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1.
Appl Microbiol Biotechnol ; 104(8): 3445-3457, 2020 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-32088759

RESUMO

Single-molecule real-time (SMRT) sequencing can be used to identify a wide variety of chemical modifications of the genome, such as methylation. Here, we applied this approach to identify N6-methyl-adenine (m6A) and N4-methyl-cytosine (m4C) modification in the genome of Bacillus pumilus BA06. A typical methylation recognition motif of the type I restriction-modification system (R-M), 5'-TCm6AN8TTGG-3'/3'-AGTN8m6AACC-5', was identified. We confirmed that this motif was a new type I methylation site using REBASE analysis and that it was recognized by a type I R-M system, Bpu6ORFCP, according to methylation sensitivity assays in vivo and vitro. Furthermore, we found that deletion of the R-M system Bpu6ORFCP induced transcriptional changes in many genes and led to increased gene expression in pathways related to ABC transporters, sulfur metabolism, ribosomes, cysteine and methionine metabolism and starch and sucrose metabolism, suggesting that the R-M system in B. pumilus BA06 has other significant biological functions beyond protecting the B. pumilus BA06 genome from foreign DNA.

2.
PLoS One ; 15(2): e0228439, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32027693

RESUMO

In recent years, the number of vulnerabilities discovered and publicly disclosed has shown a sharp upward trend. However, the value of exploitation of vulnerabilities varies for attackers, considering that only a small fraction of vulnerabilities are exploited. Therefore, the realization of quick exclusion of the non-exploitable vulnerabilities and optimal patch prioritization on limited resources has become imperative for organizations. Recent works using machine learning techniques predict exploited vulnerabilities by extracting features from open-source intelligence (OSINT). However, in the face of explosive growth of vulnerability information, there is room for improvement in the application of past methods to multiple threat intelligence. A more general method is needed to deal with various threat intelligence sources. Moreover, in previous methods, traditional text processing methods were used to deal with vulnerability related descriptions, which only grasped the static statistical characteristics but ignored the context and the meaning of the words of the text. To address these challenges, we propose an exploit prediction model, which is based on a combination of fastText and LightGBM algorithm and called fastEmbed. We replicate key portions of the state-of-the-art work of exploit prediction and use them as benchmark models. Our model outperforms the baseline model whether in terms of the generalization ability or the prediction ability without temporal intermixing with an average overall improvement of 6.283% by learning the embedding of vulnerability-related text on extremely imbalanced data sets. Besides, in terms of predicting the exploits in the wild, our model also outperforms the baseline model with an F1 measure of 0.586 on the minority class (33.577% improvement over the work using features from darkweb/deepweb). The results demonstrate that the model can improve the ability to describe the exploitability of vulnerabilities and predict exploits in the wild effectively.

3.
Cancer Med ; 9(5): 1638-1647, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31908156

RESUMO

PURPOSE: In this study, we aimed to investigate the viability of utilizing CytoSorter® system to detect circulating tumor cells (CTCs) and to evaluate the diagnostic value of CTCs in breast cancer (BC). METHODS: A total of 366 females patients suspected of having BC and 30 healthy female volunteers were enrolled in this study. CTCs were enriched by CytoSorter® , a microfluidic-based CTCs capturing platform. CTC detection was performed before operation or biopsy. Based on the biopsy results, patients were divided into two groups, namely patients with BC and patients with benign breast diseases (BBD). Patients with BBD and healthy volunteers were serving as controls. The correlation between CTC enumeration and patients' clinicopathological characteristics was evaluated. The receiver operating characteristic (ROC) curve was plotted to assess the diagnostic potency of CytoSorter® system in BC. RESULTS: Based on the biopsy results, 130 BC patients at different cancer stages and 236 patients with BBD were enrolled in the study. Seven subjects were dropped out from the study. CTCs were detected in 109 of 128 BC patients, in one of 29 healthy volunteers, and in 37 of 232 patients with BBD. Maximum CTC counts detected in BC patients, healthy volunteers, and patients with BBD were 8, 1, and 4, respectively. Statistical analysis showed CTCs could be used to distinguish BC patients from healthy volunteers and patients with BBD (P < .0001). Circulating tumor cells were statistically associated with patients' cancer stage (P = .0126), tumor size (tumor node metastasis [TNM] T stage, P = .0253), cancer type (invasive vs noninvasive, P = .0141), and lymph node metastasis (P = .0436). More CTCs were found in patients at advanced cancer stage or TNM T stage and in patients with invasive tumor or lymph node metastasis. Furthermore, CTC detection rates in BC patients at Tis and T1-4 stages were 50%, 81.67%, 91.07%, 100%, and 100%, respectively. When the CTC cut-off value was set to 2, the ROC curve gave an area under the curve (AUC) of 0.86 with a specificity and sensitivity of 95.4% and 76.56%, respectively. Taken together, CTCs could be used as a diagnostic aid in assistance of cancer screening and staging. CONCLUSION: Circulating tumor cells were successfully isolated in BC patients using CytoSorter® system. CTCs can be used to differentiate BC patients from the patients with BBD or healthy volunteers, and as a diagnostic aid for early cancer diagnosis and cancer staging.

