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N Nimura

Publications and source records attributed to N Nimura.

At least 19 recordsLinked to original sources
PubMed1996

Investigation of enantioselective separation of quinolonecarboxylic acids by capillary zone electrophoresis using vancomycin as a chiral selector.

When a chiral selector that is a pharmaceutical compound is added to the separation buffer in capillary electrophoresis, the enantioselectivity and the mobility of analytes which interact with that chiral selector may be altered. The changes in enantioselectivity and mobility of the analyte are a function of the strength of the affinity interaction, which depends on the structure of each. The macrocyclic antibiotic vancomycin contains a variety of functionalities that are known to be useful for enantioselective interactions (e.g., hydrogen bonding groups, hydrophobic pockets, aromatic groups, amide linkages). Capillary electrophoresis with vancomycin as a buffer additive was used to separate the enantiomers of different compounds. In this study, the chiral separation of quinolonecarboxylic acids that exhibit marked antibacterial activity and of related compounds was achieved by capillary electrophoresis using vancomycin. The correlations between the separation parameters and analyte structures were investigated. The molecular interaction, which is based on the differences of structure, and the effect of experimental parameters on the enantioselective separation between the quinolonecarboxylic acids and vancomycin are discussed.

Anti-Infective Agents↗
PubMed1996

Reversed-phase HPLC separation of proteins on chemically bonded silica gel columns.

Reversed-phase high-performance liquid chromatographic (RP-HPLC) separation of proteins on chemically bonded silica gel columns is described. Efficiency of nonporous alkylsilyl bonded silica gel is compared with that of a macroporous gel that has been widely used for the purpose. A comparative study of the separation under conventional and fast separation conditions is also given. The fast separation technique on the nonporous reversed-phase column has the advantage of improving the recovery of late-eluting hydrophobic and large proteins, such as ovalbumin and apoferritin.

Chromatography, High Pressure Liquid↗
PubMed1995

Diol-bonded silica gel as a restricted access packing forming a binary-layered phase for direct injection of serum for the determination of drugs.

Direct serum injection for drug determinations can be achieved on a diol-bonded silica gel as a restricted access packing. The diol-bonded phase, 3-(2,3-dihydroxypropoxy)propylsilylsilica, contains two different functions, a hydrophilic function at the tip of the single chemical bond and a hydrophobic function on the inside part of the bond to form a "binary-layered phase" on the support surface. Proteins, as large molecules, contact only the hydrophilic surface of the diol phase, and they are eluted at the solvent front based on size-exclusion chromatography. On the other hand, small molecules such as synthetic drugs are retained on the internal hydrophobic function and separate based on reversed-phase chromatography. Accordingly, the diol-bonded silica gel performs as a restricted access packing for direct serum injection for the determination of relatively hydrophobic drugs.

Blood Chemical Analysis↗
PubMed1994

Chiral separation by capillary affinity zone electrophoresis using an albumin-containing support electrolyte.

Chiral separations of some pharmaceutical compounds were studied by capillary affinity zone electrophoresis. Bovine serum albumin (BSA) was used as a chiral selector and added to electrolyte. For the chiral separation of new quinolone bactericidal reagents, phosphate buffer was more appropriate than borate buffer solution as the support electrolyte. The effects of BSA concentration, albumin type, pH, chiral additive, and voltage on separation were observed. As a result, chiral separations were performed in the pH range 7-8. The migration and stereoselectivities of enantiomers were changed by varying the protein concentration (more than 0.2% w/v) and voltage and by adding amino acids as chiral modifiers. This procedure is easily applicable to other compounds for chiral separation or for studies of protein binding interaction.

Anti-Infective Agents↗
PubMed1993

[Stabilization of ascorbic acid aqueous solution by protamine].

Protamine was found to stabilize ascorbic acid (AsA) in aqueous solution. The concentration of AsA (50 mumol/l) dissolved in 0.05 M phosphate buffer, pH 7, decreased by 57% after standing for 90 min at 30 degrees C, whereas 91% of AsA remained under the same conditions in the presence of 60 mumol/l protamine. When 0.5 mumol/l of copper ion (II) was added to the above AsA solution (0.05 M phosphate buffer, pH 7) in the absence of protamine, AsA decreased by 5% after standing for 15 min at 30 degrees C. On the other hand, 91% of AsA remained after 15 min and 52% of AsA remained after 90 min under the same conditions in the presence of 60 mumol/l protamine. Furthermore, the effect of protamine on the stability of AsA in various pH solutions (pH 1-10) was examined after standing for 90 min at 30 degrees C. Degradation of AsA was accelerated by increasing the pH from 1 to 10. On the other hand, the effect of protamine (60 mumol/l) on the stabilization of AsA was recognizable above pH 5 and degradation of AsA was controlled at higher pH. When 0.5 mumol/l of copper ion (II) was added to the above solutions in the absence of protamine, degradation of AsA was greatly accelerated above pH 5. When 60 mumol/l of protamine was added to the solutions, the effect of protamine on the stabilization of AsA was observed above pH 5 and degradation of AsA was controlled at higher pH.

