4-Hydroxyaminoquinoline 1-oxide can convert the Z-form of poly(dG-m5dC).poly(dG-m5dC) back to B-form-DNA.

Reactions between the chemical carcinogen 4-hydroxyaminoquinoline 1-oxide (4HAQO) and poly(dG-dC).poly(dG-dC), poly(dG-m5dC).poly(dG-m5dC) and poly(dG-br5dC).poly(dG-br5dC) were studied under B-form and Z-form conformation conditions. 4HAQO bound covalently to both B-form and Z-form-DNA. The extent of the B-form to Z-form-DNA transition was diminished by 4HAQO, as inferred by spectroscopic methods. Moreover, conversion of the Z-form-DNA back to a right handed DNA close to the B-form was observed with this carcinogen.