DNA hybridization mechanism in an interfacial environment: What hides beneath first order k (s−1) kinetic constant?

The scientific question addressed in this work is: what hides beneath first order kinetic constant k (s−1) measured for hybridization of a DNA target on a biosensor surface. Kinetics hybridization curves were established with a 27MHz quartz microbalance (9MHz, third harmonic) biosensor, constituted of a 20-base probe monolayer deposited on a gold covered quartz surface. Kinetics analysis, by a known two-step adsorption–hybridization mechanism, is well appropriate to fit properly hybridization kinetics curves, for complementary 20-base to 40-base targets over two concentration decades. It was found that the K1 (M−1) adsorption constant, relevant to the first step, concerns an equilibrium between non hybridized targets and hybridized pre-complex and increases with DNA target length. It was established that k2 (s−1), relevant to irreversible formation of a stable duplex, varies in an opposite way to K1 with DNA target length.