Molecular clustering characteristics in ternary trehalose and choline dihydrogen phosphate solutions
1 online resource (55 pages) : PDF
University of North Carolina at Charlotte
Spatial and temporal characteristics of molecular structure in ternary solutions of trehalose and choline dihydrogen phosphate (CDHP) are studied using molecular dynamics simulations at 300 K for a range of solute concentrations with a 2:1 stoichiometric ratio of trehalose to CDHP. For a given molecular configuration, water molecules are classified as interior (only neighboring other waters) or interfacial (at least one solute neighbor). As a tagged water molecule diffuses, it dynamically exchanges between interior and interfacial type as its local environment changes, with differences in hydrogen bond strength between different molecular species creating a persistent preference for interfacial water. At high solute concentrations, interfacial and interior water have similar diffusivity, which allows for water to collectively act as a plasticizer. The percolation threshold for water was found to be between 81.5% and 83%, which is slightly under the liquid-glass transition, estimated to be near 84.5% solute concentration based on the onset of a volume hysteresis effect. This region of concentrations was further studied using Markov matrices compiled from the transition probabilities for a water molecule to move from a cluster of size n in one frame to a cluster of size m in the next frame. The probability distribution functions of the magnitudes of the eigenvalues of these matrices showed a clear signature of the dynamics of the system slowing down starting at 81.5% solute concentration. In general, the structure of the systems were observed to be highly inhomogeneous, with interlaced percolating networks of water and solute coexisting at intermediate concentrations. The density of interior water was found to decrease with increasing solute concentration, creating low-density regions within the matrix.
CHOLINE DIHYDROGEN PHOSPHATEFREE VOLUME THEORYGLASS TRANSITIONMARKOV CHAINSPERCOLATIONTREHALOSE
Elliott, GloriaTrammell, Susan
Thesis (M.S.)--University of North Carolina at Charlotte, 2018.
This Item is protected by copyright and/or related rights. You are free to use this Item in any way that is permitted by the copyright and related rights legislation that applies to your use. For other uses you need to obtain permission from the rights-holder(s). For additional information, see http://rightsstatements.org/page/InC/1.0/.
Copyright is held by the author unless otherwise indicated.