Vacuum UV circular dichroism is diagnostic for the left-handed Z form of poly [d(A-C).d(G-T)] and other polydeoxynucleotides.

Circular dichroism spectra are extended into the vacuum UV to about 178 nm for four polydeoxynucleotides of various sequences capable of assuming the left-handed Z form. It is found that each of these polymers, including those with brominated bases and those with the four different bases, have a characteristic negative feature at short wavelengths when in the Z form. In contrast, the B form only has a positive band between 180 and 200 nm. Furthermore, a blue shift of the short wavelength crossover is diagnostic of the B- to Z-form transition for all polymers studied so far. These results confirm that poly[d(A-C).d(G-T)] can assume the Z form in solution at low concentration.