DNA CONDENSATION CAUSED BY LIGAND BINDING MAY SERVE AS A SENSOR

摘要

DNA is a promising construction material for the engineering of artificial nanostractured devices. One of possible DNA implications in bionanodevices is detecting of metal ions. This possibility is based on the fact that metal ions may preferentially bind to definite DNA conformation and thus metal ion binding may give rise to transition between A-, B-, or Z-DNA. Another approach based on utilizing the specific DNA sequence required to detect specific metals was reported recently. In this method single-stranded DNA forms "pocket" that accepts only lead ions. Here we consider a potential DNA-based sensor detecting metal ions which is based on the phenomenon of DNA condensation. DNA condensation in vivo is governed by complicated system containing polyamines, histones, regulatory proteins and metal ions. It is essential for DNA cyclisation, renaturation and recombination accelerating these processes in thousands times. Reversible condensation of DNA triggers gene silencing. In vitro DNA condensation may be induced by addition of multivalent cations, for example metal ions. This process is described as transition of the first kind from extended coil to compact globule. In some cases very small variation in cationic ligand concentration causes abrupt DNA condensation. We have shown previously that long-range interaction between ligands bound to a DNA molecule may give rise to adsorption with the character of phase transition. This model may describe the process of DNA condensation. From the point of view of molecular electronics, such a system shows properties of a trigger and thus may be applied for sensor manufacturing. Calculation shows that adsorption with the character of phase transition arises when the long-range potential is high enough. Here we derive the criterion for energy of ligand-ligand interaction necessary to give rise to a phase transition. Then we analyze data from literature on interactions between bivalent metal ions bound to DNA. The values for long-range potential corresponding to metal ions bound to DNA are recalculated on the basis of data from several papers. It is shown that absolute values of their interaction is enough to give rise to phase transition. Possible application of adsorption with the character of phase transition in DNA-based sensor for bivalent metal ions is discussed.