We present a theory for cooperative chiral order in the transition between right-handed B-DNA and left-handed Z-DNA. This theory, based on the random-field Ising model, predicts the characteristic length scale of Z-DNA segments. This length scale depends on whether the DNA is a homopolymer or a random sequence: it is ~4000 nucleotides in a homopolymer but only ~25 nucleotides in a random sequence. These theoretical results are consistent with experiments on DNA homopolymers and random sequences.
Selinger, J. V., & Schnur, J. M. (1997). Cooperative chiral order in the B-Z transition in random sequences of DNA. Biophysical Journal, 73(2), 966–971. https://doi.org/10.1016/S0006-3495(97)78129-3