Comparison of Implicit and Explicit Solvation Models for Iota-Cyclodextrin Conformation Analysis from Replica Exchange Molecular Dynamics

J Chem Inf Model. 2017 Apr 24;57(4):778-786. doi: 10.1021/acs.jcim.6b00595. Epub 2017 Mar 23.

Abstract

Large ring cyclodextrins have become increasingly important for drug delivery applications. In this work, we have performed replica-exchange molecular dynamics simulations using both implicit and explicit water solvation models to study the conformational diversity of iota-cyclodextrin containing 14 α-1,4 glycosidic linked d-glucopyranose units (CD14). The new quantifiable calculation methods are proposed to analyze the openness, bending, and twisted conformation of CD14 in terms of circularity, biplanar angle, and one-directional conformation (ODC). CD14 in GB implicit water model (Igb5) was found mostly in an opened conformation with average circularity of 0.39 ± 0.16 and a slight bend with average biplanar angle of 145.5 ± 16.0°. In contrast, CD14 in TIP3P explicit water solvation is significantly twisted with average circularity of 0.16 ± 0.10, while 29.1% are ODCs. In addition, classification of CD14 conformations using a Gaussian mixture model (GMM) shows that 85.0% of all CD14 in implicit water at 300 K correspond to the elliptical conformation, in contrast to 82.3% in twisted form in explicit water. GMM clustering also reveals minority conformations of CD14 such as the 8-shape, boat-form, and twisted conformations. This work provides fundamental insights into CD14 conformation, influence of solvation models, and also proposes new quantifiable analysis techniques for molecular conformation studies in the future.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Carbohydrate Conformation
  • Cyclodextrins / chemistry*
  • Molecular Dynamics Simulation*
  • Solvents / chemistry
  • Thermodynamics
  • Water / chemistry

Substances

  • Cyclodextrins
  • Solvents
  • Water