Thesis
Heavy metal induced inhibition of Aspergillus niger nitrate reductase: Applications for rapid contaminant detection in aqueous samples
Washington State University
Master of Science (MS), Washington State University
2002
Handle:
https://hdl.handle.net/2376/69
Abstract
Enzyme inhibition assays have the potential to rapidly screen and identify heavy metals in environmental samples. Inhibition of nitrate reductase (NR) was examined as a method for detecting toxic metals. The activity of NR (EC 1.6.6.2) from Aspergillus niger was assayed as a function of metal concentration in the presence of Cd2+, Cr3+, Cr6+, Cu2+, Ni2+, Pb2+ and Zn 2+. NR exhibited sensitivity to these metals at concentrations above 0.1 M. Various buffers were screened for their affinity to bind the metals tested, and 3-[N-Morpholino] propanesulfonic acid (MOPS) was selected as the buffering system for the NR assays as it exhibited the smallest degree of metal binding for providing increased assay sensitivity. The hypothesis that chelating agents could prevent the inhibition of NR activity by metal ions was tested. Results indicated that 10 mM ethylenediaminetetraacetic acid (EDTA) could protect NR activity from inhibition by Cr3+, Cu2+, Cd2+, Ni2+ and Zn2+ at concentrations below 100 M, but that the EDTA had no effect on NR inhibition by Cr6+. 10 mM nitrilotriacetic acid (NTA) prevented NR inhibition by Cd2+, Cu2+, Ni2+, Pb2+ and Zn 2+ at metal concentrations below 100 M. However, 10 mM NTA was unable to protect the enzyme from inhibition by either Cr3+ or Cr6+. These results indicated that through specific metal chelation, a NR-based method for individually quantifying Cr3+ and Cr6+ species in aqueous solutions could be developed. The ability to restore activity to NR which been previously inhibited by exposure to 100 M Pb2+, Cd2+, Zn 2+, Cu2+ and Cr3+ was explored to determine the whether NR activity could be recovered by EDTA additions for use in consecutive metal inhibition assays. The results showed NR activity could not be regained after exposure to Cr3+ or Cu2+ but did partially recover activity after Cd2+, Pb2+ and Zn 2+ exposure.
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Details
- Title
- Heavy metal induced inhibition of Aspergillus niger nitrate reductase
- Creators
- Abigail Marie Aiken
- Contributors
- Brent M. Peyton (Degree Supervisor)James N. Petersen (Degree Supervisor)
- Awarding Institution
- Washington State University
- Academic Unit
- Chemical Engineering and Bioengineering, School of
- Theses and Dissertations
- Master of Science (MS), Washington State University
- Publisher
- Washington State University; Pullman, Wash. :
- Identifiers
- 99900525174001842
- Language
- English
- Resource Type
- Thesis