although slight differences in the purine-sugar and pyrimidine-sugar intranucleotide interactions are observed , the large differences in the sugar pucker of the adenine vs. thymine nucleotide suggested by some models [ klug , a. , jack , a. , viswamitra , m. a. , kennard , o. , shakked , z. , & steitz , t. a . ( 1979 ) j. mol . biol . 131 , 669-680 ] are not evident in the solution structure of poly ( da-dt ) .
C0034140
purine
C0001407
adenine