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Regensburg 2002 – scientific programme

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SYBM: Physik biologischer Materie

SYBM 401: Physics of biological matter: Poster

SYBM 401.18: Poster

Tuesday, March 12, 2002, 18:00–19:30, H37

Electrostatic and Entropic Contributions to Conformational and Protonation Substates: Modelling of Proton Transfer in GFP — •Robert Raupp–Kossmann1, Sighart Fischer1, and Christina Scharnagl21Technische Universität München Lehrstuhl für Physik Weihenstephan Vöttingerstrasse 40 D-85350 Freising — 2Technische Universität München Physik–Department T38 James–Franck–Strasse 12 D-85747 Garching

The nature of the protonation reactions and the identification of internal acceptors determining the photophysics of Green Fluorescent Protein (GFP) are still subjects of debate. Our theoretical investigations analyse the thermodynamic stability of each of the four protonation states of the bifunctional fluorophore, a p-hydroxybenzylidene-imidazolidinone, in aqueous solvent and wild–type protein.

Microscopic solution pKas are calculated using a hybrid quantum classical approach and a continuum solvation model. They emphasize the role of the internal rotational degrees of freedom for adjusting the acid–base equilibrium constants.

pKa shifts in the protein are calculated using the multiconformational continuum electrostatic method extended to include multiple protonation equilibria for bifunctional groups. Additionally, these calculations reveal the energetics of relevant proton configurations and allow to explore driving forces and dipolar reorganization energies for proton transfer pathways.

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