X-Message-Number: 14332
Date: Thu, 17 Aug 2000 08:59:17 -0700 (PDT)
From: Doug Skrecky <>
Subject: DNA stability in cryoprotectants

  Structural stability of
  DNA in nonaqueous solvents.
  Biotechnology & Bioengineering.  68(3):339-44, 2000 May 5.
  One of the defining physicochemical features of DNA in
  aqueous solution is its ability to maintain a double-helical structure and
  for this structure to undergo a cooperative, heat-induced denaturation
  (melting). Herein we show that a 21-mer synthetic DNA can
  form and maintain such a duplex structure not only in water but even in 99%
  glycerol; moreover, this double-helical structure reversibly and
  cooperatively melts in that solvent, with a T(m) value of some 30 degrees
  lower than in water. Two much larger, natural DNAs, from
  calf thymus and salmon testes, exhibit similar behavior in glycerol. All
  three DNAs can also sustain a double-helical structure in
  99% ethylene glycol, although its thermostability (as
  reflected by the melting temperature) is some 20 degrees lower than in
  glycerol. In contrast, no duplex structure of any of the
  DNAs was detected in 99% formamide, methanol, or DMSO. This
  solvent trend resembles that previously observed in studies of protein
  structure and folding and underscores the importance of hydrophobic
  interactions in both protein and DNA structure and
  stability. Our findings suggest that water may not be unique
  as a suitable medium not only for protein structure but also for that of
  nucleic acids. Copyright 2000 John Wiley & Sons, Inc.

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