Biomedical subjects

Takashi Kaneta

Publications and source records attributed to Takashi Kaneta.

14 recordsLinked to original sources

PubMed2007

Application of Hadamard transformation to MEKC.

The Hadamard transform (HT) technique, which permits the S/N in CE to be improved, was applied to MEKC. Multiple sample injection of fluorescent analytes according to a Hadamard code sequence was performed using an optically gated sample injection technique, in which a sample plug was produced based on photodegradation by irradiation with an intense laser beam. The capillary and reservoirs were filled with a sample solution containing buffer components and SDS as a pseudostationary phase. A preliminary study confirmed that fluorescein ion could be photobleached in the presence of SDS. The optically gated sample injection technique was then applied to multiple sample injection, based on a Hadamard matrix. The S/N in the electropherogram obtained by HT-MEKC was improved substantially compared to that obtained by a single injection method. When the technique was applied to the separation of several amino acids labeled with FITC, the S/N ratio for each amino acid was enhanced, without any evidence of degradation in separation resolution. Moreover, HT-MEKC was applied to the analysis of amino acids contained in a Japanese beverage, resulting in improved S/Ns for the amino acids.

Amino Acids↗

PubMed2006

On-column capture of a specific protein in capillary electrophoresis using magnetic beads.

A method for capturing specific molecules separated by CE has been explored. To demonstrate on-column capture of migrating analyte molecules, two detection windows were fabricated on a capillary. Magnetic beads containing immobilized molecules that react with the specific molecules under study were placed between the detection windows in the capillary using magnets. Molecules in a sample solution injected into the capillary were separated and detected at the first detection window. After passing through the first detection window, the separated molecules encountered the magnetic beads, where the specific analyte was captured. As a result, the peak area for those analyte molecules decreased or disappeared completely at the second detection window. Rabbit IgG and carbonic anhydrase were employed to demonstrate on-column capture of a specific molecule. For rabbit IgG, magnetic beads containing the immobilized antibody (anti-rabbit IgG) were used. Rabbit IgG molecules were captured on the magnetic beads during CE migration. Furthermore, the capture of carbonic anhydrase was demonstrated by the reaction between magnetic beads (containing immobilized anti-rabbit IgG) and anti-carbonic anhydrase (rabbit IgG), before the beads were packed in the capillary. After packing the magnetic beads in the capillary, a mixture of two proteins was injected into the capillary. Two proteins were detected at the first detection window, while the peak corresponding to carbonic anhydrase disappeared at the second detection window. The results show that using an appropriate antibody, the present technique would be applicable to any proteins.

Animals↗

PubMed2005

Suppression of electroosmotic flow and its application to determination of electrophoretic mobilities in a poly(vinylpyrrolidone)-coated capillary.

A hydrophilic polymer, poly(vinylpyrrolidone) (PVP), was employed for suppressing the electroosmotic flow (EOF). A capillary was filled with aqueous PVP solution for coating the capillary wall with PVP; the PVP solution was then replaced by a migration buffer solution containing no PVP. Three types of PVP with different molecular weights were examined. The EOF was suppressed more effectively as the molecular weight of PVP increased. The EOF in the coated capillary was approximately 10-fold smaller than that of a bare capillary and was constant in the pH range of 6-8. The suppressed EOF was stable even when no PVP was added to the migration buffer. However, the EOF increased significantly when sodium dodecyl sulfate was added into the migration buffer. The method was applied for determining the electrophoretic mobilities of inorganic anions that have negative electrophoretic mobilities larger than the electroosmotic mobility of the bare capillary. A novel method for determining the electrophoretic mobilities was proposed based on the linear relationship between electric current and electrophoretic mobility. The electrophoretic mobility was proportional to the electric current. Therefore, the intercept of the regression equation represents the electrophoretic mobility at room temperature. The electrophoretic mobilities were in good agreement with the absolute electrophoretic mobilities.

Electrophoresis, Capillary↗

PubMed2005

Capillary electrophoresis immunoassay based on an on-column immunological reaction.

An on-column immunological reaction was employed to achieve simple and rapid analysis in an immunoassay based on capillary electrophoresis using semiconductor laser-induced fluorescence detection. Human serum albumin (HSA) labeled with sulfoindocyanine succinimidyl ester (Cy5), a fluorescent compound with an absorption maximum at 649 nm, was used as a fluorescent probe for the immunoassay. In a binding assay, with anti-HSA as the analyte molecule, Cy5-HSA was injected in a capillary column followed by the injection of anti-HSA so as to form individual zones. By applying a potential, the anti-HSA reacted with Cy5-HSA at the boundary between Cy5-HSA and anti-HSA zones, since anti-HSA has a higher electrophoretic mobility than Cy5-HSA. Furthermore, the on-column method enhances the sensitivity by injecting a large volume of the sample. Free Cy5-HSA and its immunocomplex with anti-HSA were separated with less degradation in resolution than that predicted from the injection time of anti-HSA, even when the injection time for anti-HSA was increased. The ratio of the peak area of the complex to that of the total Cy5-HSA (free Cy5-HSA and the complex) increased in proportion to the injection time of anti-HSA. As a result, the detection limit was improved up to eight-fold (the concentration detection limit, 0.007 mg mL(-1), for an injection time of 240 s, compared to that obtained using an off-column sample preparation. Furthermore, the on-column reaction method was applicable to an immunoassay to determine native HSA, in which native HSA and Cy5-HSA react with anti-HSA stepwise. The detection limit in the stepwise reaction immunoassay was 0.005 mg mL(-1), which is 14 times lower than that in an off-column method, with the analysis time less than 10 min as the result of increasing the injection time of native HSA. In addition, the present on-column immunoassay was applied to the sample containing a high concentration of salts for investigating the effect of salts in the sample solution.

