Iron autoxidation in Mops and Hepes buffers

Area of Science:

• Biochemistry
• Environmental Chemistry

Background:

• Iron autoxidation is a critical process in various biological and environmental systems.
• Understanding the influence of buffer composition on iron oxidation kinetics is essential for accurate experimental design.

Purpose of the Study:

• To investigate the autoxidation of iron (Fe2+) in different buffer systems, specifically MOPS, HEPES, and phosphate buffers.
• To elucidate the reaction mechanisms and identify factors affecting iron oxidation rates and products.

Main Methods:

• Studied iron autoxidation kinetics by varying FeCl2 concentration and pH in MOPS, HEPES, and phosphate buffers.
• Utilized nitro blue tetrazolium (NBT) to detect reactive oxygen species and employed various hydroxyl radical scavengers (mannitol, sorbitol, catalase).
• Characterized iron oxidation products using absorption spectroscopy and reactivity assays with thiocyanate.

Main Results:

• Iron autoxidation in MOPS and HEPES buffers exhibited a pH and FeCl2-dependent lag phase, forming a distinct iron product.
• Mannitol and sorbitol significantly inhibited Fe2+ oxidation, yellow color development, and NBT reduction in MOPS/HEPES.
• Phosphate buffer showed no lag phase, produced Fe3+, and was inhibited only by catalase, indicating a different reaction pathway.

Conclusions:

• The autoxidation mechanism of iron in Good's buffers (MOPS, HEPES) differs significantly from that in phosphate buffer.
• Buffers with low iron affinity, like MOPS and HEPES, allow for Fe2+ stability under specific experimental conditions.
• The findings provide critical insights into controlling iron speciation in biochemical and environmental research.