these measurements were performed on three synthetic polynucleotides having different overall conformations , poly- ( da-dt ) .poly ( da-dt ) ( alternating b-dna ) , poly ( dg-dc ) .poly ( dg-dc ) at low salt ( b-dna ) , and br-poly ( dg-dc ) .br-poly ( dg-dc ) ( left-handed z-dna ) , and on four types of natural dna differing in base composition , clostridium perfringens ( 26 % gc ) , calf thymus ( 40 % gc ) , escherichia coli ( 50 % gc ) , and micrococcus lysodeikticus ( 72 % gc ) .
C0012854
dna
C0919262
b-dna