Carbocyanines↗

PubMed2005

On-line concentration of a protein using denaturation by sodium dodecyl sulfate.

A novel method for the on-column sample stacking of proteins is described. The strategy takes advantage of interactions between protein molecules and sodium dodecyl sulfate (SDS) monomers. A long plug of a protein sample (either acidic or basic) is injected into a capillary filled with a background electrolyte (BGE) containing SDS. When a potential is applied, the proteins interact with SDS monomers in the BGE to form protein-SDS complexes that migrate more slowly than the corresponding uncomplexed protein, resulting in protein stacking. Both acidic and basic proteins migrate at an almost identical electrophoretic velocity after stacking, which indicates that the protein-SDS complexes formed in the BGE zone have a similar charge/mass ratio. The mechanism of stacking was investigated using a sample consisting of a basic protein, lysozyme, and a small molecule, methylene blue. The findings clearly show that two interactions with SDS occur, a stepwise binding interaction between protein molecules and SDS monomers and an interaction in which the small molecules enter into micelles formed by SDS molecules. The method was also applied to the detection of a protein labeled with a fluorescent labeling reagent at trace levels. The labeled protein was detected even under labeling conditions where the labeling efficiency was too low to detect by short-plug injection.

Electrophoresis↗

PubMed2004

Hadamard transform capillary electrophoresis combined with absorption spectrometry.

A novel injection device for applying absorption spectrometry to Hadamard transform (HT) capillary electrophoresis is described. A small hole, at the center part of the capillary, functions as an inlet port for the sample. The hole is immersed in a sample solution and the end of the capillary that is usually employed for sample introduction is immersed in a buffer solution. An ultraviolet absorption detector is placed between the sample injection port and the other end of the capillary filled with a buffer solution. A high potential is continuously applied between the injection port and the end of the capillary, which allows the sample solution to be introduced into the separation capillary. By application of a higher potential modulated according to a Hadamard code between both ends of the capillary, the buffer solution is injected into the separation capillary. In some preliminary experiments, this injection device was utilized to introduce a single sample segment into a capillary. As expected, a single peak was observed in the electropherogram for a sample containing a single component. This device was then employed for multiple sample injection in HT capillary electrophoresis. An 8-fold improvement in the S/N ratio was observed when the HT technique was used, in which a 255-order of a Hadamard matrix was used, as expected from theory. The present approach was also utilized for the sensitive detection of a sample comprised of multiple components.

Journal Article↗

PubMed2004

On-line sample concentration techniques in capillary electrophoresis: velocity gradient techniques and sample concentration techniques for biomolecules.

Methods with a high sensitivity and high separation efficiency are goals in analytical separation techniques. On-line sample concentration techniques in capillary electrophoresis (CE) separations have rapidly grown in popularity over the past few years because they achieve this goal. This review describes the methodology and theory associated with a number of different techniques, including electrokinetic and chromatographic methods. For small molecules, several on-line concentration methods based on velocity gradient techniques are described, in which the electrophoretic velocities of the analyte molecules are manipulated by field amplification, sweeping, and isotachophoretic migration, resulting in the on-line concentration of the analyte zones. In addition, the on-line concentration methods for macromolecules are described, since the techniques used for macromolecules (DNAs and proteins), are different from those for small molecules, with respect to either mechanism or methodology. Recent studies relating to this topic are also discussed, including electrophoretic and chromatographic techniques on capillary or microchip.

DNA↗

PubMed2003

Hadamard transform microchip electrophoresis combined with diode laser fluorometry.

The application of a Hadamard transform technique to microchip electrophoresis is described. The sample is electrokinetically injected into a separation channel and is then detected by diode laser-induced fluorometry. The sample and buffer solutions are introduced into the channel by controlling the high voltages applied to the solutions, according to a code determined by a Hadamard matrix. The S/N ratio of the signal in the electropherogram can be improved by a factor of 5 in comparison with that obtained by a conventional single-injection method, although an 8-fold improvement is theoretically predicted when a 255-order matrix is used.

Journal Article↗

PubMed2003

Detection of 27 molecules in a single injection volume by Hadamard transform capillary electrophoresis.

