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1.
Artigo em Inglês | MEDLINE | ID: mdl-38783488

RESUMO

PURPOSE: To explore the severity of posterior capsule opacification (PCO) using objective detection techniques and its relationship with visual acuity. SETTING: The First Affiliated Hospital of Soochow University, Suzhou, Jiangsu, China. DESIGN: Prospective cohort study. METHODS: All patients underwent slit-lamp examination, intraocular pressure measurement (IOP), best-corrected visual acuity (BCVA) before neodymium: yttrium aluminium garnet (Nd:YAG) laser capsulotomy, followed by examination after fully dilated, including IOLMaster 700, optical coherence tomography (OCT), Sirius anterior segment analysis system (Sirius), color fundus photography (CFP). Conducting BCVA and IOP post-treatment again. Recording the thickness and density of posterior capsule, color fundus photography quality (CFPQ) and OCT Signal Strength (OCTSS). Analysis using Spearman correlation analysis, heatmaps, and ROC curves. RESULTS: A total of 83 eyes in 78 patients were included in this study. Spearman correlation analysis revealed correlations between pre-treatment BCVA and IOLMaster 700 PCO thickness (MT), IOLMaster 700 cumulative effect (MCE), Sirius PCO thickness (ST), Sirius maximum density (SMD), Sirius cumulative effect (SCE), OCTSS, and CFPQ (correlation coefficients were 0.500, 0.484, 0.465, -0.256, 0.317, -0.442, -0.412, all P<0.05). The improvement of Vision Acuity (ImpVA) showed correlations with MT, MCE, ST, SCE, OCTSS, and CFPQ (correlation coefficients were -0.452, -0.471, -0.346, -0.278, 0.320, 0.381, all P<0.05). For ImpVA, the predictive ability of IOLMaster 700 was superior to Sirius, and the joint model was significantly better than single factors. CONCLUSIONS: Posterior capsule thickness and cumulative effect were reliable indicators for evaluating PCO. Compared to Sirius, IOLMaster 700 demonstrates superior predictive ability and higher correlation.

2.
Phys Chem Chem Phys ; 26(1): 304-313, 2023 Dec 21.
Artigo em Inglês | MEDLINE | ID: mdl-38062783

RESUMO

To control the transport stability and release efficiency of loaded theranostic drugs in triblock copolymer carriers, the reversible crosslinking ability is of great significance. A molecular level exploration of such a function is needed to extend existing stabilizing and responsive dissociation mechanisms of carriers. Here, dissipative particle dynamics simulations were used to first demonstrate the formation of triblock copolymer vesicular carriers. Chemical crosslinking was used to strengthen the structural stability of the vesicle shell to avoid drug leakage. Reversible decrosslinking along with dissociation of the vesicle and release of loaded drugs were then explored. The structural, energetic and dynamical properties of the system were discussed at the molecular level. The regulation mechanism of drug release patterns was revealed by systematically exploring the effect of intra and intermolecular repulsive interactions. The results indicate that the chemical crosslinking of copolymers enhanced the compactness of the vesicle shell with a strengthened microstructure, increased binding energy, and limited chain migration, thus achieving more stable delivery of drugs. In terms of drug release, we clarified how the pairwise interactions of beads in the solution system affect the responsive dissociation of the vesicle and associated release patterns (speed and amount) of drugs. More efficient delivery and smart release of theranostic drugs are achieved using such reversible crosslinked triblock copolymer vesicles.

3.
Nat Commun ; 14(1): 6457, 2023 10 13.
Artigo em Inglês | MEDLINE | ID: mdl-37833282

RESUMO

Mechanotransduction in endothelial cells is critical to maintain vascular homeostasis and can contribute to disease development, yet the molecules responsible for sensing flow remain largely unknown. Here, we demonstrate that the discoidin domain receptor 1 (DDR1) tyrosine kinase is a direct mechanosensor and is essential for connecting the force imposed by shear to the endothelial responses. We identify the flow-induced activation of endothelial DDR1 to be atherogenic. Shear force likely causes conformational changes of DDR1 ectodomain by unfolding its DS-like domain to expose the buried cysteine-287, whose exposure facilitates force-induced receptor oligomerization and phase separation. Upon shearing, DDR1 forms liquid-like biomolecular condensates and co-condenses with YWHAE, leading to nuclear translocation of YAP. Our findings establish a previously uncharacterized role of DDR1 in directly sensing flow, propose a conceptual framework for understanding upstream regulation of the YAP signaling, and offer a mechanism by which endothelial activation of DDR1 promotes atherosclerosis.


