Abstract
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DNA is well-known as bearer of the genetic code.
Since its structure
elucidation nearly seven decades ago by Watson, Crick, Wilkins, and
Franklin, much has been learned about its detailed structure, function,
and genetic coding. The development of automated solid-phase synthesis,
and with it the availability of synthetic DNA with any desired sequence
in lengths of up to hundreds of bases in the best case, has contributed
much to the advancement of the field of DNA research. In addition,
classic organic synthesis has allowed introduction of a very large
number of modifications in the DNA in a sequence specific manner,
which have initially been targeted at altering the biological function
of DNA. However, in recent years DNA has become a very attractive
scaffold in supramolecular chemistry, where DNA is taken out of its
biological role and serves as both stick and glue molecule to assemble
novel functional structures with nanometer precision. The attachment
of functionalities to DNA has led to the creation of supramolecular
systems with applications in light harvesting, energy and electron
transfer, sensing, and catalysis. Functional DNA is clearly having
a significant impact in the field of bioinspired nanosystems.
Of particular interest is the use of porphyrins in supramolecular
chemistry and bionanotechnology, because they are excellent functional
groups due to their electronic properties that can be tailored through
chemical modifications of the aromatic core or through insertion of
almost any metal of the periodic table into the central cavity. The
porphyrins can be attached either to the nucleobase, to the phosphate
group, or to the ribose moiety. Additionally, noncovalent templating
through Watson–Crick base pairing forms an alternative and
attractive approach. With this, the combination of two seemingly simple
molecules gives rise to a highly complex system with unprecedented
possibilities for modulation of function, and with it applications,
particularly when combined with other functional groups. Here, an
overview is given on the developments of using porphyrin modified
DNA for the construction of functional assemblies. Strategies for
the synthesis and characterization are presented alongside selected
applications where the porphyrin modification has proven to be particularly
useful and superior to other modifiers but also has revealed its limitations.
We also discuss implications on properties and behavior of the porphyrin–DNA,
where similar issues could arise when using other hydrophobic and
bulky substituents on DNA. This includes particularly problems regarding
synthesis of the building blocks, DNA synthesis, yields, solubility,
and intermolecular interactions.
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