The chiral separation of several amino acid (AA) enantiomers derivatized with naphthalene-2,3-dialdehyde (NDA) was achieved by use of cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC). Both neutral hydroxypropyl beta-cyclodextrin (HP-beta-CD) and charged carboxymethyl beta-cyclodextrin (CM-beta-CD) were used as buffer additives for optical resolution of derivatized amino acids. The order of elution and the mechanism of separation for different CDs were explained by considering important chemical equilibria in the sodium dodecyl suphate, CD and amino acid system. Furthermore, the importance of SDS for the separation of a mixture of AAs, and the effect of CD and analyte concentration on the resolution will be discussed.

Amino Acids↗

PubMedDate not supplied

Fluorescence and chemiluminescence detection of oxazole-labelled amines and thiols.

Fluorescence and chemiluminescence analyses of amino acids and thiols derivatized with 2-fluoro-4,5-diphenyloxazole (DIFOX) and 2-chloro-4,5-bis(p-N,N-dimethylaminosulphonylphenyl)oxazole (SAOX-Cl) were investigated. Thirteen diphenyloxazole (DIOX)-derivatized amino acids were separated within 38 min by a linear gradient elution from 100% A [0.05 M phosphate (pH 7.0): CH3CN (75:25)] to 100% B [0.05 M phosphate (pH 7.0):CH3CN (1:1)] over 30 min and an isocratic elution of 100% B for 30 min. The detection limits (S/N = 2) with fluorescence detection were in the range of 19-64 fmol. Thiols derivatized with SAOX-Cl were separated by an isocratic elution using 0.1 M H3PO4:CH3CN (65:35) and detected fluorimetrically. The detection limits (S/N = 2) of reduced glutathione, N-acetylcysteine, 2-mercaptopropionylglycine, cysteine, homocysteine and captopril were 1.2, 1.5, 1.9, 5.7, 6.4 and 7.9 fmol, respectively. Peroxyoxalate chemiluminescence (CL) intensities of sulphonyl-5-N,N-dimethylaminonaphthalene (DNS), SAOX and DIOX derivatives were compared using three different oxalate esters (DFPO, TCPO and TDPO) by flow injection analysis. The relative chemiluminescence intensity (RCL) of SAOX-proline and DIOX-proline were 76-80% and 19-25% of DNS-proline (100%), respectively. Other SAOX and DIOX derivatives showed lower CL intensities (< 12%). Extremely low CL intensities were obtained for the fluorescent tagging reagents (< 0.11%) and their hydrolysis products (< 0.80%). Secondary amino acids and peptides, derivatized with DIFOX in aqueous media at room temperature for 1 h, were detected using DFPO/H2O2. TCPO/H2O2 and TDPO/H2O2 after separation by high performance liquid chromatography.(ABSTRACT TRUNCATED AT 250 WORDS)

Amines↗

PubMedDate not supplied

Chiral separation of naphthalene-2,3-dialdehyde labelled peptides by cyclodextrin-modified electrokinetic chromatography.

The chiral separation of several dipeptide enantiomers, derivatized by naphthalene-2,3-dialdehyde (NDA), was achieved by use of cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC). The dipeptides contained one or two chiral centers. In the case of several dipeptides containing two chiral centers, all four of the optical isomers could be separated and baseline resolved in less than 15 min with 20 mM gamma-CD and 50 mM sodium dodecyl sulphate (SDS) in the background electrolyte. The order of elution of these derivatized dipeptides was explained by considering important chemical equilibria in the SDS, CD and peptide system. Additionally, the influence of geometric location of the chiral center, the structure of the side-chain and the effect of CD concentration on the resolution are discussed.

Chromatography↗

PubMedDate not supplied

Methylmercury poisoning in common marmosets--a study of selective vulnerability within the cerebral cortex.

Neuropathological lesions found in chronic human Minamata disease tend to be localized in the calcarine cortex of occipital lobes, the pre- and postcentral lobuli, and the temporal gyri. The mechanism for the selective vulnerability is still not clear, though several hypotheses have been proposed. One hypothesis is vascular and postulates that the lesions are the result of ischemia secondary to compression of sulcal arteries from methylmercury-induced cerebral edema. To test this hypothesis, we studied common marmosets because the cerebrum of marmosets has 2 distinct deep sulci, the calcarine and Sylvian fissures. MRI analysis, mercury assays of tissue specimens, histologic and histochemical studies of the brain are reported and discussed. Brains sacrificed early after exposure to methylmercury showed high contents of methylmercury and edema of the cerebral white matter. These results may explain the selective cortical degeneration along the deep cerebral fissures or sulci.

Animals↗