Amino-Acid-Based Metallo-Hydrogel That Acts Like an Esterase

Abstract

A histidine based amphiphile containing a C14 fatty acyl chain, N-histidyl N-myristry ethyl amine (AM1, 14.7mM) forms hydrogels in the presence of Fe 3+ (within the range 1.47 to 4.41mM) and Hg 2+ (within the range 3.67 to 11.02 mM) ions in aqueous dispersions at pH 6.6 (27C). The imidazole ring of the histidine residue plays a vital role to interact with these metalions. The thermal and mechanical stability of these metallo-hydrogels can be tuned by changing the proportion of amphiphile to metal ion ratio (1:0.1 to 1:0.3 for Fe 3+ containing gel and 1:0.25 to 1:0.75 for Hg 2+ containing gel). The metallo-hydrogels were characterized by different spectroscopic and microscopic techniques, low-and wide-angle powder X-ray diffraction and small-angle X-ray scattering studies. FT-IR and NMR spectroscopic studies indicate the participation of the imidazole ring in metal-ion binding. Low-and wide-angle powder X-ray diffraction and small-angle X-ray scattering data are in favour of a layered structure of the supramolecular assembly of the AM1 in presence of metal-ions. Both, the amphiphiles and the metal ion induced hydrogels reveal catalytic activity of p-nitrophenyl esters hydrolysis for the acetyl, n-butyl and n-octyl esters. Ferric ion containing metallo-hydrogel exhibits higher catalytic activity than the corresponding AM1 aggregate in the absence of metal-ions.

Supramolecular Gel as the Template for Catalysis, Inorganic Superstructure, and Pharmaceutical Crystallization

“…Finally, in one of the most recent examples, Banerjee et al synthesized a histidine-based amphiphile 9 which formed hydrogels in the presence of Fe 3+ . While both, the amphiphile and the metal ion induced hydrogels demonstrated catalytic activity of p-nitrophenyl esters hydrolysis for the acetyl, n-butyl and n-octyl esters, metallo-hydrogel exhibited a higher catalytic efficiency [66].…”

The aging effect on the enhancement of thermal stability, mechanical stiffness and fluorescence properties of histidine-appended naphthalenediimide based two-component hydrogels

“…In some cases the single gelator molecule alone is unable to form a gel. However, in presence of an additive 23,24 (metal ion, organic molecule) or co-assembly of two different types of gelator molecules 25,26 can promote gelation. This kind of gel formation is termed as two component gelatio 27,28 .…”

Biocatalysis of d,l-Peptide Nanofibrillar Hydrogel

“…Indeed, typical approaches to activate the His residue toward catalysis comprise either inclusion of Ser and/or aspartate (Asp) to reconstitute the hydrolase catalytic triad as described by Luisi et al and many others, such as Ulijn and Matsui [10,11], as well as Guler et al [12], or metal coordination usually featuring divalent zinc, as shown for instance in an elegant study by DeGrado and Korendovych [13]. Other ions were studied by Hamley and Banerjee, such as trivalent iron or divalent mercury [14]. Arginine (Arg) also proved to be a useful inclusion to enhance catalytic activity when featured on supramolecular systems based on peptides developed by Liu et al [15,16].…”