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arXiv · 1710.03684

Sampling the protonation states: pH-dependent UV absorption spectrum of a polypeptide dyad

Elisa Pieri·Vincent Ledentu·Nicolas Ferré
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Abstract

When a chromophore interacts with titrable molecular sites, the modeling of its photophysical properties requires to take into account all their possible protonation states. We have developed a multi-scale protocol, based on constant-pH molecular dynamics simulations coupled to QM/MM excitation energy calculations, aimed at sampling both the phase space and protonation state space of a short polypeptide featuring a tyrosine--tryptophan dyad interacting with two aspartic acid residues. We show that such a protocol is accurate enough to reproduce the tyrosine UV absorption spectrum at both acidic and basic pH. Moreover, it is confirmed that UV-induced radical tryptophan is reduced thanks to an electron transfer from tyrosine, ultimately explaining the complex pH-dependent behavior of the peptide spectrum.

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Elisa Pieri, Vincent Ledentu, Nicolas Ferré. 2017-10-10. Sampling the protonation states: pH-dependent UV absorption spectrum of a polypeptide dyad. https://doi.org/10.1039/c8cp03557a

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