Assuntos
Receptor com Domínio Discoidina 1 , Receptores Proteína Tirosina Quinases , Receptor com Domínio Discoidina 1/metabolismo , Receptores Proteína Tirosina Quinases/metabolismo , Mecanotransdução Celular , Células Endoteliais/metabolismo , Transdução de Sinais
4.
Matrix Biol ; 119: 1-18, 2023 05.
Artigo em Inglês | MEDLINE | ID: mdl-36958467

RESUMO

Decreased vascular compliance of the large arteries as indicated by increased pulse wave velocity is shown to be associated with atherosclerosis and the related cardiovascular events. The positive correlation between arterial stiffening and disease progression derives a hypothesis that softening the arterial wall may protect against atherosclerosis, despite that the mechanisms controlling the cellular pathological changes in disease progression remain unknown. Here, we established a mechanical-property-based screening to look for compounds alleviating the arterial wall stiffness through their actions on the interaction between vascular smooth muscle cells (VSMCs) and the wall extracellular matrix (ECM). We found that echinatin, a chalcone preferentially accumulated in roots and rhizomes of licorice (Glycyrrhiza inflata), reduced the stiffness of ECM surrounding cultured VSMCs. We examined the potential beneficial effects of echinatin on mitigating arterial stiffening and atherosclerosis, and explored the mechanistic basis by which the compound exert the effects. Administration of echinatin in mice fed on an adenine diet and in hyperlipidemia mice subjected to 5/6 nephrectomy mitigated arterial stiffening and atherosclerosis. Mechanistic insights were gained from the RNA-sequencing results showing that echinatin upregulated the expression of glutamate cysteine ligases (GCLs), both the catalytic (GCLC) and modulatory (GCLM) subunits. Further study indicated that upregulation of GCLC/GCLM in VSMCs by echinatin maintains the homeostasis of glutathione (GSH) metabolism; adequate availability of GSH is critical for counteracting arterial stiffening. As a consequence of regulating the GSH synthesis, echinatin inhibits ferroptosis and matrix remodeling that being considered two contributors of arterial stiffening and atherosclerosis. These data demonstrate a pivotal role of GSH dysregulation in damaging the proper VSMC-ECM interaction and uncover a beneficial activity of echinatin in preventing vascular diseases.


Assuntos
Aterosclerose , Chalconas , Camundongos , Animais , Chalconas/metabolismo , Músculo Liso Vascular/metabolismo , Análise de Onda de Pulso , Artérias , Aterosclerose/metabolismo , Homeostase , Glutationa/metabolismo , Miócitos de Músculo Liso/metabolismo
5.
Circ Res ; 132(1): 87-105, 2023 01 06.
Artigo em Inglês | MEDLINE | ID: mdl-36475898

RESUMO

BACKGROUND: The Hippo-YAP (yes-associated protein) signaling pathway is modulated in response to various environmental cues. Activation of YAP in vascular smooth muscle cells conveys the extracellular matrix stiffness-induced changes in vascular smooth muscle cells phenotype and behavior. Recent studies have established a mechanoreceptive role of receptor tyrosine kinase DDR1 (discoidin domain receptor 1) in vascular smooth muscle cells. METHODS: We conduced 5/6 nephrectomy in vascular smooth muscle cells-specific Ddr1-knockout mice, accompanied by pharmacological inhibition of the Hippo pathway kinase LATS1 (large tumor suppressor 1), to investigate DDR1 in YAP activation. We utilized polyacrylamide gels of varying stiffness or the DDR1 ligand, type I collagen, to stimulate the cells. We employed multiple molecular biological techniques to explore the role of DDR1 in controlling the Hippo pathway and to determine the mechanistic basis by which DDR1 exerts this effect. RESULTS: We identified the requirement for DDR1 in stiffness/collagen-induced YAP activation. We uncovered that DDR1 underwent stiffness/collagen binding-stimulated liquid-liquid phase separation and co-condensed with LATS1 to inactivate LATS1. Mutagenesis experiments revealed that the transmembrane domain is responsible for DDR1 droplet formation. Purified DDR1 N-terminal and transmembrane domain was sufficient to drive its reversible condensation. Depletion of the DDR1 C-terminus led to failure in co-condensation with LATS1. Interaction between the DDR1 C-terminus and LATS1 competitively inhibited binding of MOB1 (Mps one binder 1) to LATS1 and thus the subsequent phosphorylation of LATS1. Introduction of the single-point mutants, histidine-745-proline and histidine-902-proline, to DDR1 on the C-terminus abolished the co-condensation. In mouse models, YAP activity was positively correlated with collagen I expression and arterial stiffness. LATS1 inhibition reactivated the YAP signaling in Ddr1-deficient vessels and abrogated the arterial softening effect of Ddr1 deficiency. CONCLUSIONS: These findings identify DDR1 as a mediator of YAP activation by mechanical and chemical stimuli and demonstrate that DDR1 regulates LATS1 phosphorylation in an liquid-liquid phase separation-dependent manner.


