Your browser doesn't support javascript.
Mostrar: 20 | 50 | 100
Resultados 1 - 13 de 13
Filtrar
Mais filtros










Base de dados
Tipo de estudo
Intervalo de ano de publicação
1.
ACS Appl Mater Interfaces ; 11(39): 36278-36285, 2019 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-31490648

RESUMO

Carbon nanotube (CNT) buckypapers, or films, have the potential for wide applications because of their unique properties. Neat buckypapers or pristine CNT (PCNT) films have relatively large elongation but low strength and low modulus due to the weak interaction between CNTs. Chemical modifications of PCNT films can significantly strengthen the interaction between CNTs, resulting in high strength and high modulus but usually accompanied by low elongation. Here, we report the functionalization of pristine CNT films by thiol-ended hyperbranched polymers (THBP-n) via a thiol-ene click reaction that can introduce simultaneous improvements on the strength, modulus, and elongation to the PCNT film by 689, 812, and 32.4%, respectively. The high thiol content of THBP-n enables the formation of a network with a high degree of cross-linking between carbon nanotubes, which provides high-efficiency load transfer that increases the tensile strength and modulus of the resulting films and at the same time a compressible hyperbranched structure that allows for deformation and slip between CNTs and consequently improved elongation. The main factors affecting the mechanical performance of the functionalized CNT film are also investigated.

2.
Atherosclerosis ; 289: 8-13, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31437611

RESUMO

BACKGROUND AND AIMS: Epidemiological evidence on the association between elevated lipoprotein (a) (Lp (a)) with risk of stroke remains inconsistent. We aimed to investigate the association between serum Lp (a) level and the risk of stroke among middle-aged and elderly Chinese. METHODS: A community-based prospective cohort study of 8500 participants aged 40 years or older was conducted in Jiading district, Shanghai, China, in 2010. The incident strokes were documented at follow-up visit during 2014-2015. RESULTS: During a mean follow-up of 5.1 years, 444 incident cases of stroke occurred. The incidences of stroke were 4.44%, 5.14% and 6.14% from the lowest to the highest serum Lp (a) tertile, respectively. A significant association between serum Lp (a) tertile and the risk of incident stroke was observed (p for trend<0.05). Compared with individuals in the lowest tertile of serum Lp (a), the multivariable adjusted hazards ratio (HR) and 95% confidence interval (CI) for incident stroke in Lp (a) tertile 3 were 1.34 (1.06-1.70). CONCLUSIONS: Serum Lp (a) concentration was associated with increased risk of incident stroke in Chinese adults.

3.
Diabetes Care ; 42(11): 2117-2126, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31455687

RESUMO

OBJECTIVE: Comprehensive assessment of serum lipidomic aberrations before type 2 diabetes mellitus (T2DM) onset has remained lacking in Han Chinese. We evaluated changes in lipid coregulation antecedent to T2DM and identified novel lipid predictors for T2DM in individuals with normal glucose regulation (NGR). RESEARCH DESIGN AND METHODS: In the discovery study, we tested 667 baseline serum lipids in subjects with incident diabetes and propensity score-matched control subjects (n = 200) from a prospective cohort comprising 3,821 Chinese adults with NGR. In the validation study, we tested 250 lipids in subjects with incident diabetes and matched control subjects (n = 724) from a pooled validation cohort of 14,651 individuals with NGR covering five geographical regions across China. Differential correlation network analyses revealed perturbed lipid coregulation antecedent to diabetes. The predictive value of a serum lipid panel independent of serum triglycerides and 2-h postload glucose was also evaluated. RESULTS: At the level of false-discovery rate <0.05, 38 lipids, including triacylglycerols (TAGs), lyso-phosphatidylinositols, phosphatidylcholines, polyunsaturated fatty acid (PUFA)-plasmalogen phosphatidylethanolamines (PUFA-PEps), and cholesteryl esters, were significantly associated with T2DM risk in the discovery and validation cohorts. A preliminary study found most of the lipid predictors were also significantly associated with the risk of prediabetes. Differential correlation network analysis revealed that perturbations in intraclass (i.e., non-PUFA-TAG and PUFA-TAGs) and interclass (i.e., TAGs and PUFA-PEps) lipid coregulation preexisted before diabetes onset. Our lipid panel further improved prediction of incident diabetes over conventional clinical indices. CONCLUSIONS: These findings revealed novel changes in lipid coregulation existing before diabetes onset and expanded the current panel of serum lipid predictors for T2DM in normoglycemic Chinese individuals.

