Berlin 2018 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 38: Modeling and Simulation of Soft Matter II (joint session CPP/DY)

DY 38.8: Talk

Wednesday, March 14, 2018, 11:45–12:00, C 230

Molecular Origin of Urea-driven Hydrophobic Collapse of Polyacrylamides — •Divya Nayar, Angelina Folberth, and Nico van der Vegt — Technische Universität Darmstadt, Alarich-Weiss-Straße 10, 64287 Darmstadt, Germany

Osmolytes modulate protein folding and affect the water solubility of macromolecules [1]. The osmolyte-induced hydrophobic polymer collapse due to osmolyte depletion from the solvation shell is well-known, however, evidences have indicated direct preferential osmolyte binding that may lead to polymer collapse [2]. To understand the underlying molecular mechanisms better, we examine the role of urea in strengthening and attenuating the hydrophobic collapse of thermo-responsive polyacrylamides i.e. Poly-N-isopropylacrylamide (PNIPAM, secondary amide) and Poly-N,N,-diethylacrylamide (PDEA, tertiary amide) respectively [3]. Using extensive molecular dynamics simulations and large-scale polymer conformational sampling, we show that urea collapses PNIPAM by "preferentially binding" to it. We propose an osmolyte stabilizing mechanism driving PNIPAM collapse, based on the balance in opposing loss of entropic degrees of freedom of urea and water [4]. The study provides new physical insights into the interplay between polymer side-chain chemistry, solvent entropic degrees of freedom and polymer-solvent interactions to understand the osmolyte effects on hydrophobic collapse. [1] D. R. Canchi et al. Annu. Rev. Phys. Chem., 2013, 64, 273. [2] N. F. A. van der Vegt et al. J. Phys. Chem. B 2017, 121, 9986. [3] J. Wang et al. Macromolecules, 2016, 49, 234. [4] D. Nayar et al. Phys. Chem. Chem. Phys. 2017, 19, 18156.