Multi-scale molecular modeling of fluorescent rosette nanotubes

Abstract

Event Abstract Back to Event Multi-scale molecular modeling of fluorescent rosette nanotubes Arthur Gonzales1, Takeshi Yamazaki2, Belete Legesse1 and Hicham Fenniri1 1 Northeastern University, Chemical Engineering, United States 2 National Institute for Nanotechnology, Canada Rosette nanotubes (RNTs) are soft organic nanomaterials self-assembled under aqueous conditions from Watson-Crick inspired guanine-cytosine (G∧C) hybrid building blocks with complementary hydrogen bonding sites[1]. These materials have substantial design flexibility and a range of applications, which is partly attributed to their diverse surface functionalization and a chemically/physically tunable channel for guest molecule loading. Several studies have established their biocompatibility and applications in nanomedicine such as in coatings for medical devices, materials for tissue engineering and for drug display and delivery. With novel applications in mind and in an effort to streamline its synthesis, a new tricyclic G∧C motif was designed to self assemble into fluorescent RNT in various solvents. Its self-assembly and fluorescence properties were verified by scanning electron microscopy (SEM), atomic force microscopy (AFM), transmission electron microscopy (TEM), and UV-visible spectroscopic studies. Temperature, pH and other solvent properties affect the self-assembly process and structure of the RNTs. To aid in the characterization of this new RNT, multi-scale molecular modeling techniques were applied to predict its structure in various solvent conditions. Molecular dynamics (MD), molecular mechanics (MM), and the statistical mechanical theory of solvation, also known as the 3 dimensional reference interaction site model (3D-RISM) theory were applied to predict the conformation of RNTs. MM was used to determine the possible conformations of the individual motifs. From these, RNT models were built and MD simulations were run in different solvent properties to determine the stability and probable structure of the nanotubes. The results suggest that this tricyclic G∧C motif can either form ring stacks (RSs) or helical coils (HCs) depending on the solvent used. 3D-RISM integral equations were then solved for the system to determine the solvation structure, energetics, and to propose a self-assembly pathway for the RNTs.