Polymerization of aniline using a peroxidase-mimetic catalyst

Rh-coordinated histidyl bolaamphiphile assembly: a catalyst for the isomerization of cis-stilbene and cis-alkene

In this study, we present a colloidal assembly of histidyl bolaamphiphiles whose imidazoles coordinate with rhodium ions (HisC7[Rh]) to exhibit catalytic isomerization activity for cis-stilbene and cis-alkene molecules. The histidyl bolaamphiphiles self-assemble to form a soft scaffold that functions analogously to an apoenzyme. This scaffold exposes multiple histidyl imidazoles and carboxylates on its surface, to which rhodium ions bind, generating catalytically active sites. The Rh coordination with the biochemical functional groups was verified through comprehensive vibrational spectroscopy and calorimetry. The colloidal HisC7[Rh] demonstrated a significant catalytic effect on the isomerization of cis- to trans-stilbene under mild H2 conditions, resulting in 69% yield of trans-stilbene. In contrast, when Rh(cod)2BF4 was employed as a control catalyst, only the hydrogenated products of bibenzyl were obtained. These findings underscore the crucial role of histidyl motifs in exhibiting unique catalytic isomerization activity through the coordination with Rh. The catalytic activity of HisC7[Rh] is governed by several factors, such as rhodium content, solvent composition, temperature, and H2 pressure. Moreover, HisC7[Rh] displayed moderate isomerization activity towards not only stilbene but also unsaturated fatty acid isomers, highlighting its expansive potential as an isomerization catalyst.

Self-Assembling Peptidic Bolaamphiphiles for Biomimetic Applications

Bolaamphiphile, which is a class of amphiphilic molecules, has a unique structure of two hydrophilic head groups at the ends of the hydrophobic center. Peptidic bolaamphiphiles that employ peptides or amino acids as their hydrophilic groups exhibit unique biochemical activities when they self-organize into supramolecular structures, which are not observed in a single molecule. The self-assembled peptidic bolaamphiphiles hold considerable promise for imitating proteins with biochemical activities, such as specific affinity toward heterogeneous substances, a catalytic activity similar to a metalloenzyme, physicochemical activity from harmonized amino acid segments, and the capability to encapsulate genes like a viral vector. These diverse activities give rise to large research interest in biomaterials engineering, along with the synthesis and characterization of the assembled structures. This review aims to address the recent progress in the applications of peptidic bolaamphiphile assemblies whose densely packed peptide motifs on their surface and their stacked hydrophobic centers exhibit unique protein-like activity and designer functionality, respectively.