Mechanism Of Cleavage Research Articles

Engineered receptors for soluble cellular communication and disease sensing.

Despite recent advances in mammalian synthetic biology, there remains a lack of modular synthetic receptors that can robustly respond to soluble ligands and in turn activate bespoke cellular functions. Such receptors would have extensive clinical potential to regulate the activity of engineered therapeutic cells, but to date only receptors against cell surface targets have approached clinical translation1. To address this gap, we developed a receptor architecture called synthetic intramembrane proteolysis receptor (SNIPR), that has the added ability to be activated by soluble ligands, both natural and synthetic, with remarkably low baseline activity and high fold activation, through an endocytic, pH-dependent cleavage mechanism. We demonstrate the therapeutic capabilities of the receptor platform by localizing the activity of CAR T cells to solid tumors where soluble disease-associated factors are expressed, bypassing the major hurdle of on-target off-tumor toxicity in bystander organs. We further applied the SNIPR platform to engineer fully synthetic signaling networks between cells orthogonal to natural signaling pathways, expanding the scope of synthetic biology. Our design framework enables cellular communication and environmental interactions, extending the capabilities of synthetic cellular networking in clinical and research contexts.

Assessment on the rings cleavage mechanism of polycyclic aromatic hydrocarbons in supercritical water: A ReaxFF molecular dynamics study

The ring opening reaction of polycyclic aromatic hydrocarbons (PAHs) is one of the rate-determining steps of coal gasification within supercritical water, while the involvement of water remains debated between addition and hydrogen abstraction theories. In this study, reactive molecular dynamics (MD) simulations were performed to explore the ring opening reaction of naphthalene, the simplest PAH, at temperatures of 2500–2700 K. Species and elementary reactions were quantitatively extracted from bond order trajectories using an in-house program. Reaction path analysis shows that ring opening paths of naphthalene mainly include thermolysis, H˙ atom abstraction, and O˙H radical addition. Flux analysis indicates O˙H radical largely from the H˙ + ▪ = O˙H + ▪ reaction, while the water dissociation ▪ = O˙H + H˙ reaction is near equilibrium, seldom contributing to the O˙H source. This atomistic kinetics analysis is intended to help the modeling of supercritical water gasification of coal.

Oxophilic Sn to promote glucose oxidation to formic acid in Ni nanoparticles.

The electrochemical glucose oxidation reaction (GOR) presents an opportunity to produce hydrogen and high-value chemical products. Herein, we investigate the effect of Sn in Ni nanoparticles for the GOR to formic acid (FA). Electrochemical results show that the maximum activity is related to the amount of Ni, as Ni sites are responsible for catalyzing GOR via the NiOOH/Ni(OH)2 pair. However, the GOR kinetics increases with the amount of Sn, associated with an enhancement of the OH- supply to the catalyst surface for Ni(OH)2 reoxidation to NiOOH. NiSn nanoparticles supported on carbon nanotubes (NiSn/CNT) exhibit excellent current densities and direct GOR via C-C cleavage mechanism, obtaining FA with a Faradaic efficiency (FE) of 93% at 1.45 V vs. reversible hydrogen electrode. GOR selectivity is further studied by varying the applied potential, glucose concentration, reaction time, and temperature. FE toward FA production decreases due to formic overoxidation to carbonates at low glucose concentrations and high applied potentials, while acetic and lactic acids are obtained with high selectivity at high glucose concentrations and 55 °C. Density functional theory calculations show that the SnO2 facilitates the adsorption of glucose on the surface of Ni and promotes the formation of the catalytic active Ni3+ species.

Mechanism of Nucleic Acid Phosphodiester Bond Cleavage by Human Endonuclease V: MD and QM/MM Calculations Reveal a Versatile Metal Dependence.

