Catalytic Transition State Research Articles

U and Co Dual Single-Atom Doped MXene for Accelerating Electrocatalytic Hydrogen Evolution Activity.

A large amount of radioactive waste is accumulated in the process of nuclear fuel preparation, causing serious pollution to the environment and abundant depleted uranium resources to be abandoned. One of the key issues affecting the development of nuclear energy is how to make full use of depleted uranium resources efficiently. Here, U element with unique coordination mode of 5f electron is spacer bonded to transition metal with 3d orbit through the adsorption and anchoring effect of MXene, thus U and Co dual doped MXene catalyst is constructed along with the comprehensive utilization of depleted uranium resources. The as-prepared U-Co/MXene catalyst demonstrates excellent overpotential of only 184mV at -10mA cm-2 and excellent stability up to 150h, significantly surpassing the bare MXene substrate. Theoretical calculations indicate that the U and Co dual doping optimizes the electronic structure of MXene catalyst by forming the U-O-Co network, thereby improving the thermodynamics of H* adsorption during the catalytic transition state. This research opens up a new path for the recovery of depleted uranium resources and the development of functional actinide catalysts.

An in vitro experimental study on the interference of glyphosate on the urease enzyme

Purpose: Exposure to glyphosate is increasing due to the density of agricultural areas in Türkiye. In this study, the possible interference effect of glyphosate on urease, an enzyme that is frequently used in the diagnosis and follow-up of many diseases and in the measurement of urea in biological samples was examined. Materials and Methods: First, glyphosate was observed to have a negative interference in experiments using solutions of varying concentrations of urea. Second, blood samples were examined using the urease-glutamate dehydrogenase (GLDH) and indirect nesslerization procedures to determine the effects of glyphosate on the results before and after its addition. To determine the morphological and chemical alterations, scanning electron microscope (SEM) and Fourier-transform infrared spectroscopy (FTIR) analyses were conducted, and binding patterns were established through molecular docking. Urea measurements conducted with urease-GLDH and indirect nesslerization demonstrated a negative interference on the results with glyphosate concentrations of 10–3, 10–4, and 10–5 M. Results: Morphological changes observed in the SEM analysis were supported by the 3228.25 (O-H), 1642.08 (C=C), and 1531.20 (N-O) cm–1 bonds formed in the FTIR analysis. Furthermore, the molecular docking analysis showed that glyphosate affected the urease via hydrogen bonding (Gly13, Ser12, Lys14, Thr15, and Asp37) and hydrophobic interactions (Val10, Asp37, and Glu98). It was hypothesized that these interacting amino acids limit the accessibility of the urease’s active catalytic conformation and/or impact the stability of the catalytic transition state. Conclusion: Glyphosate leads to negative interference in human serum urea assays, leading to incorrect test results in clinical biochemistry, microbiology, and agricultural laboratories. This effect should be considered when conducting analysis, and clinicians as well as hospital information management systems should be informed ahead of time, with special emphasis devoted to this interference.

Synergistic Binding of ATP and Nucleic Acids Necessitates UPF1's ATPase Functional Cycle.

UPF1 is a core protein in the nonsense mRNA degradation (NMD) surveillance pathway that degrades aberrant mRNA. UPF1 has both ATPase and RNA helicase activities, but it exhibits mutually exclusive binding of ATP and RNA. This suggests intricate allosteric coupling between ATP and RNA binding that remains unresolved. In this study, we used molecular dynamics simulations and dynamic network analyses to probe the dynamics and free energy landscapes covering UPF1 crystal structures resolved in the Apo state, the ATP bound state, and the ATP-RNA bound (catalytic transition) state. Free energy calculations show that in the presence of ATP and RNA, the transition from the Apo state to the ATP bound state is an uphill process but becomes a downhill process when transitioning to the catalytic transition state. Allostery potential analyses reveal that the Apo and catalytic transition states are mutually allosterically activated toward each other, reflecting the intrinsic ATPase function of UPF1. The Apo state is also allosterically activated toward the ATP bound state. However, binding ATP alone leads to an allosterically trapped state that is difficult to revert to either the Apo or the catalytic transition state. The high allostery potential of Apo UPF1 toward different states results in a "first come, first served" mechanism that requires the synergistic binding of ATP and RNA to drive the ATPase cycle. Our results reconcile UPF1's ATPase and RNA helicase activities within an allostery framework and may apply to other SF1 helicases, as we demonstrate that UPF1's allostery signaling pathways prefer the RecA1 domain over the equally fold-conserved RecA2 domain, and this preference coincides with higher sequence conservation in the RecA1 domain across typical human SF1 helicases.

