This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Our goal is to use self-assembled two-dimensional (2D) DNA lattices to direct periodic assembly of membrane proteins to obtain high quality crystals. In recent years, cryo-EM crystallography has been used to obtain high-resolution structures from 2D crystals of protein molecules provided that quality 2D crystals can be achieved. Currently the methods for 2D crystallization of macromolecules heavily rely on unpredictable interaction between the surfaces of the protein molecules (e.g. hydrophobic and electrostatic interaction). Methods have been developed to use biotin-tagged or nickel chelated lipids to organize streptavidin or histidine-tagged proteins into 2D crystal. However, controlled spacing or periodicity of the protein molecule is still hard to control in these designs. Such control is needed to organize proteins of various dimensions. By combining the expertise from Allen on 3D membrane crystallography and Yan on DNA self-assembly, we propose to develop a robust and modular technology to use self-assembled 2D DNA lattices to organize transmembrane proteins into periodical 2D crystals. This modular technology will enable us to rationally organize the protein of interest into an ordered 2D crystal which will facilitate the elucidation of their molecular structures using cryo-electron microscopy studies. Structural studies of membrane proteins will help us understand cellular membrane functions and will have significant impact in designing drug delivery across the membrane.