Modeling of Radiation-Induced Chemistry
Pulsed radiolysis of molecules in solution, conducted at ELYSE, whether reductive or oxidative, produces short-lived radical species characterized by their absorption spectra. These transient species are sometimes exotic, and molecular simulation allows for testing and discriminating among various candidate species. We developed an effective method years ago for simulating these species, using classical Monte Carlo simulation of the solute, DFT calculation of its electronic system, and reducing the solvent to a polarizable continuum model. With this method, we were able to calculate and compare the spectra of two reverse peptides, valine–methionine and methionine–valine, which are very different [Archirel2019]. We predicted the spectrum of the radical AgII(CN)2•, which was subsequently observed experimentally [Léonard2020]. We studied the oxidation of an antioxidant, crocin, which is a polyene with two sugars, the gentiobioses. We were able to calculate the spectrum of the oxidized species by the OH• radical and deduce the subtle oxidation mechanism, which we referred to as the ‘sugar-governed’ mechanism [Al Gharib2023].

Comparison of Theory and Experiment for the Oxidation of Silver Cyanide Ag(CN)2⁻ by the OH° Radical
Collaborations
Mehran Mostafavi (TEMiC, ICP) and Chantal Houée Levin (CPSysBio, ICP)