On the Complexation of Ferric Ions by Reduced Nicotinamide Adenine Dinucleotide

Menachem Gutman, Michael Eisenbach

Research output: Contribution to journalArticlepeer-review

Abstract

In acid aqueous solutions, ferric ions and NADH were found to react rapidly to form a blue charge-transfer complex with a stoichiometry of Fe3+(NADH)2. This complex is unstable and decomposes in a redox reaction with Fe2+ and NAD+ as products. The formation of the complex was studied under similar conditions by the stopped-flow technique and found to be a two-step reaction (see eq 1 and 2 of text). The rate constants of these two reactions were calculated from both kinetics and equilibrium studies. Within experimental error the results obtained by the two methods were the same (k1 = (5.0 ± 0.2) × 103 m–1 sec–1, k–1 = 0.6 ± 0.1 sec–1; k2 = (1.30 ± 0.05) × 103 M–1 sec–1, k–2 = 0.03 ± 0.01 sec–1). The relatively small magnitude of k–2 is the explanation for the complete conversion of Fe3+ into the Fe3+(NADH)2 complex. The two complexes have similar absorption spectra with a maximum at 540 nm, except that the extinction coefficient of the Fe3+(NADH) is lower than that of Fe3+(NADH)2. The properties of the Fe3+(NADH) complex are discussed.

Original languageEnglish
Pages (from-to)2314-2317
Number of pages4
JournalBiochemistry
Volume12
Issue number12
DOIs
StatePublished - 1 Jun 1973

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