We gratefully acknowledge support from the following agencies:
National Science Foundation
Defense Advanced Research Projects Agency
Department of Defense
Burroughs Wellcome Fund
Institute for Collaborative Biotechnologies
Our research has also been supported previously by the National Institutes of Health, National Science Foundation, American Chemical Society, Office of Naval Research, Searle Scholars Program, Alfred P. Sloan Foundation, Research Corporation for Science Advancement, Arnold & Mabel Beckman Foundation, and Camille & Henry Dreyfus Foundation.