Atomistic models of chemical and biological charge transfer

Understanding oxidative stress, sensor applications and the perspective of using a replicable, conducting biopolymer in nanoelectronics have made DNA conductivity a subject of considerable scientific interest. Establishing and efficiently solving the extended Su-Schrieffer-Heeger Hamiltonian, we have a nonphenomenological, atomistic model at hand that is able to describe DNA charge transfer in accord with experiments both in solution and in nanoscopic setups. With the help of this model, we have studied other systems of relevance in biology and nanoelectronics, such as the nucleosome, three-way junctions, DNA networks and DNA-nanotube intercalation compounds.

This model has been extended to describe charge transfer in proteins. For complex I, a protein aggregate central to the respiratory chain, we have been able to show that not only iron-sulphur clusters are key players of the charge transfer process, but that aromatic amino acid side chains feature as stepping stones in hopping conduction; a conclusion also supported by a multiple sequence alignment of the genome of a large variety of organisms. Currently, we are also looking for such bridges in bacterial photoreaction centers. For a DNA repair enzyme triggered by blue light, the CPD photolyase, we have applied thermodynamic integration to charge transfer and have found a simple rationalization for the energetic preference of some charge transfer pathes over others. Figure: charge transfer chain in complex I of T. thermophilus.