectal cancer patients and one hundred and two controls were enrolled; based on the T factor of the TNM system, intraepithelial carcinoma and submucosally invasive carcinoma were defined as early cancer, and invasion into the muscularis propria or deeper was defined as advanced cancer. The plasma levels of glucose, fasting insulin, total cholesterol, triglyceride, and total and HMW adiponectin levels were measured. Each factor level was designated as low or high, and the risk of cancer was estimated by univariate and multivariate logistic regression analyses. In the patients with early cancer, high waist/hip ratio (WHR), high fasting insulin, high HOMA model insulin resistance index (HOMA-IR), low total adiponectin and HMW adiponectin were all associated with a significant increase in the odds ratio (OR) by univariate analysis. In multivariate analysis, WHR, HOMA-IR, total adiponectin and HMW adiponectin were all related to increased cancer risk. However, in the patients with advanced cancer, only low HMW adiponectin was associated with a significant increase in the OR by univariate analysis. In multivariate analysis, a low HMW adiponectin level was still related to increased cancer risk, with an adjusted OR of 3.971 (P = 0.036). In conclusion, a decreased level of adiponectin was a strong risk factor not only for early colorectal cancer but also for advanced colorectal in Chinese male patients. HMW adiponectin might be more closely associated with colorectal cancer risk than total adiponectin.


Assuntos
Adiponectina/sangue , Biomarcadores Tumorais/sangue , Carcinoma/sangue , Neoplasias Colorretais/sangue , Adulto , Povo Asiático , Biomarcadores Tumorais/análise , Pressão Sanguínea , Índice de Massa Corporal , Carcinoma/patologia , Neoplasias Colorretais/patologia , Humanos , Resistência à Insulina , Masculino , Pessoa de Meia-Idade , Razão de Chances , Fatores de Risco
13.
Environ Sci Technol ; 42(17): 6631-6, 2008 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-18800541

RESUMO

Chemical composition measurements of individual ambient nanoparticles were performed with a nanoaerosol mass spectrometer (NAMS) in Wilmington, DE, in May 2006. The atomic composition of each particle was determined from the relative signal intensities of multiply charged atomic ions in the mass spectra. The characteristics of particles with a mass-normalized-diameter of 25 nm analyzed on May 9 and 10, 2006, were studied in detail. Most of these particles contained carbon, nitrogen, oxygen, and sulfur. Almost half of the particles contained silicon, although its contribution to the total atomic composition was usually less than 1%. Alkali and transition metals were observed in a few percent of the particles, also with a contribution to the total atomic composition that was usually less than 1%. A method was developed to infer the amounts of ammonium sulfate, ammonium nitrate, and carbonaceous matter in single particles from the measured atomic compositions. The procedure also permitted estimation of the oxygen to carbon (O:C) atomic ratio of the carbonaceous matter. Two distinct types of particles were found: those having an O:C ratio less than 0.01 and those having a ratio 0.5 or greater. Particles in the low O:C ratio group are consistent with a hydrocarbon composition. Their prevalence during shortterm (1-min) spikes in concentration are consistent with nanoparticle emissions from individual vehicles. Ammonium sulfate was also found in many of these particles. Particles in the high O:C group are consistent with secondary organic aerosol. Most of these particles also contained ammonium sulfate and ammonium nitrate. A steady increase of these particles during the daytime suggested that their formation was photochemically driven.


Assuntos
Poluentes Atmosféricos/química , Nanopartículas/química , Saúde da População Urbana , Espectrometria de Massas , Tamanho da Partícula
14.
Environ Sci Technol ; 41(17): 6129-36, 2007 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-17937292

RESUMO

The formation of secondary organic aerosol (SOA) by reaction of ozone with monoterpenes (beta-pinene, delta3-carene, limonene, and sabinene) was studied on a short time scale of 3-22 s with a flow tube reactor. Online chemical analysis was performed with the Photoionization Aerosol Mass Spectrometer (PIAMS) to obtain molecular composition and the Nanoaerosol Mass Spectrometer (NAMS) to obtain elemental composition. Molecular composition data showed that dimers and higher order oligomers are formed within seconds after the onset of reaction, indicating that there is no intrinsic kinetic barrier to oligomer formation. Because oligomer formation is fast, it is unlikely that a large number of steps are involved in their formation. Therefore, ion distributions in the PIAMS spectra were interpreted through reactions of intermediates postulated in previous studies with monomer end products or other intermediates. Based on ion signal intensities in the mass spectra, organic peroxides appear to comprise a greater fraction of the aerosol than secondary ozonides. This conclusion is supported by elemental composition data from NAMS that gave C:O ratios in the 2.2-2.7 range.