A concentration detection limit of 100 fM was achieved for the fluorescein ion by improving the experimental setup used for Hadamard transform capillary electrophoresis. Two argon-ion lasers, a gating laser for sample injection and a probe laser for the excitation of analyte molecules, were employed for the efficient photodegradation of analyte molecules in laser-induced fluorescence detection using an optically gated sample-injection method. In addition, a dichroic mirror, located in the pathway of the probe laser was used to exclude the other lines of the argon-ion laser. Using a Hadamard matrix on the order of 2046, the concentration limit of detection for fluorescein ion was determined to be 100 fM at S/N = 3, in which the average number of molecules in a single injection volume was calculated to be 27. The influences of the output power in both the gating and probe lasers on the sensitivity are also discussed.

Journal Article↗

PubMed2003

Absorption spectrometry using a diffractive optical element constructed by gel electrophoresis.

A novel diffractive optical element was constructed by means of gel electrophoresis. Five capillaries were filled with a methylene blue solution and inserted into a slab gel. An electrical potential was then applied to the slab gel. Methylene Blue in the capillaries underwent electrophoretic migration, forming clear blue bands in the gel. The bands functioned as a transmission grating, and diffracted a laser beam. The intensity of the diffracted light increased with increasing the concentration of methylene blue.

Journal Article↗

PubMed2002

Band broadening caused by the multiple labeling of proteins in micellar electrokinetic chromatography with diode laser-induced fluorescence detection.

When a labeling reagent is used, in the determination of proteins by capillary electrophoresis with laser-induced fluorescence detection, the multiple labeling of proteins frequently occurs, which can degrade the separation efficiency. In order to understand the influence of the multiple labeling of proteins on separation efficiency, the band broadening caused by a labeling reaction between bovine serum albumin (BSA) and a cyanine fluorescent dye (Cy5) was investigated using micellar electrokinetic chromatography in conjunction with diode laser-induced fluorometry. With the aid of an internal standard, methylene blue, the height equivalent to the theoretical plate (HETP) ratio of BSA to methylene blue was used as an indicator for band broadening under optimum separation conditions. Labeling conditions, including reaction buffer pH, reaction time, and initial concentration of Cy5 to bovine serum albumin, were found to influence the HETP ratio. The separation efficiency for the labeled protein was degraded by experimental conditions employed in the labeling, which indicates an increase in the heterogeneity of the final products.

Chromatography, Micellar Electrokinetic Capillary↗

PubMed2002

Ultratrace analysis based on Hadamard transform capillary electrophoresis.

Hadamard transform capillary electrophoresis, which is based on a multiple sample injection technique, was combined with laser-induced fluorometry and utilized in the determination of analytes at subpicomolar levels. The sensitivity was substantially improved by increasing the order, i.e., the number of elements, of the Hadamard matrix. In fact, the signal-to-noise ratio was enhanced 18-fold by the use of a matrix of order 2047. A feasibility study was carried out by computer simulation to study the detection of an average of less than a single molecule in a single injection volume. The signal peak was clearly observable even under conditions at which only 0.3 molecule is present in the volume. Thus, this approach is potentially useful for ultratrace analysis, in which conventional single-injection capillary electrophoresis cannot be applied.

Journal Article↗

PubMed2002

Micellar electrokinetic chromatography with diode laser-induced fluorescence detection as a tool for investigating the fluorescence labeling of proteins.

We describe the use of micellar electrokinetic chromatography with diode laser-induced fluorometry (MEKC-DLIF) as a tool to characterize a labeling reaction between sulfoindocyanine succinimidyl ester (Cy5), a cyanine fluorescent dye, and a model protein, bovine serum albumin (BSA). To decrease the influence of imprecise injection, methylene blue was added as an internal standard. Labeled BSA was completely separated from the unconjugated Cy5, and methylene blue under optimized conditions. A kinetic study of the reaction was performed by changing some parameters, such as reaction buffer pH, reaction buffer concentration and the initial concentration of BSA. A comparison between the current method and traditional methods was made.

Animals↗

PubMed2002

Determination of dye/protein ratios in a labeling reaction between a cyanine dye and bovine serum albumin by micellar electrokinetic chromatography using a diode laser-induced fluorescence detection.

The degree of labeling, i.e., dye/protein ratio (D/P) is important for characterizing properties of dye labeling with proteins. A method for the determination of this ratio between a fluorescent cyanine dye and bovine serum albumin (BSA), based on the separation of the labeling mixture using micellar electrokinetic chromatography with diode laser-induced fluorescence detection, is described. Two methods for the determination of D/P were examined in this study. In these methods, a hydrolysis product and impurities, which are usually unfavorable compounds that are best excluded for protein analysis, were utilized to determine the amounts of dye bound to BSA. One is a direct method in which a ratio of the peak area of BSA to the total peak area of all the products produced in the labeling reaction was used for determining the average number of dye molecules bound to a single BSA molecule. The other is an indirect determination, which is based on diminution of all peak areas related to the products except for the labeled BSA. These methods were directly compared by means of a spectrophotometric method. The experimental results show that the indirect method is both reliable and sensitive. Therefore, D/P values can be determined at trace levels using the indirect method.

Animals↗