Conformational Ensembles from Experimental Data and Computer Simulations

Conformational Ensembles from Experimental Data and Computer Simulations Board 23 Lukasz Mioduszewski , Marek Cieplak. Polish Academy of Sciences, Warsaw, Poland. 63-POS

Poster Abstracts

Gluten proteins do not seem to have one clearly defined tertiary structure, and can form covalently and non-covalently joined megadalton-sized complexes. They form a mechanochemical network, responsible for the viscoelastic properties of wheat dough. The properties can be characterized by the dynamic Young modulus G* = G' + G′′, which describes the response to small-amplitude oscillating deformation: G′ for the in-phase (elastic) part and G′′ for the out-of-phase (viscous) part. The main goal of this work is to present a model that can recreate this elastic response of gluten in computer simulations. The existing theories of gluten elasticity point out the crucial role of hydrogen and disulfide bonds between different gluten protein chains. The theories provide some predictions that can be incorporated into a simple coarse-grained model of gluten. In the model amino acids are represented as pseudoatoms, connected harmonically to form protein chains. Non-bonded interactions include Lenard-Jones potential, which mimics hydrogen bonding, and a dynamic potential for disulfide bonds. Initial chain conformations are generated randomly, and then evolve according to the simplified potential, forming large complexes. The results were obtained by periodically deforming the box containing gluten proteins and recording the response force. The amplitude of the response force seems to increase, indicating strain hardening, an effect observed in experiments. It is accompanied by changes in the protein network structure: the number of inter-chain hydrogen and disulfide bonds increases. The connection between those conformational changes and system response to deformation is discussed, as well as the ability of simple models to predict properties of large complexes of disordered proteins.

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