Infrared and vibrational circular dichroism spectra of methyl β‐D‐glucopyranose in water: The application of the quantum cluster growth and clusters‐in‐a‐liquid solvation models

Abstract

The infrared (IR) and vibrational circular dichroism (VCD) spectra of methyl β‐D‐glucopyranose in water were measured. Both implicit and explicit solvation models were utilized to explain the observed spectra. The vast body of existing experimental and theoretical data suggested that about eight explicit water molecules are needed to account for the solvent effects, supported by the current Quantum Cluster Growth (QCG) analysis. Extensive manual and systematic conformational searches of the molecular target and its water clusters were carried out by using a recently developed conformational searching tool, conformer‐rotamer ensemble sampling tool (CREST), and the microsolvation model in the associated QCG code. The Boltzmann averaged IR and VCD spectra of the methyl β‐D‐glucopyranose‐(water)n (n = 8) conformers in the PCM of water provide better agreement with the experimental ones than those with n = 0, 1, and 2. The explicit solvation with eight water molecules was shown to greatly modify the conformational preference of methyl β‐D‐glucopyranose from its monomeric form. Further analyses show that the result is consistent with the existence of long‐lived methyl β‐D‐glucopyranose monohydrates with the additional explicit water effects being accounted for with the quantum mechanical treatment of the other seven close‐by water molecules in the PCM of water.

Vibrational circular dichroism spectra of proline in water at different pH values

“…A common approach to model the IR and VCD spectra of solutes in water (and other hydrogen bonding solvents) is to build hydrogen bonded clusters containing several solvent molecules. 7,13–16,38 We attempted such a micro-solvation approach for ZwPro and built clusters with five water molecules (Fig. 3).…”

Conformational Distributions of Phenyl β-D-Glucopyranoside and Gastrodin in Solution by Vibrational Optical Activity and Theoretical Calculations

“…Such deviation is likely caused by some explicit solvent effects which have not been taken into account in the current modeling. However, in a recent IR and VCD study of methyl-β-D-glucose in water by some of the authors [ 46 ], we attempted solvation with multiple water molecules with the help of the newly developed Quantum Cluster Growth (QCG) program [ 47 ]. The choice to stay with the implicit solvation model was made because of the complexity of the two molecular targets and the challenge to sample all important solvation positions of solvent molecules like water.…”

Modelling solute–solvent interactions in VCD spectra analysis with the micro-solvation approach

“…New methodologies for conformational searches, 28 such as the easy-to-use metadynamics-based Quantum Cluster Growth method introduced by Grimme and co-workers, 72,73 may potentially simplify the workflows. They will narrow down the problem of conformational sampling of solute-solvent interactions to the quality of the underlying computational methods and thus again to computer time.…”