Catalytic Enhancement Research Articles

Nitrogen-Doped Graphene-Supported Tungsten Oxynitride Nanoparticles as an Efficient Bidirectional Polysulfide Convertor for Advanced Lithium-Sulfur Batteries.

Catalytic materials are considered pivotal in addressing the sluggish kinetics and shuttle effect in lithium-sulfur batteries (LSBs). However, effectively harnessing the utilization rate of active sites within catalytic materials remains a pivotal challenge. In this study, a novel conductive nitrogen-doped graphene-loaded tungsten oxynitride nanoparticle (WNO/NG) with abundant active sites is prepared through a polymer-assisted templating method for serving as a sulfur host. Electrochemical analysis coupled with in situ XRD confirm the dual-directional electrocatalytic behavior of WNO/NG for accelerating the conversion of lithium polysulfide (LiPSs). Theoretical calculations demonstrate that the intrinsic mechanism underlying the performance enhancement is attributed to the high inherent conductivity of WNO/NG and the efficient interface charge transfer with LiPSs. The assembled 500 mAh pouch cell delivers a 97% capacity retention after 25 cycles. This strategy provides valuable insights for designing catalytic materials with abundant activity sites and sheds light on the mechanisms of catalytic enhancement in Li-S chemistry.

Oxygen Defect Site Filling Strategy Induced Moderate Enrichment of Reactants for Efficient Electrocatalytic Biomass Upgrading.

The electrocatalytic oxidation of 5-hydroxymethylfurfural (HMF) provides a feasible approach for the efficient utilization of biomass. Defect regulation is an effective strategy in the field of biomass upgrading to enhance the adsorption capacity of reactants and thus increase the activity. However, how to select appropriate strategies to regulate the over-enrichment of reactants induced by excessive oxygen vacancy is still a huge challenge. In this work, the defect-filling strategy to design and construct an element-filled oxygen vacancy site layered double hydroxide (S─Ov─LDH) is adopted, which achieves a significant reduction in the electrolysis potential of biomass platform molecule HMF oxidation reaction and a significant increase in current density. Physical characterizations, electrochemical measurements, and theoretical calculations prove that the formation of metal─S bond in the second shell effectively regulates the electronic structure of the material, thus weakening the over-strong adsorption of HMF and OH- induced by excessive oxygen vacancy, promoting the formation of high-valence Co3+ during the reaction, and forming new adsorption sites. This work discusses the catalytic enhancement mechanism of defect filling in detail, fills the gap of defect filling in the field of biomass upgrading, and provides favorable guidance for the further development of defect regulation strategies.

Effective Enrichment of Free Radicals through Nanoconfinement Boosts Electrochemiluminescence of Carbon Dots Derived from Luminol.

Local enrichment of free radicals at the electrode interface may open new opportunities for the development of electrochemiluminescence (ECL) applications. The sensing platform was constructed by assembling ECL-emitting luminol derived carbon dots (Lu CDs) onto the heterojunction Tungsten disulfide/Covalent organic frameworks (WS2@COF) for the first time, establishing a nanoconfinement-reactor with significantly heightened ECL intensity and stability compared to the Lu CDs-H2O2 system. This enhanced performance is credited to the COF domain's restricted pore environment, where WS2@COF exhibits a more negative adsorption energy for H2O2, effectively enriching H2O2 in the catalytic edge sites of WS2. Furthermore, the internal electric field at the WS2 and COF interface accelerates electron flow, boosting WS2's catalytic activity and achieving domain-limited catalytic enhancement of ECL. Self-designed DNA nanomachines combined with cascading molecular keypad locking mechanisms are integrated into the biosensors, effectively guaranteeing the accuracy of the sensing process while providing crucial safeguards for molecular diagnostics and information security applications. In essence, this innovative approach represents the first system to enhance local free radical concentrations by enriching co-reactants on the electrode surface through nanoconfinement catalysis, yielding heightened ECL intensity. The potential impact of this novel strategy and sensing mechanism on real-bioanalysis applications is promising.