4.
Am J Med ; 131(12): 1515.e1-1515.e10, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30075104

RESUMO

BACKGROUND: Cardiovascular health has been proven to be associated with major cardiometabolic diseases. However, little is known of associations between cardiovascular health and nonalcoholic fatty liver disease. METHODS: This study included 3424 adults aged ≥40 years who were free of nonalcoholic fatty liver disease at baseline from a community cohort followed for up to 5 years. Liver ultrasonography was conducted at baseline and at follow-up to diagnose incident nonalcoholic fatty liver disease. Six metrics including smoking, physical activity, body mass index, total cholesterol, blood pressure, and fasting glucose were used to define cardiovascular health status. Associations of individual cardiovascular health metrics, number of cardiovascular health metrics, and overall cardiovascular health status at baseline, as well as changes in cardiovascular health during follow-up with risks of developing nonalcoholic fatty liver disease, were examined. RESULTS: A total of 649 participants developed nonalcoholic fatty liver disease during follow-up. Risks of nonalcoholic fatty liver disease reduced in a dose-response manner in participants with 3-4 ideal cardiovascular health metrics (odds ratio 0.50; 95% confidence interval, 0.41-0.61) and in participants with 5-6 ideal metrics (odds ratio 0.34; 95% confidence interval 0.22-0.51) compared with participants with 0-2 ideal metrics. An overall ideal or intermediate cardiovascular health was associated with 37% reduction in developing nonalcoholic fatty liver disease compared with poor cardiovascular health. In addition, improving cardiovascular health during follow-up reduced the risk by 71% compared with deteriorating cardiovascular health. Furthermore, an overall ideal or intermediate cardiovascular health was significantly associated with a lower fibrosis score in nonalcoholic fatty liver disease patients compared with an overall poor cardiovascular health. CONCLUSIONS: Ideal cardiovascular health was inversely associated with risks of nonalcoholic fatty liver disease. Although treatment of nonalcoholic fatty liver disease and subsequent inflammation and fibrosis remains a challenge, cardiovascular health goals should be advocated for nonalcoholic fatty liver disease prevention.

5.
J Pharm Biomed Anal ; 155: 148-156, 2018 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-29631075

RESUMO

Esophageal squamous cell carcinoma (ESCC) is a major health threat worldwide. Research focused on molecular events associated with ESCC carcinogenesis for diagnosis, treatment and prevention is needed. Our goal is to discover novel biomarkers and investigate the underlying molecular mechanisms of ESCC progression by employing a global metabolomic approach. Sera from 34 ESCC patients and 32 age and sex matched healthy controls were profiled using two-dimensional liquid chromatography-mass spectrometry (2D LC-MS). We identified 120 differential metabolites in ESCC patient serums compared to healthy controls. Several amino acids, serine, arginine, lysine and histidine were significantly changed in ESCC patients. Most importantly, we found dysregulated lipid metabolism as an important characteristic in ESCC patients. Several free fat acids (FFA) and carnitines were found down-regulated in ESCC patients. Choline was significantly increased and phosphatidylcholines (PC) were significantly decreased in ESCC serum. The high expression of choline and low expression of total PC in patient serum were associated with the high expression of choline kinase (Chok) and activated Kennedy pathway in ESCC cells. Chok expression can serve as a significant biomarker for ESCC prognosis. In conclusion, metabolite profiles in the ESCC patient serum were significantly different from those in the healthy controls. Phosphatidylcholines and Chok, the key enzyme in the PC metabolism pathway, may serve as novel biomarkers for ESCC.


Assuntos
Carcinoma de Células Escamosas/metabolismo , Colina Quinase/metabolismo , Colina/metabolismo , Neoplasias Esofágicas/metabolismo , Aminoácidos/metabolismo , Biomarcadores Tumorais/metabolismo , Carcinoma de Células Escamosas/patologia , Cromatografia Líquida de Alta Pressão/métodos , Progressão da Doença , Neoplasias Esofágicas/patologia , Carcinoma de Células Escamosas do Esôfago , Ácidos Graxos não Esterificados/metabolismo , Feminino , Humanos , Masculino , Metabolômica/métodos , Pessoa de Meia-Idade , Prognóstico , Espectrometria de Massas em Tandem/métodos
6.
Anal Chem ; 89(23): 12902-12908, 2017 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-29098853

