Speaker: Luca Grisanti
Title: Structure-function relation in the color expression of natural dyes: a multi-level computational study of Anthocyanins
Abstract: Anthocyanins are among the most abundant natural pigments in nature, which, depending on chemical environment (such as acidity and other species such as metals and co-pigments), give rise to a variety of colors and shades in the red-purple-blue gamut. We introduce a new multiscale modeling protocol to reveal the intricate relationship existing between the electronic and geometrical factors that determine the optical properties and hence the color function of anthocyanins in a broad pH range (1-9). Our protocol is based on enhanced sampling from classical force-fields based molecular dynamics (MD) in explicit solvent, advanced statistical analysis to identify the relevant molecular conformers, ab-initio MD to accurately sample thermal fluctuations within individual conformers, and time-dependent density-functional theory to compute absorption spectra on selected molecular frames. Our simulations reveal that the broad range of colors expressed by anthocyanins crucially depend on the modulation of the electronic conjugation, as determined by thermal fluctuations and molecular distortions.
Luca Grisanti, from Scuola Internazionale Superiore di Studi Avanzati (SISSA), Trieste, Italy, is visiting Michele Casella.
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