Assuntos
Via de Sinalização Hippo , Histidina , Camundongos , Animais , Proteínas Serina-Treonina Quinases/genética , Proteínas Serina-Treonina Quinases/metabolismo , Transdução de Sinais , Colágeno , Colágeno Tipo I
6.
Front Aging Neurosci ; 14: 934725, 2022.
Artigo em Inglês | MEDLINE | ID: mdl-36177481

RESUMO

Due to the high clinical heterogeneity of neuronal intranuclear inclusion disease (NIID), it is easy to misdiagnose this condition and is considered to be a rare progressive neurodegenerative disease. More evidence demonstrates that NIID involves not only the central nervous system but also multiple systems of the body and shows a variety of symptoms, which makes a clinical diagnosis of NIID more difficult. This review summarizes the clinical symptoms in different systems and demonstrates that NIID is a multiple-system intranuclear inclusion disease. In addition, the core triad symptoms in the central nervous system, such as dementia, parkinsonism, and psychiatric symptoms, are proposed as an important clue for the clinical diagnosis of NIID. Recent studies have demonstrated that expanded GGC repeats in the 5'-untranslated region of the NOTCH2NLC gene are the cause of NIID. The genetic advances and possible underlying mechanisms of NIID (expanded GGC repeat-induced DNA damage, RNA toxicity, and polyglycine-NOTCH2NLC protein toxicity) are briefly summarized in this review. Interestingly, inflammatory cell infiltration and inflammation were observed in the affected tissues of patients with NIID. As a downstream pathological process of NIID, inflammation could be a therapeutic target for NIID.

7.
Adv Sci (Weinh) ; 9(32): e2203995, 2022 11.
Artigo em Inglês | MEDLINE | ID: mdl-36106364

RESUMO

Vascular smooth muscle cells (SMCs) can adapt to changes in cellular geometric cues; however, the underlying mechanisms remain elusive. Using 2D micropatterned substrates to engineer cell geometry, it is found that in comparison with an elongated geometry, a square-shaped geometry causes the nuclear-to-cytoplasmic redistribution of DNA methyltransferase 1 (DNMT1), hypermethylation of mitochondrial DNA (mtDNA), repression of mtDNA gene transcription, and impairment of mitochondrial function. Using irregularly arranged versus circumferentially aligned vascular grafts to control cell geometry in 3D growth, it is demonstrated that cell geometry, mtDNA methylation, and vessel contractility are closely related. DNMT1 redistribution is found to be dependent on the phosphoinositide 3-kinase and protein kinase B (AKT) signaling pathways. Cell elongation activates cytosolic phospholipase A2, a nuclear mechanosensor that, when inhibited, hinders AKT phosphorylation, DNMT1 nuclear accumulation, and energy production. The findings of this study provide insights into the effects of cell geometry on SMC function and its potential implications in the optimization of vascular grafts.


Assuntos
Músculo Liso Vascular , Proteínas Proto-Oncogênicas c-akt , Proteínas Proto-Oncogênicas c-akt/metabolismo , Músculo Liso Vascular/metabolismo , DNA Mitocondrial/genética , DNA Mitocondrial/metabolismo , Fosfatidilinositol 3-Quinases/metabolismo , Metilação de DNA/genética , Mitocôndrias/metabolismo , Metabolismo Energético
8.
ACS Biomater Sci Eng ; 8(1): 16-31, 2022 01 10.
Artigo em Inglês | MEDLINE | ID: mdl-34913688

