Spotlights on Recent JACS Publications

■ DNA GETS THE GOLDEN TOUCH Combining gold nanoparticles (AuNPs) with DNA has a history now spanning two decades, with potential applications in biodiagnostics, medicines, and biosensors. In a recent study, Haojun Liang and Tingjie Song show a new way of using AuNPs and DNA together, taking advantage of a technique called toehold-mediated DNA strand displacement (DOI: 10.1021/ja304746k). This technique involves displacing a single-stranded DNA on a double-stranded complex with another single-stranded stretch with the help of short sequences of bases known as a toehold. Here, the researchers develop a method to control assembly of AuNPs using a similar toehold technique. They start with two types of DNA-modified AuNPs, each functionalized with one of two oligonucleotides. In a series of reactions, short, single DNA strands are successively base-paired and displaced from these AuNPs. Finally, the short, single-stranded DNA is displaced by the opposing DNA−AuNP complex. The end result is a double-strand of DNA carrying two AuNPs. Through this technique, the researchers effectively aggregate AuNPs linked by strands of DNA. Additionally, by using the programmable aspect of DNA base pairing, they create AND and OR logic gates with DNA−AuNP complexes that display their results by changing the opacity of the solution. The authors suggest that this simple system might be used as a building block for more complicated multi-component logic gates and molecular machines. Christen Brownlee