1. Biochemical Science Division; National Institute of Standards and Technology; 100 Bureau Dr., MS 8312 Gaithersburg MD 20878
2. Dep. of Molecular and Cell Biology; Univ. of Connecticut; 91 N. Eagleville, U-3125 Storrs CT 06269
3. Surface and Microanalysis Division; National Institute of Standards and Technology; 100 Bureau Dr., MS 8371 Gaithersburg MD 20878