RESUMO

Annulus fibrosus fissure and fibrosis of nucleus pulposus are severe morphological characteristics of intervertebral disc degeneration. Currently, surgery or drugs are used to relieve pain in such cases. Tissue engineering is a new multidisciplinary strategy with great potential for use in joint replacement and organ regeneration. Based on the natural anatomy of intervertebral discs, intervertebral disc scaffolds are fabricated by exploiting the special arrangement of extracellular matrix fibers. Electrospun nanofibers possess clear advantages in repairing degenerated intervertebral discs. This article reviews and summarizes recently developed methods for improving and fabricating electrospun nanofiber annulus fibrosus scaffolds in terms of nanofiber alignment, material selection, loading additives, and the progress made in combining other advanced technologies with electrospun nanofibers. In addition, the improvement in mechanical properties and biocompatibility of nucleus pulposus scaffolds by electrospun nanofiber-reinforced hydrogels is discussed. Finally, complete intervertebral disc scaffolds can be fabricated using the disc-like angle-ply structure and other emerging fabrication methods. Taken together, electrospun nanofiber intervertebral disc scaffolds are promising for clinical applications.


Assuntos
Degeneração do Disco Intervertebral , Disco Intervertebral , Nanofibras , Humanos , Degeneração do Disco Intervertebral/cirurgia , Regeneração , Engenharia Tecidual
9.
Sensors (Basel) ; 19(7)2019 Mar 28.
Artigo em Inglês | MEDLINE | ID: mdl-30925826

RESUMO

In wireless sensor networks (WSNs), there are many challenges for outlier detection, such as fault detection, fraud detection, intrusion detection, and so on. In this paper, the participation degree of instances in the hierarchical clustering process infers the relationship between instances. However, most of the existing algorithms ignore such information. Thus, we propose a novel fault detection technique based on the participation degree, called fault detection based on participation degree (FDP). Our algorithm has the following advantages. First, it does not need data training in labeled datasets; in fact, it uses the participation degree to measure the differences between fault points and normal points without setting distance or density parameters. Second, FDP can detect global outliers without local cluster influence. Experimental results demonstrate the performance of our approach by applying it to synthetic and real-world datasets and contrasting it with four well-known techniques: isolation forest (IF), local outlier factor (LOF), one-class support vector machine (OCS), and robust covariance (RC).

10.
ACS Appl Mater Interfaces ; 10(7): 6737-6746, 2018 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-29389110

RESUMO

Organometal mixed-halide perovskite materials hold great promise for next-generation solar cells, light-emitting diodes, lasers, and photodetectors. Except for the rapid progress in the efficiency of perovskite-based devices, the stability issue over prolonged light illumination has severely hindered their practical application. The deterioration mechanism of organometal halide perovskite materials under light illumination has seldom been conducted to date, which is indispensable to the understanding and optimization of photon-harvesting process inside perovskite-based optoelectronic devices. Here, explicit degradation pathways and comprehensive microscopic understandings of white-light-induced degradation have been put forward for two organometal mixed-halide perovskite materials (e.g., MAPbI3-xClx and MAPbBr3-xClx) under high vacuum conditions. In situ compositional analysis and real-time film characterizations reveal that the decomposition of both mixed-halide perovskites starts at the grain boundaries, leading to the formation of hydrocarbons and ammonia gas with the residuals of PbI2(Cl), Pb, or PbClxBr2-x in the films. The degradation has been correlated to the localized trap states that induce strong coupling between photoexcited carriers and the crystal lattice.

11.
J Chromatogr A ; 1270: 104-10, 2012 Dec 28.
Artigo em Inglês | MEDLINE | ID: mdl-23159197

RESUMO

The feasibility to attach plasma low-density lipoprotein (LDL) particles covalently onto 5 µm silica particles and use them as stationary phase in nano-liquid chromatography (nano-LC) for interaction and oxidation studies was clarified. Before the immobilization, both epoxy silica and aldehyde-activated particles were synthesized, LDL was immobilized to the particles via its protein component and capillary columns were packed with LDL-modified silica materials. The performance of the capillary columns was tested with neutral steroids, and the column with LDL immobilized to aldehyde-activated silica was selected for further studies due to its stronger retention toward steroids. The retention factors of the steroids were used as indicators of the column stability, and the RSDs from 0.8 to 5.7% (n=12) for 168 successive runs within 14 days carried out in the same capillary column and from 0.8 to 3.6% (n=6) in three different capillaries demonstrated that the capillary column was stable and that the capillary column-to-capillary column reproducibility was good. The lifetime of LDL-modified silica stationary phase was around 14 days. The applicability of the column for the separation of steroids and ß-blockers was based mainly on the hydrophobic interactions with lipids of LDL in the stationary phase. The LDL immobilized silica column was successfully exploited also in the copper-mediated in situ oxidation of LDL. The results achieved demonstrated that nano-LC with plasma LDL immobilized silica phase can be exploited as nano-biomimicking tool for interaction studies and as a microreactor for oxidation studies with low consumption of reagents and human materials.