RESUMO

Acyl-coenzyme A (CoA) is a pivotal metabolic intermediate in numerous biological processes. However, comprehensive analysis of acyl-CoAs is still challenging as the properties of acyl-CoAs greatly vary with different carbon chains. Here, we designed a two-dimensional liquid chromatography method coupled with high-resolution mass spectrometry (2D LC/HRMS) to cover all short-, medium-, and long-chain acyl-CoAs within one analytical run. Complex acyl-CoAs were separated into two fractions according to their acyl chains by the first dimensional prefractionation. Then, two fractions containing short-chain acyl-CoAs or medium- and long-chain acyl-CoAs were further separated by the two parallel columns in the second dimension. Nineteen representative standards were chosen to optimize the analytical conditions of the 2D LC/HRMS method. Resolution and sensitivity were demonstrated to be improved greatly, and lowly abundant acyl-CoAs and acyl-CoA isomers could be detected and distinguished. By using the 2D LC/HRMS method, 90 acyl-CoAs (including 21 acyl-dephospho-CoAs) were identified from liver extracts, which indicated that our method was one of the most powerful approaches for obtaining comprehensive profiling of acyl-CoAs so far. The method was further employed in the metabolomics study of malignant glioma cells with an isocitrate dehydrogenase 1 (IDH1) mutation to explore their metabolic differences. A total of 46 acyl-CoAs (including 2 acyl-dephospho-CoAs) were detected, and 12 of them were dysregulated in glioma cells with the IDH1 mutation. These results demonstrated the practicability and the superiority of the established method. Therefore, the 2D LC/HRMS method provides a robust and reproducible approach to the comprehensive analysis of acyl-CoAs in tissues, cells, and other biological samples.

7.
Anal Chim Acta ; 966: 34-40, 2017 May 08.
Artigo em Inglês | MEDLINE | ID: mdl-28372724

RESUMO

Increasing metabolite coverage by combining data from different platforms or methods can improve understanding of related metabolic mechanisms and the identification of biomarkers. However, no one method can obtain metabolomic and lipidomic information in a single analysis. In this work, aiming at collecting comprehensive information on metabolome and lipidome in a single analytical run, we developed an on-line heart-cutting two-dimensional liquid chromatography-mass spectrometry (2D-LC-MS) method. Complex metabolites from biological samples are divided into two fractions by using a precolumn. The first fraction is directly transferred and subjected to metabolomics analysis. Most lipids are retained on the precolumn until the mobile phases for lipidomics flow through; then they are subjected to lipidomics analysis. Up to 447 and 289 metabolites in plasma, including amino acids, carnitines, bile acids, free fatty acids, lyso-phospholipids, phospholipids, sphingomyelins etc. were identified within 30 min in the positive mode and negative mode, respectively. A comparison of the newly developed method with the conventional metabolomic and lipidomic approaches showed that approximately 99% features obtained by the two conventional methods can be covered with this 2D-LC method. Analytical characteristics evaluation showed the method had a wide linearity range, high sensitivity, satisfactory recovery and repeatability. These results demonstrate that this method is reliable, stable and well qualified in metabolomics analysis, particularly for large-scale metabolomics studies with small amount of samples.


Assuntos
Cromatografia Líquida , Lipídeos/análise , Metaboloma , Espectrometria de Massas em Tandem , Animais , Biomarcadores/sangue , Linhagem Celular Tumoral , Lipídeos/sangue , Fígado/metabolismo , Metabolômica , Camundongos
8.
Anal Chem ; 89(3): 1433-1438, 2017 Feb 07.
Artigo em Inglês | MEDLINE | ID: mdl-28208283

RESUMO

In this work, a novel online three dimensional liquid chromatography (3D-LC) system was first developed by effectively coupling of preseparation and comprehensive 2D-LC using a stop-flow interface, aiming at improving the separation of complex samples. The sample was separated into two or several fractions through the first dimensional separation, and then each fraction was transferred in an orderly way into the following comprehensive 2D-LC part for further analysis. More optimal conditions could be operated in the second and third dimensions according to the properties of each fraction. Thus, the resolution of the 3D-LC system was substantially improved. Analysis of soybean extract was taken as a proof-of-principle to demonstrate the powerful separation of the established 3D-LC system. The amide column was selected as the first dimension column. Weakly polar metabolites (such as lipids, aglycones, etc.) and polar metabolites (such as glycosides, etc.) were separated into different fractions. Fluorophenyl and C18 columns were used in the second and third dimensions of the 3D-LC system for further separation, respectively. There were 83 flavonoids characterized in the soybean extract, including many difficult to separate isomers and low-abundance flavonoids; in total, they were nearly 30% more than those identified in the comparative comprehensive 2D-LC approach. In conclusion, this 3D-LC system is flexible in construction and applicable to complex sample analysis.

