Glutathioneに関する研究-8-
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概要
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The behaviour of KIO3 on ascorbic acid (AA) and glutathione (GSH) in OGAWA's method(1), has been examd, and discussed. The iodometric titration of GSH was carried out theoretically under the four conditions described in preceding paper(5) and within 1min. It must be, there-fore, observed that the iodometric titration times (ITT) of GSH and AA present in soln. are differently estmd. at 0° in OGAWA's method. The author will propose the necessity of GSH- detn. with a definite ITT by the following exptl. results, otherwise the remarkable error is induced. The dependence of ITT on pH and temp. of GSH pure soln. was shown in Table 1. This relation was as same as the extg. reagents used for GSH. ITT of AA in N/4 S. S. A. at 0° on OGAWA's terms was about 4min. (Table 2), but in the vital material (VM) ext., about 5min. (Table 4). From the studies of pH ranges of GSH and AA possible to be titrated within 1min., it was found that both were titrated within 1min. at pH 2 (Table 3). But it was required 3min. for titration of AA in VM ext., even though pH was adjusted to 2 (Table 4). The substance which put off the end point of the titration was proved to be present in VM (Table 5). When pH of VM ext. was adjusted to 2, the blank test value should be estmd. after GSH and AA in soln. were destroyed by HCOH and AA-oxidase resp. As this treatment was tedious and complicated, the author adopted 3min.-titration in N/20 S. S. A. or 2% HPO3. Because these reagents showed about pH 2 and they have advantage that the blank test value to N/20 S. S. A. or 2% HPO3 may be recognized as that of VM ext. itself. The author has a view that 2% HPO3 is more suitable than N/20 S. S. A., considering the problems attendant on the iodometric titration, such as the presence of Fe+++, dissocn. of KI and reaction between iodine and the other substances in extract.
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