Effective Enrichment of Free Radicals through Nanoconfinement Boosts Electrochemiluminescence of Carbon Dots Derived from Luminol

AbstractLocal enrichment of free radicals at the electrode interface may open new opportunities for the development of electrochemiluminescence (ECL) applications. The sensing platform was constructed by assembling ECL‐emitting luminol derived carbon dots (Lu CDs) onto the heterojunction Tungsten disulfide/Covalent organic frameworks (WS2@COF) for the first time, establishing a nanoconfinement‐reactor with significantly heightened ECL intensity and stability compared to the Lu CDs‐H2O2 system. This enhanced performance is credited to the COF domain‘s restricted pore environment, where WS2@COF exhibits a more negative adsorption energy for H2O2, effectively enriching H2O2 in the catalytic edge sites of WS2. Furthermore, the internal electric field at the WS2 and COF interface accelerates electron flow, boosting WS2′s catalytic activity and achieving domain‐limited catalytic enhancement of ECL. Self‐designed DNA nanomachines combined with cascading molecular keypad locking mechanisms are integrated into the biosensors, effectively guaranteeing the accuracy of the sensing process while providing crucial safeguards for molecular diagnostics and information security applications. In essence, this innovative approach represents the first system to enhance local free radical concentrations by enriching co‐reactants on the electrode surface through nanoconfinement catalysis, yielding heightened ECL intensity. The potential impact of this novel strategy and sensing mechanism on real‐bioanalysis applications is promising.

In Situ Encapsulation of Atomically Precise Nanoclusters in Reticular Frameworks via Mechanochemical Synthesis.

The combination of atomically precise nanoclusters (APNCs) and reticular frameworks is promising for generating component-specific nanocomposites with emergent properties. However, traditional liquid-phase synthesis often hampers this potential by damaging APNCs and limiting combination diversity. Here, mechanochemical synthesis to explore the encapsulation of diverse oil- and water-soluble APNCs within various reticular frameworks is employed, establishing a database of 21 unique APNC-framework combinations, including metal-organic frameworks (MOFs), covalent-organic frameworks (COFs), hydrogen-bonded organic frameworks (HOFs), and multivariate MOFs. These framework coatings not only spatially immobilize APNCs but also secure their structures, preventing aggregation and degradation while enhancing stability and activity. Encapsulating Au25 in HOFs resulted in a remarkable 315-fold increase in catalytic activity compared to Au25 homogeneous catalyst, highlighting the framework's crucial role in catalytic enhancement. The mechanochemical synthesis strategy facilitates tailored support screening, catering to specific needs, and shows promise for developing multifunctional systems, including enzyme-APNC@frameworks material for cascade reactions.

A computational strategy to improve the activity of tyrosine phenol-lyase for the synthesis of L-DOPA

Enzymes with high catalytic activity and stability are essential for industrial production, yet most natural enzymes do not meet these requirements. Therefore, efficient strategies for enzyme engineering are crucial. In this study, we developed a cost-effective computational design strategy to enhance the activity of tyrosine phenol-lyase (TPL) for the production of L-DOPA. By integrating structural analysis with computational design, and guided by our understanding of conformational flexibility of TPL, we identified a region where enhanced stability is most likely to facilitate enzyme activity. We screened stabilizing mutations by Cartesian_ddg in Rosetta. After identifying single stabilizing mutations, we grouped the nearby positions harboring multiple stabilizing mutations and calculated the energy of combinatorial variants. We found two promising groups where most variants exhibited lower calculated energy than the wild-type. Experimental validation showed five variants in these groups exhibit increased activity, with the two best variants showing catalytic activity enhancements of 1.8-fold and 1.6-fold compared to the wild-type enzyme.

