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Biomedical subjects

H Homma

Publications and source records attributed to H Homma.

224 records · Page 13Linked to original sources
PubMedDate not supplied

1-(5-Dimethylamino-1-naphthalenesulphonyl)-(S)-3-aminopyrrolidine (DNS-Apy) as a fluorescence chiral labelling reagent for carboxylic acid enantiomers.

1-(5-Dimethylamino-1-naphthalenesulphonyl)-(S)-3-aminopyrrolidi ne (DNS-Apy) has been synthesized for the separation of carboxylic acid enantiomers by high-performance liquid chromatography (HPLC) and sensitive detection. The reagent reacts with carboxylic acids at room temperature in the presence of activation agents 2,2'-dipyridyl disulphide (DPDS) and triphenylphosphine (TPP). The maximum emission of the diastereomeric amide derived from (S)-phenylpropionic acid and ketoprofen derivatives of DNS-Apy was at 530 nm with excitation at 340 nm. The emission wavelength shifted towards the blue and the fluorescence intensities increased with increasing acetonitrile concentration in the medium. The diastereomers derived from anti-inflammatory drugs were efficiently resolved with a reverse-phase column using water:acetonitrile mixture as mobile phase. All of the racemate of arylpropionic acid derivatives gave equal fluorescence intensity of the two enantiomers with the exception of ketoprofen derivatives where the intensity of the first eluting enantiomer was half that of the second.

Benzopyrans↗
PubMedDate not supplied

Enantiomeric separation of d-/l-norepinephrine and -epinephrine by high-performance liquid chromatography with a beta-cyclodextrin type chiral stationary phase.

Enantiomeric separation of d-/l-norepinephrine (NE) and d-/l-epinephrine (E) was investigated with various mobile phases by high-performance liquid chromatography using a beta-cyclodextrin type chiral stationary phase as a chiral column. The mobile phase of 2.5 M phosphate buffer (pH 3.0) gave separation factors (alpha s) of 1.04 and 1.06 for NE and E, respectively.

Buffers↗
PubMedDate not supplied

Enantiomeric determination of amines by high-performance liquid chromatography using chiral fluorescent derivatization reagents.

4-(2-carboxypyrrolidin-1-yl)-7-nitro-2,1,3-benzoxadiazole (NBD-Pro), 4-(2-carboxypyrrolidin-1-yl)-7-(N,N-dimethylamino-sulphonyl)-2,1,3 - benzoxadiazole DBD-Pro), 4-(N-1-carboxyethyl-N-methyl)amino-7-nitro-2,1,3-benzoxadiazole NBD-N-Me-Ala), 4-(N-1-carboxyethyl-N-methyl) amino-7-(N,N-dimethylamino-2,1,3-benzoxadiazole. (DBD-N-Me-Ala) have been synthesized for the resolution of enantiomers of amines by high performance liquid chromatography (HPLC). The reagents react with amino group at room temperature in the presence of activation agents, 2,2'-dipyridyl disulphide (DPDS) and triphenylphosphine (TPP) to produce the corresponding diastereomers. The derivatives were detected at lambda ex = 469, lambda em = 569 for DBD-moeity and lambda ex = 469, lambda em = 535 for NBD moeity. The resulting diastereomers were efficiently resolved using reversed-phase column with aqueous acetonitrile and aqueous methanol as the mobile phase. The elution order of the derivatives were D and L when proline was used as the chiral selector but the order was reversed when the diastereomers were prepared with the reagent containing N-methyl alanine as the chiral selector. DBD-Pro and NBD-Pro seem to give better separation as compared to DBD-N-Me-Ala and NBD-N-Me-Ala.

Amines↗
PubMedDate not supplied

A novel method for the amino acid sequence/configuration determination of peptides containing D/L-amino acids utilizing a fluorogenic Edman reagent, 7-N,N-dimethylaminosulphonyl-4-(2,1,3-benzoxadiazolyl)isothiocyanate (DBD-NCS).

