X-Message-Number: 9889
Date: Thu, 11 Jun 1998 21:37:21 -0700 (PDT)
From: Doug Skrecky <>
Subject: stabilizing dry membranes

Authors
  Crowe JH.  Oliver AE.  Hoekstra FA.  Crowe LM.
Institution
  Section of Molecular and Cellular Biology, University of California, Davis
  95616, USA.
Title
  Stabilization of dry membranes by mixtures of hydroxyethyl starch and
  glucose: the role of vitrification.
Source
  Cryobiology.  35(1):20-30, 1997 Aug.
Abstract
  R. P. Goodrich and co-workers (1989, U.S. Patent 4,874,690; 1992, Proc. Natl.
  Acad. Sci. USA 89,967-971) have reported that red blood cells can be
  preserved in the dry state by addition of mixtures of hydroxyethyl starch
  (HES) and glucose. More recently, Spieles and co-workers (1996, Cryo-Lett.
  17, 43-52) found that HES alone is insufficient to preserve the dry cells and
  concluded on this basis that the studies of Goodrich et al. were incorrect.
  In the present paper we revisit that suggestion, using liposomes as a model
  to study effects of HES and glucose on membrane stability. In previous
  studies we and others have established that liposomes can be stabilized in
  the dry state if they are dried in the presence of disaccharides.
  Monosaccharides have not been effective. Measurements of effects of glucose
  on phase transitions in the dry lipids and vibrational frequency of the
  phosphate headgroup suggest that glucose shows an interaction with dry egg
  phosphatidylcholine similar to that seen with disaccharides. Nevertheless,
  glucose does not inhibit fusion in liposomes during drying,
  and it does not prevent leakage. Hydroxyethyl starch, which has a very high
  glass transition (Tg), inhibits fusion in the dry liposomes, but it does not
  depress the liquid crystalline to gel phase transition temperature (Tm) in
  the dry phospholipids, does not cause a shift in the phosphate vibration
  indicative of hydrogen bonding of the sugar to the phosphate, and does not
  stop leakage of trapped carboxyfluorescein. However, if glucose is added to
  the HES-containing samples, the liposomes are stabilized, so long as the
  samples are maintained below the Tg of the mixture. If they are heated above
  that Tg they fuse and leak their contents. We conclude that both glass
  formation and depression of Tm in the dry lipids are required. The role of
  glass formation in stabilization during drying of liposomes
  appears to be inhibition of fusion.

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