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Shigeru Terabe

Publications and source records attributed to Shigeru Terabe.

At least 19 recordsLinked to original sources
PubMed2006

Capillary-assembled microchip as an on-line deproteinization device for capillary electrophoresis.

A capillary-assembled microchip (CAs-CHIP), prepared by simply embedding square capillaries in a lattice polydimethylsiloxane (PDMS) channel plate with the same channel dimensions as the outer dimensions of the square capillaries, has been used as a diffusion-based pretreatment attachment in capillary electrophoresis (CE). Because the CAs-CHIPs employ square-section channels, diffusion-based separation of small molecules from sample solutions containing proteins is possible by using the multilayer flow formed in the square section channel. When a solution containing high-molecular-weight and low-molecular-weight species makes contact with a buffer solution, the low-molecular-weight species, which have larger diffusion coefficients than the high-molecular-weight species, can be collected in a buffer-solution phase. The collected solution containing the low-molecular-weight species is introduced into the separation capillary to be analyzed by CE. This type of system can be used for CE analysis in which pretreatment is required to remove proteins. In this work a fluorescently labeled protein and rhodamine-based molecules were chosen as model species and a feasibility study was performed.

Journal Article↗
PubMed2006

Sample enrichment techniques in capillary electrophoresis: focus on peptides and proteins.

Compared to chromatography-based techniques, the concentration limits of detection (CLOD) associated with capillary electrophoresis are worse, and these have largely precluded their use in many practical applications. To overcome this limitation, researchers from various disciplines have exerted tremendous efforts toward developing strategies for increasing the concentration sensitivities of capillary electrophoresis (CE) systems, via the so-called sample enrichment techniques. This review highlights selected developments and advances in this area as applied to the analyses of proteins and peptides in the last 5 years.

Electrophoresis, Capillary↗
PubMed2006

Protein tryptic digests analyzed by carrier ampholyte-based capillary electrophoresis coupled to ESI-MS.

In this study, narrow pH cuts of carrier ampholytes have been used as buffers in CE for the analysis of protein tryptic digests. Their low conductivity allows very efficient separations under high electric field strength without inducing any significant Joule heating. In this study, the capabilities of narrow pH cuts of carrier ampholytes for the separation of protein tryptic digests have been assessed. Three proteins of different molecular masses have been studied: cytochrome C (horse heart), beta-lactoglobulin B (bovine) and human transferrin. Efficient, rapid and repeatable separations of the peptides resulting from the tryptic digestion have been achieved in this buffer. Moreover, the feasibility of the coupling of carrier ampholyte-based capillary electrophoresis with ESI-MS has been demonstrated through the study of the cytochrome C tryptic digest.

Ampholyte Mixtures↗
PubMed2005

Measurement of monomolecular binding constants of neutral phenols into the beta-cyclodextrin by continuous frontal analysis in capillary and microchip electrophoresis via a competitive assay.

Measurement of binding constant by chip electrophoresis is a very promising technique for the high throughput screening of non-covalent interactions. Among the different electrophoretic methods available that yield the binding parameters, continuous frontal analysis is the most appropriate for a transposition from capillary electrophoresis (CE) to microchip electrophoresis. Implementation of this methodology in microchip was exemplified by the measurement of inclusion constants of 2-naphtalenesulfonate and neutral phenols (phenol, 4-chlorophenol and 4-nitrophenol) into beta-cyclodextrin by competitive assays. The issue of competitor choice is discussed in relation to its appropriateness for proper monitoring of the interaction.

Electrophoresis, Capillary↗
PubMed2005

Dynamic pH junction technique for on-line preconcentration of peptides in capillary electrophoresis.

A method based on the presence of a dynamic pH junction within the capillary to induce band narrowing for enhanced detection sensitivity for some peptides is presented. This technique is predicated on a sharp reduction in an analyte's migration velocity following a reversal of its electrophoretic direction from the acidic sample zone to the basic BGS zone. Larger-than-usual injection volumes of samples in relatively high-conductivity matrices were enabled, without degrading peak shape, resolution and efficiency. The size of the original sample plug was reduced by as much as 38-fold, and improvement in detector response in terms of peak height by as much as 124-fold was obtained. The effects of pH and concentration of the sample matrix, and the length of sample injection on the efficiency of the technique are discussed.

