Metal complexes as structure-selective binding agents for nucleic acids

Concomitant with our increasing knowledge of the structure and biological role of nucleic acids is the interest in the development of small molecules that can regulate DNA and RNA function. While considerable effort has been devoted to synthesising compounds that can target specific DNA and RNA sequences, there is growing interest in developing agents that can recognise nucleic acid structural features. In particular, it has now been established that a variety of non-duplex structures – such as bulges, hairpins and junctions – play an important role in the regulation of DNA transcription and RNA translation. Metal complexes have great diversity in size and structure, as well as useful photophysical and electrochemical properties in many cases, and consequently they have become an important class of structure-selective binding agents for nucleic acids. The present review addresses the range and biological significance of non-duplex structures that are found in DNA and RNA, as well as the specific types of metal complexes that recognise these structural features. Particular attention is given to dinuclear ruthenium complexes that have been shown to bind duplex DNA and RNA weakly, but associate strongly with non-duplex structures.