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ABSTRACT: In response to binding to amine and ammonium guests of varying types, a pyridine-based folding oligomer displays fingerprint regions in its (1)H NMR spectra that allow for the easy identification and classification of the bound guests.
Chemical Communications 04/2012; · 6.17 Impact Factor
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ABSTRACT: Tetrabutylammonium chloride (TBACl) salt alone has not been shown previously to be capable of removing methoxy groups. It is demonstrated here that the use of TBACl achieves efficient folding-promoted chemo- and regioselective demethylations, eliminating up to two out of five methyl groups situated in similar macrocyclic chemical microenvironments.
Organic Letters 11/2011; 13(23):6212-5. · 5.86 Impact Factor
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ABSTRACT: Water-binding foldamers have been rarely studied. By orienting both H-bond donors and acceptors toward their interior, two pyridine-derived crescent-shaped folding oligoamides were found to be capable of trapping both conventional and unconventional water dimer clusters in their cavity (∼2.5 Å radius). In the unconventional water dimer cluster, the two water molecules stay in contact via an unusual H-H interaction (2.25 Å) rather than the typical H-bond.
Organic Letters 06/2011; 13(12):3194-7. · 5.86 Impact Factor
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ABSTRACT: There is always a need to detect the presence of microorganisms, either as contaminants in food and pharmaceutical industries
or bioindicators for disease diagnosis. Hence, it is important to develop efficient, rapid, and simple methods to detect microorganisms.
Traditional culturing method is unsatisfactory due to its long incubation time. Molecular methods, although capable of providing
a high degree of specificity, are not always useful in providing quick tests of presence or absence of microorganisms. Microchip
elec-trophoresis has been recently employed to address problems associated with the detection of microorganisms due to its
high versatility, selectivity, sensitivity, and short analysis times. In this work, the potential of PDMS-based microchip
electrophoresis in the identification and characterization of microorganism was evaluated. Enteropathogenic E. coli (EPEC) was selected as the model microorganism. To obtain repeat-able separations, sample pretreatment was found to be essential.
Microchip electrophoresis with laser-induced fluorescence detection could potentially revolutionize certain aspects of microbiology
involving diagnosis, profiling of pathogens, environmental analysis, and many others areas of study.
Key wordsPDMS–Microchip electrophoresis–Microfluidic devices–Laser-induced fluorescence detection–Microorganism analysis–
Enteropathogenic E. coli
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02/2009: pages 169-179;
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ABSTRACT: Microchip capillary electrophoresis (MCE) is gaining popularity due to the developments of simple microfabrication methods under nonstringent laboratory conditions. Moreover, the low material and production costs of polymer-based microchips have further stimulated advances in the applications of MCE in various fields, including clinical analysis, drug screening, biomarker identification, and biosensing. In this chapter, a simple and robust protocol for fabrication of microchips for lab-on-chip testing and microchip electrophoresis is described. The microchips are hybrid poly(dimethylsiloxane) (PDMS)/glass microchips, which are produced by a combination of photolithography and micromolding processes. This type of microchip has been used in a wide range of analyses.
Methods in molecular biology (Clifton, N.J.) 02/2009; 509:159-68.
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ABSTRACT: There is always a need to detect the presence of microorganisms, either as contaminants in food and pharmaceutical industries or bioindicators for disease diagnosis. Hence, it is important to develop efficient, rapid, and simple methods to detect microorganisms. Traditional culturing method is unsatisfactory due to its long incubation time. Molecular methods, although capable of providing a high degree of specificity, are not always useful in providing quick tests of presence or absence of microorganisms. Microchip elec-trophoresis has been recently employed to address problems associated with the detection of microorganisms due to its high versatility, selectivity, sensitivity, and short analysis times. In this work, the potential of PDMS-based microchip electrophoresis in the identification and characterization of microorganism was evaluated. Enteropathogenic E. coli (EPEC) was selected as the model microorganism. To obtain repeat-able separations, sample pretreatment was found to be essential. Microchip electrophoresis with laser-induced fluorescence detection could potentially revolutionize certain aspects of microbiology involving diagnosis, profiling of pathogens, environmental analysis, and many others areas of study.
Methods in molecular biology (Clifton, N.J.) 02/2009; 509:169-79.