Angiotensin I↗
PubMed2005

Integration of valving and sensing on a capillary-assembled microchip.

A simple integration of both flow control valves and a reaction-based sensing function on a single microchip was performed by using capillary-assembled microchip (CAs-CHIP: Hisamoto, H.; Nakashima, Y.; Kitamura, C.; Funano, S.-i.; Yasuoka, M.; Morishima, K.; Kikutani, Y.; Kitamori, T.; Terabe, S. Anal. Chem. 2004, 76, 3222-3228.). In contrast to the previously reported on-chip valving systems, where the simple valving functions were integrated, our system can integrate not only valving function but also many other chemical functions to perform a complex chemical operation on a single microchip. Here, an enzymatic reaction-based readout system is employed as an example. A square capillary immobilizing N-isopropylacrylamide polymer monolith (referred to as "valving capillary") is used as a thermoresponsive "valving part" and the immobilizing enzyme-modified glycidyl methacrylate polymer monolith (referred to as "sensing capillary") is used as a "sensing part" of the CAs-CHIP. These capillaries are embedded into a lattice microchannel network fabricated on poly(dimethylsiloxane), which has the same channel dimensions as the outer dimensions of the square capillaries. After bonding, a small Peltier device (2 mm x 2 mm) for temperature control is placed on the embedded valving capillaries to control fluid flow. Using this for heating or cooling, fast operation times of 1.4 and 3.2 s for opening and closing valves, respectively, are successfully achieved. Finally, two valving capillaries are independently controlled to trap sample solution within a bypass channel, where the enzyme-immobilized capillary is embedded, and then enzymatic reaction-based sensing of chemical species is performed as an example. The fundamental characteristics of the valve-integrated microchip are fully investigated, and an application to the analysis of an enzyme substrate by using two independent valving capillaries and a sensing capillary is demonstrated.

Journal Article↗
PubMed2005

Microfluidic chip toward cellular ATP and ATP-conjugated metabolic analysis with bioluminescence detection.

In this article, a microfluidic platform integrating capillary electrophoresis and bioluminescence (BL) detection that was fabricated in poly(dimethylsiloxane) (PDMS) with lab-on-a-chip technology was demonstrated for cellular metabolic analyses. A microchannels network, "cross combining with Y", was designed to perform on-chip sample preparation, separation, and BL detection of ATP and ATP-conjugated metabolites, using firefly luciferin-luciferase BL system. A dynamic modification of the channel wall of PDMS proved to be crucial to reverse the direction of electroosmotic flow (EOF), which was uniquely achieved by a prewash cycle with a cationic surfactant didodecyldimethylammonium bromide. The influences of surfactant on the EOF and BL reaction were also investigated. Quantitative analyses revealed a dynamic linear range over 2 orders of magnitude for ATP, with a detection limit down to submicromolar (midattomole). The method was validated by measuring cellular ATP of E. coli. with direct on-chip cell lysis. Further work was emphasized on ATP-conjugated metabolite analysis, using galactose as an example. Assays of galactose in human urine samples confirmed the reliability of the protocol, which revealed good prospect of this platform for ATP-conjugated submetabolomic profiling.

Adenosine Triphosphate↗
PubMed2005

Two-dimensional separation system of coupling capillary liquid chromatography to capillary electrophoresis for analysis of Escherichia coli metabolites.

A two-dimensional (2-D) separation system of coupling chromatography to electrophoresis was developed for profiling Escherichia coli metabolites. Capillary liquid chromatography (LC) with a monolithic silica-octadecyl silica column (500 x 0.2 mm ID) was used as the first dimension, from which the effluent fractions were further analyzed by capillary electrophoresis (CE) acting as the second dimension. Field-enhanced stacking was selectively employed as a concentration strategy to interface the two dimensions, which proved to be beneficial for the detection of metabolites. An artificial sample containing 118 standards, some of which lack chromophores or have weak UV absorbance, was used to optimize the 2-D separation system. Under the optimum conditions, 63 components in the artificial sample having absorbance at 254 nm could be well resolved and detected. The utility of the system was demonstrated by comprehensive analysis of E. coli metabolites. Comparing with the previous 2-D separation system we published in Anal. Chem. 2004, 76, 1419-1428, using a longer monolithic column in the first dimension improved the separation efficiency and offered the possibility of increasing the injection volume without compromising the separation efficiency. In the second dimension, field-enhanced stacking was used to improve the concentration sensitivity of the metabolites, and more metabolites in E. coli cell extract were detected and identified using the developed 2-D separation system. In addition, preliminary investigation for future CE-mass spectrometry coupling was also made in the study by using volatile buffers in the capillary LC and CE techniques.