Assuntos
Aerossóis/química , Poluentes Atmosféricos/química , Monoterpenos/química , Ozônio/química , Polímeros/química , Atmosfera , Carbono/análise , Dimerização , Cinética , Espectrometria de Massas , Oxigênio/análise , Tamanho da Partícula , Peróxidos/química , Volatilização
15.
Anal Chem ; 78(6): 1750-4, 2006 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-16536407

RESUMO

A nanoaerosol mass spectrometer (NAMS) is described for real-time characterization of individual airborne nanoparticles. The NAMS includes an aerodynamic inlet, quadrupole ion guide, quadrupole ion trap, and time-of-flight mass analyzer. Charged particles in the aerosol are drawn through the aerodynamic inlet, focused through the ion guide, and captured in the ion trap. Trapped particles are irradiated with a high-energy laser pulse to reach the "complete ionization limit" where each particle is thought to be completely disintegrated into atomic ions. In this limit, the relative signal intensities of the atomic ions give the atomic composition. The method is first demonstrated with sucrose particles produced with an electrospray generator. Under the conditions used, the particle detection efficiency (fraction of charged particles entering the inlet that are subsequently analyzed) reaches a maximum of 10(-4) at 9.5 nm in diameter and the size distribution of trapped particles has a geometric standard deviation of 1.1 based on a log-normal distribution. A method to deconvolute overlapping multiply charged ions (e.g. C3+ and O4+) is presented. When applied to sucrose spectra, the measured C/O atomic ratio is 1.1, which matches the expected ratio from the molecular formula. The spectra of singly charged bovine serum albumin (BSA) molecules are also presented, and the measured and expected C/N/O atomic ratios are within 15% of the each other. Also observed in the BSA spectra are signals from 13C and 32S which arise from 40 and approximately 34 atoms per molecule (particle), respectively. Potential applications of NAMS to atmospheric chemistry and biotechnology are briefly discussed.


Assuntos
Poluentes Atmosféricos/análise , Soroalbumina Bovina/análise , Espectrometria de Massas/instrumentação , Espectrometria de Massas/métodos , Tamanho da Partícula , Sensibilidade e Especificidade
16.
Environ Sci Technol ; 40(6): 1843-8, 2006 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-16570606

RESUMO

A flow-tube reactor was used to study the formation of particles from alpha-pinene ozonation. Particle phase products formed within the first 3-22 s of reaction were analyzed online using a scanning mobility particle sizer and two particle mass spectrometers. The first, a photoionization aerosol mass spectrometer (PIAMS), was used to determine the molecular composition of nascent particles between 30 and 50 nm in diameter. The second, a nano-aerosol mass spectrometer (NAMS), was used to determine the elemental composition of individual particles from 50 nm to below 10 nm in diameter. Molecular composition measurements with PIAMS confirm that both the stabilized Criegee intermediate and hydroperoxide channels of alpha-pinene ozonolysis are operative. However, these channels alone cannot explain the high oxygen content of the particles measured with NAMS. The carbon-to-oxygen mole ratios of suspected nucleating agents are in the range of 2.25-4.0, while the measured ratios are from 1.9 for 9 nm particles to 2.5 and 2.7 for 30 and 50 nm particles, respectively. The large oxygen content may arise by cocondensation of small oxygenated molecules such as water or multistep reactions with ozone, water, or other species that produce highly oxygenated macromolecules. In either case, the increasing ratio with increasing particle size suggests that the aerosol becomes less polar with time.


Assuntos
Aerossóis , Poluentes Atmosféricos/análise , Monoterpenos/química , Oxidantes Fotoquímicos/química , Ozônio/química , Poluentes Atmosféricos/química , Monoterpenos Bicíclicos , Carbono/análise , Espectrometria de Massas , Oxigênio/análise , Tamanho da Partícula , Água/química
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