GAP positions catalytic H-Ras residue Q61 for GTP hydrolysis in molecular dynamics simulations, complicating chemical rescue of Ras deactivation

Functional interaction of Ras signaling proteins with upstream, negative regulatory GTPase activating proteins (GAPs) represents a crucial step in cellular decision making related to growth and survival. Key components of the catalytic transition state for Ras deactivation by GAP-accelerated hydrolysis of Ras-bound guanosine triphosphate (GTP) are thought to include an arginine residue from the GAP (the arginine finger), a glutamine residue from Ras (Q61), and a water molecule that is likely coordinated by Q61 to engage in nucleophilic attack on GTP. Here, we use in-vitro fluorescence experiments to show that 0.1–100 mM concentrations of free arginine, imidazole, and other small nitrogenous molecule fail to accelerate GTP hydrolysis, even in the presence of the catalytic domain of a mutant GAP lacking its arginine finger (R1276A NF1). This result is surprising given that imidazole can chemically rescue enzyme activity in arginine-to-alanine mutant protein tyrosine kinases (PTKs) that share many active site components with Ras/GAP complexes. Complementary all-atom molecular dynamics (MD) simulations reveal that an arginine finger GAP mutant still functions to enhance Ras Q61-GTP interaction, though less extensively than wild-type GAP. This increased Q61-GTP proximity may promote more frequent fluctuations into configurations that enable GTP hydrolysis as a component of the mechanism by which GAPs accelerate Ras deactivation in the face of arginine finger mutations. The failure of small molecule analogs of arginine to chemically rescue catalytic deactivation of Ras is consistent with the idea that the influence of the GAP goes beyond the simple provision of its arginine finger. However, the failure of chemical rescue in the presence of R1276A NF1 suggests that the GAPs arginine finger is either unsusceptible to rescue due to exquisite positioning or that it is involved in complex multivalent interactions. Therefore, in the context of oncogenic Ras proteins with mutations at codons 12 or 13 that inhibit arginine finger penetration toward GTP, drug-based chemical rescue of GTP hydrolysis may have bifunctional chemical/geometric requirements that are more difficult to satisfy than those that result from arginine-to-alanine mutations in other enzymes for which chemical rescue has been demonstrated.

Bimetallic tandem catalysis-enabled enantioselective cycloisomerization/carbonyl-ene reaction for construction of 5-oxazoylmethyl α-silyl alcohol.

A bimetallic tandem catalysis-enabled enantioselective cycloisomerization/carbonyl-ene reaction was developed. The reaction proceeded well with a broad range of N-propargylamides and acylsilanes, affording the target chiral 5-oxazoylmethyl α-silyl alcohols in up to 95% yield and 99% ee under mild conditions. Importantly, this facile protocol was available for the late-stage modification of several bioactive molecules. Based on the mechanistic study and control experiments, a possible catalytic cycle and transition state are proposed to elucidate the reaction process and enantioinduction.

Highly Efficient Visible-Light-Driven CO2-to-CO Conversion by Coordinatively Unsaturated Co-Salen Complexes in a Water-Containing System.

The development of cost-effective catalysts for CO2 reduction is highly desired but remains a significant challenge. The unsaturated coordination metal center in a catalyst is favorable for the process of catalytic CO2 reduction. In this paper, two asymmetric salen ligands were used to synthesize two coordinatively unsaturated Co-salen complexes. The two Co-salen complexes exhibit an unsaturated coordination pattern and display high activity and CO selectivity for visible-light-driven CO2 reduction in a water-containing system. The photocatalytic performance of 2 is higher than that of 1 because the reduction potential of the catalytic CoII center and the energy barrier of the catalytic transition states of 2 are lower than those of 1, with turnover numbers (TONCO), turnover frequencies (TOF), and CO selectivity values of 8640, 0.24 s-1, and 97% for 2, respectively. The photocatalytic reduction of CO2 to CO for 2 is well supported by control experiments and density functional theory (DFT) calculations.

