# Title: Identification of Redox State Based on the Difference in Solvation Dynamics

## TL;DR

A new non-invasive method using near-infrared spectroscopy and water molecule analysis is introduced to monitor redox states of glutathione in real time.

## Contribution

The study introduces a novel non-destructive method to distinguish redox states of glutathione using aquaphotomics NIR spectroscopy and water conformation analysis.

## Key findings

- NIR spectral features at 1362 nm and 1381 nm reflect differences in redox states of glutathione.
- Molecular dynamics simulations confirm distinct hydration patterns around the reaction site for GSH and GSSG.
- The method enables continuous, non-invasive redox state assessment with potential bioreactor applications.

## Abstract

Oxidation‐reduction (Redox) reactions are crucial for many biological processes, yet there is no method available to evaluate redox states in a non‐invasive, continuous manner. Here we introduce a novel approach to distinguish between reduced and oxidized states of glutathione (GSH and GSSG, respectively) using aquaphotomics near‐infrared (NIR) spectroscopy and multivariate analysis. We identified clear differences in NIR spectra reflecting not only glutathione itself, but different redox states of glutathione based on the spectral features of water molecular conformations interacting with the reaction site. Molecular dynamic simulations also revealed the difference in water molecule coordination and hydration numbers around the reaction site. This approach not only sheds light on the significance of water molecules in redox reactions but also enables non‐destructive, continuous assessment of redox states, with potential applications for bioreactor optimization.

Redox reactions play a crucial role in biological systems, yet non‐invasive, continuous evaluation remains challenging. This study utilizes aquaphotomics NIR spectroscopy and multivariate analysis to differentiate reduced and oxidized glutathione (GSH/GSSG) by analyzing water molecular conformations depicted as spectral pattern. Key spectral features at 1362 nm and 1381 nm highlight redox state differences, supported by molecular dynamics simulations. This method provides a novel, non‐destructive tool for real‐time redox monitoring with potential applications in bioreactors.