Interfaces DPPE/Salmoura, um estudo sobre membranas celulares via dinâmica molecular clássica

Abstract

In this work, a computational study regarding structural properties and ionic conductivity between phospholipid membranes formed by DPPE, a phospholipid present in most cells of living beings, such as the E. coli bacterium, was carried out. For this, we used the Classic Molecular Dynamics (DMC) methodology, implemented through the LAMMPS software and visualized by the VMD software, based on the Born-Oppenheimmer approach in which the particles are governed by Newtonian interactions, subject to classical interaction potentials. In our cell membrane model, phospholipid bilayers are used, with a Gramicidin channel inside. Above and below the phospholipid layers, an ionic solution of KCl (potassium chloride) was introduced, aiming at the exchange of ions from one end to the other in the system, through the Gramicidine channel. Two distinct systems were modeled, one containing a conductive polymer (PEDOT: PSS) and the other not, so that the role of the polymer to be investigated in this system would be to facilitate the passage of K cations through the Gramicidin channel. From the simulations, we noticed a greater structural organization in the system that contained PEDOT: PSS, observed through the analysis of density profiles and radial distribution of pairs. In addition, a greater flow of K cations was observed. Measurements such as surface pressure were also performed and are in accordance with experimental results. Analysis of effects in the application of an external electrical potential, were also used since there is the presence of a conductive polymer. With the presence of the electric potential, the exchange of ions present in the two systems was intensified, where the presence of PEDOT: PSS caused an increase in the flow of ions through the Gramicidin A channel, however, electric fields greater than 0.1V proved not to be effective, due to the fragmentation of the phospholipid membrane. Based on our simulations, it is possible to verify that the presence of the conductive polymer PEDOT: PSS, close to a cell membrane, can alter the flow of ions in this membrane. It is also possible to state that a model of biological sensor, based on PEDOT: PSS, can analyze a bacterial activity, for example, through the analysis of the ion flow. And yet, be used as a way to neutralize and destroy bacterial activity.