Eur. Phys. J. E (2019) 42: 19
https://doi.org/10.1140/epje/i2019-11776-0

Regular Article

Resolving solution conformations of the model semi-flexible polyelectrolyte homogalacturonan using molecular dynamics simulations and small-angle x-ray scattering

¹ Department of Chemical Engineering, National Tsing Hua University, 30013, Hsinchu, Taiwan
² Institute of Fundamental Sciences, Massey University, 4474, Palmerston North, New Zealand
³ Australian Synchrotron, 3168, Clayton, VIC, Australia
⁴ School of Chemical Sciences, University of Auckland, Private Bag 90219, Auckland, New Zealand
⁵ The MacDiarmid Institute for Advanced Materials and Nanotechnology, 6140, Wellington, New Zealand
⁶ Riddet Institute, Massey University, 4474, Palmerston North, New Zealand

^* e-mail: bmansel@gmail.com

Received: 13 October 2018
Accepted: 4 January 2019
Published online: 21 February 2019

Abstract

The conformation of polyelectrolytes in the solution state has long been of interest in polymer science. Herein we utilize all atom molecular dynamics simulations (MD) and small-angle x-ray scattering experiments (SAXS) to elucidate the molecular structure of the model polyelectrolyte homogalacturonan. Several degrees of polymerization were studied and in addition partial methylesterification of the otherwise charge-carrying carboxyl groups was used in order to generate samples with varying intra-chain charge distributions. It is shown that at length scales above around 1nm the conformation of isolated chains has surprisingly little dependence on the charge distribution or the concentration of attendant monovalent salts, reflective of the intrinsic stiffness of the saccharide rings and the dynamical constraints of the glycosidic linkage. Indeed the conformation of isolated chains over all accessible length scales is well described by the atomic coordinates available from fibre diffraction studies. Furthermore, in more concentrated systems it is shown that, after careful analysis of the SAXS data, the form of the inter-particle effects heralded by the emergence of a so-called polyelectrolyte peak, can be extracted, and that this phenomena can be reproduced by multiple chain MD simulations.