Human endonuclease V (EndoV) catalytically removes deaminated nucleobases by cleaving the phosphodiester bond as part of RNA metabolism. Despite being implicated in several diseases (cancers, cardiovascular diseases, and neurological disorders) and potentially being a useful tool in biotechnology, details of the human EndoV catalytic pathway remain unclear due to limited experimental information beyond a crystal structure of the apoenzyme and select mutational data. Since a mechanistic understanding is critical for further deciphering the central roles and expanding applications of human EndoV in medicine and biotechnology, molecular dynamics (MD) simulations and quantum mechanics/molecular mechanics (QM/MM) calculations were used to unveil the atomistic details of the catalytic pathway. Due to controversies surrounding the number of metals required for nuclease activity, enzyme-substrate models with different numbers of active site metals and various metal-substrate binding configurations were built based on structural data for other nucleases. Subsequent MD simulations revealed the structure and stability of the human EndoV-substrate complex for a range of active site metal binding architectures. Four unique pathways were then characterized using QM/MM that vary in metal number (one versus two) and modes of substrate coordination [direct versus indirect (water-mediated)], with several mechanisms being fully consistent with experimental structural, kinetic, and mutational data for related nucleases, including members of the EndoV family. Beyond uncovering key roles for several active site amino acids (D240 and K155), our calculations highlight that while one metal is essential for human EndoV activity, the enzyme can benefit from using two metals due to the presence of two suitable metal binding sites. By directly comparing one- versus two-metal-mediated P-O bond cleavage reactions within the confines of the same active site, our work brings a fresh perspective to the "number of metals" controversy.

Mechanism of enterovirus VP0 maturation cleavage based on the structure of a stabilised assembly intermediate.

Molecular details of genome packaging are little understood for the majority of viruses. In enteroviruses (EVs), cleavage of the structural protein VP0 into VP4 and VP2 is initiated by the incorporation of RNA into the assembling virion and is essential for infectivity. We have applied a combination of bioinformatic, molecular and structural approaches to generate the first high-resolution structure of an intermediate in the assembly pathway, termed a provirion, which contains RNA and intact VP0. We have demonstrated an essential role of VP0 E096 in VP0 cleavage independent of RNA encapsidation and generated a new model of capsid maturation, supported by bioinformatic analysis. This provides a molecular basis for RNA-dependence, where RNA induces conformational changes required for VP0 maturation, but that RNA packaging itself is not sufficient to induce maturation. These data have implications for understanding production of infectious virions and potential relevance for future vaccine and antiviral drug design.

Entropy-driven amplification reaction and the CRISPR/Cas12a system form the basis of an electrochemical biosensor for E.coli-specific detection

We present an innovative biosensor designed for the precise identification of Escherichia coli (E.coli), a predominant pathogen responsible for gastrointestinal infections. E.coli is prevalent in environments characterized by substandard water quality and can lead to severe diarrhea, especially in hospital settings. The device employs entropy-driven reactions to synthesize copious amounts of double-stranded DNA (dsDNA), which, upon binding with crRNA, triggers the CRISPR/Cas12a system’s cleavage mechanism. This process results in the separation of a ferrocene (Fc)-tagged DNA strand from the electrode, enhancing the electrochemical signal for E.coli’s rapid and accurate detection. Our tests confirm the biosensor’s ability to quantify E.coli across a dynamic range from 100 to 10 million CFU/mL, achieving a detection threshold of just over 5 CFU/mL. The development of this electrochemical biosensor highlights its exceptional selectivity, high sensitivity, and user-friendly interface for E.coli detection. It stands as a significant step forward in pathogen detection technology, promising new directions for identifying various bacterial infections through the CRISPR/Cas mechanism.

Structural insights into the diversity and DNA cleavage mechanism of Fanzor

Fanzor (Fz) is an ωRNA-guided endonuclease extensively found throughout the eukaryotic domain with unique gene editing potential. Here, we describe the structures of Fzs from three different organisms. We find that Fzs share a common ωRNA interaction interface, regardless of the length of the ωRNA, which varies considerably across species. The analysis also reveals Fz's mode of DNA recognition and unwinding capabilities as well as the presence of a non-canonical catalytic site. The structures demonstrate how protein conformations of Fz shift to allow the binding of double-stranded DNA to the active site within the R-loop. Mechanistically, examination of structures in different states shows that the conformation of the lid loop on the RuvC domain is controlled by the formation of the guide/DNA heteroduplex, regulating the activation of nuclease and DNA double-stranded displacement at the single cleavage site. Our findings clarify the mechanism of Fz, establishing a foundation for engineering efforts.

An Insight into the Mechanism of DNA Cleavage by DNA Endonuclease from the Hyperthermophilic Archaeon Pyrococcus furiosus.

