Porphyrins conjugated to DNA as CD reporters of the salt-induced B to Z-DNA transition

The effects of of a bulk porphyrins on the salt-induced B- to Z-DNA transitions were analyzed. The sensitive detection of conformational changes associated with the B- to Z-DNA transition in the broad spectral region was achieved by circular dichroism (CD) spectroscopy. It was found that if the twist and distance were favorable, the porphyrin chromophore can serve as a real reporter of the B- to Z transition via Soret band CD signal. It was also found that a tetraarylporphyrin attached in the 5′- position of the studied oligodeoxynucleotide (ODN) enhanced the high salt concentration cooperative B-Z transition and stabilized the Z-form with a smaller helical twist with respect to the unmodified sequence.