4.
BMC Genomics ; 20(1): 327, 2019 Apr 30.
Artigo em Inglês | MEDLINE | ID: mdl-31039790

RESUMO

BACKGROUND: Bacillus pumilus is a Gram-positive and endospore-forming bacterium broadly existing in a variety of environmental niches. Because it produces and secrets many industrially useful enzymes, a lot of studies have been done to understand the underlying mechanisms. Among them, scoC was originally identified as a pleiotropic transcription factor negatively regulating protease production and sporulation in B. subtilis. Nevertheless, its role in B. pumilus largely remains unknown. RESULTS: In this study we successfully disrupted scoC gene in B. pumilus BA06 and found increased total extracellular protease activity in scoC mutant strain. Surprisingly, we also found that scoC disruption reduced cell motility possibly by affecting flagella formation. To better understand the underlying mechanism, we performed transcriptome analysis with RNA sequencing. The result showed that more than one thousand genes were alternated at transcriptional level across multiple growth phases, and among them the largest number of differentially expressed genes (DEGs) were identified at the transition time point (12 h) between the exponential growth and the stationary growth phases. In accordance with the altered phenotype, many protease genes especially the aprE gene encoding alkaline protease were transcriptionally regulated. In contrast to the finding in B. subtilis, the aprN gene encoding neutral protease was transcriptionally downregulated in B. pumilus, implicating that scoC plays strain-specific roles. CONCLUSIONS: The pleiotropic transcription factor ScoC plays multiple roles in various cellular processes in B. pumilus, some of which were previously reported in B. subtilis. The supervising finding is the identification of ScoC as a positive regulator for flagella formation and bacterial motility. Our transcriptome data may provide hints to understand the underlying mechanism.


Assuntos
Bacillus pumilus/genética , Proteínas de Bactérias/antagonistas & inibidores , Regulação Bacteriana da Expressão Gênica , Pleiotropia Genética , Transcriptoma , Bacillus pumilus/citologia , Bacillus pumilus/crescimento & desenvolvimento , Bacillus pumilus/metabolismo , Proteínas de Bactérias/genética , Proteínas de Bactérias/metabolismo , Movimento Celular , Endopeptidases/metabolismo , Flagelos/fisiologia , Fenótipo
5.
Int J Surg ; 53: 93-97, 2018 May.
Artigo em Inglês | MEDLINE | ID: mdl-29555528

