Molecular Insight Into the Hydrogen Bonding and Micro-Segregation of a Cryoprotectant Molecule

Abstract

Glycerol-water liquid mixtures are intriguing hydrogen-bonded systems and essential in many fields of chemistry, ranging from basic molecular research to widespread use in industrial and biomedical applications as cryoprotective solutions. Despite much research on these mixtures, the details of their microscopic structure are still not understood. One common notion is that glycerol acts to diminish the hydrogen bonding ability of water, a recurring hypothesis that remains untested by direct experimental approaches. The present work characterizes the structure of glycerol-water mixtures, across the concentration range, using a combination of neutron diffraction experiments and computational modeling. Contrary to previous expectations, we show that the hydrogen bonding ability of water is not diminished in the presence of glycerol. We show that glycerol-water hydrogen bonds effectively take the place of water-water hydrogen bonds, allowing water to maintain its full hydrogen bonding capacity regardless of the quantity of glycerol in the environment. We provide a quantitative measurement of all hydrogen bonding in the system and reveal a concentration range where a microsegregated, bipercolating liquid mixture exists in coexistence with a considerable interface region. This work highlights the role of hydrogen bonding connectivity rather than water structuring/destructuring effects in these important cryoprotective systems.

On the solvation of the phosphocholine headgroup in an aqueous propylene glycol solution

“…[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23] Neutron diffraction experiments have been used to study an aqueous solution of 30 mol% PG, containing 200 mM of 1,2-dipropionyl-sn-glycero-3-phosphocholine (C 3 -PC). The neutron diffraction experiments were performed on the SAN-DALS diffractometer at the ISIS neutron facility, UK.…”

“…Empirical Potential Structure Refinement (EPSR) modeling 7 can be used to create a model which 'fits' the measured diffraction data and has been used for a variety of systems to gain a better understanding of the structure of molecules in solution. [11][12][13][14][19][20][21][22] EPSR is Monte Carlo-based simulation which begins with a set of established potentials and then refines these potentials iteratively until a good fit between the measured data and the model is achieved. The EPSR simulation box here contained 10 C 3 -PC lipids, 750 PG molecules (375 R-and 375 S-) and 1750 water molecules (Fig.…”

Slow rheological mode in glycerol and glycerol–water mixtures

“…al. used neutron scattering in combination with Reverse Monte Carlo (RMC) simulations to study the hydrogen-bonded structure in glycerol [59] as well as in glycerol-water mixtures [60][61][62][63]. They find that in neat glycerol each molecule forms on average 5.68 ± 1.51 hydrogen bonds, while for neat water the average number of hydrogen bonds per molecule is about 3.56±1.10.…”

Low-Density Water Structure Observed in a Nanosegregated Cryoprotectant Solution at Low Temperatures from 285 to 238 K

“…This method has been applied previously to study pure glycerol and glycerol-water mixtures at room temperature. [67][68][69][70][71] In the present study we examine the structure at low temperature for the first time and compare with the room temperature data. The SPC model was employed as the RP for water molecules.…”

“…56,[65][66] In the last 4 years we have completed experimental, structural studies of pure glycerol and glycerol-water mixtures at 298 K using a combination of neutron diffraction and computational modeling. [67][68][69][70][71] Our studies have shown that at intermediate concentrations (between x g = 0.25 to 0.50) the mixture segregates on the nanometer length scale to form waterrich and glycerol-rich clusters. [70][71] This nano-segregation results in regions which exist as hydrogen bonded clusters which differ in size across the concentration range.…”