Many “nano properties” are based on the fact that the surface/volume ratio increases dramatically with the decrease of particle size. New protein based devices – such as protein fuel cell, protein photovoltaic cell and protein motor – are under rapid development for their promising potentials to efficiently generate and consume energy. The key element in these devices is the immobilized protein pattern. In such protein pattern, the access of reactants to, and the release of products from each specific protein molecule are partially blocked by the surface and the neighboring proteins. Therefore, the activity of the protein might be reduced upon its immobilization on the surface. The more accessible proteins might retain their activity better. The border proteins are more accessible than the center proteins. Reducing the protein pattern size will increase the border protein content in the protein pattern, thus increases the unit protein activity. Our study with antigen-antibody binding provided supporting evidence for this speculation. When a well-packed lysozyme nano-pattern is exposed to the anti-lysozyme antibody, the antibodies preferentially bind to the lysozyme molecules on the borders. Since the lysozyme molecules on the border are more spatially accessible than those in the center, we believe the difference in antibody binding preference is controlled by this accessibility.

Understanding this effect will help us to drastically improve the efficiency of the protein-based devices.

AFM image shows the antibodies (red) preferentially bind to the lysozyme pattern (green) over the OTS film (blue) surface. The lysozyme line is about 150 nm wide.