Molecular dynamics simulations of aqueous glycine solutions

Abstract

Simulations of glycine aqueous solutions have been carried out to study the effect of increasing solute concentration on the aggregation of glycine zwitterions. AMBER force field coupled with three atomic charge sets was employed for the simulations of the aqueous solutions. The number of glycine monomers in solutions rapidly decreases with increase in concentration. The properties of the glycine clusters in the solutions were studied. It was shown that the clusters are strongly hydrated entities with a liquid-like character. The residence lifetimes of water and glycine from the first solvation shell of glycine molecules were calculated. The lifetime values show that the clusters are highly dynamic solutes that change configuration within hundreds of picoseconds. We observed long-living pairs of glycine molecules, which move together in the solutions for ca. 1 ns. The effect of the electric-field-induced orientation of the highly polar glycine molecules in the clusters was studied. A preferential parallel arrangement of the molecules was observed as the distinctive feature of the γ-polymorph, which was crystallized from the solutions in a static electric field.

Real-time monitoring of crystallization from solution by using an interdigitated array electrode sensor

“…3C: this is the concentration at which the solution will crystallize immediately, without any water evaporation. The corresponding critical supersaturation ratio (S*) is 1.08 as the saturation concentration (C sat ) for glycine in aqueous solution at 25 1C is 3.33 M. 29 This value is in good agreement with the one determined by a previous study based on microdroplet crystallization experiments (1.12 at 21 1C). 28 Fig.…”

Optical Spectroscopy of Crystal Nucleation One Nucleus at a Time

“…This is the first time that Raman spectrum of pre-nucleation aggregates was identified, and this provides us a crucial link to the theoretical investigation of its structure. Recent studies based on molecular dynamics simulation suggested the presence of aggregates at high concentration of glycine aqueous solution, 34,38,39 which agree with our observation. In this work, we were determined to gain an insight into the conformations of the pre-nucleation aggregates.…”

“…it is the simplest amino acid, its crystallization process has been shown rather complex and is under active debates. [30][31][32][33][34][35][36] Fig. 1c-f shows a series of Raman spectra obtained in-situ during a single crystal nucleation of glycine which highlights the dynamic nature of crystal nucleation (see the movie SI1 for the whole experiment).…”

4-Oxoproline as a Site-Specific Infrared Probe: Application To Assess Proline Isomerization and Dimer Formation

“…While it is impossible to determine the structure of the aggregates based on the C=O stretching frequency of P ox alone, this information is nevertheless sufficient to allow identification of the underlying mode of interaction. For example, should proline (glycine) molecules aggregate through dimerization via H-bond formation, as that depicted in several studies, 34–37 we expect to observe a red-shift in the stretching frequency of the C=O oscillator of P ox in 2.0 M proline (glycine) solution in comparison to that in D 2 O. This is because in such dimers the –NH 2 + group of P ox would interact with the –COO − group of another amino acid (e.g., proline), effectively decreasing the positive charge density on the N atom of P ox .…”

“…Therefore, these results are in agreement with previous studies indicating that association of proline (glycine) molecules occurs through dimerization. 34–37…”