Two silver(I) complexes: Synthesis, structures, and electrochemicalH2O2sensing

AbstractTwo new silver(I) complexes, formulated as [Ag2(L1)2](picrate)2(1), {[Ag2(L2)2(terephthalate)](C2H5OH)3(H2O)}n(2) (L1 = 1,3‐bis(2‐benzimidazyl)benzene, L2 = 1,3‐bis(1‐methylbenzimidazol‐2‐yl)‐2‐thiapropane), were synthesized and characterized by X‐ray crystallography, elemental analysis, infrared, and UV–Vis spectroscopy. The crystal analysis results showed that the complexes exhibited different structures: binuclear for1and one‐dimensional polymeric for2. Their Ag(I) centers displayed different coordination geometric structures: two‐coordinated linear in1, whereas four‐coordinated distorted tetrahedron in2. The electrochemical sensing performance of Ag(I) complexes modified carbon paste electrode (CPE‐1 and CPE‐2) toward hydrogen peroxide (H2O2) was evaluated by chronoamperometry in 0.2 M phosphate buffer saline (pH = 6) at −0.2 V. The CPE‐1 was found to have a wide linear response from 1.0 × 10−5to 4.0 × 10−3 M, lower detection limit of 1.73 μM, excellent anti‐interference ability, and stability. The CPE‐2 does not have recognition properties for H2O2, which may be due to the large steric hindrance around Ag(I) centers that is not easy to combine with H2O2to form a catalytic transition state. The above studies proved that Ag(I) complexes can be used as effective components of electrode materials for the electrochemical recognition of H2O2.

Synthesis, structure and electrochemical H2O2-sensing of two silver(I) complexes with bisbenzimidazole ligands

Two new binuclear Ag(I) complexes of the types, [Ag2(Mebba)2(fumarate)]·2C2H5OH (1) and [Ag2(Meobb)2(μ-Cl)2] (2) (Mebba = bis(N-methylbenzimidazol-2-ylmethyl) aniline, Meobb = 1,3-bis(N-ethyl-benzimidazol-2-yl)-2-oxopropan), have been synthesized and characterized. Structural analysis showed that silver(I) centre in two complexes were both four-coordinated distorted tetrahedron geometry, but their bridging modes are significantly different: bridged by the fumarate in complex 1, μ2-Cl monoatomic bridging in complex 2. The electrochemical sensing performances of carbon paste electrode modified with silver(I) complex 1 (CPE-1) and complex 2 (CPE-2) towards H2O2 were investigated by chronoamperometry in 0.2 M phosphate buffer solution (PBS, pH = 6) at −0.2 V. The CPE-1 exhibits a wide linear detection range from 0.5 μM to 4.0 mM and lower detection limit 0.61 μM with a relatively high sensitivity of 9.9935 µA/mM, and has excellent anti-interference ability and stability. There is not electrochemical H2O2-sensing performance for the CPE-2, which may be due to the fact that silver(I) ions and chloride ions form a more stable complex that is not easy to combine with hydrogen peroxide to form a catalytic transition state. The research results show that silver(I) complexes based on bisbenzimidazole ligands have the potential to become electrode materials.

Enantioselective Isocyanide-based Multicomponent Reaction with Alkylidene Malonates and Phenols.

A highly enantioselective isocyanide-based multicomponent reaction catalyzed by a chiral N,N'-dioxide/MgII complex was reported. A wide range of substrates were tolerated in this reaction, including alkyl- and aryl-substituted isocyanides with alkylidene malonates and various phenols, affording the corresponding phenoxyimidate products in good to excellent yields (up to 94% yield) with good to excellent enantioselectivities (up to 95.5:4.5 er). A catalytic cycle and transition state were proposed to rationalize the reaction process and enantiocontrol.

Loop Dynamics and Enzyme Catalysis in Protein Tyrosine Phosphatases.