Assuntos
Cromatografia Líquida/métodos , Lipoproteínas LDL/sangue , Lipoproteínas LDL/química , Nanotecnologia/instrumentação , Dióxido de Silício/química , Antagonistas Adrenérgicos beta/química , Antagonistas Adrenérgicos beta/metabolismo , Cromatografia Líquida/instrumentação , Cobre/química , Estabilidade de Medicamentos , Reutilização de Equipamento , Humanos , Interações Hidrofóbicas e Hidrofílicas , Lipoproteínas LDL/metabolismo , Nanotecnologia/métodos , Oxirredução , Esteroides/química , Esteroides/metabolismo
12.
Electrophoresis ; 33(11): 1613-23, 2012 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-22736364

RESUMO

Chiral monolithic silica capillary columns were prepared by immobilization of amylose-3,5-dimethylphenylcarbamate (ADMPC) bearing a small fraction of 3-(triethoxysilyl)propyl residues through intermolecular polycondensation of the triethoxysilyl groups. The obtained columns were used for chiral separations in capillary electrochromatography (CEC). The effects of the silica monolith nature and the used chiral selector concentration on the resulting enantiomeric separations were investigated. Fifteen chiral compounds, including acidic, neutral, and basic substances were evaluated and twelve showed partial or baseline separation at some of the different conditions tested. These results demonstrated the promising applicability of ADMPC-immobilized monolithic silica columns in CEC enantioseparations, but also revealed the need for further improvements on the level of baseline separations and efficiencies.


Assuntos
Amilose/análogos & derivados , Eletrocromatografia Capilar/métodos , Fenilcarbamatos/química , Dióxido de Silício/química , Amilose/química , Eletrocromatografia Capilar/instrumentação , Modelos Químicos , Preparações Farmacêuticas/análise , Preparações Farmacêuticas/isolamento & purificação , Reprodutibilidade dos Testes , Estereoisomerismo
13.
Electrophoresis ; 32(19): 2708-17, 2011 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-21983820

RESUMO

The 3,5-dimethylphenylcarbamate derivatives of cellulose bearing 3-(triethoxysilyl)propyl residues were immobilized in a capillary format onto a monolithic silica support by intermolecular polycondensation of the triethoxysilyl groups. The resulting columns were used for chiral separations using capillary electrochromatography. The effects of the synthesizing solvent, the selector coating procedure, the chiral selector concentration onto the silica monolith and the mobile phase pH value, on the separation of enantiomers were studied. The column-to-column reproducibility and stability also were evaluated. A test set of 14 chiral substances, including acidic, neutral, bifunctional and basic compounds, was used to investigate the effects of the factors mentioned above. Twelve pairs of enantiomers showed enantioselectivity at some of the different conditions tested. The column-to-column repeatability was satisfactory, and the prepared columns were stable under the adopted analysis conditions.


Assuntos
Eletrocromatografia Capilar/instrumentação , Celulose/análogos & derivados , Fenilcarbamatos/química , Dióxido de Silício/química , Acetamidas/química , Acetonitrilas/química , Eletrocromatografia Capilar/métodos , Celulose/química , Concentração de Íons de Hidrogênio , Cloreto de Lítio/química , Preparações Farmacêuticas/química , Preparações Farmacêuticas/isolamento & purificação , Reprodutibilidade dos Testes , Estereoisomerismo
14.
Talanta ; 80(5): 1713-8, 2010 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-20152401

RESUMO

Three monodispersed, molecularly imprinted polymers (MIPs) for cinchonidine (CD) have been synthesized by precipitation polymerization. MIP1 was prepared using methacrylic acid (MAA) as a functional monomer and divinylbenzene (DVB) as a cross-linker and MIP2 was prepared with further addition of 2-hydroxyethyl methacrylate (HEMA) as a co-monomer. For the preparation of MIP3, core-shell type MIP, monodispersed DVB homopolymers, which are prepared by precipitation polymerization, were used as a core and CD-imprinted MAA-DVB copolymer phases were coated onto the core. Three MIPs synthesized gave monodispersed, spherical beads in micrometer sizes. The binding characteristics and molecular recognition properties of MIP1-3 were examined by Scatchard analysis and chromatographic studies. The association constant of CD with MIP1 was the highest among MIPs prepared, while that with MIP3 was the lowest. The template molecule, CD, was more retained than its stereoisomer, cinchonine, on the three MIPs, and the stereoseparation factor of 38 was obtained with MIP3.


