An information ratchet improves selectivity in molecular recognition under non-equilibrium conditions

Abstract

Molecular recognition is essential for controlling chemical processes, passing molecular instructions to elicit responses including structure formation, signalling and replication. Usually, the selectivity of molecular recognition is under thermodynamic control; however, when a higher fidelity is required, nature improves recognition selectivity by an error correction mechanism under an energy-dissipating kinetic-control regime. Here, exploiting DNA hybridization as a model, we present an abiotic example of an information ratchet mechanism that increases selectivity for the ‘correct’ duplex from 2:1 at equilibrium to 6:1 under energy-dissipating conditions. Structural asymmetry in the DNA strands introduces kinetic asymmetry in the reaction network, enabling enrichment under non-equilibrium conditions. We quantify the free-energy cost associated with enhanced selectivity using Shannon entropy formalism, finding that an increase in information of 0.33 bits is associated with at least 3.0 kJ mol⁻¹ of free energy. Moreover, the minimalistic structures of our error reduction system demonstrates that biomachinery is not necessary to increase molecular recognition fidelities above the thermodynamically expected values, thereby pointing a way towards solving Eigen’s paradox.