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Interactions of Dimethylsulfoxide with a Dipalmitoylphosphatidylcholine Monolayer Studied by Vibrational Sum Frequency Generation
 

Summary: Interactions of Dimethylsulfoxide with a Dipalmitoylphosphatidylcholine Monolayer Studied
by Vibrational Sum Frequency Generation
Xiangke Chen and Heather C. Allen*
The Ohio State UniVersity, Department of Chemistry, 100 West 18th AVenue, Columbus, Ohio 43210
ReceiVed: May 29, 2009; ReVised Manuscript ReceiVed: August 19, 2009
The interactions between phospholipid monolayers and dimethylsulfoxide (DMSO) molecules were investigated
by vibrational sum frequency generation (VSFG) spectroscopy in a Langmuir trough system. Both the head
and the tail groups of dipalmitoylphosphatidylcholine (DPPC) as well as DMSO were probed to provide a
comprehensive understanding of the interactions between DPPC and DMSO molecules. A condensing effect
is observed for the DPPC monolayer on a concentrated DMSO subphase (>20 mol %). This effect results in
a well-ordered conformation for the DPPC alkyl chains at very large mean molecular areas. Interactions
between DMSO and DPPC headgroups were also studied. DMSO-induced dehydration of the DPPC phosphate
group is revealed at DMSO concentration above 10 mol %. The average orientation of DMSO with DPPC
versus dipalmitoylphosphate sodium salt (DPPA) monolayers was compared. The comparison revealed that
DMSO molecules are perturbed and reorient because of the interfacial electric field created by the charged
lipid headgroups. The orientation of the DPPC alkyl chains remains nearly unchanged in the liquid condensed
phase with the addition of DMSO. This suggests that DMSO molecules are expelled from the condensed
monolayer. In addition, implications for the DMSO-induced permeability enhancement of biological membranes
from this work are discussed.
Introduction

  

Source: Allen, Heather C.- Department of Chemistry, Ohio State University

 

Collections: Chemistry