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Issue 36, 2018
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Sampling the protonation states: the pH-dependent UV absorption spectrum of a polypeptide dyad

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Abstract

When a chromophore interacts with several titratable 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 help in the interpretation of the experimental tyrosine UV absorption spectrum at both acidic and basic pH. Moreover, it is confirmed that radical tryptophan probably contributes to the peptide spectrum, thanks to a UV-induced electron transfer from tyrosine to tryptophan, ultimately shedding light on the complex pH-dependent behavior of the peptide spectrum.

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

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Publication details

The article was received on 05 Jun 2018, accepted on 24 Aug 2018 and first published on 27 Aug 2018


Article type: Paper
DOI: 10.1039/C8CP03557A
Phys. Chem. Chem. Phys., 2018,20, 23252-23261

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

    E. Pieri, V. Ledentu, M. Huix-Rotllant and N. Ferré, Phys. Chem. Chem. Phys., 2018, 20, 23252
    DOI: 10.1039/C8CP03557A

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