Receptor-based design of dihydrofolate reductase inhibitors: comparison of crystallographically determined enzyme binding with enzyme affinity in a series of carboxy-substituted trimethoprim analogues. - Kuyper, L; Roth, B; Baccanari, D; Ferone, R; Beddell, C; Champness, J; Stammers, D; Dann, J; Norrington, F; Baker, D; Goodford, P (1982)