Catalytic enhancement of water gas shift reaction with Cu/ZnO/ZSM-5: Overcoming challenges of CO2 and H2 rich feeds

Water gas shift (WGS) reaction commonly converts CO to CO2 using H2O and produces H2 and CO2 in a catalytic fixed bed reactor. This study aims to develop a Cu/ZnO/ZSM-5 catalyst loaded in water gas shift reactor for converting typical synthesis gas produced from dry reforming of methane (DRM) at medium temperature shift (MTS, 200–350 oC) conditions and for preventing reverse reaction due to high feed concentrations of CO2 and H2. The Cu/ZnO/ZSM-5 catalyst was prepared by impregnation method with lower Cu metal loading of 5, 10, and 15 wt%, respectively, compared to commercial catalysts. The synthesized catalyst was characterized using XRF, XRD, SEM, H2-TPR, NH3-TPD, and TGA. The catalyst activity and stability for the WGS reaction were tested in the fixed bed reactor at atmospheric pressure and temperature of 325 °C. The experimental results show that CO conversion increases with increasing Cu loading. The 15 wt% Cu/ZnO/ZSM-5 catalyst showed the best results with a CO conversion of 35% and a yield of H2 of 36% and showed good stability for 32 h. Based on the TGA, the 15 wt% Cu/ZnO/ZSM-5 catalyst forms a 0.04 g carbon/g catalyst, which is much lower when compared to commercial catalyst (0.105 g carbon/g catalyst). The relative activity of the synthesized catalyst indicates 2.4 times better when compared to commercial catalysts. High concentrations of H2 and CO2 in the feed may initiate side reactions, including reverse WGS, methanation, and carbon formation, which will decrease H2 yield.

Catalytic enhancement in the performance of the microscopic two-stroke heat engine.

We consider a model of heat engine operating in the microscopic regime: the two-stroke engine. It produces work and exchanges heat in two discrete strokes that are separated in time. The working body of the engine consists of two d-level systems initialized in thermal states at two distinct temperatures. Additionally, an auxiliary nonequilibrium system called catalyst may be incorporated with the working body of the engine, provided the state of the catalyst remains unchanged after the completion of a thermodynamic cycle. This ensures that the work produced by the engine arises solely from the temperature difference. Upon establishing the rigorous thermodynamic framework, we characterize twofold improvement stemming from the inclusion of a catalyst. Firstly, we prove that in the noncatalytic scenario, the optimal efficiency of the two-stroke heat engine with a working body composed of two-level systems is given by the Otto efficiency, which can be surpassed by incorporating a catalyst with the working body. Secondly, we show that incorporating a catalyst allows the engine to operate in frequency and temperature regimes that are not accessible for noncatalytic two-stroke engines. We conclude with a general conjecture about the advantage brought by a catalyst: including the catalyst with the working body always allows to improve efficiency over the noncatalytic scenario for any microscopic two-stroke heat engines. We prove this conjecture for two-stroke engines where the working body is composed of two d-level systems initialized in thermal states at two distinct temperatures, as long as the final joint state leading to optimal efficiency in the noncatalytic scenario is not a product state, or at least one of the d-level system is not thermal.

Hydrogenation‐Driven Metal Dispersion and Catalytic Enhancement of Borophane‐Supported Single‐Atom Catalysts for Electrochemical Nitrogen Reduction

AbstractThe present study delves into electrochemical nitrogen reduction reaction (NRR) for ammonia synthesis using borophane‐supported single‐atom catalysts (SACs) through density functional theory (DFT) calculations. In comparison to previously reported borophene, which serves as a potential substrate for SACs in NRR, hydrogenated borophane, especially borophane‐2H(B5H2), not only prevents metal aggregation, resulting in stable atomically dispersed metal centers, but also enhances catalytic activity by modulating the metal's charge state. Among all candidates, atomic tungsten anchored on W1/borophane‐2H(B5H2) displays the most favorable NRR activity and product selectivity.

