When a DNA triple helix melts: an analogue of the Efimov state

Abstract

The base sequences of DNA contain the genetic code, and, to decode it, a double helical DNA has to be unzipped to reveal the bases. Recent studies have shown that a third strand can be used to identify the base sequences, not by opening the double helix but rather by forming a triple helix. It is predicted here that a three-strand DNA exhibits the unusual behaviour of the existence of a three-chain bound state in the absence of any two being bound. Such a state can occur at or above the duplex melting point. This phenomenon is analogous to the Efimov state in three-particle quantum mechanics. A scaling theory is used to justify the Efimov connection. Real space renormalization group (RG) and exact numerical calculations are used to validate the prediction of a biological Efimov effect.