Effect of rubber pollutants 6PPD and 6PDQ on a complex membrane

Abstract

Rubber products have been widely used with the development of industrial production, and hundreds of thousands of tons of the antioxidant and antiozonant molecule 6PPD has been widely used in their manufacture. The reaction of 6PPD with oxygen or ozone produces 6PDQ, and both 6PPD and 6PDQ has been shown to be toxic to living organisms. 6PPD and 6PDQ are hydrophobic and could insert into the biological membrane, and therefore able of affecting membrane structure and lipid components. I employed molecular dynamics to attain the behaviour of 6PPD and 6PDQ in a complex biomembrane. Both 6PPD and 6PDQ spontaneously insert into the membrane and can reside at different membrane depths, always in the monomeric state. 6PDQ, in some instances, attach to the membrane surface and move into the membrane, whereas in other instances insert into the membrane surface and leave it again at later times, without inserting into the membrane. 6PPD and 6PDQ insert between the phospholipids, increasing their fluidity. 6PPD and 6PDQ avoid PSM or CHOL and do not form hydrogen bonds with lipids, indicating that their displacement inside the membrane is not constrained by any form of interaction. Therefore, 6PPD and 6PDQ spontaneously insert into the biological membrane, affecting its physico-chemical properties. The insertion of 6PPD and 6PDQ into the biological membrane might be responsible for some of their harmful effects on living organisms.