High salt and solvent induced Z-conformation in native calf thymus DNA

The Z-DNA forming potentiality of native calf thymus DNA using spectrophotometric measurements and diethyl pyrocarbonate reactivity have been investigated. The Z value was evaluated from absorbance ratio for B- and Z-DNA and compared with the values obtained for native DNA. The results suggest that native DNA undergoes B- to Z-/Z-analogous transition to an extent of 20 per cent under constraint conditions. Possible Z-DNA formation was also characterized by hyper-reactivity of native DNA towards diethyl pyrocarbonate in aqueous solvent. The thermal melting profile of native and modified DNA and nuclease S1 digestibility data, in addition, reflects B- to Z-/Z-analogous transition in native DNA.