Hyperthermophilic archaea such as Pyrococcus furiosus survive under very aggressive environmental conditions by occupying niches inaccessible to representatives of other domains of life. The ability to survive such severe living conditions must be ensured by extraordinarily efficient mechanisms of DNA processing, including repair. Therefore, in this study, we compared kinetics of conformational changes of DNA Endonuclease Q from P. furiosus during its interaction with various DNA substrates containing an analog of an apurinic/apyrimidinic site (F-site), hypoxanthine, uracil, 5,6-dihydrouracil, the α-anomer of adenosine, or 1,N6-ethenoadenosine. Our examination of DNA cleavage activity and fluorescence time courses characterizing conformational changes of the dye-labeled DNA substrates during the interaction with EndoQ revealed that the enzyme induces multiple conformational changes of DNA in the course of binding. Moreover, the obtained data suggested that the formation of the enzyme-substrate complex can proceed through dissimilar kinetic pathways, resulting in different types of DNA conformational changes, which probably allow the enzyme to perform its biological function at an extreme temperature.

A Theoretical Exploration of the Photoinduced Breaking Mechanism of the Glycosidic Bond in Thymine Nucleotide.

DNA glycosidic bond cleavage may induce cancer under the ultraviolet (UV) effect. Yet, the mechanism of glycosidic bond cleavage remains unclear and requires more detailed clarification. Herein, quantum chemical studies on its photoinduced mechanism are performed using a 5'-thymidine monophosphate (5'-dTMPH) model. In this study, four possible paths were examined to study the glycosidic bond cleavage. The results showed that, upon excitation, the electronic transition from the π bonding to π antibonding orbitals of the thymine ring leads to the damage of the thymine ring. Afterwards, the glycosidic bond is cleaved. At first, the doublet ground state (GS) path of glycosidic bond cleavage widely studied by other groups is caused by free electron generated by photoirradiation, with a kinetically feasible energy barrier of ~23 kcal/mol. Additionally, then, the other three paths were proposed that also might cause the glycosidic bond cleavage. The first one is the doublet excited state (ES) path, triggered by free electron along with UV excitation, which can result in a very-high-energy barrier ~49 kcal/mol that is kinetically unfavorable. The second one is the singlet ES path, induced by direct UV excitation, which assumes DNA is directly excited by UV light, which features a very low-energy barrier ~16 kcal/mol that is favored in kinetics. The third one is the triplet ES path, from the singlet state via intersystem crossing (ISC), which refers to a feasible ~27 kcal/mol energy barrier. This study emphasizes the pivotal role of the DNA glycosidic bond cleavage by our proposed direct UV excitation (especially singlet ES path) in addition to the authorized indirect free-electron-induced path, which should provide essential insights to future mechanistic comprehension and novel anti-cancer drug design.

Synthesis of a Palladium Dimer Supported by a C-Bound Trifluoroacetonate Bridge Formed by Cleavage of a Hexafluoroacetylacetonate Ligand.

Palladium(II) hexafluoroacetylacetonate (Pd(Hfacac)2) is known to form adducts of bases, such as lutidine (2,6-dimethylpyridine). When treated with approximately 3 equiv of lutidine, Pd(Hfacac)2 yields a 1:1 complex as reported in the literature, Pd(O,O-Hfacac)(C-Hfacac)(lutidine), 1. However, when the amount of excess lutidine is increased, a new complex, 2, is formed. A single-crystal X-ray structure of 2 proves it is a rare example of a dimeric palladium complex containing two Pd(Hfacac)(lutidine) fragments bridged by a dianionic trifluoroacetonate ligand, μ-CHC(O)CF3. The formation of 2 is accompanied by a white precipitate determined to be a mixture of trans-Pd(O2CCF3)2(lutidine)2 (3), confirming the fate of the missing trifluoroacetate fragment from the cleavage of the Hfacac ligand, and [lutidinium][Hfacac] (4). Subsequent experiments revealed the determinative role that water played in this reaction. The mechanism of cleavage of the Hfacac ligand was explored by DFT methods.