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ABSTRACT: A simple method based on capillary electrophoresis with potential gradient detection was developed to separate and detect neomycin components within 4 min without a derivatization step. Satisfactory separation and good repeatability were obtained using a separation buffer composed of 1 mM ammonium citrate (pH 3.5). The linearity of the method ranged from 10 to 1000 ppm with a limit of detection for neomycin B of about 7 ppm. After a simple dilution and filtering pretreatment step, neomycin components in three real samples were successfully analyzed without any major interference. Due to its simplicity and reliability, this method could provide an excellent alternative to the assays currently listed in U.S. and European Pharmacopoeia. The experiments were performed on a portable capillary electrophoresis system and, hence, the method can be readily applied to field analysis and point-of-care testing. Figure Photo of portable CE-P2-PGD system.
Analytical and Bioanalytical Chemistry 09/2006; 385(8):1575-9. · 3.78 Impact Factor
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Clinical Chemistry 03/2006; 52(2):331-2. · 7.91 Impact Factor
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ABSTRACT: There is an urgent need to analyze drugs and pharmaceuticals at nanoscale detection, both now and in the future. Capillary electrophoresis is a growing technique that is continuously developing with improved detectors, sample preparation units, and other components. This article describes the analysis of drugs and pharmaceuticals by capillary electrophoresis at nanoscale detection in various standard solutions, dosage formulations, and biological samples. Nanoscale detection analysis is discussed in terms of the advancement in the detectors and sample preparation methods. The coupling of the detectors and sample preparation units to capillary electrophoresis is also discussed. Attempts have been made to evaluate the optimization strategies of capillary electrophoresis conditions to achieve detection at the nanoscale. Applications of capillary electrophoresis for the analyses of simple and chiral mixtures of several drugs and pharmaceuticals at nanoscale detection are included.
Journal of capillary electrophoresis and microchip technology. 02/2006; 9(5-6):85-99.
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ABSTRACT: Clinical analysis often requires rapid, automated, and high-throughput analytical systems. Microchip capillary electrophoresis (CE) has the potential to achieve very rapid analysis (typically seconds), easy integration of multiple analytical steps, and parallel operation. Although it is currently still in an early stage of development, there are already many reports in the literature describing the applications of microchip CE in clinical analysis. At the same time, more fully automated and higher throughput commercial instruments for microchip CE are becoming available and are expected to further enhance the development of applications of microchip CE in routine clinical testing. To put into perspective its potential, we briefly compare microchip CE with conventional CE and review developments in this technique that may be useful in diagnosis of major diseases.
Clinical Chemistry 02/2006; 52(1):37-45. · 7.91 Impact Factor
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ABSTRACT: This report describes a novel online field-amplified sample stacking (FASS) procedure to analyze 16 chlorinated acid herbicides. By using a poly(vinyl alcohol) (PVA)-coated capillary to reduce electroosmotic flow and introducing a methanol-water plug before sample loading, the sample injection time could be very long without loss of sample and separation efficiency. Under the optimized condition, the FASS procedure could provide great sensitivity enhancement (5000-10 000-fold) and satisfactory reproducibility (relative standard deviations of migration times less than 2.4%, relative standard deviations of peak areas less than 8.0%). Combined with cationic surfactant-assisted solid-phase extraction (CSA-SPE), the limit of detection of the herbicides ranged from 0.269 to 20.3 ppt, which are two orders lower than those of the US Environmental Protection Agency standard method 515.1. The CSA-SPE-FASS-CE method was successfully applied to the analysis of local pond water.
Electrophoresis 10/2005; 26(18):3507-17. · 3.30 Impact Factor
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ABSTRACT: Field-amplified sample stacking (FASS) is used to separate basic proteins in a poly-(vinyl alcohol)-coated bubble cell capillary. To our knowledge, this is the first paper describing the on-column stacking of proteins (as cations) using FASS in bubble cell capillary. The bubble cell capillary is fabricated using a one-step method. Cetyltrimethylammonium chloride is added into the running buffer to reverse the EOF and, thus, to pump the water plug out during the sample stacking step. The effect of the water plug lengths and sample injection durations were investigated and optimized. The results obtained were compared with those for the normal capillary without bubble cell in terms of resolution and sensitivity enhancement. Under the optimal condition, this method can improve the sensitivity of the peak areas ranging from 5000- to 26 000-fold. The RSDs (n = 5) of the migration time and peak area are satisfactory (less than 0.6 and 12%, respectively). Application of the capillary electrophoresis method with bubble cell, FASS, and UV detection thereby leads to the determination of these proteins at concentrations ranging from 3 to 10 ng/mL, based on a signal-to-noise ratio of 3:1.
