Partition of indocyanine green in model polarized biological membranes: computational simulations approach

SOSA, MICAELA; DEL PÓPOLO, MARIO; GALASSI, VANESA

San Luis

Encuentro; XLVIII Reunión anual de la sociedad Argentina de biofísica.; 2019

Universidad Nacional de San Luis

Partition of indocyanine green in model polarized biological membranes:computational simulations approachSosa Mi, Del Pópolo Ma, Galassi Vaa - Facultad de Ciencias Exactas y Naturales (FCEN), UNCUYO, Mendoza, ArgentinaOne of the key features of life development is the selective exchange of ions through cell membrane, which gives rise to the so called ?membrane potential?. This electrostatic potential is determinant of the interfacial activity regulation, providing the driving force for many fundamental processes such as cell breathing, cardiac activity and nervous synapse. The classical determination methods are inconveniently invasive or of very low resolution. Much effort is currently invested on developing non-electrofisiologicdetermination methods, based on the use of voltage sensitive dyes (VSD) withelectrochromic response.In this context, we have addressed a detailed computational study of a novel probe: indocyanine green (ICG). This CSV is characterized by its optical activity which lies in the near infrared spectrum. It has also been approved by the FDA for human clinical use.These peculiarities turns ICG into a highly promising molecule for imaging diagnosis, being possible to irradiate and detect through a thin layer of skin, implying lower invasiveness than any other known CSV.In this work we show a computational study of the interactions of ICG with polarized lipid bilayers of palmitoyloleoylphosphatidylcholine. We parameterized an atomistic force field for the probe, and built model systems with the dye integrated in the interphase. We approached the free energy of partition through umbrella sampling calculations, combined with weighted histogram analysis method (WHAM). The computation of the potential of mean force profile was carried out, for the sake of comparison, in two different systems: one without membrane polarization, and another with ions imbalance such that the transmembrane potential was 1.9V. We analyzed the effect of the polarization on binding energetics and configuration.