LAUSR

The concentration of macromolecules in cells can reach up to 50–400 mg/mL. They occupy 40%(volume fraction) of the whole cellar space, known as molecular crowding. The diluted solution condition in vitro is different from the crowded physiological condition in vivo . Therefore, the simulation of the physiological condition is necessary for obtaining the reliable results. It has been reported that G-quadruplex can bind to hemin to enhance its catalytic function for generating oxygen radicals, which can oxidize the lipids, proteins and DNA, thus leading to the damage of cells and tissues. In this paper, we chose PEG400 as molecular crowding reagent to simulate the molecular crowding environment in vivo . The catalytic characteristics of G-quadruplex-hemin complex in H 2 O 2 -ABTS system have been investigated[ABTS=2,2′-azinobis-(3-ethylbenzthiazoline-6-sulphonate)]. The results showed that the binding affinity of G-quadruplex and hemin was decreased with the increasing of PEG400 concentration. They even lose their binding affinity in the presence of 40% PEG400. As a result, the peroxidase activity of G-quadruplex-hemin also reduced. Therefore, in physiological condition, hemin might not bind to G-quadruplex and it might not be the main reason to cause the damages of cells and tissues.