Molecular clustering characteristics in ternary trehalose and choline dihydrogen phosphate solutions

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Nikulsin, N. (2018). Molecular clustering characteristics in ternary trehalose and choline dihydrogen phosphate solutions. Unc Charlotte Electronic Theses And Dissertations.
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Abstract

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.

Details
Author

Nikulsin, Nikita

Title

Molecular clustering characteristics in ternary trehalose and choline dihydrogen phosphate solutions

Physical Description

1 online resource (55 pages) : PDF

Date

2018

Degree Granting Institution

University of North Carolina at Charlotte

Abstract

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.

Genre

masters theses

Subjects--Topics

Physics

Degree

M.S.

Keywords

Choline Dihydrogen Phosphate
Free Volume Theory
Glass Transition
Markov Chains
Percolation
Trehalose

Subject Area

Applied Physics

Advisor(s)

Jacobs, Donald

Committee Members

Elliott, Gloria
Trammell, Susan

Degree Note

Thesis (M.S.)--University of North Carolina at Charlotte, 2018.

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Rights Holder Information

Copyright is held by the author unless otherwise indicated.

Identifier

Nikulsin_uncc_0694N_11818

Permalink

http://hdl.handle.net/20.500.13093/etd:931