Two decades ago Lewis and Wasielewski began a collaborative investigation of photoinduced charge separation in DNA.  Initial studies employed femtosecond transient absorption spectroscopy to determine composite charge separation and charge recombination times for DNA hairpins possessing aromatic hydrocarbon linkers serving as hole donors and the natural base guanine as the hole acceptor.  Since no intermediates were observed in the charge separation process, it was assumed to occur via a single step superexchange or tunneling process.  Subsequent advances in synthetic DNA hairpin design and in transient spectroscopy have made it possible to directly observe all of the key intermediates in the charge separation processes: the initially formed contact radical ion pair, the final charge separated state, and both the localized and delocalized purine cation radicals that are the essential hole carriers in the charge separation process.  Advances in theoretical analysis of charge separation and transport in DNA have enhanced our understanding of these processes.

Moving charge through duplex DNA: Injection, separation, transport and trapping

255th National Meeting (2018)

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