9.
Anal Bioanal Chem ; 407(1): 331-41, 2015 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-25410638

RESUMO

A method based on stop-flow two-dimensional liquid chromatography coupled with electrospray ionization mass spectrometry (2D LC-ESI MS) was established and applied to analyze triterpenoid saponins from the main root of ginseng. Due to the special structure of triterpenoid saponins (they contain polar sugar side chains and nonpolar aglycones), hydrophilic interaction chromatography (HILIC) and reversed-phase liquid chromatography (RPLC) were used for the two dimensions, respectively. A trap column was used to connect the two dimensions. The dilution effect, which is one of the main shortcomings of traditional comprehensive 2D LC methods, was largely avoided. The peak capacity of this system was 747 and the orthogonality was 56.6 %. Compared with one-dimensional HILIC or RP LC MS analysis, 257 and 185 % more mass spectral peaks (ions with intensities that were higher than 1,000) were obtained from the ginseng main root extracts, and 94 triterpenoid saponins were identified based on MS(n) information and summarized aglycone structures. Given its good linearity and repeatability, the established method was successfully applied to classify ginsengs of different ages (i.e., years of growth), and 19 triterpenoid saponins were found through statistical analysis to vary in concentration depending on the age of the ginseng.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Espectrometria de Massas/métodos , Panax/química , Extratos Vegetais/química , Saponinas/química , Triterpenos/química , Automação , Cromatografia Líquida de Alta Pressão/instrumentação , Extratos Vegetais/isolamento & purificação , Raízes de Plantas/química , Saponinas/isolamento & purificação , Triterpenos/isolamento & purificação
10.
J Chromatogr A ; 1360: 240-7, 2014 Sep 19.
Artigo em Inglês | MEDLINE | ID: mdl-25129388

RESUMO

Glucaminium-based ionic liquids are a new class of recently developed ionic liquids and prepared by functionalizing the amine group of N-methyl-d-glucamine, which renders them good hydrophilicity due to the presence of the glucose structure and charged quaternary ammonium group. In the present study, a glucaminium-based ionic liquid N,N-diallyl-N-methyl-d-glucaminium bromide was synthesized and subsequently bonded to the surface of 3-mercaptopropyl modified silica materials through "thiol-ene" click chemistry. The obtained stationary phase was characterized by elemental analysis and infrared spectroscopy, and then packed as a HPLC column. A mixture of five nucleosides was used to characterize the separation performance of the obtained column under HILIC mode and the column efficiency was determined with cytidine as the test solute, reaching 80,000plates/m. Then, the retention behavior was evaluated by investigating the effect of various chromatographic factors on retention of different types of solutes, and the results revealed that the developed surface-confined glucaminium-based ionic liquid stationary phase exhibited a hydrophilic interaction/anion-exchange mixed-mode retention mechanism. Finally, two mixtures of nucleotides and flavonoids were separated on the glucaminium-based ionic liquid column, respectively under hydrophilic interaction and hydrophilic interaction/anion-exchange mixed-mode chromatography. In conclusion, the multimodal retention capabilities of the glucaminium-based ionic liquid column could offer a wider range of retention behavior and flexible selectivity toward polar and hydrophilic compounds.


Assuntos
Cromatografia por Troca Iônica/métodos , Glucanos/química , Interações Hidrofóbicas e Hidrofílicas , Líquidos Iônicos/química , Ânions/química , Cromatografia por Troca Iônica/instrumentação , Cromatografia Líquida/métodos , Química Click , Concentração de Íons de Hidrogênio , Nucleosídeos , Dióxido de Silício/química , Propriedades de Superfície
11.
J Chromatogr A ; 1330: 40-50, 2014 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-24484692

