Variable nanocomposites: Small, rigid DNA rings
with a gap for the incorporation of functional molecules.
What appear under an atomic force microscope to be tiny rings with
little bits missing are actually nanoscopic rings made of
double-stranded DNA with a little gap in the form of a short
single-stranded fragment. As Michael Famulok and his team from the
University of Bonn, Germany, explain in the journal Angewandte Chemie , this gap is a place to attach other molecules that have the potential to
transform the rings into versatile nanocomposites for various
applications.
The programmable aggregation of molecular building blocks into
structures with higher order plays a key role in the construction of
nanomaterials. Nucleic acids are interesting building block candidates,
being easy to synthesize and exhibiting unique molecular recognition
characteristics. The difficulty lies in the fact that the construction
of defined two- or three-dimensional geometries requires rigid
building blocks. However, DNA molecules are normally flexible
structures.
�From the structural point of view, miniature rings represent the
simplest form for a rigid object made of DNA,� says Famulok. His team
thus took on the challenge of producing DNA molecules with a smooth
circular structure, free of ring deformations, twists, or knots. This
was not an easy endeavor. DNA is usually found in the form of a double
strand with a helical twist and can, if it is too short, close on
itself to form a ring. On the other hand, if the ring gets too large,
it is no longer rigid. Famulok and his team have now succeeded, by
careful selection of the sequence and number of nucleotides as well as
a clever synthetic route, in producing the desired rigid rings.
Even better, the researchers were able to build a �gap� into their
rings - a short sequence that does not occur in
normal base pairing, instead exiting as a single-stranded segment.
This should make it possible to �fit� the ring with tailored
functionality for special applications. All that needs to be done is
to produce a short single strand of DNA complementary to the
single-stranded part of the ring and to attach it to a molecule with
the desired properties. This single strand then fits perfectly into
the gap. This allows the ring to be equipped as desired, depending on
the requirements of the application in question. For example, it can
be given �anchors� that precisely bind the rings to other components.
�Our new, uncomplicated method for the production of rigid DNA
nanorings with variable, tailor-made functionality opens new pathways
for the construction of DNA objects with higher levels of organization,�
Famulok is convinced.
Further Information and Source:
-
Goran Rasched, Damian Ackermann, Dr., Thorsten L. Schmidt, Peter
Broekmann, Dr., Alexander Heckel, Dr., Michael Famulok, Prof. Dr.: DNA Minicircles with Gaps for Versatile Functionalization.
In: Angewandte Chemie;
doi: 10.1002/ange.200704004
