Document 0858
 DOCN  M9590858
 TI    Role of interactions at the lipid-water interface for domain formation.
 DT    9509
 AU    Gawrisch K; Barry JA; Holte LL; Sinnwell T; Bergelson LD; Ferretti JA;
       Laboratory of Membrane Biochemistry and Biophysics, NIAAA, NIH,;
       Rockville, MD 20852, USA.
 SO    Mol Membr Biol. 1995 Jan-Mar;12(1):83-8. Unique Identifier : AIDSLINE
       MED/95284893
 AB    The lipid-water interface is critical for the packing of lipid molecules
       in membranes. We have demonstrated that lateral phase separation in
       membranes can be driven by electrostatic interactions such as those
       involving charged lipid species and oppositely charged peptides, in
       addition to hydration effects at the lipid-water interface. By using
       nuclear magnetic resonance (NMR), circular dichroism and fluorescence
       spectroscopy we have shown that binding of a 21-amino acid peptide
       containing six positively charged arginine residues to mixed
       phosphatidylcholine (PC)/phosphatidylglycerol (PG) membranes results in
       a conformational change in the peptide from a random coil to a helical
       structure and causes the formation of domains of negatively charged PG.
       Binding of the peptide to PG membranes disorders the lipid hydrocarbon
       chains. The strength of lipid-peptide binding at the interface, the
       conformational change in the peptide, and domain formation with the
       negatively charged lipid are coupled energetically. The lipid-peptide
       association constant is lower for membranes containing 20 mol% PG in
       PC/PG mixtures than for 100% PG membranes. We suggest that one of the
       factors that lower the association constant in PC/PG membranes is
       entropic energy of formation of PG domains. Besides electrostatic
       interactions, hydration of lipids is important for domain formation. We
       have shown that dipalmitoylphosphatidylcholine and
       dipalmitoylphosphatidylethanolamine separate under conditions of
       decreased water activity. Furthermore, water activity controls lipid
       packing stress in the hydrocarbon core and the headgroups of membranes
       as demonstrated by induction of an inverse-hexagonal-to-lamellar phase
       transition in dioleoylphosphatidylethanolamine.(ABSTRACT TRUNCATED AT
       250 WORDS)
 DE    Amino Acid Sequence  Biophysics  Chemistry, Physical  Gene Products,
       env/*CHEMISTRY/*METABOLISM  Lipid Bilayers/CHEMISTRY/METABOLISM
       Membrane Lipids/*CHEMISTRY/*METABOLISM  Molecular Sequence Data  Nuclear
       Magnetic Resonance  Peptide Fragments/CHEMISTRY/METABOLISM
       Phosphatidylcholines/CHEMISTRY/METABOLISM
       Phosphatidylglycerols/CHEMISTRY/METABOLISM  Phosphorus Isotopes  Protein
       Precursors/*CHEMISTRY/*METABOLISM  Protons  Spectrometry, Fluorescence
       Structure-Activity Relationship  Surface Properties  Water/CHEMISTRY
       JOURNAL ARTICLE

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