Study of Quaternary System of Salicylic Acid, Water, Ozone, and PAL by Molecular Dynamics

In the plant defense-response against ozone, phenylalanine ammonia-lyase (PAL) is biosynthesized along with salicylic acid (SA) in the plant leaf. Therefore, the important components involved in the defense activity can be considered water as well as SA, ozone, and PAL, which are used to make abstract systems based on whereabouts of ozone. By building the model systems, we systematically investigate adsorption and absorption behaviors of ozone, which could be the main concern in the front-line of the defense-response, in the solution composed of water and SA via molecular dynamics method. An ultimate model system, which is the ternary solution of SA, ozone, and water with an immersed PAL, is constructed based on thermodynamic conditions obtained from hierarchical studies on different phases. From studying the quaternary liquid system, a fact, which has been intuitively accepted in public, is definitized for the first time with the simulation perspective that PAL attracts SA through hydrogen bondings while SA plays a key role as the absorbent medium for accommodating ozone.