PubMed · 1246298
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N T Ott. 1976-02-12. Letter: Nitroprusside and renal function.. https://doi.org/10.1056/nejm197602122940719
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A novel chemiluminescence (CL) sensor for folic acid combined flow-injection (FI) technology was presented in this paper. The analytical reagents involved in the CL reaction, including luminol and hexacyanoferrate(III), were both immobilized on an anion-exchange column in FI system. The CL signal produced by the reaction between luminol and hexacyanoferrate(III), which were eluted from the column through sodium phosphate injection, was decreased in the presence of folic acid. The CL emission was correlated with the folic acid concentration in the range from 0.01 to 15 microg ml(-1), and the detection limit was 3.5 ng ml(-1) folic acid (3sigma). At a flow rate of 2.0 ml min(-1), including sampling and washing, could be performed in 2 min with a relative standard deviation of < 2.5%. The flow sensor could be reused more than 300 times and has been applied to the analysis of folic acid in pharmaceutical preparations. and the recovery was from 97.4% to 100.4%.
The copper- and zinc-containing superoxide dismutase can catalyze the oxidation of ferrocyanide by O(2) as well as the reduction of ferricyanide by O(2). Thus, it can act as a superoxide dismutase (SOD), a superoxide reductase (SOR), and a superoxide oxidase (SOO). The human manganese-containing SOD does not exert SOR or SOO activities with ferrocyanide or ferricyanide as the redox partners. It is possible that some biological reductants can take the place of ferrocyanide and can also interact with human manganese-containing superoxide dismutase, thus making the SOR activity a reality for both SODs. The consequences of this possibility vis à vis H(2)O(2) production, the overproduction of SODs, and the role of copper- and zinc-containing superoxide dismutase mutations in causing familial amyotrophic lateral sclerosis are discussed, as well as the likelihood that the biologically effective SOD mimics, as described to date, actually function as SORs.
The intermediates in the oxidation of deoxyhemoglobin by ferricyanide in 0.1 M KCl, at 20 degrees C and three pH values, were studied by cryogenic techniques. Data analysis was carried out according to a simple four rate constant model, ignoring the functional heterogeneity of the subunits, to simulate the time courses of the oxidation reaction, as studied by the stopped-flow technique [Antonini et al., (1965) Biochemistry 4, 345], which show anticooperativity at neutral pH and cooperativity at alkaline pH. Data analysis according to a 12 rate constant model indicated that the rate of oxidation of the beta subunit in the first oxidation reaction was 4 times faster than the rate of oxidation of the alpha subunit at pH 6.2 and 12 times faster at pH 8.5. The reactions involving the alpha subunit were noncooperative except for the last oxidation step at acid and neutral pH, but were cooperative at alkaline pH. The reactions involving the beta subunit were partly noncooperative and partly anticooperative. These complex mechanistic patterns suggest that a simple two-state model requiring the concerted transition of the tertiary structures of the subunits from the T to the R conformation is not adequate to interpret the oxidation reaction and that tertiary structures contribute, positively and negatively, to cooperativity. A structural hypothesis is suggested to explain the difference in the reactivities of the alpha and beta subunits.