Highly efficient bimetallic counter cations-based tungsten bronzes electrocatalysts developed for sustainable oxygen evolution in acidic solution

This study involves the designing of monophosphate tungsten bronzes (MPTBs) with a combination of earth-abundant Al and Ni counter cations synthesized via the solution combustion as robust, highly efficient electrocatalysts for oxygen evolution reaction (OER) in 1.0 M H2SO4 solution. A series of mixed Al and Ni counter cations-based MPTBs was prepared at different temperatures and characterized with various sophisticated techniques concerning their compositions, morphologies, microstates, and electronic states. The catalyst with Al/Ni ratio of 1:3 of tetragonal cube-shaped MPTB calcined at 700 °C ((Al1/3,Ni)-MPTB7) exhibited an extraordinary OER performance with a larger electrochemically active surface area, almost zero onset overpotential (η), and a lower solar cell-equivalent η (i.e., at 10 mA cm−2) of 199 mV that is lower than that obtained with the state-of-the-art RuO2 catalyst. A progressive enhancement of the performance of the catalysts was noticed for a 12 h OER run, ensuring the robustness of the materials developed for a long-term application. The mixed valency states of tungsten (W), i.e., W5+/W6+ states, along with higher oxygen vacancies of (Al1/3,Ni)-MPTB7 are evaluated to tender suitably oriented active sites for effective adsorption of H2O during the OER. A substantial increase in oxygen vacancies and W5+ state, particularly the W5+4f7/2 state in the catalysts, resulted from a spin-exchange phenomenon during a long-term OER is associated with OER catalytic enhancement. The thus-developed acid-stable, robust MPTBs with mixed Al and Ni counter cations would be an alternative to the pricy noble metal counterparts used in clean energy water splitting technology.

Electrostatic Preorganization in Three Distinct Heterogeneous Proteasome β-Subunits.

The origin of the enzyme's powerful role in accelerating chemical reactions is one of the most critical and still widely discussed questions. It is already accepted that enzymes impose an electrostatic field onto their substrates by adopting complex three-dimensional structures; therefore, the preorganization of electric fields inside protein active sites has been proposed as a crucial contributor to catalytic mechanisms and rate constant enhancement. In this work, we focus on three catalytically active β-subunits of 20S proteasomes with low sequence identity (∼30%) whose active sites, although situated in an electrostatically miscellaneous environment, catalyze the same chemical reaction with similar catalytic efficiency. Our in silico experiments reproduce the experimentally observed equivalent reactivity of the three sites and show that obliteration of the electrostatic potential in all active sites would deprive the enzymes of their catalytic power by slowing down the chemical process by a factor of 1035. To regain enzymatic efficiency, besides catalytic Thr1 and Lys33 residues, the presence of aspartic acid in position 17 and an aqueous solvent is required, proving that the electrostatic potential generated by the remaining residues is insignificant for catalysis. Moreover, it was found that the gradual decay of atomic charges on Asp17 strongly correlates with the enzyme's catalytic rate deterioration as well as with a change in the charge distributions due to introduced mutations. The computational procedure used and described here may help identify key residues for catalysis in other biomolecular systems and consequently may contribute to the process of designing enzyme-like synthetic catalysts.

Unlocking OER potential: Tailoring layered double perovskites through self-reconstruction

