# Resonance Raman Spectroscopy and Density Functional Theory Reveal the Hemin Release Mechanism of Fish and Mammalian Hemoglobin

## TL;DR

This paper explains why fish hemoglobin causes more oxidation than mammalian hemoglobin using spectroscopy and theory.

## Contribution

The study reveals a novel mechanism of hemin release in fish hemoglobin through resonance Raman and DFT analysis.

## Key findings

- Trout IV hemoglobin shows enhanced distal histidine protonation at low pH.
- This protonation increases hemin dissociation and oxidative capacity in salmonid hemoglobin.
- Salmonid hemoglobin's oxidative potential is significantly higher than mammalian hemoglobin.

## Abstract

Salmonids are an
incredibly valuable agricultural commodity, with
large market growth expected over the next 10 years. Salmonids have
a high feed conversion ratio and are rich in vital nutrients; however,
their post-mortem tissues are subject to deterioration due in part
to their labile hemoglobin (Hb). In this work, we aimed to understand
the driving force for the pro-oxidative nature of salmonid (trout
IV) Hb. We utilized resonance Raman spectroscopy (rR), electronic
absorption spectroscopy (EA), and density functional theory (DFT)
calculations to probe the distal and proximal heme pocket architectures
of trout IV and bovine Hb. Using fluoride as a H-bond-sensitive ligand,
we found that at low pH, trout IV ferric Hb is more likely to have
a protonated distal His. The enhanced distal His protonation and mobility
play a crucial role in hemin dissociation, explaining the oxidative
capacity of salmonid Hb, which dwarfs that of mammalian Hb.