Mechanisms for HNH-mediated target DNA cleavage in type I CRISPR-Cas systems

The metagenome-derived type I-E and type I-F variant CRISPR-associated complex for antiviral defense (Cascade) complexes, fused with HNH domains, precisely cleave target DNA, representing recently identified genome editing tools. However, the underlying working mechanisms remain unknown. Here, structures of type I-FHNH and I-EHNH Cascade complexes at different states are reported. In type I-FHNH Cascade, Cas8fHNH loosely attaches to Cascade head and is adjacent to the 5' end of the target single-stranded DNA (ssDNA). Formation of the full R-loop drives the Cascade head to move outward, allowing Cas8fHNH to detach and rotate ∼150° to accommodate target ssDNA for cleavage. In type I-EHNH Cascade, Cas5eHNH domain is adjacent to the 5' end of the target ssDNA. Full crRNA-target pairing drives the lift of the Cascade head, widening the substrate channel for target ssDNA entrance. Altogether, these analyses into both complexes revealed that crRNA-guided positioning of target DNA and target DNA-induced HNH unlocking are two key factors for their site-specific cleavage of target DNA.

Investigations on cleavage fracture mechanism and surface damage of indium phosphide by molecular dynamics simulation

The quality and undamaged size in the resonant cavity surface directly affect the operational stability and output power of semiconductor lasers. To meet the demand for large-size and high-quality mirror facets, a deep understanding of fracture mechanisms of mechanical cleavage is essential. Nevertheless, 3D models of cleavage fracture are rarely investigated. In this work, a molecular dynamics study on the cleavage mechanisms of indium phosphide is reported through examining the effects of the cleavage gap, scratch depth, and cleavage rate on the cleavage damage morphology. The proposed molecular dynamics approach provides insights into the details of cleavage fracture at the atomic level. The simulation results reveal that the cleavage fracture mechanism includes the deviation of cracks between adjacent cleavage surfaces. The predominant damage manifestations on the cleavage surfaces are mainly characterized by cleavage terraces that begin at the bottom of the scratched groove. The cleavage terraces propagate along the [001] crystal direction on the (110) cleavage surface and deviate from their path. This phenomenon is essentially related to the stress released during the crack propagation process. Compared with the cleavage gap and scratch depth, the cleavage rate significantly affects the critical cleavage load. Additionally, a good correlation between the density of the cleavage terraces and the maximum undamaged length is achieved and reasonably explained. Mastering the correlation between various cleavage conditions and cleavage surface damage will facilitate and guide the fabrication of nanoscale resonant cavity mirrors and advance the development of mechanical cleaving processes.

DFT study on the depolymerization of PET by Ca-catalyzed glycolysis reaction model

Poly(ethylene terephthalate) (PET) is the most common plastics produced for applications in food and drinking containers. It is degraded to valuable product by several methods. Glycolysis of PET gains bis(2-hydroxyethylene) terephthalate (BHET) as the main product utilized as plasticizer. Calcium catalysts, Ca2+ and Ca(OH)2∙2H2O were explored to study the mechanism of PET cleavage by DFT calculations at B3LYP/6-311++G** level. Two possible pathways, coordination, and non-coordination of ethylene glycol on the calcium in glycolysis reaction, have been investigated. In addition, poly(ethylene furanoate) (PEF), considered as a sustainable polymer with the similar functional properties, was chose for the comparison of conformational structures with PET. The understanding of the relationship between PET (and PEF) structures and calcium catalysts is useful for the future development of linear sustainable polyesters.

High-Efficiency Degradation of PET Plastics by Glutathione S-Transferase under Mild Conditions.

Plastic pollution is a significant environmental concern globally. Plastics are normally considered chemically inert and resistant to biodegradation. Although many papers have reported enzyme-induced biodegradation of plastics, these studies are primarily limited to enzymes of microbial origin or engineered enzymes. This study reveals that poly(ethylene terephthalate) (PET, ∼6000 Da and 100 kDa) particles and plastic bottle debris (PBD, 24.9 kDa) can be efficiently degraded by a mammal-origin natural phase II metabolic isozyme, glutathione S-transferase (GST), under mild conditions. The degradation efficiency of PET plastics reached 98.9%, with a degradation rate of 2.6 g·L-1·h-1 under ambient or physiological conditions at 1 atm. PET plastics can be degraded by GST with varying environmental or biological factors (i.e., temperature, light irradiation, pH, and presence of humic acid or protein). We suggest a novel mechanism for PET degradation other than hydrolysis, i.e., the mechanism of cleavage and release of PET plastic monomers via nitridation and oxidation. This finding also reveals a novel function of GST, previously thought to only degrade small molecules (<1000 Da). This method has been successfully applied in real human serum samples. Additionally, we have tested and confirmed the ability to degrade PET of a mammal-origin natural digestive enzyme (trypsin) and a human-derived natural metabolic enzyme (CYP450). Overall, our findings provide a potential new route to plastic pollution control and contribute to our understanding of the metabolism and fate of plastics in organisms.

