loop_ _pdbx_audit_author.name _pdbx_audit_author.address _pdbx_audit_author.ordinal 'Fitzgerald, Paula M.D.' ; Department of Biophysical Chemistry Merck Research Laboratories P. O. Box 2000, Ry80M203 Rahway, New Jersey 07065 USA ; 1 'McKeever, Brian M.' ; Department of Biophysical Chemistry Merck Research Laboratories P. O. Box 2000, Ry80M203 Rahway, New Jersey 07065 USA ; 2 'Van Middlesworth, J.F.' ; Department of Biophysical Chemistry Merck Research Laboratories P. O. Box 2000, Ry80M203 Rahway, New Jersey 07065 USA ; 3 'Springer, James P.' ; Department of Biophysical Chemistry Merck Research Laboratories P. O. Box 2000, Ry80M203 Rahway, New Jersey 07065 USA ; 4