Protein patterning for nanobiodevice applications

(Berrie, Richter, and Wu)

The Richter and Berrie groups are currently collaborating on a project that involves tethering of F1 ATP Synthase to surfaces which have been engineered on the nanometer length scale to provide specific binding sites for the molecules. This molecule is of particular interest in nanobiodevice applications as a molecular motor, spinning the central gamma subunit upon addition and binding of ATP. In order to investigate the mechanism of torque generation and also to develop platforms for possible incorporation of these motors into nanoscale devices, the molecules must be bound to solid supports in a functionally active conformation and with an appropriate orientation. Self-assembled monolayer films will be patterned using the AFMbased nanoshaving/nanografting method initially developed by Liu (see Figure 3). Protein resistant SAM films will be patterned with nanometer sized domains of SAM molecules (e.g., nitrilotriacetic acid) which will react with specific target sites on the protein (e.g., histidine). In this way, it should be possible to position the protein on the surface with nanoscale precision down to the single molecule level with a specific orientation. Preliminary results indicate that using AFM imaging orientational or conformational differences between individual protein molecules on the surface can be observed (Figure 4). The AFM imaging part of this project is being carried out primarily by undergraduate students working in conjunction with a postdoctoral research associate on the project, which demonstrates the suitability of this project for undergraduates.

One potential difficulty associated with patterning these films using the force-based AFM methods mentioned above is that the patterning process is serial and efficiency is quite slow. The patterns must be created one at a time by scanning the probe tip over the sample. While this works quite well for smallscale arrays of proteins, this is probably not a practical way to generate large scale devices. Electron beam lithography (EBL), in collaboration with Dr. Wu, will be used to fabricate large-scale arrays of these patterned molecules. Considering her experience in training undergraduates in generating nanoscale devices using EBL, this would make an ideal interdisciplinary project for undergraduate students to be involved in that would expose them to a wide range of different research areas, all focused on one particular problem.