RESUMO

BACKGROUND: Diaphragmatic resection is not common in patients undergoing hepatectomy for hepatocellular carcinoma (HCC). This study aims to evaluate retrospectively the clinical characteristics and surgical results of HCC patients undergoing hepatectomy plus diaphragmatic resection. METHODS: Between January 2000 and December 2013, 52 HCC patients underwent curative resections combined with diaphragmatic resection, with 11 patients had pathological diaphragmatic invasion (DI), 41 patients had diaphragmatic fibrous adhesion (DFA). The clinicopathological features and results were compared between the two groups. RESULTS: 86.5% of the patients had HBV infection. Diameter of tumors was 8.6 ±â€¯3.4 cm, and 34.6% had multiple tumors. In addition, 28.8% had microvascular invasion, 3.8% had macrovascular invasion, but none of the patients had lymph node metastasis or distant metastasis. Moreover, 21.2% had tumor rupture before surgical resection. The DI group exhibited similar clinicopathological features with the DFA group. There were no treatment-related deaths, and major complication was postoperative pleural effusion (46.2%). Other clinical pulmonary issues, such as pneumothorax (5.8%) and pneumonia (3.8%), were also detected. OS at 1, 3 and 5 years was 82.0%, 41.2% and 35.7%, respectively. There was no significant difference in OS and DFS between the DI and DFA groups (P = 0.499 and P = 0.956, respectively). CONCLUSIONS: En bloc resection of diaphragm was associated with acceptable morbidity and mortality, and there was no difference in OS and DFS between HCC patients with DI or DFA. Therefore, it would be advisable to perform en bloc diaphragmatic resection when HCC patients present with gross diaphragmatic involvement.


Assuntos
Carcinoma Hepatocelular/cirurgia , Diafragma/cirurgia , Hepatectomia/métodos , Neoplasias Hepáticas/cirurgia , Adulto , Idoso , Intervalo Livre de Doença , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Resultado do Tratamento
6.
BMC Microbiol ; 17(1): 156, 2017 Jul 11.
Artigo em Inglês | MEDLINE | ID: mdl-28693413

RESUMO

BACKGROUND: Bacillus pumilus can secret abundant extracellular enzymes, and may be used as a potential host for the industrial production of enzymes. It is necessary to understand the metabolic processes during cellular growth. Here, an RNA-seq based transcriptome analysis was applied to examine B. pumilus BA06 across various growth stages to reveal metabolic changes under two conditions. RESULTS: Based on the gene expression levels, changes to metabolism pathways that were specific to various growth phases were enriched by KEGG analysis. Upon entry into the transition from the exponential growth phase, striking changes were revealed that included down-regulation of the tricarboxylic acid cycle, oxidative phosphorylation, flagellar assembly, and chemotaxis signaling. In contrast, the expression of stress-responding genes was induced when entering the transition phase, suggesting that the cell may suffer from stress during this growth stage. As expected, up-regulation of sporulation-related genes was continuous during the stationary growth phase, which was consistent with the observed sporulation. However, the expression pattern of the various extracellular proteases was different, suggesting that the regulatory mechanism may be distinct for various proteases. In addition, two protein secretion pathways were enriched with genes responsive to the observed protein secretion in B. pumilus. However, the expression of some genes that encode sporulation-related proteins and extracellular proteases was delayed by the addition of gelatin to the minimal medium. CONCLUSIONS: The transcriptome data depict global alterations in the genome-wide transcriptome across the various growth phases, which will enable an understanding of the physiology and phenotype of B. pumilus through gene expression.


Assuntos
Bacillus pumilus/crescimento & desenvolvimento , Bacillus pumilus/metabolismo , Proteínas de Bactérias/genética , Regulação Bacteriana da Expressão Gênica , Bacillus pumilus/genética , Proteínas de Bactérias/metabolismo , Ciclo do Ácido Cítrico , Perfilação da Expressão Gênica , Regulação da Expressão Gênica no Desenvolvimento , Transcriptoma
7.
ACS Appl Mater Interfaces ; 9(24): 20620-20629, 2017 Jun 21.
Artigo em Inglês | MEDLINE | ID: mdl-28570074

RESUMO

Noble metallic nanomaterials with surface plasmon resonance (SPR) effects and hot electron cell effects open new opportunities for designing efficient visible-light-driven hybrid photocatalysts. In this work, we reported a broadband visible-light responsive photocatalyst by incorporating Au nanorods (AuNRs) into Ag3PO4 nanostructures. The longitudinal plasma of AuNRs enabled AuNRs/Ag3PO4 heterostructures to harvest light energy up to 800 nm. The obtained AuNRs/Ag3PO4 hybrid exhibited enhanced photocatalytic efficiency toward the degradation of rhodamine B (RhB) under solar irradiation. Ag3PO4, RhB, and AuNRs played different roles according to the distinct optical properties of each individual component. The dominant photocatalytic process in the different light regions were divided as follows: direct excitation of Ag3PO4 for λ ≥ 420 nm, RhB sensitization for λ ≥ 550 nm, and SPR effect for λ ≥ 600 nm. The relationship between the pathway of charge transfer and the photocatalytic activity of the AuNRs/Ag3PO4 heterostructures was investigated systematically, revealing the specific role of AuNRs in regulating the photocatalytic activity. This work presents an innovative strategy for determining the comprehensive function of the SPR effect in relevant semiconductor-based photocatalysis and functional nanodevices with a broadband light responses.

