# Virus Capsid Modifications Accompanying Inactivation during Iron Electrocoagulation Revealed by Proteomics, Infrared Spectroscopy, and Molecular Modeling

## TL;DR

Iron electrocoagulation rapidly inactivates viruses by modifying their protein coats through reactive oxygen species interactions.

## Contribution

This study reveals nonproteolytic capsid damage and specific amino acid interactions during virus inactivation via iron electrocoagulation.

## Key findings

- Electrocoagulation achieves virus LRVs ≳6.7 in 11.5 minutes using low-carbon steel and graphite electrodes.
- Reactive oxygen species interact with arginine 49 and tryptophan 32 residues in viral coat proteins.
- Protein secondary structure changes correlate strongly with virus inactivation and protein alterations.

## Abstract

Society’s
drinking water needs are increasingly met by reusing
municipal wastewater, necessitating high virus Log10 Reduction
Values (LRVs). Concurrently, electrified processes are gaining prominence
for water/wastewater treatment. Herein, we report that electrocoagulation
with a low-carbon steel anode and graphite cathode at pH 6.5 and 5.5
and iron dose of 20 mg/L reduced the MS2 coliphage below detection
limits (LRVs ≳6.7) in just 11.5 min. Matrix Assisted
Laser Desorption Ionization-Time-of-Flight Mass Spectrometry (MALDI-TOF-MS)
of electrocoagulated viruses revealed single, double, and triple oxygen
adducts and a negative mass shift peak in its coat protein without
cleavage/scission. Density functional theory calculations coupled
with computational spatial interaction mapping evidenced the formation
of the quintet ferryl ion-cysteine 46 cluster. Hence, inactivation
appears to have been accompanied by nonproteolytic capsid damages
induced by reactive oxygen species (ROS). Evidence also pointed to
possible ROS interactions with arginine 49 and tryptophan 32 residues.
The
α‐helixβ‐sheet
ratio of viral
protein secondary structures
quantified by deconvoluting the amide I region of infrared spectra
strongly and negatively correlated with inactivation, carbonyl group
content, and MALDI-TOF-MS-derived protein alterations. Hence, iron
electrocoagulation achieved high virus LRVs by removal (through enmeshment)
and inactivation (via specific ROS interactions with coat protein
residues).