The sluggish rate of the anode oxygen evolution reaction (OER) is a major bottleneck for green hydrogen production, making a room-temperature alkaline water electrolyser critical to unlocking the full potential of this technology. Using a perovskite oxide as an electrochemical matrix and forming a self-assembled oxyhydroxide (OOH) layer on the surface via a self-reconstruction activation process (SRAP) is a promising strategy to enhance OER catalytic activity. However, the mechanistic details and long-term impact of SRAP, especially its relationship to catalytic activity, oxygen collection efficiency, and catalyst dissolution, are not fully understood. To address this knowledge gap, we used layered double perovskite (LDP) PrBa0·75Ca0·25Co1·5Fe0·5O5+δ(PBCCF) and PrBa0·75Ca0·25Co1·5Fe0·4Ni0·1O5+δ (PBCCFN) as model electrochemical catalysts and then triggered SRAP. Subsequently, chronoamperometry (CA), rotating ring disk electrode (RRDE) and in-situ electrochemical quartz crystal microbalance (EQCM) were used to study the effect of the Ni-doping on PBCCF SRAP in terms of catalytic activity, oxygen collection efficiency and catalyst stability. The results showed that the OER catalytic current of the LDP PBCCF and PBCCFN was enhanced via SRAP and the oxygen collection efficiency can be maintained, suggesting that the increase in catalytic current is attributed to OER catalytic activity increase rather than electrochemical catalyst dissolution. Additionally, the effect of the catalytic activity enhancement was more significant in PBCCFN. More importantly, the stability of the LDP PBCCF and PBCCFN after SRAP are higher than simple perovskite Ba0·5Sr0·5Co0·8Fe0·2O3-δ (BSCF) because of the increase in the redeposition rate. The observations suggest that using LDP PBCCF and PBCCFN as matrices followed by triggering SRAP can provide valuable insights for designing LDP based OER electrocatalysts.

Activation of automethylated PRC2 by dimerization on chromatin

Polycomb repressive complex 2 (PRC2) is an epigenetic regulator that trimethylates lysine 27 of histone 3 (H3K27me3) and is essential for embryonic development and cellular differentiation. H3K27me3 is associated with transcriptionally repressed chromatin and is established when PRC2 is allosterically activated upon methyl-lysine binding by the regulatory subunit EED. Automethylation of the catalytic subunit enhancer of zeste homolog 2 (EZH2) stimulates its activity by an unknown mechanism. Here, we show that human PRC2 forms a dimer on chromatin in which an inactive, automethylated PRC2 protomer is the allosteric activator of a second PRC2 that is poised to methylate H3 of a substrate nucleosome. Functional assays support our model of allosteric trans-autoactivation via EED, suggesting a previously unknown mechanism mediating context-dependent activation of PRC2. Our work showcases the molecular mechanism of auto-modification-coupled dimerization in the regulation of chromatin-modifying complexes.

Strengthening the activity and CO tolerance with bi-component PtNi/NbN-C catalyst for methanol alkaline electrooxidation

It is critical to create the anodic catalysts with high efficiency and economy for direct methanol fuel cells (DMFCs). Here, a series of PtNi/NbN-C catalysts (M=Co, Sn, Ni) are developed using the glycol solvothermal process, to investigate the catalytic effficiency for alkaline methanol oxidation reaction (MOR). Catalytic performance evaluation experiments show that the doped Ni species bring the enhancement effect on Pt/NbN-C for the alkaline MOR. The mass activities of PtxNiy/NbN-C show a volcanic trend with the increased Ni contents. PtNi/NbN-C has the highest mass activity (6025.5 mA·mg-1Pt) for alkaline MOR, 18.3 times greater than that of the Pt/C commercial catalyst. The LSV, EIS, Tafel, CA and CO stripping results imply PtNi/NbN-C also exhibits the lowest onset potential, charge transfer resistance, fastest kinetics, highest CO tolerance and stability. When the XRD, HRTEM, and XPS analysis are combined, it is discovered that the electronic effect between the Pt, Ni, and NbN species is mostly responsible for the catalytic performance enhancement is mainly depend on the electronic effect among the Pt, Ni and NbN species. The presence of Pt in an electron-deficient state can enhance the conversion of adsorbed methanol and intermediates, evidenced by a direct relationship between the d-band centers and the mass activities for MOR of different catalysts. This study may provide guidance for the development of anodic materials for DMFCs.