8.
J Gastrointest Surg ; 21(7): 1128-1135, 2017 07.
Artigo em Inglês | MEDLINE | ID: mdl-28397025

RESUMO

BACKGROUND: Hepatocellular carcinoma (HCC) occurs rarely in children and adolescents (C&A), and its clinical characteristics, prognostic factors, and treatment were rarely explored. METHODS: This retrospective study focused on 65 HCC patients aged ≤20 years from August 1994 to August 2012. Cox regression models and Kaplan-Meier curves were used to investigate prognostic factors and compare overall survival (OS), respectively. RESULTS: We found 61.5% of patients to have multiple tumors, 30.8% to have portal vein tumor thrombus, and 16.9% to have distant metastasis. Diameter of tumors was 10.2 ± 4.1 cm. OS at 5 years was 15.8%. Multivariate analyses showed initial treatment (P < 0.001) to be a predictor for OS. For moderate-stage HCC, the median OS of patients who underwent resection was longer than that of patients who underwent transarterial chemoembolization (TACE) or supportive treatment (ST) (P < 0.001). For advanced-stage HCC, the median OS of patients who underwent TACE was longer than that of patients who underwent ST (P = 0.045). CONCLUSIONS: HCC in C&A tends to be more advanced than that in adults, and resection remains the mainstay of treatment for those patients. Moreover, compared with ST, TACE may benefit C&A with moderate- and advanced-stage HCC, which needs further study.


Assuntos
Carcinoma Hepatocelular/patologia , Neoplasias Hepáticas/patologia , Adolescente , Adulto , Fatores Etários , Carcinoma Hepatocelular/mortalidade , Carcinoma Hepatocelular/terapia , Criança , Feminino , Humanos , Estimativa de Kaplan-Meier , Neoplasias Hepáticas/mortalidade , Neoplasias Hepáticas/terapia , Masculino , Análise Multivariada , Modelos de Riscos Proporcionais , Estudos Retrospectivos , Resultado do Tratamento
9.
Mitochondrial DNA A DNA Mapp Seq Anal ; 27(4): 2740-1, 2016 07.
Artigo em Inglês | MEDLINE | ID: mdl-27158789

RESUMO

The genus Apodemus are the most common small rodents in fields. They are also one of the best species for biogeographic study and understanding the environmental changes. In this study, the complete mitochondrial genome sequence of Apodemus draco is determined. The mitogenome is 16 220 bp in length and contains 13 protein-coding genes, 2 ribosomal RNA genes, 22 transfer RNA genes and a control region, with a base composition of 35.1% A, 29.0% T, 23.8% C and 12.1% G. The nucleotide sequence data of 12 heavy-strand protein-coding genes of Apodemus draco and other 23 rodents were used for mitochondrial genome phylogenetic analyses. The monophyly of the genus Apodemus was well supported with sister to the genus Mus. Bayesian analysis also suggested that Apodemus draco was a sister to Apodemus latronum. The present study may facilitate further investigation of the molecular evolution and biogeographic study of the genus Apodemus.