Electrophoresis 08/2005; 26(18):3486 - 3494. · 3.30 Impact Factor
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ABSTRACT: Miniaturization of genetic tests represents the convergence of molecular biology and engineering and is leading to a new class of small analyzers and test systems for genetic testing with improved analytical characteristics. Miniaturization initially focused on devices that contained micrometer-sized features designed for a particular analytical purpose (e.g., filters for cell isolation and chips for capillary electrophoresis). Now, the focus is shifting to analytical applications based on nano-sized objects such as nanotubes, nanochannels, nanoparticles, nanopores and nanocapacitors. These nanofabricated objects provide new tools for sequencing of nucleic acids and rapid, multiplexed, nucleic acid detection.
Expert Review of Molecular Diagnostics 08/2005; 5(4):549-59. · 4.86 Impact Factor
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ABSTRACT: A portable capillary electrophoresis (CE) system with a novel potential gradient detection (PGD) was utilized to separate DNA fragments. For the first time it was demonstrated that separation of DNA fragments in polymer solution could be detected by a portable CE system integrated with PGD, with a limit of detection (LOD) comparable to that of the CE-ultraviolet (UV) method. Effects of buffer solution, sieving medium, and applied voltage were also investigated. The portable CE-PGD system shows several potential advantages, such as simplicity, cost effectiveness, and miniaturization.
Electrophoresis 03/2005; 26(3):517-23. · 3.30 Impact Factor
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ABSTRACT: A simple and fast method was developed to determine non-UV active compounds directly without derivatization. The usefulness of the method was demonstrated by detecting the major components in aminoglycoside antibiotic mixtures using capillary zone electrophoresis with potential gradient detection. Under optimized separation conditions (0.2 mM cetyltrimethylammonium bromide (CTAB), 1 mM ammonium citrate, pH 3.5), gentamicin was separated into three major peaks (C1, C1a, and C2+C2a) within 15 min. This method showed better sensitivity than other capillary electrophoresis (CE) methods for determining underivatized gentamicin. The linear range was from 10 to 500 ppm. Because of its good repeatability and simplicity, this new method could be a good alternative for the current assays given by US Pharmacopoeia and European Pharmacopoeia.
Electrophoresis 02/2005; 26(1):196-201. · 3.30 Impact Factor
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ABSTRACT: A portable chip-CE system with potential gradient detection (PGD) was developed and applied to the determinations of alkali metals and alkaloids. The separation efficiency appeared to be satisfactory and nonaqueous capillary electrophoresis (NACE) proved to be applicable to PGD or conductivity detection. The power supplies, separation and detection were built on a device of 3 kg in weight. A branch channel near the end of the separation channel was designed to perform PGD and make the application of relatively high field strength possible. The study is the first report on the application of PGD on the microchip platform. The design of the chip-CE system shows several advantages, such as simplicity, miniaturization and wide applicability.
Electrophoresis 04/2004; 25(6):909-13. · 3.30 Impact Factor
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ABSTRACT: A modified field amplification sample injection method was proposed and evaluated by using positively mono charged cyclodextrin (CD) as carrier and 1-adamantanecarboxylate as displacer for on-capillary preconcentration of neutral compounds and improvement of the concentration limit of detection in micellar electrokinetic chromatography. In modified sample injection mode a displacer plug was introduced before sample injection to reduce the length of the concentrated sample zone and increase the peak height by slowing down the forward movement of the neutral sample associated with beta-CD-NH2 and the backward movement of the neutral sample partitioned in the micelles of sodium dodecyl sulfate. Stability of the inclusion complexes formed between the carrier and the solute was found to be an important factor affecting stacking efficiency in both the conventional field amplification sample injection mode and the modified one. However, further enhancement of the stacking efficiency in the modified mode rested on the relative stability of the displacer-carrier complex to that of the solute-carrier complex. Practical limits to the stacking efficiencies in both modes were discussed as well.
