  We show that a long DNA molecule can form a novel condensed phase of matter,
the pseudoscalar liquid crystal, that consists of aperiodically ordered DNA
fragments in right-handed B and left-handed Z forms. We discuss the possibility
of transformation of B-DNA into Z-DNA and vice versa via first-order phase
transitions as well as transformations from the phase with zero total chirality
into pure B- or Z-DNA samples through second-order phase transitions. The
presented minimalistic phenomenological model describes the pseudoscalar liquid
crystal phase of DNA and the phase transition phenomena. We point out to a
possibility that a pseudoscalar liquid nano-crystal can be assembled via
DNA-programming.
