Multiwalled carbon nanotubes with surface grafted transition state analogue imprints as chymotrypsin mimics for the hydrolysis of amino acid esters: Synthesis and kinetic studies

Structure and functional group regulation of plastics for efficient ammonia capture

Activated carbon and metal organic frameworks have been tested as NH₃ recovery adsorbents, however, they are limited due to low NH₃ adsorption capacity and high cost, respectively. In this study, ethylene glycol dimethacrylate (EGDMA) polymers as the representative ester plastics were tested, and their structure and adsorption sites were regulated using HNO₃, HCl, or H₂SO₄ with varied H⁺ concentrations. The results showed that the EGDMA polymers all used hydrolysis which promoted NH₃ adsorption via different mechanisms. With HNO₃ and HCl optimization, an increased surface area promoted NH₃ adsorption via physical forces. H₂SO₄ optimization resulted in -COOH, -OH, and -SO₃H formation, which reacted with NH₃ by chemical adsorption and hydrogen bonds. This significantly increased the NH₃ adsorption capacity (85.99 mg·g^-1) compared to the material before optimization (0.36 mg·g^-1). This study presents a novel low-cost and efficient method to recycle waste plastics as NH₃ adsorbents.

Recent development in the design of artificial enzymes through molecular imprinting technology

Enzymes, a class of proteins or RNA with high catalytic efficiency and specificity, have inspired generations of scientists to develop enzyme mimics with similar capabilities. Many enzyme mimics have been...

Enzyme mimics based membrane reactor for di(2-ethylhexyl) phthalate degradation

Di(2-ethylhexyl) phthalate (DEHP), the most abundantly used plasticizer, was considered to be a hazardous chemical that was difficult to be degraded naturally. In this study, inspired by the "catalytic triad'' in serine proteases, an enzyme mimic material was developed by combining the proteases's active sites of serine, histidine and aspartate (S-H-D) with the self-assembling sequence of LKLKLKL and the aromatic group of fluorenylmethyloxycarbonyl (Fmoc). By mixing the monomer of peptides containing separate S, H and D residues with a ratio of 2:1:1, the enzyme mimics were found to co- assemble into nanofibers (Co-HSD) and showed the highest activity towards DEHP degradation because of the synergistic effects of active sites, orderly secondary structure and stable molecular conformation. To further improve ability and applicability, the high active mimetic enzyme was immobilized onto regenerated cellulose (RC) membranes for DEHP degradation in a continuous recycling mode. The RC membranes were first functionalized by the NaIO₄ oxidation method to form aldehyde groups and then conjugated with the enzyme mimics via Schiff-base reaction. As a biocatalytic membrane, this membrane could not only effectively degrade DEHP, but also showed good stability, thus establishing a promising biomaterial for large scale biodegradation of DEHP in water decontamination and liquid food depollution.

Flow-Through Macroporous Polymer Monoliths Containing Artificial Catalytic Centers Mimicking Chymotrypsin Active Site

Synthetic catalysts that could compete with enzymes in term of the catalytic efficiency but surpass them in stability have a great potential for the practical application. In this work, we have developed a novel kind of organic catalysts based on flow-through macroporous polymer monoliths containing catalytic centers that mimic the catalytic site of natural enzyme chymotrypsin. It is known that chymotrypsin catalytic center consists of L-serine, L-histidine, and L-aspartic acid and has specificity to C-terminal residues of hydrophobic amino acids (L-phenylalanine, L-tyrosine, and L-tryptophan). In this paper, we have prepared the macroporous polymer monoliths bearing grafted polymer layer on their surface. The last one was synthesized via copolymerization of N-methacryloyl-L-serine, N-methacryloyl-L-histidine, and N-methacryloyl-L-aspartic acid. The spatial orientation of amino acids in the polymer layer, generated on the surface of monolithic framework, was achieved by coordinating amino acid-polymerizable derivatives with cobalt (II) ions without substrate-mimicking template and with its use. The conditions for the preparation of mimic materials were optimized to achieve a mechanically stable system. Catalytic properties of the developed systems were evaluated towards the hydrolysis of ester bond in a low molecular substrate and compared to the results of using chymotrypsin immobilized on the surface of a similar monolithic framework. The effect of flow rate increase and temperature elevation on the hydrolysis efficiency were evaluated for both mimic monolith and column with immobilized enzyme.

Enzyme mimics based on self-assembled peptides for di(2-ethylhexyl)phthalate degradation

Enzyme mimics inspired by serine proteases are developed through self-assembled peptides to degrade di(2-ethylhexyl)phthalate (DEHP).

Novel ionic surface imprinting technology: design and application for selectively recognizing heavy metal ions

Traditional bulk polymerization imprinted technology and existing surface imprinted technology have some congenital defects. Therefore, it is necessary to design more efficient surface imprinted technology. In this paper, novel surface imprinting technology with higher imprinting efficiency is well designed. It fully realizes the synchronization of polymer crosslinking and template imprinting. Then the surface imprinted polymers (SIPs) are synthesized using metal ions as a template. The physicochemical characteristics of the SIPs are characterized by scanning electron microscopy (SEM), Brunauer–Emmett–Teller (BET) studies, Fourier transform infrared spectroscopy (FTIR) and elemental analysis. The adsorption performances and recognition selectivity of the SIPs towards the template are investigated by a batch method. The experimental results show that the SIPs possess excellent adsorption ability and selectivity towards the template. The selectivity coefficients of the SIPs prepared in this study are higher than those of IIPs prepared by other imprinting methods. The adsorption process could be well described by the Lagergren-first-order model and Langmuir monolayer chemical adsorption. The SIPs have good chemical stability and reusability. Consecutive adsorption–desorption experiments show that the exhausted SIPs could be effectively regenerated, and the regenerated SIPs could be reused without a significant reduction in adsorption capacity or selectivity coefficient.

SIPs have good chemical stability and reusability. They could be reused without a significant reduction in adsorption capacity and selectivity coefficient.