X-Message-Number: 13023
Date: Thu, 30 Dec 1999 08:23:22 -0800 (PST)
From: Doug Skrecky <>
Subject: effects of solute methoxylation

Cryobiology 1999 Nov;39(3):215-27

Effects of Solute Methoxylation on Glass-forming Ability and Stability 
of Vitrification Solutions.

Wowk B, Darwin M, Harris SB, Russell SR, Rasch CM
21st Century Medicine, Inc., 10844 Edison Court, Rancho Cucamonga, 
California, 91730, USA.

  The effects of replacing hydroxyl groups with methoxyl (OCH(3)) 
groups in the polyols ethylene glycol (EG), propylene glycol (PG),
glycerol, and threitol were studied by differential scanning calorimetry
(DSC) during cooling of aqueous solutions to -150 degrees C and subsequent
rewarming. For 35% (w/w) PG, 40% EG, and 45% glycerol, a single
substitution of a terminal hydroxyl group with a methoxyl group reduced
the critical cooling rate necessary to avoid ice on cooling (vitrify) from
approximately 500 to 50 degrees C/min. This reduction was approximately
equivalent to increasing the parent polyol concentration by 5% (w/w). The
critical warming rate calculated to avoid formation of ice on rewarming
(devitrification) was also reduced by methoxyl substitution, typically by
a factor of 10(4) for dilute solutions. Double methoxylation (replacement of
both terminal hydroxyls) tended to result in hydrate formation, making these
compounds less interesting. An exception was threitol, for which substituting
both terminal hydroxyls by methoxyls reduced the critical warming rate of a 50%

solution by a factor of 10(7) without any hydrate formation. These glass-forming
and stability properties of methoxylated compounds, combined with their low
viscosity, enhanced permeability, and high glass transition temperatures, make
them interesting candidate cryoprotective agents for cryopreservation by
vitrification or freezing.

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