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Title: Packing stress reduction in polymer-lipid monolayers at the air-water interface: An X-ray grazing-incidence diffraction and reflectivity study

Abstract

Using synchrotron grazing-incidence X-ray diffraction (GIXD) and reflectivity (XR), the authors have determined the in-plane and out-of-plane structure of phospholipid monolayers at the air-water interface as a function of hydrophilic lipid headgroup size. Di-stearoyl-phosphatidyl-ethanolamine (DSPE) lipid monolayers were systematically modified by chemically grafting hydrophilic poly(ethylene glycol) (PEG) chains of MW = 90 g/mol (2 ethylene oxide, EO, units), MW = 350 g/mol (8 EO units), and MW = 750 g/mol (17 EO units) to the lipid headgroups. The monolayers were studied in the solid phase at a surface pressure of 42 mN/m. At these high lipid packing densities, the PEG chains are submerged in the water subphase. The increased packing stresses from these bulky polymer headgroups distort the unit cell and the in-plane packing modes of the monolayers, leading to large out-of-plane alterations and staggering of the lipid molecules. Surprisingly, a change in the molecular packing of the monolayer toward higher packing densities (lower area per molecule) was observed on increasing the PEG MW to 750 g/mol (17 EO units). This rearrangement of the monolayer structure may be due to a conformational change in the PEG chains.

Authors:
; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Univ. of California, Santa Barbara, (US)
Sponsoring Org.:
USDOE; National Science Foundation (NSF)
OSTI Identifier:
20000135
DOE Contract Number:  
W-7405-ENG-36; AC02-98CH10886
Resource Type:
Journal Article
Journal Name:
Journal of the American Chemical Society
Additional Journal Information:
Journal Volume: 121; Journal Issue: 33; Other Information: PBD: 25 Aug 1999; Journal ID: ISSN 0002-7863
Country of Publication:
United States
Language:
English
Subject:
55 BIOLOGY AND MEDICINE, BASIC STUDIES; LAYERS; LIPIDS; POLYMERS; STRESS RELAXATION; AIR; WATER; INTERFACES; X-RAY DIFFRACTION; REFLECTIVITY; MOLECULAR STRUCTURE

Citation Formats

Kuhl, T.L., Majewski, J., Howes, P.B., Kjaer, K., Nahmen, A. von, Lee, K.Y.C., Ocko, B., Israelachvili, J.N., and Smith, G.S. Packing stress reduction in polymer-lipid monolayers at the air-water interface: An X-ray grazing-incidence diffraction and reflectivity study. United States: N. p., 1999. Web. doi:10.1021/ja991048j.
Kuhl, T.L., Majewski, J., Howes, P.B., Kjaer, K., Nahmen, A. von, Lee, K.Y.C., Ocko, B., Israelachvili, J.N., & Smith, G.S. Packing stress reduction in polymer-lipid monolayers at the air-water interface: An X-ray grazing-incidence diffraction and reflectivity study. United States. doi:10.1021/ja991048j.
Kuhl, T.L., Majewski, J., Howes, P.B., Kjaer, K., Nahmen, A. von, Lee, K.Y.C., Ocko, B., Israelachvili, J.N., and Smith, G.S. Wed . "Packing stress reduction in polymer-lipid monolayers at the air-water interface: An X-ray grazing-incidence diffraction and reflectivity study". United States. doi:10.1021/ja991048j.
@article{osti_20000135,
title = {Packing stress reduction in polymer-lipid monolayers at the air-water interface: An X-ray grazing-incidence diffraction and reflectivity study},
author = {Kuhl, T.L. and Majewski, J. and Howes, P.B. and Kjaer, K. and Nahmen, A. von and Lee, K.Y.C. and Ocko, B. and Israelachvili, J.N. and Smith, G.S.},
abstractNote = {Using synchrotron grazing-incidence X-ray diffraction (GIXD) and reflectivity (XR), the authors have determined the in-plane and out-of-plane structure of phospholipid monolayers at the air-water interface as a function of hydrophilic lipid headgroup size. Di-stearoyl-phosphatidyl-ethanolamine (DSPE) lipid monolayers were systematically modified by chemically grafting hydrophilic poly(ethylene glycol) (PEG) chains of MW = 90 g/mol (2 ethylene oxide, EO, units), MW = 350 g/mol (8 EO units), and MW = 750 g/mol (17 EO units) to the lipid headgroups. The monolayers were studied in the solid phase at a surface pressure of 42 mN/m. At these high lipid packing densities, the PEG chains are submerged in the water subphase. The increased packing stresses from these bulky polymer headgroups distort the unit cell and the in-plane packing modes of the monolayers, leading to large out-of-plane alterations and staggering of the lipid molecules. Surprisingly, a change in the molecular packing of the monolayer toward higher packing densities (lower area per molecule) was observed on increasing the PEG MW to 750 g/mol (17 EO units). This rearrangement of the monolayer structure may be due to a conformational change in the PEG chains.},
doi = {10.1021/ja991048j},
journal = {Journal of the American Chemical Society},
issn = {0002-7863},
number = 33,
volume = 121,
place = {United States},
year = {1999},
month = {8}
}