Amino Acids↗
PubMed2005

Metal complex separation with on-line sample preconcentration in micellar electrokinetic chromatography.

Micellar electrokinetic chromatography (MEKC) using a cationic surfactant as a pseudostationary phase was examined to separate anionic metal cyclohexane-1,2-diaminetetraacetic acid (CDTA) complexes. Cetyltrimethylammonium chloride (CTAC) was employed as the cationic surfactant micelle, its addition leading to EOF reversal. Cu(II), Co(II), Zn(II), Mn(II) and Pb(II) were used as test analytes, and the complete separation was obtained by MEKC. On-line sample preconcentration by sweeping was also examined to improve the detection sensitivity. From 15- to 42-fold increases in the detection sensitivity in terms of the peak heights were obtained by sweeping with a cationic micelle in the presence of high EOF. The limits of detection were in the range (0.6 - 1.8) x 10(-6) M with UV detection without any off-line preconcentration step.

Journal Article↗
PubMed2005

Recent developments in capillary electrophoresis-mass spectrometry of proteins and peptides.

Many researchers have invested considerable efforts toward improving capillary electrophoresis (CE)-mass spectrometry (MS) systems so they can be applied better to standard analyses. This review highlights the developments in CE-MS of proteins and peptides over the last five years. It includes the developments in interfaces, sample-enrichment techniques, microfabricated devices, and some applications, largely in capillary zone electrophoresis (CZE), capillary isoelectric focusing (CIEF) and capillary isotachophoresis formats.

Electrophoresis, Capillary↗
PubMed2004

Capillary liquid chromatographic determination of cellular flavins.

A capillary LC system was set up and optimized, in which a UV absorbance detector was used and a monolithic silica-ODS column as the separation column. Two on-line concentration techniques, namely, gradient elution mode and in-tube solid-phase ion-pair microextraction (SPIPME), were combined with the capillary LC system, which proved to be beneficial to enhance the concentration sensitivity by enabling the injection of large volumes of samples. The limits of detection at ppb levels for the flavins [riboflavin, flavin mononucleotide (FMN) and flavin adenine dinucleotide (FAD)] were achieved using the two techniques. For in-tube SPIPME, a monolithic silica-ODS column was employed as the extraction column, on which FAD and FMN were retained b y interaction with an ion-pair reagent, tetrabutylammonium phosphate, resulting in greater than 110-fold enhancement in their concentration sensitivities relative to conventional injection method. The reproducibility and linearity of the two methods were investigated. The two methods were applied to analyze trace amounts of flavins in bacterial Escherichia coli cell extracts and recombinant flavoenzymes.

Chromatography, Liquid↗
PubMed2004

Capillary-assembled microchip for universal integration of various chemical functions onto a single microfluidic device.

A novel concept for assembling various chemical functions onto a single microfluidic device is proposed. The concept, called a capillary-assembled microchip, involves embedding chemically functionalized capillaries into a lattice microchannel network fabricated on poly(dimethylsiloxane) (PDMS). The network has the same channel dimensions as the outer dimensions of the capillaries. In this paper, we focus on square capillaries to be embedded into a PDMS microchannel network having a square cross section. The combination of hard glass square capillary and soft square PDMS channel allows successful fabrication of a microfluidic device without any solution leakage, and which can use diffusion-based two-solution mixing. Two different types of chemically modified capillaries, an ion-sensing capillary and a pH-sensing capillary, are prepared by coating a hydrophobic plasticized poly(vinyl chloride) membrane and a hydrophilic poly(ethyleneglycol) membrane containing functional molecules onto the inner surface of capillaries. Then, they are cut into appropriate lengths and arranged on a single microchip to prepare a dual-analyte sensing system. The concept proposed here offers advantages inherent to using a planar microfluidic device and of chemical functionality of immobilized molecules. Therefore, we expect to fabricate various types of chemically functionalized microfluidic devices soon.

