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Research project: Stulz: DNA bio-nanotechnology

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We are using DNA as a supramolecular template, mainly with porphyrins, to create novel bio-inspired materials for electronics, in particular energy or electron transfer. This leads to the formation of programmable chiral stacks of chromophores.

Project Overview

We aim to explore the use of a naturally derived template, namely DNA, to connect different chromophores and place the units in a predetermined spatial orientation via formation of the double stranded helix of DNA (dsDNA). The nucleobases are being substituted with chromophores, in particular porphyrins, and subsequently incorporated into DNA. The thus obtained functionalised DNA is being explored for its abilities to act as nanoscale electronic wire, as mimic of the natural photosynthetic system, and as FRET system for structural analysis of DNA. Different electronically active substituents such as metal complexes, small organic chromophores or nano particles are being studied as well, eventually leading to multifunctional molecules on the nanometre scale. The research, which can be termed DNA nanoarchitectonics, is highly interdisciplinary, and reaches into materials science, nanotechnology, analytical science, and into biological sciences.

So far, we have synthesised DNA with the highest number of the large and hydrophobic substituent porphyrin. The DNA containing 11 porphyrins in a row corresponds to a porphyrin wire of approximately 10 nm in length, which is synthesised simply by programming the DNA synthesiser (JACS 2007, OBC 2008). The array destabilises the DNA duplex significantly, but also induces a stable secondary helical structure in the single strand. The 'second generation' zipper array has proven to be thermodynamically very stable. The availability of differently metallated porphyrins leads to the first example of reversible formation of a potential photonic wire based on a DNA scaffold (HOT paper in Angew. Chem. 2009, OBC 2011/2016). We are now exploring these systems for their energy and electron transfer efficiency.

The structural analysis of biomolecules is normally not trivial, and standard methods such as NMR spectroscopy are not easily applicable. Other spectroscopic techniques of interest include circular dichroism (CD) spectroscopy. Using the Diamond B23 beamline as primary light source, we are evaluating the structure of DNA and proteins using this versatile technique. This has already proven the be very helpful in the determination of the thermodynamic stability of substituted DNA (OBC 2011, OBC 2008) and analysis of secondary structure induction in modified DNA including intermolecular interactions (OBC 2016, New J. Chem. 2014, JACS 2007). The use of the beamline will certainly prove very useful in further structure analysis of DNA and proteins.

Our students have achieved many prizes in this field, including best poster (MChem, PGR Merck Prize), best MChem Project (John Mellor Prize), and most notably the STEM for Britain Best Poster Prize and Roscoe Medal 2010.

Modelled structure of a porphyrin zipper DNA wire with general nucleoside building block, and CD spectra demonstrating the differences in induced CD signals based on different metalation states.