J. Am. Chem. Soc. 134, 15193–15196 (2012)

Protein nanostructures are important in the development of applications such as biosensors and in the study of systems such as enzyme networks. However, the properties of these assemblies are affected by the arrangement of the biomolecules within the structure and the controlled assembly of precise nanostructures is challenging. Diana Pippig and colleagues at the University of Munich have now shown that patterns of proteins can be formed one molecule at a time using a technique called single-molecule cut-and-paste.

The researchers used green fluorescent proteins that were initially bound to DNA anchor molecules in a 'depot' area of a glass substrate via DNA hybridization. A structural motif known as zinc fingers is incorporated into the biomolecules, which allows them to connect to the DNA anchors through complementary DNA connector strands. An atomic force microscope with an antibody fragment covalently attached to its tip is used to pick up the proteins from the depot. The tip binds to a small antigenic peptide tag on the protein and when the tip is retracted the DNA is unzipped. The protein units can then be transferred to a target area on the substrate and deposited at a specific site through hybridization of the connector DNA with a target DNA anchor.

To illustrate the capabilities of the technique, Pippig and colleagues used 900 cut-and-paste cycles to assemble a micrometre-sized pattern of a red-traffic-light man. The DNA connectors are labelled with a dye molecule and their red emission was recorded with a fluorescence microscope. A green man pattern was then assembled and the green emission of the proteins recorded.