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Peptide amphiphiles are a class of molecules that can self-assemble into a variety of supramolecular structures, including high-aspect-ratio nanofibers. It is challenging to model and predict the charges in these supramolecular nanofibers because the ionization state of the peptides are not fixed but liable to change due to the acid-base equilibrium that is coupled to the structural organization of the peptide amphiphile molecules. Here, we have developed a theoretical model to describe and predict the amount of charge found on self-assembled peptide amphiphiles as a function of pH and ion concentration. In particular, we computed the amount of charge of peptide amphiphiles nanofibers with the sequence C16 − V2A2E2. In our theoretical formulation, we consider charge regulation of the carboxylic acid groups, which involves the acid-base chemical equilibrium of the glutamic acid residues and the possibility of ion condensation. The charge regulation is coupled with the local dielectric environment by allowing for a varying dielectric constant that also includes a position-dependent electrostatic solvation energy for the charged species. We find that the charges on the glutamic acid residues of the peptide amphiphile nanofiber are much lower than the same functional group in aqueous solution. There is a strong coupling between the charging via the acid-base equilibrium and the local dielectric environment. Our model predicts a much lower degree of deprotonation for a position-dependent relative dielectric constant compared to a constant dielectric background. Furthermore, the shape and size of the electrostatic potential as well as the counterion distribution are quantitatively and qualitatively different. These results indicate that an accurate model of peptide amphiphile self-assembly must take into account charge regulation of acidic groups through acid–base equilibria and ion condensation, as well as coupling to the local dielectric environment.

Skeletal muscles are impressive as they can achieve reversible, macroscopic, anisotropic motion in soft materials. Here the authors show a bottom-up design of macroscopic hydrogel tubes containing supramolecular nanofibers that can undergo anisotropic actuation by thermal stimuli.

Small-molecule self-assembly has proven to be a rich field for the controlled synthesis of supramolecular objects with the size scale of polymers and interesting properties. Using several recent examples from our laboratory, we discuss the development of chemical structure codes for supramolecular self-assembly objects with defined shapes. The resulting materials formed by these objects are promising for electronic functions and biological functions for regenerative medicine. [ABSTRACT FROM AUTHOR]

Symmetric oligothiophene derivatives containing hydrogen bond forming segments create self-supporting organogels consisting of self-assembled 1D nanostructures at low concentrations. Hydrogen bond formation and π–π stacking were both found to be crucial for the formation of conductive supramolecular networks of 1D nanostructures. [ABSTRACT FROM AUTHOR]