It is well known that the tertiary structure of nucleic acids results
from
equilibria between the electrostatic interactions due to negatively
charged
phosphates, stacking interactions of nucleic acid bases as well as to
hydrogen bonds between polar atoms and water molecules, and finally on
conformational energy of the sugar phosphate backbone. A nucleic acid
conformation depends on the conditions their chain exposes phosphate
groups
to the solvent (water) and initiates the stacked helical arrangement of
adjacent bases. Therefore a strong relation between solvent and nucleic
acid
structure constitutes the physico-chemical basis for DNA and RNA
polymorphism. In the tertiary structure of nucleic acids almost all
atoms
are available to the solvent except for those involved in the hydrogen
bond
network formation. Also water molecules contribute to the overall
stability
of helical conformations of nucleic acids by screening the charges of
the
phosphates, binding and bridging between polar exocyclic atoms of the
bases
and influencing conformations of residues with methyl groups via
hydrpphobic
interactions. Ion pairs in aquenos solution are strongly destabilised by
hydrostatic pressure. This phenomenon is attributed to the
electrostrictive
effect of the separated charges, each of them arranging water molecules
in
its vicinity more densly than bulk water. Thus the overall volume change
s
favor the dissociation of ionic interactions under pressure.
My laboratory is interested in high pressure effect on conformation and
properties of nucleic acids We have shown that both DNA and RNA change
their
conformation at high pressure. High pressure mediates also synthesis of
ester and peptide bonds. The results of these studies will be discussed
in
the lecture.
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