Journal Article↗
PubMed2004

Field-enhanced sample injection for high-sensitivity analysis of peptides and proteins in capillary electrophoresis-mass spectrometry.

Field-enhanced sample injection (FESI) was used to improve the concentration sensitivity of a capillary electrophoresis (CE)-mass spectrometry (MS) system with sheath flow configuration. Using some bioactive peptides, more than 3000-fold improvement in signal was obtained, permitting analysis in the low nM (fmol/microl) levels. The system was further evaluated for analysis of complex peptide mixtures by using low concentration tryptic digests of standard proteins. Rapid identification of the original protein was obtained by database searching using the observed molecular masses of the peptides, and by comparison of actual MS-MS spectra of selected peptides with the predicted fragmentation patterns.

Amino Acid Sequence↗
PubMed2004

Characterization of molecular transport in poly(dimethylsiloxane) microchannels for electrophoresis fabricated with synchrotron radiation-lithography and UV-photolithography.

In the present paper, a study was undertaken of molecular transport in ploy(dimethylsiloxane) microchannels that were fabricated by ultraviolet (UV)-photolithography and synchrotron radiation (SR)-lithography characterized and compared for microchip capillary electrophoresis by evaluating in-channel molecular dispersion. A fluorescent tag, sulforhodamine B was used as the probing molecule. It was found that microchannels made by SR-lithography fabrication were superior to those made by UV-photolithography fabrication in terms of molecular transport performance. A deep insight into surface conditions characterized by scanning electron microscopy suggested it was related to the difference in surface roughness. Chromatographic retention in electropherograms further supported such a conclusion, which depended on the phase ratio of the channel surface. The results revealed for PDMS microchannels in this work were in good agreement with the phenomenon found for glass microchannels in the literature.

Dimethylpolysiloxanes↗
PubMed2004

Two-dimensional separation method for analysis of Bacillus subtilis metabolites via hyphenation of micro-liquid chromatography and capillary electrophoresis.

A novel two-dimensional separation method, which hyphenated chromatography and electrophoresis, was developed for analysis of Bacillus subtilis metabolites. Micro-liquid chromatography (LC) with a monolithic silica-ODS column was used as the first dimension, from which the effluent fractions were further analyzed by capillary electrophoresis (CE) acting as the second dimension. Concentration strategies, namely, dynamic pH junction and sweeping, were selectively employed to interface the two dimensions, which proved to be beneficial for the detection of metabolites. For system evaluation, an artificial sample containing 54 standard metabolites was separated according to their hydrophobicity by micro-LC with gradient mode. The early-eluting fractions were separated by capillary zone electrophoresis in combination with dynamic pH junction, while the late-eluting fractions were separated by sweeping micellar electrokinetic chromatography. The middle fractions were analyzed by both modes of CE. Under the optimum conditions, all the components in the artificial sample could be well resolved. The method was applied to profile B. subtilis metabolites. Some crucial metabolites were identified. This method provided great potential for resolving complex biological samples containing compounds having different characteristics.

Bacillus subtilis↗
PubMed2004

Effects of the length and modification of the separation channel on microchip electrophoresis-mass spectrometry for analysis of bioactive compounds.

Analyses of amino acids and peptides were performed using a quartz microchip and an interface for microchip electrophoresis-electrospray ionization mass spectrometry (MCE-ESI-MS). In MCE-ESI-MS, negative pressure caused by ESI increased band broadening and deteriorated separation. We tried to suppress the negative pressure and improve separation using a microchip with a long separation channel. Separations of peptide standards were compared using two microchips with long separation channel (58.9 mm) and short one (22.9 mm). Theoretical plate numbers and resolution were improved significantly using the former. The theoretical plate numbers of [Val4]angiotensin was 8600 using the former and 1700 using the latter. When background electrolytes of low pH were used in an uncoated quartz microchip, electrokinetic injection was difficult because of weak electroosmotic flow. The use of successive multiple ionic polymer layers coating of the microchip channel stabilized electrokinetic injection and permitted analysis of amino acids and peptides even under low pH conditions. Separation of amino acids was successfully performed using formic acid solution (pH 2.5) as background electrolyte.

Electrophoresis↗