Synergistic enhancement of plasmon induced photocatalytic and photoelectrochemical performance on ZnWO4/Ag2O@Ag hybrid-heterostructures

A novel hybrid photocatalyst, ZnWO4/Ag2O@Ag heterostructure was synthesized using a simple one-pot microwave treatment with varying concentrations of silver. Physico-chemical characterization was performed to elucidate the synthesized nanohybrids' properties. The photocatalytic activity of both pristine and heterostructure samples was evaluated through the degradation of cationic MB dye. Among the varied Ag concentrations, the 9 % Ag-doped ZnWO4/Ag2O heterostructure exhibited superior degradation performance, with a degradation rate of 93 % achieved within 45 min, surpassing both other Ag concentrations (89 % (90 min) for 1 % Ag, 87 % (80 min) for 3 % Ag, 90 % (80 min) for 5 % Ag and 91 % (45 min) for 7 % Ag) and pristine ZnWO4 (91 % (90 min)) samples. This catalytic enhancement can be attributed to the formation of heterostructures, plasmon-induced absorption enhancement within specific wavelength ranges, and reduced charge recombination rates. UV–visible studies revealed Ag nanoparticles of various sizes in the heterostructures, supported by surface plasmon resonance (SPR) peaks at 480 and 550 nm, respectively. Trapping experiments indicated that •OH and •O2− were the active species in MB reduction for pure and heterostructure samples. Furthermore, the hybrid heterostructure samples exhibited high stability and reusability in photocatalytic degradation. These findings suggest that the ZnWO4/Ag2O heterostructure photocatalysts are promising candidates for environmental remediation applications.

Thiourea enhanced oxidase-like activity of CeO2/CuxO nanozyme for fluorescence/colorimetric detection of thiourea and glutathione

A novel fluorescence/colorimetric dual-mode sensor, based on enhancement of the oxidase-like activity of CeO2/CuxO nanozyme towards the oxidation of o-phenylenediamine (OPD) induced by thiourea (TU), has been proposed for TU detection. The catalytic activity enhancement on CeO2/CuxO can be attributed to the strong electron-donation ability of TU, which promoted hydroxyl radical generation and amplified OPD oxidization with enhanced dual-signal readout. By integrating a portable paper-chip and smartphone system, this CeO2/CuxO-OPD system achieved on-site visual colorimetric analysis of TU. The dual-mode sensor demonstrated high sensitivity and specificity in recognizing TU, with a detection limit (LOD) of 1.90 μM and a linear range (LR) 2.5–80 μM in fluorescent mode; as well as an LOD of 6.69 μM and an LR 10–250 μM in colorimetric mode. Furthermore, the CeO2/CuxO-TU-OPD system has been designed for dual-mode glutathione (GSH) detection with enhanced sensitivity, achieving an LOD of 0.19 μM and an LR 0.5–10 μM in fluorescent mode; as well as an LOD of 1.24 μM and an LR 1.25–25 μM in colorimetric mode. Additionally, GSH discrimination (fluorescent mode) was successfully achieved in different biological samples, showing good consistency with the standard method. The recoveries ranged from 96.8 % to 116.7 % in serum samples and from 97.3 % to 107.7 % in cell lysates, with RSDs less than 2 %. This work not only introduced a novel approach to enhance oxidase-like activity of nanozymes but also provided an efficient field-suitable tool for enhanced dual-mode response towards TU and GSH.

The catalytic enhancement of the hydrogen evolution reaction facilitated by Pd coating on SrTiO3

The wide bandgap structure of 3.2 eV has made SrTiO3 (STO) well-known for its exclusive responsiveness to ultraviolet (UV) light. By anchoring Pd to the surface oxygen atoms of STO, we have successfully reduced the forbidden bandwidth of STO to 2.75 V, thereby extending its light absorption range to visible light. Simultaneously, trace amounts of low-valent Pd were distributed on the surface, significantly enhancing the photocatalytic hydrogen precipitation rate to 7366.07 μmol·g-1·h-1. This innovative approach led to the development of a novel nanocatalyst with numerous tailored active sites specifically designed for efficient photocatalytic hydrogen evolution. X-ray fine spectroscopy confirms Pd was successfully anchored to the STO surface and coordinated with surface O and the occurrence of Pd and Pd coordination at 2.0 Å from the Pd center in the R-space. Density functional theory (DFT) calculations further validate that anchoring Pd onto the STO surface reduces the free energy of adsorption for H* on these active sites. This discovery presents a promising strategy for immobilizing metal catalysts at perovskite STO’s unit sites.