RESUMO

In the present study, several geminal dicationic ionic liquids based on 1,4-bis(3-allylimidazolium)butane and 1,8-bis(3-allylimidazolium)octane in combination with different anions bromide and bis(trifluoromethanesulphonyl)imide were prepared and then bonded to the surface of 3-mercaptopropyl modified silica materials through the "thiol-ene" click chemistry as stationary phases for hydrophilic interaction chromatography (HILIC). Compared with their monocationic analogues, the dicationic ionic liquids stationary phases presented effective retention and good selectivity for typical hydrophilic compounds under HILIC mode with the column efficiency as high as 130,000 plates/m. Moreover, the influence of different alkyl chain spacer between dications and combined anions on the retention behavior and selectivity of the dicationic ionic liquids stationary phases under HILIC mode was displayed. The results indicated that the longer linkage chain would decrease the hydrophilicity and retention on the dicationic ionic liquid stationary phase, and while differently combined anions had no difference due to the exchangeability under the common HILIC mobile phase with buffer salt. Finally, the retention mechanism was investigated by evaluating the effect of chromatographic factors on retention, including the water content in the mobile phase, the mobile phase pH and buffer salt concentration. The results showed that the dicationic ionic liquids stationary phases presented a mixed-mode retention behavior with HILIC mechanism and anion exchange.


Assuntos
Compostos Alílicos/química , Cromatografia Líquida/métodos , Imidazóis/química , Líquidos Iônicos/química , Tampões (Química) , Cátions , Química Click , Concentração de Íons de Hidrogênio , Interações Hidrofóbicas e Hidrofílicas , Nucleosídeos/análise , Dióxido de Silício , Compostos de Sulfidrila/química , Água
12.
J Chromatogr A ; 1321: 65-72, 2013 Dec 20.
Artigo em Inglês | MEDLINE | ID: mdl-24238711

RESUMO

A novel on-line two dimensional liquid chromatography (2D LC) based on stop-flow mode coupled with electrospray ionization mass spectrometry (ESI-MS) method was established to separate lipids in human plasma. Hydrophilic interaction liquid chromatography (HILIC) in the first dimension and reversed-phase liquid chromatography (RP LC) in the second dimension were used to separate the lipids into six fractions based on their polar head groups and further into peaks based on aliphatic chains, respectively. A new stop-flow interface with a trap column and an extra make-up flow was designed to construct this system and trap the components eluted from the first dimension. Moreover, the same length of analytical columns and similar flow rates were used in the first and second dimensions. Therefore, the new stop-flow 2D LC system can avoid the sensitivity decrease caused by the dilution effect, which is the shortcoming of comprehensive 2D LC. Three hundred and seventy-two lipids were identified from plasma extract using this 2D LC coupled with ESI-MS in positive mode, and 88 more lipids were detected than one-dimensional RP LC analysis. Peak capacity of this stop-flow 2D LC was 415, which is similar to that of comprehensive 2D LC. The linearity, repeatability and sensitivity of this method were satisfactory, which demonstrated that this method was also suitable for quantitative analysis. All these results indicated that this on-line 2D LC method is powerful for qualitative and quantitative analysis of complex lipids.


Assuntos
Cromatografia Líquida/métodos , Lipídeos/sangue , Espectrometria de Massas por Ionização por Electrospray/métodos , Humanos , Interações Hidrofóbicas e Hidrofílicas , Limite de Detecção , Padrões de Referência , Reprodutibilidade dos Testes
13.
Se Pu ; 30(10): 1037-42, 2012 Oct.
Artigo em Chinês | MEDLINE | ID: mdl-23383493

RESUMO

An analytical strategy for the metabolic profiling of rice grain was developed based on gas chromatography-mass spectrometry (GC-MS). For the purpose of obtaining abundant metabolite information, sample preparation step prior to instrumental analysis is necessary to be optimized. D-optimal experimental design was applied to optimize the extraction solvent. Four solvents, including water, methanol, isopropanol and acetonitrile, and their combinations were evaluated for the extraction efficiency using multivariate statistical analysis (partial least square regression). The count of resolved peaks and the sum of peak areas were taken as the evaluation indexes. Methanol/water (80:20, v/v) mixture was highly efficient for rice metabolites and was selected as the suitable solvent formulation. Then, the analytical characteristics of the method were measured. More than 90% of the metabolites had satisfactory precisions, reproducibilities and stabilities (relative standard deviations (RSDs) < 30%). Most of the detected metabolites (about 88.0% of total peak area) showed good linear responses. With the optimized analytical protocol, 315 metabolites were detected in rice and 86 of which were structurally identified by searching in the NIST 08/Wiley standard mass spectral library, covering carbohydrates, amino acids, organic acids, steroids and so on which showed a broad coverage of metabolite data. The established method is expected to be useful for the metabolomic studies of rice.


Assuntos
Grão Comestível/metabolismo , Cromatografia Gasosa-Espectrometria de Massas/métodos , Metabolômica/métodos , Oryza/metabolismo , Aminoácidos/análise , Carboidratos/análise , Esteroides/análise
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA