pH and Medium Polarity Induced Self-Assembly of Fmoc-Tryptophan into Multiple Superstructures: An Experimental and Theoretical investigations.

Abstract

Self-assembly of functionalized molecular building blocks is an effective and resource-saving bottom-up technique to generate multiple superstructures with various functionality and morphologies. Furthermore, the nature of the molecule and the factors controlling the overall self-assembly process are extremely vital in fundamental aspects of self-assembly, which deliver insights into the fabrication of multiple assemblies with specific functionality.  The self-assembly of suitably functionalized amino acids leads to the formation of diverse structures with distinct properties, making them ideal bio-organic scaffolds for various applications. The present study reports, the pH and solvent polarity-induced self-assembly of 9-fluorenylmethoxycarbonyl (Fmoc)-Tryptophan into various self-assembled superstructures with morphological individualities, explore the plausible pathway of morphological transformation of Fmoc-Trp into multiple superstructures having a wide range of well-defined morphologies, including spheres, hollow spheres, nanoflowers, nanosheets, nanorods, and cube-like structures, as characterized through conventional microscopic techniques. Detailed UV-Vis, fluorescence, PXRD, and FTIR analyses revealed significant insights into the intermolecular interactions, which trigger the overall self-assembly process. The computational studies, including full geometry optimization and molecular dynamics (MD) simulations, were conducted to investigate the aggregation properties of modified amino acids (Fmoc-Trp). These studies highlighted the crucial role of π-π stacking and hydrogen bonding in tuning the overall self-assembly with morphological variation.