From Precious to Earth-Abundant Metallic Nanoparticles: A Trend of Interband Transitions in Photocatalyzed Nitrobenzene Reduction.

Metallic nanoparticles have been demonstrated to be versatile photocatalysts, as exemplified by those made from noble and precious metals. Transitioning from precious to earth-abundant metals for sustainable photocatalysis requires benchmarking their catalytic performance. In this work, we attempt to compare the photocatalytic activities of Au, Pd, and Co-B nanoparticles in the reduction of nitrobenzene by hydrazine. Despite their different morphologies and surface structures, Co-B nanoparticles offer the highest catalytic enhancement when comparing their reaction rates under irradiation to those under nonirradiation conditions. The trend of improved photocatalytic performance when transitioning from Au to Pd, and then to Co-B, can be explained by the nature of their d-band positions and corresponding hot carriers photogenerated from interband transitions.

Photoresponsive microfluidic three-phase emulsions for tandem reactions

The long-term objective of tandem reaction is to investigate ‘intelligent’ tandem reaction systems akin to living cells. Here we’ve prepared an ‘intelligent’ droplet microreactor for the tandem reaction using droplet microfluidic technology constructing a photoresponsive microfluidic tandem reaction system. The method leverages a three-phase emulsion’s ‘two membranes and three phases’ structure to segregate incompatible reagents, and introduces a stimulating surfactant to control the structure of this emulsion structure for intelligent reaction sequence control, enablingefficient,orderlytandem reactionwithin the same system. Validating this concept, we applied the droplet microreactor to the condensation-reduction cascade reaction, as envisioned, incompatible condensation and reduction reactions, were coordinated by cycling the UV light on /off for a smooth cascade reaction. Compared to batch reaction, the droplet microreactor showed sixfold catalytic efficiency enhancement and > 99 % reaction selectivity. Our work offers novel insights into realizing intelligent cascade reactions.

Substrate access tunnel engineering of a Fe-type nitrile hydratase from Pseudomonas fluorescens ZJUT001 for substrate preference adjustment and catalytic performance enhancement

Substrate access tunnel engineering is a useful strategy for enzyme modification. In this study, we improved the catalytic performance of Fe-type Nitrile hydratase (Fe-type NHase) from Pseudomonas fluorescens ZJUT001 (PfNHase) by mutating residue Q86 at the entrance of the substrate access tunnel. The catalytic activity of the mutant PfNHase-αQ86W towards benzonitrile, 2-cyanopyridine, 3-cyanopyridine, and 4-hydroxybenzonitrile was enhanced by 9.35-, 3.30-, 6.55-, and 2.71-fold, respectively, compared to that of the wild-type PfNHase (PfNHase-WT). In addition, the mutant PfNHase-αQ86W showed a catalytic efficiency (kcat/Km) towards benzonitrile 17.32-fold higher than the PfNHase-WT. Interestingly, the substrate preference of PfNHase-αQ86W shifted from aliphatic nitriles to aromatic nitrile substrates. Our analysis delved into the structural changes that led to this altered substrate preference, highlighting an expanded entrance tunnel region, theenlarged substrate-binding pocket, and the increased hydrophobic interactions between the substrate and enzyme. Molecular dynamic simulations and dynamic cross-correlation Matrix (DCCM) further supported these findings, providing a comprehensive explanation for the enhanced catalytic activity towards aromatic nitrile substrates.