The DNA (Deoxyribonucleic acid), first isolated by the Swiss physician Friedrich Miescher in 1869, and subsequently made famous by Watson and Crick by their discovery of the structure of DNA in 1953 (for which they were awarded the Nobel Prize for Physiology/Medicine in 1962), is now acquiring a new avatar and is opening up new vistas in the field of nanoscience and technology.
At the National Centre for Biological Sciences (NCBS), here in Bangalore, is where Dr.Yamuna Krishnan, Assistant Professor works, and is studying the structure and dynamics of nucleic-acid based assemblies in the hopes of one day building artificial nucleic-acid based molecular machines.
She says, “we seek to control the structure of matter in three-dimensions on the finest possible scale and we work on branched DNA molecules to do this.”
Dr.Yamuna goes on to explain the reasons why DNA related research is at the forefront again. She says, “for the most part DNA was considered Nature’s instruction manual for life leading to the popular description ‘blueprint of life’. However, DNA is now taking on a new aspect where it is finding use as a construction element for architecture on the nanoscale.
Apart from its well-known role as the cellular storehouse of information, DNA is now being used to construct “rigid scaffolds in one, two and three dimension on the nanoscale”. The emerging field is termed as ‘Structural DNA Nanotechnology’.
Dr Yamuna also adds that, a very challenging aspect of nanotechnology is the development of an efficient and potentially universal way to organize nanosized building blocks into designed architectures.
Among the various possible materials, DNA is a superior molecule for the following reasons: (1) DNA can be made to form well-defined nanostructures by rational design; (2) DNA can be chemically modified and operated on by enzymes; (3) DNA itself is an environmentally benign biochemical reagent.
Dr.Yamuna and her group of students at NCBS, work on Translational Biology, which involves taking a biological device or component out of its cellular context and harnessing its function in a completely new setting such as in materials or diagnostics.
Nature has designed nucleic acid assemblies that self-assemble into unusual and complex motifs that carry out specialized functions on superfast time-scales with tremendous efficiency. Her current research involves understanding the structure and dynamics of these unusual nucleic acid motifs and translating this knowledge to create DNA-based nanodevices.
Exciting finding
Her group recently created the first four-stranded DNA-based nanowires (published in a recent issue of the prestigious International Journal Angewandte Chemie 2007).
In the race to make machines smaller, faster and more powerful, electronic components are becoming smaller and smaller in order to achieve high density configurations that enable powerful computing. It is envisaged that these components will soon reach the size of a rather large molecule and this has driven the field of molecular electronics.
In order to connect these molecular-size components, we will need wires that are also the size of a molecule, or molecular wires.
Molecular wires are simply molecules that are linear polymers and have conducting properties. Double stranded B-DNA, discovered by Watson and Crick, has been envisaged as a nanowire. However, it’s the conduction property that has been the subject of much controversy.
Wires that don’t melt
This could be because B-DNA is intrinsically vulnerable and constantly melting when provided with gentle physiological stimuli to enable its information to be read.
So Dr.Yamuna’s group has created the first linear polymer of B-DNA that is four-stranded, extremely resistant to melting and functions as a highly uniform nanowire template. This is based on a four-stranded structure of DNA called the I-tetraplex or the i-motif.
Her lab is now looking to measure the conductivity of these extremely rigid, lengthy and robust DNA scaffold.
Dr Yamuna’s lab is also currently creating custom sensors to visualize RNA targets in-vivo and in real-time for cellular and diagnostic applications.
Dr Yamuna who returned to India after working abroad says that “I knew India was the one place in the world where I could feel both professionally and personally fulfilled. Not to forget the sense of belonging!”