Assuntos
Arvicolinae/genética , Genoma Mitocondrial/genética , Animais , Arvicolinae/classificação , Composição de Bases/genética , Teorema de Bayes , Filogenia , RNA Ribossômico/genética , RNA de Transferência/genética , Roedores/classificação , Roedores/genética
10.
Oncotarget ; 7(32): 50963-50971, 2016 Aug 09.
Artigo em Inglês | MEDLINE | ID: mdl-26918355

RESUMO

We investigated whether elevated neutrophil-to-lymphocyte ratio ( NLR ) was associated with poor anti-tumor immunity and prognosis in patients with intrahepatic cholangiocarcinoma ( ICC ). Clinicopathologic data of 102 patients with ICC who underwent hepatectomy was retrospectively analyzed. The Kaplan-Meier method and Cox regression model were used to analyze the survival and prognosis. The percentage of overall lymphocytes , T cells and CD8+ T cells in the high NLR group was lower than that in the low NLR group. The percentage of PD-1+CD4+ and PD-1+CD8+ T cells was higher and the percentage of IFN-γ+CD4+ and IFN-γ+CD8+ T cells was lower in the high NLR group than that in the low NLR group ( p = 0.045, p = 0.008; p = 0.012, p = 0.006 ). Density of tumor-infiltrating CD3+ T cells in the high NLR group was lower than that in the low NLR group ( p < 0.001 ). Elevated NLR was an independent predictor for poor overall survival ( OS; p = 0.035 ) and recurrence-free survival ( RFS; p = 0.008 ). These results indicate that elevated NLR is associated with poor anti-tumor immunity and could be a poor biomarker for prognosis in patients with ICC.


Assuntos
Neoplasias dos Ductos Biliares/imunologia , Colangiocarcinoma/imunologia , Linfócitos/imunologia , Neutrófilos/imunologia , Adulto , Idoso , Neoplasias dos Ductos Biliares/mortalidade , Colangiocarcinoma/mortalidade , Intervalo Livre de Doença , Feminino , Humanos , Estimativa de Kaplan-Meier , Contagem de Linfócitos , Masculino , Pessoa de Meia-Idade , Prognóstico , Modelos de Riscos Proporcionais , Estudos Retrospectivos
11.
Mitochondrial DNA A DNA Mapp Seq Anal ; 27(6): 3966-3967, 2016 11.
Artigo em Inglês | MEDLINE | ID: mdl-25541314

RESUMO

The Asian Gray Shrews, Crocidura attenuate, belongs to the family Soricidae. This widespread Asian species ranges from India and perhaps Pakistan in the west of its range, through much of eastern China and mainland Southeast Asia. In this study, the complete mitochondrial genome sequence of Crocidura attenuata was determined. The mitogenome is 17,534 base pairs in length and contains 13 protein-coding genes, two ribosomal RNA genes, 22 transfer RNA genes, and one control region, with a base composition of 32.8% A, 31.8% T, 22.4% C and 13.0% G. The present study contributes to illuminating taxonomic status of Crocidura attenuata, and may facilitate further investigation of the molecular evolution of Soricidae.


Assuntos
Ordem dos Genes , Genes Mitocondriais , Genoma Mitocondrial , Musaranhos/genética , Animais , Composição de Bases , Evolução Molecular , Análise de Sequência de DNA
12.
Cancer Lett ; 354(2): 320-8, 2014 Nov 28.
Artigo em Inglês | MEDLINE | ID: mdl-25194504

RESUMO

Epithelial-mesenchymal transition (EMT) is a major factor that facilitates the invasiveness and metastasis of cancer. Recent studies have demonstrated that EMT plays a key role in generating cancer stem cells (CSCs). This study aimed to investigate the effect of EMT on CSCs that were identified as positive for aldehyde dehydrogenase (ALDH) in cholangiocarcinoma (CCA). We demonstrated that transforming growth factor-ß1 (TGF-ß1)-induced EMT in the human cholangiocarcinoma (CCA) cell line, TFK-1, resulted in the acquisition of mesenchymal traits, as well as the expression of ALDH, which was accompanied by decreased sensitivity to the chemotherapeutic agent, 5-fluorouracil. ALDH-positive cells isolated from TFK-1 cells had higher proliferation potential in vitro and tumourigenic ability in vivo. They also expressed mesenchymal markers. Moreover, the expression levels of TGF-ß1 and ALDH1 were correlated with poor prognosis in patients. We conclude that ALDH acts as a marker for CSCs in CCA, and TGF-ß1-induced EMT is involved in the generation of CSCs. These findings offer a new tool for the study of CCA stem cells and illustrate a direct link between EMT and the gain of stem-cell properties.