Ascorbic Acid↗
PubMed1992

High performance liquid chromatography of nucleic acids and the related compounds on a fluorinated silica gel column.

Separations of nucleic acids and the related compounds were investigated by HPLC on a new fluorinated bonded silica gel column. Polyadenylate (Poly (A)) enzymatic partial hydrolysate sample and the mixture of various polynucleotide samples were sufficiently separated by the reversed-phase mode using a gradient elution with aqueous ammonium acetate/acetonitrile system. Mixed-mode separation on the fluorinated bonded phase coated with a tert-alkylammonium salt was also examined for the separation of the various polynucleotides including tRNAs.

Chromatography, High Pressure Liquid↗
PubMed1991

Fast protein separation by reversed-phase high-performance liquid chromatography on octadecylsilyl-bonded nonporous silica gel. II. Improvement in recovery of hydrophobic proteins.

Recovery of hydrophobic proteins from an RP-HPLC column was improved using a fast-separation RP-HPLC system operated at room temperature. Hydrophobic proteins such as ovalbumin could be adequately eluted from a nonporous octadecylsilyl (C18) spherical silica gel with a particle diameter of 20 microns using steep gradient elution with a 0.1% aqueous trifluoroacetic acid-acetonitrile system at a constant flow rate of 4 ml/min. Recoveries improved under fast separation since the protein sample suffered only a slight amount of irreversible denaturation on the hydrophobic surface of the stationary phase. The fast-separation system was also applied to the separation of larger proteins such as apo-ferritin (443 kDa) and thyroglobulin (669 kDa) as well as egg white proteins.

Animals↗
PubMed1990

Precolumn derivatization technique for high-performance liquid chromatographic determination of penicillins with fluorescence detection.

A precolumn derivatization method was developed for the high-performance liquid chromatographic (HPLC) determination of penicillins using fluorescence detection. Penicillins were derivatized by a two-step reaction, the beta-lactam ring being opened by hydrolysis in aqueous sodium carbonate solution in the first step to give a secondary amine functionality, and the secondary amino group being reacted with 7-fluoro-4-nitrobenzo-2-oxa-1,3-diazole in the second step to give a fluorescent derivative. The resulting reaction mixture was injected directly onto a reversed-phase column and analysed by HPLC. At a penicillin concentration of 10 micrograms/ml, the precision (relative standard deviation) ranged from 1.49 to 2.20%. In the concentration range 0.2-100 micrograms/ml, a linear response was observed. The detection limits of this method were 30-85 ng/ml for five different penicillins at a signal-to-noise ratio of 3:1. The proposed method was applied to the determination of penicillins added to serum following pretreatment by deproteinization and removal of compounds containing amino functionalities with a cation-exchange resin.

Chromatography, High Pressure Liquid↗
PubMed1988

New preparation method for 9-anthryldiazomethane (ADAM) as a fluorescent labeling reagent for fatty acids and derivatives.

A preparation method for 9-anthryldiazomethane (ADAM) as a fluorescent labeling reagent for carboxylic acids is described. 9-Anthraldehyde hydrazone is oxidized with an organic oxidant, N-chlorosuccinimide, in an organic solvent such as ethyl acetate to give ADAM, and then the reaction mixture is directly used as the reagent solution for the derivatization of carboxylic acids. Both the oxidation and the derivatization reaction are carried out at room temperature, and an aliquot of the derivatization mixture is directly injected into a chromatograph. 9-Anthrylmethyl ester derivatives formed from ADAM and various carboxylic acids are sufficiently separated on a reversed-phase column and are sensitively detected fluorometrically. The present method was applied to the high-performance liquid chromatographic determination of long and short chain fatty acids, keto acids, and hydroxy acids.

Anthracenes↗
PubMed1988

Determination of carnitine by high-performance liquid chromatography using 9-anthryldiazomethane.

The high-performance liquid chromatographic determination of carnitine chloride was investigated by using 9-anthryldiazomethane (ADAM) as a pre-column derivatization reagent. Carnitine chloride and the internal standard N,N-dimethylglycine reacted with ADAM to give a stable ester derivative in the presence of sodium dodecyl sulphate (SDS) used to mask the basic function. The ADAM derivative of carnitine was separated from decomposition products of the reagent and related compounds such as amino acid derivatives on a silica gel column eluted with methanol-5% aqueous SDS-phosphoric acid (990:10:1). The calibration plot was linear over a sample concentration range from 0.02 to 100 ng per injection. The detection limit for carnitine chloride was about 1 pg per injection (signal to noise ratio = 4), by fluorometric detection.

Anthracenes↗
PubMed1987

Amino acid analysis by reversed-phase high-performance liquid chromatography. Automatic pre-column derivatization with activated carbamate reagent.

