Activatable Tiles: Demonstration of Linear and Directed Self Assembly

(Rothemund and Winfree, 2000) showed in theory that any computable function can be imple-mented via a set of tiles with carefully designed sticky ends. Unfortunately experimental demon-stration of complex tilings have been limited by significant assembly errors. A major source of errors are co-operative binding errors which occur when a tile partially satisfies the programming at a lattice point, i.e. its sticky ends match with only some of its neighbors but that is sufficient for it to be wrongly incorporated into the assembly.(Majumder et al., 2007) described a novel protec-tion/deprotection strategy, termed an activatable tiling scheme, to strictly enforce the direction of tiling assembly growth to ensure the robustness of the assembly process. In their system tiles are initially inactive, meaning that each tiles output sticky ends are protected and cannot bind with other tiles. Only after other tiles bind to the tiles input sticky ends, the tile transitions to an active state and its output sticky ends are exposed, allowing further growth. Here we report on the first experimental demonstration of the activatable tiling scheme. Our system consists of two tiles that form a linear co-polymer. These tiles are initially protected such that they do not react with each other. Then via the use of a strand displacing polymerase (BST), we activate the tiles which leads to the formation of the linear co-polymer. The 2 tiles, Tile A an