DNA Ring Crystals
C. Arun Richard1*, B. Madhanagopal1*, Pradeep Kumar Mandal2, P. Satheesh
Kumar2, N. Gautham2#
1National
Centre for Nanoscience and Nanotechnology, University of Madras,
Chennai 600025, India. 2Centre of Advanced Study in Crystallography and
Biophysics, University of Madras, Chennai 600025, India.
Crystalline self-assembly of nanoscale materials into micron-sized structures has
drawn considerable interest. Of particular interest are ring-shaped structures, as this
morphology confers unique magnetic and optical properties. Several ring-shaped
crystals of inorganic materials have been reported in the literature. DNA is a
significant biological nanoparticle. Using its base-pairing capabilities, it could be
designed to self-assemble into almost any two or three-dimensional nanostructure.
Interactions between the helical molecules of DNA could also be used to construct
various structures. We report the formation of ring-shaped crystals by certain
oligodeoxyribonucleotide sequences. We studied the growth of such unusual
crystals of the hexameric duplexes d(CACGCG).d(CGCGTG) in the presence of
cobalt hexammine ions and identified the different stages of the formation of such
structures. Our study showed that crystals of size 40 μm first grew as hexagonal
plates. These metamorphosed into ring crystals by radial dissolution from the center
of the crystal. This process occurred over a period of 135 hours and the growth
stages included the following: hexagonal plate, to roughness on surface, to surface
dissolution leading to depressions on both sides, to formation of a hole at the center,
to ring formation. This transformation may be a result of a transition in the crystal
packing. Structural transitions between hexagonal and orthorhombic structures have
earlier been predicted for helical polymers such as DNA. A study of the properties of
these ring-shaped DNA crystals may, in future lead to applications involving
assembly of nanoscale materials, nanomembrane formation, etc.
DNA Ring Crystal
* These authors contributed equally to this work.
whom correspondence should be addressed. E-mail: n_gautham@hotmail.com
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