Title

Induced Changes in Solvent Structure by Phospholipid Monolayer Formation at a Liquid–Liquid Interface

Author Info

R. A. Walker, University of Oregon
D. E. Gragson, University of OregonFollow
G. L. Richmond, University of Oregon

Recommended Citation

Postprint version. Published in Colloids and Surfaces A: Physicochemical and Engineering Aspects, Volume 154, Issue 1-2, August 1, 1999, pages 175-185.

NOTE: At the time of publication, the author Derek E. Gragson was not yet affiliated with Cal Poly.

The definitive version is available at https://doi.org/10.1016/S0927-7757(98)00895-4.

Abstract

Vibrational sum frequency spectroscopy has been used in conjunction with dynamic surface tension measurements to study formation of a 1,2-dilauroyl-sn-phosphatidylcholine (DLPC) monolayer at a water–carbon tetrachloride interface. Surface tension measurements show that an aqueous solution of liquid crystalline phosphocholine vesicles (4.5 μM DLPC) requires several hours to form a tightly packed, fully equilibrated monolayer of DLPC monomers. Vibrational spectra of the interfacial region at different stages in the monolayer formation process indicate that the solvent structure undergoes dramatic re-organization as the monolayer forms. Initial adsorption of DLPC monomers severely disrupts the interfacial hydrogen bonding. Intensity in the OH stretching region oscillates in a systematic fashion during the first 2 h of monolayer formation before finally settling to a level characteristic of the fully equilibrated monolayer. Frequency shifts of the OH stretching vibration show that water molecules with their C₂ axes aligned parallel to the interface experience a markedly different environment than those water molecules aligned perpendicular to the interface. This difference is attributed to the effect of the adsorbed, zwitterionic DLPC head-groups which, if aligned parallel to the interface, can stabilize in-plane water molecules.

Disciplines

Biochemistry | Chemistry

Copyright

1999 Elsevier.