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

NH Rhys and MA Al-Badri and RM Ziolek and RJ Gillams and LE Collins and MJ Lawrence and CD Lorenz and SE McLain, JOURNAL OF CHEMICAL PHYSICS, 148, 135102 (2018).

DOI: 10.1063/1.5024850

The atomic-scale structure of the phosphocholine (PC) headgroup in 30 mol.% propylene glycol (PG) in an aqueous solution has been investigated using a combination of neutron diffraction with isotopic substitution experiments and computer simulation techniques-molecular dynamics and empirical potential structure refinement. Here, the hydration of the PC headgroup remains largely intact compared with the hydration of this group in a bilayer and in a bulk water solution, with the PG molecules showing limited interactions with the headgroup. When direct PG interactions with PC do occur, they are most likely to coordinate to the N(CH3)(3)(+) motifs. Further, PG does not affect the bulk water structure and the addition of PC does not perturb the PG-solvent interactions. This suggests that the reason why PG is able to penetrate into membranes easily is that it does not form strong-hydrogen bonding or electrostatic interactions with the headgroup allowing it to easily move across the membrane barrier. Published by AIP Publishing.

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