Length and Sequence Effect on the B-Z Transition of [d(A-T)] Oligonucleotide Induced by a Cationic Porphyrin

trans-BMPyP induced the B-Z transition for alternated AT oligonucleotides as it was evident by inversed CD spectrum. The transition occurred simultaneously with appearance of the extensive stacking of porphyrin. Complete B-Z transition required at least 14 base-pairs long. Insertion of one or two GC base pairs prevented the B-Z transition.