Conformational Ensembles from Experimental Data and Computer Simulations

Conformational Ensembles from Experimental Data

and Computer Simulations

Poster Abstracts

42-POS

Board 2

Atomistic Structures of Detergent Micelles Refined Against X-ray Solution Scattering Data

Milos T. Ivanovic

, Jochen S. Hub.

Georg August University, Goettingen, Germany.

Detergent micelles have been studied using a range of methods, including small-angle neutron

scattering (SANS), small-angle X-ray scattering (SAXS), high frequency rheology, NMR self-

diffusion, fluorescence techniques, as well as density, viscosity and dielectric constant

measurements. Such methods provide data of limited information content and low spatial

resolution. Therefore, simplified continuum models of certain ad-hoc symmetries, such as

symmetrized ellipsoids, were fitted to such data, but the data alone was insufficient to infer

atomic models. Molecular dynamics (MD) simulations were instead used to derive atomic

models of detergent micelles. However, since simulations were not yet directly compared with

structural experimental data, it remained unclear whether force field imperfections bias the

structure and shape of the simulated micelle. Hence, methods that integrate experimental data

into MD simulations are needed to derive reliable atomic models of micelles. Here, we derived

atomistic models of two maltoside micelles, n-Dodecyl-β-D-Maltoside (DDM) and n-Decyl-β-D-

Maltoside (DM) at temperatures between 10 and 70◦C, by combining experimental SAXS data

with all-atom MD simulations. We incorporated the SAXS data as a energetic restraint into MD

simulations, allowing us to refine micellar structures against structural data. Because all SAXS

calculations were based on explicit-solvent models, the calculations involve accurate physical

models for the hydration layer and the excluded solvent, thereby avoiding any solvent-related

fitting parameters and, in turn, enabling highly predictive structural modelling. The study

highlights that the combination of experiments and simulations provides more detailed and

reliable structures of soft matter systems, as compared to each of the methods alone.