A novel method for the amino acid sequence and configuration determination of peptides containing D- or L-amino acids is presented. An enkephalin analogue, [D-Ala2, D-Leu5]enkephalin (Tyr-Ala-Gly-Phe-Leu) was derivatized with a fluorogenic Edman reagent, 7-N,N-dimethylaminosulphonyl-4-(2,1,3-benzoxadiazolyl) isothiocyanate (DBD-NCS), cleaved and cyclized with trifluoroacetic acid at 50 degrees C for 1 min and the resultant thiazolinone derivative (DBD-thiazolinyl-L-Tyr) was separated from the racemized DBD-thiazolinyl-D-Tyr (about 20% as compared to the L-isomer) on a phenylcarbamylated cyclodextrin column: The separation factor (alpha) for D- and L-isomers was 1.09. The column eluate was monitored fluorometrically at 524 nm with excitation at 387 nm. The detection limit was about pmol range. The same treatment adopted for the residual peptide, Ala-Gly-Phe-Leu, gave DBD-thiazolinyl-D-Ala (alpha = 1.09 for D,L-Phe) with the lesser amount of L-analogue (about 20%). In the same manner, Gly and L-Phe (alpha = 1.09) were detected. The method might be useful for the study of aging of proteins such as eye lens and amyloid proteins derived from Alzheimer's disease.

Amino Acid Sequence↗
PubMedDate not supplied

Determination of D-amino acids, derivatized with 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F), in wine samples by high-performance liquid chromatography.

The concentrations of D-amino acids and their enantiomeric ratios in wind samples were determined by high-performance liquid chromatography with fluorometric detection. We used Pirkle type chiral stationary phases and fluorogenic reagent, 4-fluoro-7-nitro-2,1,3-benzoxadiazole (NBD-F) for simplicity and high sensitivity. The amino acids determined were D-enantiomers of alanine (Ala), aspartic acid, glutamic acid, isoleucine (Ile) and leucine (Leu), D-Asparagine, -glutamine and -lysine were not detected. D-Leu was detected in red and rosé wine samples, and D-Ile was determined only in rosé wine. In contrast, neither D-Leu nor Ile were detected in white wine samples. The concentration of D-Ala was the most prominent among these amino acids with the highest content of approximately 180 microns (D/D + L ratio; 25%) in rosé wine.

4-Chloro-7-nitrobenzofurazan↗
PubMedDate not supplied

Availability of phenylisothiocyanate for the amino acid sequence/configuration determination of peptides containing D/L-amino acids.

A potential use for phenylisothiocyanate (PITC), the most popular Edman reagent, is presented for analysis of the amino acid sequence and configuration in peptides containing D/L-amino acids. After derivatization with PITC of the N-terminal amino acid (L-Tyr) of an enkephalin analogue, [D-Ala2, D-Leu5]-enkephalin, followed by cleavage/cyclization with trifluoroacetic acid at 50 degrees C for 5 min, the liberated 2-anilino-5-thiazolinone-L-Tyr (ATZ-L-Tyr) was further treated with 20% aqueous trifluoroacetic acid at 50 degrees C for 10 min. The resultant phenylthiohydantoin (PTH)-L-Tyr was then separated on a chiral stationary phase (a penylcarbamoylated cyclodextrin column), retaining its configuration. The residual sequence and configurations of the peptide (D-Ala-Gly-L-Phe-D-Leu) were also determined by separating the corresponding PTH-D- or L-amino acids on chiral columns. This method may be applicable to an automatic Edman sequence analyzer for the configuration determination of peptides containing D/L-amino acids.

Amino Acid Sequence↗
PubMedDate not supplied

Biochemistry and molecular biology of drug-metabolizing sulfotransferase.

Sulfation is an important conjugation reaction in the metabolism of various xenobiotics and endogenous compounds and is catalyzed by sulfotransferase (ST) present in cytosols. The cloning studies on STs have provided the basis for the understanding of the ST multigene family. STs are classified into hydroxysteroid (or alcohol), aryl (or phenol), estrogen, flavonol and polysaccharide STs and recent developments in the molecular characterization of these isoforms are reviewed. Regulation and localization of ST isoforms in various tissues are characterized at the molecular level by virtue of the specific antibodies and the corresponding cDNA probes. The recent developments are summarized. ST inhibitors are potent tools for the study on ST multiplicity and for the characterization of the enzyme structure. It also appears to be important to understand exogenous and endogenous ST inhibitors in clinical environment. The recent developments are reviewed.

Animals↗