X-Message-Number: 13242
Date: Thu, 10 Feb 2000 19:32:28 -0800 (PST)
From: Doug Skrecky <>
Subject: membrane fusion with polyethylene glycol

(Membrane fusion might be the mechanism whereby high 
molecular weight polyethylene glycol repairs crushed nerves.)

  MacDonald RI.
  Membrane fusion due to dehydration by
  polyethylene glycol, dextran, or sucrose.
  Biochemistry.  24(15):4058-66, 1985 Jul 16.
  To determine whether polyethylene glycol
  (PEG) causes growth of liposomes by affecting them directly or indirectly,
  vesicles composed of phosphatidylcholine were exposed to increasing
  concentrations of Mr 15 000-20 000 PEG or Mr 40 000 dextran either by direct
  mixing or across a dialysis membrane. After incubation at room temperature
  and dilution below at least 5% (w/w) polymer, the vesicles were monitored for
  fluorescence energy transfer and for absorbance at 400 nm. PEG induced the
  same levels of dequenching or lipid mixing and increased turbidity,
  regardless of whether the vesicles had been mixed directly with or dialyzed
  against PEG. These changes occurred within 5-15 min of polymer application.
  It is concluded that the increased lipid mixing and/or increased turbidity,
  indicating vesicle growth, resulted from an indirect effect of PEG on the
  vesicles--most likely dehydration. Dextran, in contrast to
  PEG, induced less dequenching and/or less turbidity increase when vesicles
  were directly mixed with, as opposed to dialyzed against, dextran. Although
  dextran not in contact with vesicles and with osmotic activity comparable to
  PEG was able to cause a degree of membrane fusion similar to that of PEG,
  therefore, the dehydrating effect of dextran could be mitigated if it were
  allowed to interact with vesicles. In further support of membrane
  dehydration as a precursor to membrane fusion, lipid mixing
  among sonicated and sonicated, frozen-thawed vesicles dialyzed against
  sucrose increased as a function of sucrose concentration. Vesicle morphology
  generally determined the maximal degree of membrane fusion inducible by the

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