Bibliographical noteFunding Information:
We thank Drs. Yvonne Angell and Michael Hare for helpful comments and critical reading of the manuscript. Our experimental work was supported by National Institutes of Health Grants GM 26242 (C. W.) and GM 51628 (G. B. and C. W.) and an NIH postdoctoral fellowship GM 17341 (E. B.).
We gratefully acknowledge the technical assistance of Cynthia A. Guy. This research is supported by the Center for Interracial Engineering (an NSF ERC), the Earl E. Bakken Chair for Biomedical Engineering, and National Institutes of Health Grants KD444 94, AR01929, and CA63671.