Succinimido alpha-naphthylcarbamate, an activated carbamate reagent, facilitated the simple and rapid pre-column derivatization of amino acids for fluorimetric detection. The method is based on the formation of naphthylcarbamyl derivatives of amino acids. The carbamylation of amino acids is completed within 1 min at room temperature, and the reaction mixture can be injected directly into a liquid chromatograph equipped with an octadecylsilyl reversed-phase column. The effluent stream is monitored fluorimetrically at 370 nm excited at 290 nm at the sub-picomole level. Naphthylcarbamyl derivatives of common protein amino acids were separated within 30 min by gradient elution with aqueous sodium acetate and acetonitrile. Excess of the reagent does not interfere with the analysis of amino acids, because it is hydrolysed in 2-3 min to give naphthylamine, which is more strongly retained than any amino acid derivatives.

Amino Acids↗
PubMed1987

Optical resolution of enantiomeric amino acid derivatives on a naphthylethylurea multiple-bonded chiral stationary phase prepared via an activated carbamate intermediate.

A new chiral stationary phase (CSP) was developed for the direct optical resolution of enantiomeric amino acid derivatives. The CSP was readily prepared by a three-step reaction carried out in a pre-packed aminopropylsilyl silica gel column. In the first step, a solution of disuccinimido carbonate (DSC) was delivered through the pre-packed column to give a succinimido carbamyl aminopropylsilyl-bonded, activated-carbamate type silica gel (ACsil) column. Through the column was then delivered a solution of pentaethylenehexamine to afford a polyamine-bonded column. Finally, a solution of optically active succinimido (S)- or (R)-naphthylethyl carbamate was delivered through the polyamine column, to give a naphthylethylurea multiple-bonded CSP. p-Bromophenylcarbamyl derivatives of enantiomeric protein amino acids were resolved on these CSPs by elution with an aqueous mobile phase. Simultaneous analysis of these amino acid enantiomers by means of gradient elution was also accomplished.

Amino Acids↗
PubMed1987

Postcolumn fluorometric detection system for liquid chromatographic analysis of amino and imino acids using o-phthalaldehyde/N-acetyl-L-cysteine reagent.

A high-performance liquid chromatographic system for the determination of amino acid and imino acid was developed using a two-step reaction with sodium hypochlorite and o-phthalaldehyde/N-acetyl-L-cysteine (OPTA/AcCys) reagent. This reagent improved the sensitivity in the analysis of proline presumably because the fluorophore is more stable to hypochlorite which has been used for the oxidative cleavage of the imino linkage. The use of OPTA/AcCys facilitated the detection of imino acids at the same concentration level as that of amino acids. The detection limit for all the amino and imino acids was a few picomoles. This detection system, together with cation-exchange chromatographic separation, was applied to the determination of amino and imino acids in biological samples.

Acetylcysteine↗
PubMed1986

Phorbol myristate acetate-stimulated release of cyclooxygenase products in rat pleural cells: derivatization of prostaglandins with 9-anthryldiazomethane for fluorometric determination by high performance liquid chromatography.

White cells were collected from the wash of rat pleural cavity after exsanguination. The incubation mixture of the pleural cells with 1 microM phorbol myristate acetate (PMA) was extracted with acidified ethanol and purified with a Sep-pak C18. The resultant fraction containing prostaglandins (PG) and thromboxane (TX) was allowed to react with 9-anthryldiazomethane (ADAM). After removing contaminants and degraded reagent by silica gel Sep-pak, samples were applied to reversed phase high performance liquid chromatography of octadecylsilyl silica gel and monitored by a fluorescent detector. ADAM derivatives of the authentic PGD2, PGE2, PGF2 alpha, 6-keto-PGF1 alpha, 6-keto-PGE1, TXB2, 15-keto-PGE2, 13,14-dihydro-15-keto-PGF2 alpha and 13,14-dihydro-15-keto-PGE2 showed linear regression lines of peak heights within a range of 0.5-25 ng. By using this method PGD2, 6-keto-PGF1 alpha and TXB2 were detected in the incubation mixture of the rat pleural cells with PMA. The result clarified the origin of these PGs and TX found in the exudate of rat pleurisy induced by PMA. ADAM method for HPLC with a help of clean-up by Sep-pak could be a useful tool for detection of a series of arachidonate metabolites in biological materials.

Animals↗
PubMed1980

Novel post-column derivatization method for the fluorimetric determination of norepinephrine and epinephrine.

A novel method is described in which catecholamines are converted into fluorescent products by heating in alkaline borate buffer. The method was applied to the determination of norepinephrine and epinephrine after separation by high-performance liquid chromatography using a pellicular, strong cation exchanger. The new system is simpler than the system based on the trihydroxyindole reaction. It is suitable for the measurement of catecholamines in the range of 0.25-20 ng. The assay of catecholamines in human urine is also described.

Borates↗
PubMedDate not supplied

Study of chemobiological reactions. 1. Selectivity of aromatic amino compounds and saccharides in glycosylation reactions.

The reactivities between saccharides and primary amino compounds were studied by liquid chromatography on an amino-bonded column and by measurement of the reaction rates of aromatic amines with saccharides. The recoveries from the column and the reaction rates were correlated with their physicochemical properties calculated by the CAChe program. The reactivities between amines and saccharides correlated well with their hydrogen bonding energies calculated by molecular mechanics.

Amines↗