Assuntos
Aldeído Desidrogenase/metabolismo , Neoplasias dos Ductos Biliares/patologia , Ductos Biliares Intra-Hepáticos/patologia , Colangiocarcinoma/patologia , Células-Tronco Neoplásicas/efeitos dos fármacos , Fator de Crescimento Transformador beta1/farmacologia , Animais , Neoplasias dos Ductos Biliares/enzimologia , Ductos Biliares Intra-Hepáticos/efeitos dos fármacos , Ductos Biliares Intra-Hepáticos/enzimologia , Linhagem Celular Tumoral , Colangiocarcinoma/enzimologia , Transição Epitelial-Mesenquimal/efeitos dos fármacos , Humanos , Masculino , Camundongos , Camundongos Endogâmicos NOD , Camundongos SCID , Células-Tronco Neoplásicas/enzimologia , Células-Tronco Neoplásicas/patologia
13.
Anal Bioanal Chem ; 406(17): 4157-72, 2014 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-24705961

RESUMO

In the present study, the theory of the data treatment with scaling techniques for moving-window two-dimensional (scaling-MW2D) correlation analysis was first proposed. This new analytical method of spectroscopy can significantly enhance the resolving capacity of the moving-window two-dimensional (MW2D) correlation infrared spectroscopy in the direction of the perturbation variable. So, it strengthened the ability of MW2D to highlight the weak transitions. The in situ infrared spectra of four common polymers, including polyamide 66 (PA66), polystyrene-block-polybutadiene-block-polystyrene block copolymer (SBS), isotactic polypropylene (iPP), and polyoxymethylene (POM), were employed to illustrate the advantages of scaling-MW2D. In the applications of the present study, the conventional autocorrelation MW2D can only distinguish the melting point of PA66, the maximum crystallization temperature of POM, and the primary oxidation of SBS. However, the autocorrelation scaling-MW2D not only can more easily determine the above transitions, but also can identify PA66 brill transition, the dissociation of adsorbed water in PA66, POM secondary crystallization, the glass transition of hard blocks in SBS, and the generation of the aldehyde and hydroxyl groups during SBS oxidation. Our further study found that the selection of the scaling factor α was very important. The golden point α = 0.618 was the best value, and satisfactory application results can be achieved. The slice scaling-MW2D was also investigated. The scaling-MW2D method of spectroscopy can be used elsewhere. The application of this analytical method should not be limited to the infrared spectra, and it also should not be limited to transitions in polymers. This method can be easily extended and applied to other materials and spectra.

14.
Anal Chem ; 79(22): 8796-802, 2007 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-17939743

RESUMO

A biosensor system for detection of pathogens was developed by using CdSe/ZnS core/shell dendron nanocrystals with high efficiency and stability as fluorescence labels and a flowing chamber with a microporous immunofilter. The antibody-immobilized immunofilter captured the targeted pathogens, Escherichia coli O157:H7 as an example for bacteria and hepatitis B being a model system for viruses. The CdSe/ZnS core/shell dendron nanocrystals were conjugated with the corresponding antibodies and then passed through the microporous membrane where they attached to the membrane-antigen-antibody. The efficient and stable photoluminescence (PL) of the CdSe/ZnS nanocrystals on the formed "sandwich" structure complexes (membrane-antigen-antibody conjugated with the nanocrystals) was used as the detection means. The effects of the pore size of the membranes, buffer pH, and assay time on the detection of E. coli O157:H7 were investigated and optimized. The detectable level of this new system was as low as 2.3 CFU/mL for E. coli O157:H7 and 5 ng/mL for hepatitis B surface Ag (HBsAg). The assay time was shortened to 30 min without any enrichment and incubation.