Two-metal ion mechanism of DNA cleavage by activated, filamentous SgrAI

Enzymes that form filamentous assemblies with modulated enzymatic activities have gained increasing attention in recent years. SgrAI is a sequence specific type II restriction endonuclease that forms polymeric filaments with accelerated DNA cleavage activity and expanded DNA sequence specificity. Prior studies have suggested a mechanistic model linking the structural changes accompanying SgrAI filamentation to its accelerated DNA cleavage activity. In this model, the conformational changes that are specific to filamentous SgrAI maximize contacts between different copies of the enzyme within the filament and create a second divalent cation binding site in each subunit, which in turn facilitates the DNA cleavage reaction. However, our understanding of the atomic mechanism of catalysis is incomplete. Herein, we present two new structures of filamentous SgrAI solved using cryo-electron microscopy (cryo-EM). The first structure, resolved to 3.3 Å, is of filamentous SgrAI containing an active site mutation that is designed to stall the DNA cleavage reaction, which reveals the enzymatic configuration prior to DNA cleavage. The second structure, resolved to 3.1 Å, is of WT filamentous SgrAI containing cleaved substrate DNA, which reveals the enzymatic configuration at the end of the enzymatic cleavage reaction. Both structures contain the phosphate moiety at the cleavage site and the biologically relevant divalent cation cofactor Mg2+ and define how the Mg2+ cation reconfigures during enzymatic catalysis. The data support a model for the activation mechanism that involves binding of a second Mg2+ in the SgrAI active site as a direct result of filamentation induced conformational changes.

Cumulative phylogenetic, sequence and structural analysis of Insulin superfamily proteins provide unique structure-function insights.

The insulin superfamily proteins (ISPs), in particular, insulin, IGFs and relaxin proteins are key modulators of animal physiology. They are known to have evolved from the same ancestral gene and have diverged into proteins with varied sequences and distinct functions, but maintain a similar structural architecture stabilized by highly conserved disulphide bridges. The recent surge of sequence data and the structures of these proteins prompted a need for a comprehensive analysis, which connects the evolution of these sequences (427 sequences) in the light of available functional and structural information including representative complex structures of ISPs with their cognate receptors. This study reveals (a) unusually high sequence conservation of IGFs (>90 % conservation in 184 sequences) and provides a possible structure-based rationale for such high sequence conservation; (b) provides an updated definition of the receptor-binding signature motif of the functionally diverse relaxin family members (c) provides a probable non-canonical C-peptide cleavage site in a few insulin sequences. The high conservation of IGFs appears to represent a classic case of resistance to sequence diversity exerted by physiologically important interactions with multiple partners. We also propose a probable mechanism for C-peptide cleavage in a few distinct insulin sequences and redefine the receptor-binding signature motif of the relaxin family. Lastly, we provide a basis for minimally modified insulin mutants with potential therapeutic application, inspired by concomitant changes observed in other insulin superfamily protein members supported by molecular dynamics simulation.

Unravelling the role of silver in addressing the nitrate radical induced photocatalytic oxidation of olefins to epoxides or carbonyl compounds

Nitrate radicals possess the unique capability to add to unsaturated bonds, leading to the formation of carbon-centred radicals evolving to organic compounds, which cannot be achieved through more common reactive oxygen centred species. Therefore, the possibility of generating nitrate radicals through heterogeneous photocatalysis endows this technology with unprecedented possibilities in the field of green organic synthesis. In particular, previous research showcased the promising potential of nitrate radicals in selectively conducting the photocatalytic oxidative cleavage of limonene to limononaldehyde. However, the role of silver ions, required for the reaction to occur, remained uncertain. This study aims at elucidating the role of silver in determining conversion of limonene and selectivity towards the corresponding oxidized compounds. In particular, it has been demonstrated that silver ions efficiently scavenge photogenerated electrons, thus making molecular oxygen available for the nitrate radical induced production of limononaldehyde, obtained with selectivity values up to 60%. In this study it is shown that, nitrate radical formation is as well boosted by silver nanoparticles, in the absence of silver ions. However, in this case, the consequent oxidation of limonene produced both 1,2-limonene epoxide and limononaldehyde. Notably, in the absence of silver ions, molecular oxygen is the main electron scavenger and its lower availability for the oxidative cleavage mechanism addresses the reaction towards the epoxide. Ab initio calculations, confirmed this hypothesis, showing that, while formation of limononaldehyde is thermodynamically and kinetically favoured, formation of the epoxide is kinetically limited. Therefore, its formation takes place when the formation of limononaldehyde is hindered by factors such as the reduced availability of molecular oxygen. The identification of key parameters governing the process offers possibilities to tune the selectivity of the reaction towards oxidative cleavage or epoxidation. Moreover, it allows to further optimize this reaction, which may become an appealing and versatile method of chemicals green synthesis.

Tailored MgAl2O4 supported Ru catalyst for selective C–O bond cleavage in diphenyl ether hydrogenolysis

The direct cleavage of C−O bonds in lignin and its derivatives via hydrogenolysis is an essential reaction process for lignin conversion. Herein, we design a MgAl2O4 supported Ru catalyst using a facile and green method involving ball milling and microwave heating. The optimal catalyst, 0.5Ru/MgAl2O4, displayed enhanced catalytic performance for 4−O−5 linkage scission compared to 0.5Ru/Al2O3 and 0.5Ru/MgO, achieving a tuenover frequency of 352.9 h−1 for diphenyl ether (DPE) conversion. 0.5Ru/MgAl2O4 with low Ru loading achieved complete conversion of DPE, with 43.8% yield of cyclohexane (CHE) and 42.6% yield of cyclohexanol (CHL) after 2 h at 160 °C and 1.5 MPa H2. The promising catalytic activity can be attributed to the abundant electron-rich Ru0 species with high dispersion formed on MgAl2O4, derived from the strong electron transfer from the support to Ru. The reaction mechanism for the direct cleavage of the 4−O−5 bond, followed by phenyl ring hydrogenation, was confirmed by rigorous experiments. This work provides an inspiring idea for developing efficient heterogeneous catalysts for the utilization of lignin resources via hydrogenolysis.

MOC1 cleaves Holliday junctions through a cooperative nick and counter-nick mechanism mediated by metal ions

Holliday junction resolution is a crucial process in homologous recombination and DNA double-strand break repair. Complete Holliday junction resolution requires two stepwise incisions across the center of the junction, but the precise mechanism of metal ion-catalyzed Holliday junction cleavage remains elusive. Here, we perform a metal ion-triggered catalysis in crystals to investigate the mechanism of Holliday junction cleavage by MOC1. We capture the structures of MOC1 in complex with a nicked Holliday junction at various catalytic states, including the ground state, the one-metal ion binding state, and the two-metal ion binding state. Moreover, we also identify a third metal ion that may aid in the nucleophilic attack on the scissile phosphate. Further structural and biochemical analyses reveal a metal ion-mediated allosteric regulation between the two active sites, contributing to the enhancement of the second strand cleavage following the first strand cleavage, as well as the precise symmetric cleavage across the Holliday junction. Our work provides insights into the mechanism of metal ion-catalyzed Holliday junction resolution by MOC1, with implications for understanding how cells preserve genome integrity during the Holliday junction resolution phase.

Effect of loading different transition metals W, Pt and Pd monolayers on quinoline hydrogenation and C–N bond cleavage over Mo2C(001)

Nitrogen-containing compounds such as quinoline in coal-based crude oils cause environmental pollution in the course of application. Consequently, dealing with the nitrogen-containing compounds from coal-based crude oil is of paramount importance. The hydrogenation and CN bond cleavage mechanisms of quinoline on the active Mo-terminated over Mo2C(001) surface, as well as on surfaces doped with W, Pt and Pd monolayers, were examined employing the density functional theory (DFT) method. The Pd and Pt-doped catalysts exhibited higher hydrogenation activity. The catalytic efficiency is enhanced by the loading of different metals, particularly with d-band center further away from the Fermi energy level. Additionally, a novel CN bond cleavage mechanism for quinoline has been proposed. The new proposed mechanism is more conducive for the CN bond cleavage. After a thorough comparison, the Pd-loaded catalyst was identified as the most effective for quinoline hydrogenation and CN bond cleavage.