POSSIBLE SEPARATION OF INTERTWINED NUCLEIC ACID CHAINS BY TRANSFER-TWIST

To separate the strands of a twisted rope it is not necessary to unravel them from the end. It is mechanically simpler and energetically easier to make a "transfertwist," pulling the strands apart in the middle and letting each strand twist about itself. This suggests a method of separating two twisted intertwined helical molecules without expending excessive energy. It might be an alternative to the method suggested by Delbruck.1 In particular, Figure 1 shows how transfer-twist might apply to intertwined duplicate nucleic acid chains like those in the Watson and Crick model of DNA.2 The A, and A2 halves of the two DNA chains are identical and are the complements to the other halves, A1' and A2'. Thus A1 will intertwine perfectly with either A,' or A2' in a"lock-and-key" relationship but not with A2, and A so on. If we now start with A, linked with A2' and A,' linked with A2 and make a transfer-twist A