Assuntos
Antracenos/química , Compostos de Cádmio/análise , Imunoensaio/métodos , Medições Luminescentes/instrumentação , Medições Luminescentes/métodos , Nanopartículas/química , Compostos de Selênio/análise , Sulfetos/análise , Compostos de Zinco/análise , Anticorpos/imunologia , Técnicas Biossensoriais , Escherichia coli/patogenicidade , Imunoensaio/instrumentação , Íons/química , Microscopia Eletrônica de Transmissão , Nanopartículas/ultraestrutura
15.
Nano Lett ; 7(2): 312-7, 2007 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-17297994

RESUMO

Mn2+-doped ZnSe quantum dots (Mn:ZnSe d-dots) with a tunable photoluminescence (PL) peak position were made to be water soluble by coating them with a monolayer of mercaptopropionic acid, a very short hydrophilic thiol. If the dopant centers were located close to the surface, thiol-coating partially quenched the PL. With about 2-3 monolayers of pure ZnSe on the surface, the PL of d-dots was actually enhanced upon thiol coating. When the doping centers were placed reasonably inside a d-dot, with about four monolayers of pure ZnSe between the doping centers and the surface ligands, the thiol ligands did not quench the PL of the d-dots, even though they did completely quench the PL of intrinsic ZnSe quantum dots. The overall size of such d-dots/ligand complex is only about 7-8 nm, implying an excellent permeability in biological issues. These d-dots were found to be exceptionally stable against continuous UV radiation in air for at least 25 days. They were also stable in boiling water with air bubbling under room light for hours. Recognition of a biotin pattern by d-dots conjugated with avidine was carried to illustrate the suitability of these efficient (about 40% PL quantum yield), stable, small, and water-soluble d-dots as biomedical labeling reagents.


Assuntos
Materiais Biocompatíveis/química , Nanopartículas Metálicas/química , Pontos Quânticos , Compostos de Selênio/química , Compostos de Zinco/química , Manganês/química , Teste de Materiais , Microscopia Eletrônica , Nanotecnologia/métodos , Tamanho da Partícula , Fotoquímica , Solubilidade , Água
16.
J Colloid Interface Sci ; 308(1): 254-7, 2007 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-17204276

RESUMO

We report a new method to synthesize monodisperse zinc blende HgTe nanocrystals at room temperature in noncoordinating solvent-octadecene. Thiol was needed to control the reaction at a suitable nucleation and growth speed. In the early stage of the reaction, HgTe nanocrystals formed aggregates, and then the aggregates were dispersed and individual dot-shaped nanocrystals were formed with stronger photoluminescence emitting. UV-vis, photoluminescence, and TEM have been used to study the properties of as-prepared HgTe nanocrystals.


Assuntos
Compostos de Mercúrio/química , Nanopartículas Metálicas/química , Telúrio/química , Temperatura Alta , Nanopartículas Metálicas/ultraestrutura , Microscopia Eletrônica de Transmissão
17.
Langmuir ; 22(14): 6341-5, 2006 Jul 04.
Artigo em Inglês | MEDLINE | ID: mdl-16800696

RESUMO

A dendron ligand with two carboxylate anchoring groups at its focal point and eight hydroxyl groups as its terminal groups was found to efficiently convert as-synthesized CdSe/CdS core-shell nanocrystals in toluene to water-soluble dendron-ligand stabilized nanocrystals (dendron nanocrystals). The resulting dendron nanocrystals retained 60% of the photoluminescence value of the original CdSe/CdS core-shell nanocrystals in toluene and were significantly brighter than the similar dendron nanocrystals with thiolate (deprotonated thiol group) as the anchoring group which retained just 10% of the photoluminescence value of the original CdSe/CdS core-shell nanocrystals in toluene. The carboxylate-based dendron nanocrystals survived UV irradiation in air for at least 13 days, about 9 times better than the thiolate-based dendron nanocrystals (35 h) and similar to that of the thiolate-based dendron-box stabilized CdSe/CdS core-shell nanocrystals (box nanocrystals). Upon UV irradiation, the dendron nanocrystals became even 2 times brighter than the original CdSe/CdS core-shell nanocrystals in toluene, and the UV-brightened PL can retain the brightness for at least several months. These stable and bright dendron nanocrystals were soluble in various aqueous media, including all common biological buffer solutions tested, for at least 1.5 years. In addition to their superior performance, the synthetic chemistry of carboxylate dendron ligands and the corresponding dendron nanocrystals is relatively simple and with high yield.


