Authors
Crowe JH. Carpenter JF. Crowe LM.
Institution
Section of Molecular and Cellular Biology, University of California, Davis
95616, USA. jhcrowe:ucdavis.edu
Title
The role of vitrification in anhydrobiosis. [Review] [86
refs]
Source
Annual Review of Physiology. 60:73-103, 1998.
Abstract
Numerous organisms are capable of surviving more or less
complete dehydration. A common feature in their biochemistry is that they
accumulate large amounts of disaccharides, the most common of which are
sucrose and trehalose. Over the past 20 years, we have provided evidence that
these sugars stabilize membranes and proteins in the dry state, most likely
by hydrogen bonding to polar residues in the dry macromolecular assemblages.
This direct interaction results in maintenance of dry proteins and membranes
in a physical state similar to that seen in the presence of excess water. An
alternative viewpoint has been proposed, based on the fact that both sucrose
and trehalose form glasses in the dry state. It has been suggested that glass
formation (vitrification) is in itself sufficient to
stabilize dry biomaterials. In this review we present evidence that, although
vitrification is indeed required, it is not in itself
sufficient. Instead, both direct interaction and
vitrification are required. Special properties have often
been claimed for trehalose in this regard. In fact, trehalose has been shown
by many workers to be remarkably (and sometimes uniquely) effective in
stabilizing dry or frozen biomolecules, cells, and tissues. Others have not
observed any such special properties. We review evidence here showing that
trehalose has a remarkably high glass-transition temperature (Tg). It is not
anomalous in this regard because it lies at the end of a continuum of sugars
with increasing Tg. However, it is unusual in that addition of small amounts
of water does not depress Tg, as in other sugars. Instead, a dihydrate
crystal of trehalose forms, thereby shielding the remaining glassy trehalose
from effects of the added water. Thus under less than ideal conditions such
as high humidity and temperature, trehalose does indeed have special
properties, which may explain the stability and longevity of anhydrobiotes
that contain it. Further, it makes this sugar useful in stabilization of
biomolecules of use in human welfare. [References: 86]