Assuntos
Antimaláricos/isolamento & purificação , Cromatografia Líquida de Alta Pressão/métodos , Alcaloides de Cinchona/isolamento & purificação , Impressão Molecular/métodos , Polímeros/química , Antimaláricos/química , Precipitação Química , Alcaloides de Cinchona/química , Tamanho da Partícula , Polímeros/síntese química , Estereoisomerismo , Temperatura
15.
Arch Virol ; 155(3): 361-6, 2010 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-20039088

RESUMO

Kaposi's sarcoma-associated herpesvirus ORF57 expression is highly responsive to replication and transcription activator (RTA) and interferon regulatory factor 7 (IRF-7). Three RTA response elements (RREs) have been identified in the ORF57 promoter. Here, we show evidence of another functional RRE located between nt 82003 and 82081, which can complement the loss of RTA activation resulting from RRE1 deletion. Repeats of a recombination signal-binding protein Jkappa (RBP-Jkappa) site enhanced RTA activation, which could not be suppressed by IRF-7. Alteration of the distance between the RBP-Jkappa site and RRE2 modulated responsiveness to RTA and IRF-7. These results will help to elucidate the precise regulation of viral gene expression.


Assuntos
Regulação Viral da Expressão Gênica , Herpesvirus Humano 8/fisiologia , Proteínas Imediatamente Precoces/metabolismo , Fator Regulador 7 de Interferon/metabolismo , Regiões Promotoras Genéticas , Elementos de Resposta , Transativadores/metabolismo , Transcrição Gênica , Sequência de Bases , DNA Viral/genética , Herpesvirus Humano 8/genética , Humanos , Dados de Sequência Molecular , Recombinação Genética/genética , Replicação Viral
16.
J Chromatogr A ; 1178(1-2): 118-25, 2008 Jan 18.
Artigo em Inglês | MEDLINE | ID: mdl-18068714

RESUMO

A two-step coating/precipitation synthetic procedure has been developed for the preparation of cellulose tris(3,5-dimethylphenylcarbamate) chiral stationary phase (CSP) having a small-pore silica support. With this synthetic strategy, monodisperse, spherical CSP particles can be produced without the need for a wasteful and time-consuming sieving process. The performance of the synthesized CSP towards a variety of racemates was evaluated in the normal-phase HPLC mode. HPLC separation experiments revealed that the synthesized CSP exhibited a chiral recognition ability fully comparable to the corresponding commercial columns prepared using conventional large-pore silica as the support. Moreover, the synthesized CSP was successfully applied to semipreparative enantioseparation of a new triazole antifungal agent.


Assuntos
Cromatografia Líquida de Alta Pressão/métodos , Preparações Farmacêuticas/análise , Pirimidinas/análise , Triazóis/análise , Celulose , Preparações Farmacêuticas/química , Preparações Farmacêuticas/isolamento & purificação , Fenilcarbamatos , Pirimidinas/química , Pirimidinas/isolamento & purificação , Dióxido de Silício , Triazóis/química , Triazóis/isolamento & purificação , Voriconazol
17.
J Sep Sci ; 29(10): 1440-6, 2006 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-16894789

RESUMO

A novel chiral stationary phase based on chitosan covalently bonded onto silica gels has been prepared and used for the separation of various alpha-amino acid enantiomers as well as alpha-hydroxycarboxylic acid enantiomers by chiral ligand-exchange chromatography with copper(II) as a complexing ion. The methanol content and copper(II) ion concentration in the eluent affected retentivity and enantioselectivity. Furthermore, a plausible chiral recognition mechanism for resolution of alpha-amino acids was proposed.


