Polyelectrolyte–Dye Interactions: An Overview

Polyelectrolytes are polymers with repeating units of ionizable groups coupled with counterions. Recently, polyelectrolytes have drawn significant attention as highly promising macromolecular materials with potential for applications in almost every sector of our daily lives. Dyes are another class of chemical compounds that can interact with substrates and subsequently impart color through the selective absorption of electromagnetic radiation in the visible range. This overview begins with an introduction to polyelectrolytes and dyes with their respective definitions, classifications (based on origin, molecular architecture, etc.), and applications in diverse fields. Thereafter, it explores the different possible interactions between polyelectrolytes and dyes, which is the main focus of this study. The various mechanisms involved in dye–polyelectrolyte interactions and the factors that influence them are also surveyed. Finally, these discussions are summarized, and their future perspectives are presented

Solvent-Induced Molecular Folding and Self-Assembled Nanostructures of Tyrosine and Tryptophan Analogues in Aqueous Solution: Fascinating Morphology of High Order

Hydrophobic derivatives of tyrosine and tryptophan, viz. octyl and dodecyl esters of tyrosine and octyl ester of tryptophan, are synthesized, and the interfacial and bulk properties in aqueous media are investigated as models for the membrane proteins. Molecular modeling by the density functional theory method is carried out to understand the molecular conformation and geometry for the purpose of determining the packing parameters. Water-induced molecular folding of the esters of both tyrosine and tryptophan, as observed using rotating frame nuclear Overhauser effect spectroscopy, indicates that the segregation of the hydrophobic and hydrophilic blocks in water is the key to the development of fascinating interfacial property displayed by the aromatic amino acid esters. The unusually high-order morphology of the aggregates, as observed using high-resolution transmission electron microscopy, is highly uncommon for single-chain amphiphiles and points to the fact that the self-assembly behavior of the present systems resembles that of block copolymers. The study of the growth of mesosized hollow aggregates with internal bilayer structures from tyrosine and tryptophan-based model systems would add to the understanding of biochemistry and biotechnology relevant to the cell membrane. The potential of biocompatible nanostructured motifs as the drug carriers is discussed. The highly functional role played by the aromatic amino acids at the membrane–water interface will be considered with the present amphiphilic models for future perspective

Interaction of Tyrosine Analogues with Quaternary Ammonium Head Groups at the Micelle/Water Interface and Contrasting Effect of Molecular Folding on the Hydrophobic Outcome and End-Cap Geometry

The surface property of the cationic micelles of cetyltrimethylammonium bromide (CTAB) in an aqueous medium is highly modified in the presence of tyrosineoctyl ester (TYOE) and tyrosinedodecyl ester (TYDE), the models for aromatic amino acid side chains of transmembrane proteins. While the synergistic interaction between the quaternary ammonium head group of CTAB and the π-electron cloud of aromatic amino acid ester is influenced by the relative orientation and the unusual molecular geometry of the latter, this eventually triggers a morphology transition of the spherical micelle to cylindrical/wormlike micelles and imparts a strong viscoelasticity in the medium. Physical characteristics of the elongated micelles have been investigated by high resolution transmission electron microscopy (HRTEM) and the small angle neutron scattering (SANS) technique; the complex fluidic nature of the system is investigated by a dynamic rheological measurement. The intermolecular interactions have been recognized via ¹H NMR and 2D nuclear Overhauser effect spectroscopy (NOESY), and the unambiguous geometry of the end-caps of the rods has been ascertained for the first time. While the interplay between lipids and transmembrane proteins is thought to be crucial in controlling the membrane shape of the cells during many vital events such as cellular fission, fusion, and virus entry, the observed tuning of the micellar surface curvature via the cation−π interaction involving tyrosine analogues is thought provoking and opens up an avenue for new physical chemistry research on a vital biological phenomena