Novel hyperpolarizable and fluorescent dyes in lipid membranes: studying membrane potentials using nonlinear optical and fluorescence

Abstract

Potentiometric optical probes gain importance. Here, we report on the application of those probes to study transmembrane potentials using nonlinear optical (NLO) and fluorescence techniques. A NLO spectroscopy method is presented which allows for precise recording of membrane potential changes. To this end the signal intensity of second harmonic generation (SHG) mediated by novel acetylenic hemicyanine dye molecules embedded in the membrane of Retzius neuron cells was used. Bichromophoric systems have been designed for efficient energy transfer measurements. In many cells these bichromophores change their behaviour from stationary fast-response dyes to slow-response redistribution dyes. Completely novel potentiometric probes acting in a different and most efficient way were constructed using one aminostyrylpyridinium (ASP) bichromophoric dye and one oxonol dye. The redistribution ability of the ASP dye can be optimised by controlled and tailor-made modification of its substituents. In combination with the anionic oxonol dye DiBAC 4(3) a bichromophoric system results with two chromophores showing opposite redistribution behaviour. Fluorescence ratio changes of 100% for a 100 mV depolarization can be recorded.