Cooperative Antibacterial Enzyme-Ag-Polymer Nanocomposites.

Biomacromolecules such as enzymes and proteins with bactericidal activity are promising for antibacterial applications in a mild, biocompatible, and environmentally friendly manner. However, low bactericidal efficiency has hindered its applications. Nanobiohybrids, constructed from biomacromolecules and functional nanomaterials, could enhance the function of biomacromolecules. However, the incompatibility between biological components and nanomaterials is still the major challenge of designing nanobiohybrids. Here, we rationally design lysozyme-Ag-polymer nanocomposites, which display high stability and antibacterial activity in a cooperative manner. The sufficient presence of Ag-N coordination between Ag and the polymer/protein contributed to the high stability of the nanocomposites. Compared with lysozyme and commercial silver nanoparticles (AgNPs) alone, the enzyme-Ag-polymer nanocomposites showed dramatically enhanced antibacterial activity. We propose a tightly encapsulated invasion (TEI) mechanism for a greatly improved antibacterial activity. The bacteria closely interacted with nanocomposites, and cell walls were hydrolyzed by lysozyme especially, facilitating the penetration of silver into the bacteria, and then reactive oxygen species (ROS) generated by silver to kill bacteria. In addition, the specific TEI mechanism resulted in high biocompatibility toward mammalian cells.

Cooperative catalysis by a single-atom enzyme-metal complex.

Anchoring single metal atoms on enzymes has great potential to generate hybrid catalysts with high activity and selectivity for reactions that cannot be driven by traditional metal catalysts. Herein, we develop a photochemical method to construct a stable single-atom enzyme-metal complex by binding single metal atoms to the carbon radicals generated on an enzyme-polymer conjugate. The metal mass loading of Pd-anchored enzyme is up to 4.0% while maintaining the atomic dispersion of Pd. The cooperative catalysis between lipase-active site and single Pd atom accelerates alkyl-alkyl cross-coupling reaction between 1-bromohexane and B-n-hexyl-9-BBN with high efficiency (TOF is 540 h-1), exceeding that of the traditional catalyst Pd(OAc)2 by a factor of 300 under ambient conditions.

Enzyme-Metal Hybrid Catalysts for Chemoenzymatic Reactions.

Enzyme-metal hybrid catalysts (EMHCs), which combine enzymatic and metal catalysis, provide tremendous possibilities for new chemoenzymatic cascade reactions. Here, an overview of the representative achievements in the design of EMHCs and their applications in chemoenzymatic cascade reactions are presented. The preparation of hybrid catalysts is classified into two categories: coimmobilized enzyme-metal heterogeneous catalysts and carrier-free enzyme-metal bioconjugates. Examples of one-pot chemoenzymatic cascade processes catalyzed by the hybrid catalysts are then provided as potential applications. Finally, the limitations and future perspectives of EMHCs are discussed.

Investigating the origin of high efficiency in confined multienzyme catalysis.

Biomimetic strategies have successfully been applied to confine multiple enzymes on scaffolds to obtain higher catalytic efficiency of enzyme cascades than freely distributed enzymes. However, the origin of high efficiency is poorly understood. We developed a coarse-grained, particle-based model to understand the origin of high efficiency. We found that a reaction intermediate is the key in affecting reaction kinetics. In the case of unstable intermediates, the confinement of multiple enzymes in clusters enhanced the catalytic efficiency and a shorter distance between enzymes resulted in a higher reaction rate and yield. This understanding was verified by co-encapsulating multiple enzymes in metal-organic framework (MOF) nanocrystals as artificially confined multienzyme complexes. The activity enhancement of multiple enzymes in MOFs depended on the distance between enzymes, when the decay of intermediates existed. The finding of this study is useful for designing in vitro synthetic biology systems based on artificial multienzyme complexes.