The peroxidase-NADH biochemical oscillator. 2. Examination of the roles of hydrogen peroxide and superoxide

Dean Olson, Alexander Scheeline

Research output: Contribution to journalArticlepeer-review

Abstract

The peroxidase-NADH oscillator examined here initially consists of a well-mixed aqueous solution of native horseradish peroxidase, reduced β-nicotinamide adenine dinucleotide (NADH), methylene blue (MB+), and dissolved oxygen combined in a semi-batch reactor under a set of standard conditions. Hydrogen peroxide and superoxide have been implicated as important chemical intermediates. A comprehensive model which includes such intermediates and all initial chemical species has appeared elsewhere. To experimentally explore the role of hydrogen peroxide in the oscillator, H2O2 was substituted for MB+ as an initial ingredient. This substitution allows relatively small, quasi-sinusoidal oscillations sensitive to the oxygen mass transport constant, and predicted earlier in a theoretical model. The oscillations become much larger when MB+ is added, suggesting that MB+ might serve as a chemical mediator between the small oscillations seen when H2O2 is substituted for MB+, and the relatively large oscillations observed when MB+ is present. Catalase and superoxide dismutase are used as enzymatic scavengers for H2O2 and O2•-, respectively. The enzymes are added individually to a working oscillator at oxygen minima and maxima to examine the roles and approximate the concentrations of H2O2 and O2•-. For the enzyme addition experiments, a perturbation model for oxygen behavior is proposed and applied to the interpretation of experimental data. Two methods of analysis for the addition of the enzyme probes indicate a higher concentration of H2O2 and O2•- at oxygen maxima than at minima. Comparison of experimental and simulated data indicate that the relatively simple model presented here is a reasonable, yet apparently incomplete, representation of oxygen dynamics for the addition of scavenger enzymes to this oscillator.

Original languageEnglish (US)
Pages (from-to)1212-1217
Number of pages6
JournalJournal of physical chemistry
Volume99
Issue number4
DOIs
StatePublished - Jan 1 1995

ASJC Scopus subject areas

  • Engineering(all)
  • Physical and Theoretical Chemistry

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