Assuntos
Compostos de Cádmio , Nanopartículas/química , Compostos de Selênio , Sulfetos , Raios Ultravioleta , Cristalização , Solubilidade/efeitos da radiação , Espectrometria de Fluorescência , Fatores de Tempo , Água/química
18.
J Food Prot ; 66(3): 512-7, 2003 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-12636312

RESUMO

A biosensor was evaluated with regard to its usefulness in the rapid detection of Escherichia coli O157:H7 inoculated in ground beef, chicken carcass, and romaine lettuce samples. The biosensor consisted of a chemiluminescence reaction cell, a fiber-optic light guide, and a luminometer linked to a personal computer in conjunction with immunomagnetic separation. The samples inoculated with E. coli O157:H7 were first centrifuged and suspended in buffered peptone water and then incubated with anti-E. coli O157 antibody-coated magnetic beads and horseradish peroxidase (HRP)-labeled anti-E. coli O157 antibodies to form antibody-coated bead-bacterium-HRP-labeled antibody sandwich complexes. Finally, the sandwich complexes were separated from the samples in a magnetic field and reacted with luminol in the reaction cell. The number of E. coli O157:H7 cells was determined by collecting the HRP-catalyzed chemiluminescence signal from the bead surface through a fiber-optic light guide and measuring the signal with a luminometer. The chemiluminescence biosensor was specific for E. coli O157:H7 in samples containing other bacteria, including Salmonella Typhimurium, Campylobacter jejuni, and Listeria monocytogenes. The chemiluminescence signal was linear on a log scale from 10(2) to 10(5) CFU of E. coli O157:H7 per ml in samples. Detection could be completed within 1.5 h without any enrichment. The detection limits for ground beef, chicken carcass, and lettuce samples were 3.2 x 10(2), 4.4 x 10(2), and 5.5 x 10(2) CFU of E. coli O157:H7 per ml, respectively.


Assuntos
Técnicas Biossensoriais , Galinhas/microbiologia , Escherichia coli O157/isolamento & purificação , Alface/microbiologia , Produtos da Carne/microbiologia , Animais , Anticorpos Antibacterianos/análise , Bovinos , Contagem de Colônia Microbiana , Tecnologia de Fibra Óptica , Fibras Ópticas , Sensibilidade e Especificidade
19.
J Microbiol Methods ; 51(3): 369-77, 2002 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-12223297

RESUMO

An assay system for detection of Escherichia coli O157:H7 was developed based on immunomagnetic separation of the target pathogen from samples and absorbance measurement of p-nitrophenol at 400 nm from p-nitrophenyl phosphate hydrolysis by alkaline phosphatase (EC 3.1.3.1) on the "sandwich" structure complexes (antibodies coated onto micromagnetic beads--E. coli O157:H7-antibodies conjugated with the enzyme) formed on the microbead surface. The effects of immunoreaction time, phosphate buffer concentration, pH and temperature on the immunomagnetic separation of E. coli O157:H7 from samples were determined and the conditions used for the separation were 1-h reaction time, 1.0 x 10(-2) M PBS, pH 8.0 and 33 degrees C in this system. The effects of MgCl(2) concentration, Tris buffer concentration, pH and temperature on the activity of alkaline phosphatase conjugated on the immuno-"sandwich" structure complexes were investigated after immunomagnetic separation of the target pathogen and the conditions used for the enzymatic amplification were 1.0 x 10(-4) M MgCl(2), 1.0 M Tris buffer, pH 8.0, 28 degrees C and 30-min reaction time during the assay. The selectivity of the system was examined and no interference from the other pathogens including Salmonella typhimurium, Campylobacter jejuni and Listeria monocytogenes was observed. Its working range was from 3.2 x 10(2) to 3.2 x 10(4) CFU/ml, and the relative standard deviation was 2.5-9.9%. The total detection time was less than 2 h.


Assuntos
Fosfatase Alcalina/metabolismo , Escherichia coli O157/isolamento & purificação , Separação Imunomagnética/métodos , Nitrofenóis/metabolismo , Contagem de Colônia Microbiana , Humanos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Espectrofotometria/métodos , Fatores de Tempo
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