Journal of Chromatography 10/2003; 1013(1-2):19-27. · 4.53 Impact Factor
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ABSTRACT: This report describes separation and detection of chlorophenoxy acid herbicides spiked in drinking water by the technique combining solid-phase extraction, field-amplified sample stacking, capillary electrophoresis, and potential gradient detection. The herbicide solution (400 mL) was concentrated to 0.1 mL by the solid-phase extraction procedure. The buffer containing 3 mM ammonia and 0.3 mM hydroxypropyl-beta-cyclodextrin was adjusted to pH 9.0 with ammonia. The sample solution was injected into the capillary to 30% of the whole length, and -9 kV and 9 kV were employed for field-amplified sample stacking and separation, respectively. The herbicides were baseline separated and the detection limits with the above combined techniques were in the range of 1-4 x 10(-2) ng/mL.
Electrophoresis 07/2003; 24(12-13):2174-9. · 3.30 Impact Factor
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Isabel Rodriguez,
Marie Lesaicherre,
Yan Tie,
Quanbo Zou,
Chen Yu,
Janak Singh,
Lim T Meng,
Sridhar Uppili, Sam F Y Li,
Ponnampalam Gopalakrishnakone,
Zachariah E Selvanayagam
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ABSTRACT: An integrated system of a silicon-based microfabricated polymerase chain reaction (microPCR) chamber and microfabricated electrophoretic glass chips have been developed. The PCR chamber was made of silicon and had aluminum heaters and temperature sensors integrated on the glass anodically bonded cover. Temperature uniformity in the reaction chamber was +/-0.3 degrees C using an improved novel "joint-heating" scheme. Thermal cycling was digitally controlled with a temperature accuracy of +/- 0.2 degrees C. Small operating volumes together with high thermal conductivity of silicon made the device well suited to rapid cycling; 16 s/cycle were demonstrated. For analysis of the PCR products, the chamber output was transferred to the glass microchip by pressure. Analysis time of PCR amplified genomic DNA was obtained in the microchip in less than 180 s. The analysis procedure employed was reproducible, simple and practical by using viscous sieving solutions of hydroxypropylmethylcellulose and dynamically coated microchip channels with poly(vinylpyrrolidone). DNA fragments that differ in size by 18 base pairs (bp) were resolved. Analysis of genomic male and female amplified DNA by microPCR was achieved in microchip, and application of the integrated microPCR-microchip for the identification of bird sex was tested. Genomic DNA samples from several bird species such as pigeon and chicken were analyzed. Hence, the system could be used as well to determine the sex of avian species.
Electrophoresis 02/2003; 24(1-2):172-8. · 3.30 Impact Factor
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ABSTRACT: Ionic liquid (IL) was covalently bonded onto the silica capillary surface and the electroosmotic flow was reversed over a pH range of 3.5 to 7. Sildenafil (SL) and its metabolite UK-103,320 (UK) in human serum were detected by solid-phase extraction followed by capillary zone electrophoresis-mass spectrometry analysis. The running buffer contained 10 mM acetic acid adjusted to pH 4.5 with 1 M ammonia, and the separating voltage was set to -25 kV. The adsorption of the analytes onto the bare capillary wall was eliminated by the IL coating and the drugs were baseline-separated within 14 min with detection limits (S/N = 3) of 14 and 17 ng/mL for SL and UK, respectively. The method developed showed good intraday precision in terms of relative standard deviation (RSD) with respect to migration time (RSD </= 0.76%, n = 5) and peak area (RSD </= 3.4%, n = 5); the relative coefficients of linear regression for both targets were better than 0.99 within linear dynamic range (SL: 50-600 ng/mL; UK: 40-400 ng/mL). Satisfactory interday precision was obtained with respect to the slope of the regression (RSD </= 4.21%, n = 9) and the migration time (RSD </= 1.1%, n = 9). The IL coating could be used with stable electroosmotic flow (RSD = 2.78%, n = 10) for at least 80 h.
Electrophoresis 12/2002; 23(24):4110-6. · 3.30 Impact Factor
