1. Howard P. Isermann Department of Chemical and Biological Engineering, Rensselaer Nanotechnology Center, and Center for Biotechnology and Interdisciplinary Studies, Rensselaer Polytechnic Institute, Troy, New York 12180
2. Present address: Chemical Engineering Department, College of Engineering and Mineral Resources, West Virginia University, Morgantown, West Virginia 26506.
3. Center for Immunology and Microbial Disease, Albany Medical College, Albany, New York 12208