Assuntos
Quitosana/química , Cromatografia Líquida , Ligantes , Estereoisomerismo , 5-Hidroxitriptofano/química , Aminoácidos/química , Ácidos Carboxílicos/química , Quitina/química , Cromatografia Líquida/instrumentação , Cromatografia Líquida/métodos , Cobre/química , Metanol/química , Estrutura Molecular , Dióxido de Silício/química , Tirosina/química
18.
J Mol Recognit ; 19(1): 39-48, 2006.
Artigo em Inglês | MEDLINE | ID: mdl-16265676

RESUMO

Beta-cyclodextrin (beta-CyD) was cross-linked by hexamethylene diisocyanate and the polymer was investigated for adsorption of aromatic amino acids (AAA) from phosphate buffer. High adsorption rates were observed at the beginning and the adsorption equilibrium was then gradually achieved in about 45 min. The adsorption of AAA decreased with the increase of initial concentration and also temperature. Under the same conditions, the adsorption efficiencies of AAA were in the order of L-tryptophan (L-Trp) > L-phenylalanine (L-Phe) > L-tyrosine (L-Tyr). Much higher adsorption values, up to 52.4 and 43.0 mg/g for L-Trp and L-Phe, respectively, at 50 mmol/L and 3.2 mg/g for L-Tyr at 2 mmol/L, were obtained with the beta-CyD polymer at 37 degrees C. It was shown that the adsorption of AAA on the beta-CyD polymer was consistent with the Freundlich isotherm equation. The adsorption of mixed aromatic amino acids and branched-chain amino acids (BCAA) showed that AAA were preferentially adsorbed with adsorption efficiencies 10-24%, while those of BCAA were lower than 2%. It seems that the structure and hydrophobicity of amino acid molecules are responsible for the difference in adsorption, by influencing the strength of interactions between amino acid molecule and the polymer.


Assuntos
Aminoácidos Aromáticos/química , beta-Ciclodextrinas/química , Adsorção , Soluções Tampão , Reagentes de Ligações Cruzadas/farmacologia , Cianatos/farmacologia , Isocianatos , Cinética , Microscopia Eletrônica de Varredura , Conformação Molecular , Polímeros/química , Espectroscopia de Infravermelho com Transformada de Fourier
19.
Electrophoresis ; 26(20): 3921-9, 2005 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-16152670

RESUMO

A chemically bonded cellulose tris(3,5-dimethylphenylcarbamate) chiral stationary phase (CSP) was prepared by a radical polymerization reaction. The prepared CSP was packed into fused-silica capillaries with inner diameter of 75 microm to perform enantiomer separations in CEC. The electrochromatographic behavior of the CSP was investigated. On the prepared CSP, high EOF could be generated under acidic mobile phases, which represented an advantage for the separation of acidic enantiomers. Several neutral, acidic, and basic enantiomers were resolved on the prepared CSP under aqueous mobile phases. The column efficiencies were between 20,000 and 100,000 plates/m, which were much higher than those of HPLC. In addition, it was observed that the separation of some enantiomers benefited from the adoption of THF as mobile phase modifier.


Assuntos
Celulose , Eletroforese Capilar/métodos , Cromatografia/métodos , Soluções , Estereoisomerismo , Água
20.
J Sep Sci ; 27(14): 1195-201, 2004 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-15537076

RESUMO

Dimethyl dicarboxy alpha-biphenyl (DDB) and its analogues represent atropisomers which have been resolved on the covalently bonded cellulose tris-(3,5-dimethylphenylcarbamate) (CDMPC) CSP. Different kinds of alcohols, tetrahydrofuran (THF), and chloroform were employed as mobile phase modifiers (MPMs), and their influence on the retention and separation of the enantiomers was investigated. Ternary mobile phases (hexane/2-propanol/THF, hexane/2-propanol/chloroform) were employed to investigate the separation of the five enantiomers. The advantages of the broader choice of solvents offered by the covalently bonded CDMPC CSP were discussed. The effect of structural variation of the enantiomers on their retention and separation was investigated.


Assuntos
Celulose/análogos & derivados , Celulose/química , Cromatografia Líquida de Alta Pressão , Hidrocarbonetos Clorados/química , Hidrocarbonetos Clorados/isolamento & purificação , Fenilcarbamatos/química , Soluções Tampão , Clorofórmio/química , Cromatografia Líquida de Alta Pressão/instrumentação , Cromatografia Líquida de Alta Pressão/métodos , Furanos/química , Isomerismo , Estrutura Molecular
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