Mueller Matrix Fluorescence Spectroscopy for Probing Self-Assembled Peptide-Based Hybrid Supramolecular Structure and Orientation

Abstract

Probing the assembly mechanism, orientation, shape and the structure function relationship of hybrid supramolecular materials is an outstanding challenge. In this regard, we have presented a novel method based on fluorescence spectroscopic Mueller matrix measurements and inverse analysis which can probe and quantify exclusive information on the molecular organization and orientation via a set of newly defined fluorescence anisotropy parameters, namely, fluorescence diattenuation and polarizance. A new dipeptide motif Boc-Xaa-Met-OMe (Xaa = Val/ Leu) containing Leucine, Valine and Methionine forms kink like structure and self-associates to form twisted sheet like structure by multiple intermolecular N-H....O hydrogen bonds and finally grown to form supramolecular nanotubes having diameter ca. 10 Å. Thus the methionine sulfurs of peptide molecules are arranged helically along the tubes, work as hot spot and help to stabilize the electron deficient paint TB-NDI around the tube. The Mueller matrix polarimetry and inverse analysis offers the insight on the molecular organization and orientation of the achiral fluorescent dye molecules around the supramolecular nanotube from chiral dipeptide. This method is promising for characterization of complex hybrid materials.