Enantioselective Activity of Hemin in Supramolecular Gels Formed by Co-Assembly with a Chiral Gelator

Graphical Supramolecular gels formed from hemin and histidine amphiphiles were tested as artificial enzymes to catalyse the oxidation of the chiral substrate L-DOPA to L-dopachrome. The supramolecular gel made up of left-handed helices enhanced the catalytic activity of hemin effectively, and more interestingly, it exhibited enantioselectivity. Supramolecular co-assembly provides an efficient way to combine structural and functional units through noncovalent interactions and produce materials with enhanced performance. Here, using a chiral amphiphilic histidine derivative (LHC18 or DHC18) as a gelator, we have successfully co-assembled the gelator and hemin through gelation. During the co-assembly, the chiral information of the gelator was transcribed into the assemblies, and thus right- and left-handed helical ribbons from LHC18-Hemin and DHC18-Hemin co-assemblies were obtained, respectively, which were confirmed by CD spectra and SEM observations. These helical ribbons were used as artificial enzymes to catalyse the oxidation reaction of 3,4-dihydroxy-L-phenylalanine (L-DOPA). The catalytic activity of hemin in supramolecular gels can be effectively enhanced over that of free hemin. Moreover, by virtue of induced chirality, the supramolecular gels of LHC18-Hemin and DHC18-Hemin exhibited obvious enantioselective activity. This work provides a way to combine chirality transfer and supramolecular asymmetric catalysis.