Search PubMed⌕ Search

Biomedical subjects

Y Oji

Publications and source records attributed to Y Oji.

42 records · Page 3Linked to original sources
PubMed1990

Enzymic method for the spectrophotometric determination of aspartame in beverages.

A sensitive spectrophotometric method for the determination of aspartame in beverages is described. The method involves the enzymic conversion of aspartame into formaldehyde by the alpha-chymotrypsin-alcohol oxidase system, followed by the formation of a chromophore with 4-aminopent-3-en-2-one. The calibration graph was linear in the range 2.0-30.0 micrograms ml-1 of aspartame. Many common ingredients of beverages do not interfere with the proposed method. The method was applied to the determination of the aspartame content of various real samples, and the results obtained were compared with those given by high-performance liquid chromatography.

Aspartame↗
PubMed1987

Effect of Inorganic Orthophosphate on in Vitro Activity of NADH-Nitrate Reductase Isolated from 2-Row Barley Leaves.

Inorganic orthophosphate (25 millimolar in assay media; Pi) was found to increase in vitro activity of NADH-nitrate reductase (NR) isolated from 2-row barley (Hordeum vulgare L.) leaves with a saturating concentration of nitrate (2 millimolar) but to decrease it with low nitrate levels (<0.1 millimolar). The response to nitrate concentrations was Pi specific. The Lineweaver-Burk plot showed that Pi increases the apparent K(m) for nitrate as well as V(max), whereas it does not alter the K(m) for NADH significantly. These results suggest that the interaction between a molybdenum site of the enzyme and Pi results in alteration of the properties of NR molecule.

Journal Article↗
PubMed1985

Separate determination of ethylenediaminetetraacetic acid and its calcium chelate in foods by colorimetry.

A simple colorimetric method is described for the separate determination of ethylenediaminetetra acetic acid (free EDTA) and its calcium chelate (Ca-EDTA) in commercial foods. The underlying principle of the method is that free EDTA is adsorbed by a cation exchange column, but Ca-EDTA is not under weak alkaline conditions. The sample was homogenized with 0,1 n-NaOH and then subjected to equilibrium dialysis against 0,02 n-NaOH at ambient temperature for a definite time (not less than 12 h). An aliquot of the dialysate was measured into a beaker. After the pH of the solution had been adjusted to 8.5 it was applied to a pre-packed cation-exchange column (Amino-form). Free EDTA was adsorbed by this column, whilst Ca-EDTA passed through it without any loss. For assay of Ca-EDTA, the pH of the eluate was adjusted to 2.5, followed by the addition of an excess amount of CuSO4 to convert Ca-EDTA into Cu-EDTA. This solution was then divided into two portions of equal volume. One portion was subjected to the assay of free copper ions, and the other to the assay of total (the sum of free and chelated) copper ions. The difference between the two values is a measure of Ca-EDTA. For the assay of free EDTA, EDTA adsorbed by the column was eluted with 0.5 n-acetate buffer (pH 5.0), followed by the treatment in the same manner as in the case of Ca-EDTA.(ABSTRACT TRUNCATED AT 250 WORDS)

Chromatography, High Pressure Liquid↗
PubMed1985

Colorimetric determination of ethylenediaminetetra-acetic acid in foods.

A simple colorimetric method is described for the determination of ethylenediaminetetra-acetic acid (EDTA) in three kinds of foods. The samples were homogenized with 0.1 N-NaOH, then subjected to equilibrium dialysis against 0.02 N-NaOH. EDTA in the dialyzate was converted into a Cu-EDTA complex by the addition of CuSO4. Afterwards, this solution was subjected to the determination of both free and total (free plus complexed) copper ion. EDTA was calculated from the difference between the absorbances (477 nm) obtained with free and total copper ions. Analyses of mayonnaise, dressings and canned mushroom samples with EDTA added at the 1-mM level showed a recovery of greater than 98%.

Colorimetry↗