SEARCH Articles Figures Tables Base Pairing in the Purine and Pyrimidine Crystal Structures Base pairing bases Base pairs Base-Pair Configurations with Purine and Pyrimidine Homo-Association Bases Base pair Purine bases Purine-pyrimidine base pairs Purine-pyrimidine base pairs Purine-pyrimidine base pairs mismatch Purines, pyrimidines Pyrimidine bases