Protein tyrosine phosphatases (PTPs) play an important role in cellular signaling and have been implicated in human cancers, diabetes, and obesity. Despite shared catalytic mechanisms and transition states for the chemical steps of catalysis, catalytic rates within the PTP family vary over several orders of magnitude. These rate differences have been implied to arise from differing conformational dynamics of the closure of a protein loop, the WPD-loop, which carries a catalytically critical residue. The present work reports computational studies of the human protein tyrosine phosphatase 1B (PTP1B) and YopH from Yersinia pestis, for which NMR has demonstrated a link between their respective rates of WPD-loop motion and catalysis rates, which differ by an order of magnitude. We have performed detailed structural analysis, both conventional and enhanced sampling simulations of their loop dynamics, as well as empirical valence bond simulations of the chemical step of catalysis. These analyses revealed the key residues and structural features responsible for these differences, as well as the residues and pathways that facilitate allosteric communication in these enzymes. Curiously, our wild-type YopH simulations also identify a catalytically incompetent hyper-open conformation of its WPD-loop, sampled as a rare event, previously only experimentally observed in YopH-based chimeras. The effect of differences within the WPD-loop and its neighboring loops on the modulation of loop dynamics, as revealed in this work, may provide a facile means for the family of PTP enzymes to respond to environmental changes and regulate their catalytic activities.

Catalytic Asymmetric Three-component Hydroacyloxylation/ 1,4-Conjugate Addition of Ynamides.

A highly enantioselective three-component hydroacyloxylation/1,4-conjugate addition of ortho-hydroxybenzyl alcohols, ynamides and carboxylic acids was developed under mild reaction conditions in the presence of a chiral N,N'-dioxide/Sc(OTf)3 complex, which went through in situ generated ortho-quinone methides with α-acyloxyenamides, delivering a range of corresponding chiral α-acyloxyenamides derivatives containing gem(1,1)-diaryl skeletons in moderate to good yields with excellent ee values. The scale-up experiment and further derivation showed the practicality of this catalytic system. In addition, a possible catalytic cycle and transition state model was proposed to elucidate the origin of the stereoselectivity based on X-ray crystal structure of the α-acyloxyenamide intermediate and product.

Catalytic asymmetric synthesis of 3,2'-pyrrolinyl spirooxindoles via conjugate addition/Schmidt-type rearrangement of vinyl azides and (E)-alkenyloxindoles.

A catalytic asymmetric conjugate addition/Schmidt-type rearrangement of vinyl azides and (E)-alkenyloxindoles was realized. It afforded a variety of optically active 3,2′-pyrrolinyl spirooxindoles with high yields (up to 98%), and excellent diastereo- and enantioselectivities (up to 98% ee, >19 : 1 dr), even at the gram-scale in the presence of a chiral N,N′-dioxide–nickel(ii) complex. In addition, a possible catalytic cycle and transition state model were proposed to rationalize the stereoselectivity.

An Unsymmetric Ligand with a N5O2 Donor Set and Its Corresponding Dizinc Complex: A Structural and Functional Phosphoesterase Model

AbstractInvited for the cover of this issue is Ebbe Nordlander from Lund University, Sweden. The cover image shows a dizinc complex that catalyzes phosphoester hydrolysis and the computed catalytic transition state with the depicted substrate.

Reaction Pathways and Microkinetic Modeling of n-Butane Oxidation to 1-Butanol on Cu, Cu3Pd, Pd, Ag3Pd, and PdZn (111) Surfaces

Density functional theory (DFT) calculations and microkinetic modeling are used to model reactions in the oxidation of n-butane to 1-butanol, 1-butanal, and 1-butene over pure metal and metal alloy (111) surfaces. Specifically, catalytic thermodynamic and kinetic energies are calculated with DFT, and linear scaling relationships are developed that link these values to simpler “descriptors” of catalytic activity. The scaling relationships are used in microkinetic modeling to identify the optimal descriptor values, which maximize the rate and selectivity to 1-butanol. Degree of rate control (DRC) analysis is performed to reveal the catalytic intermediates and transition states that have the greatest influence on the rate. The Cu3Pd(111) and Ag3Pd(111) surfaces are found to be the most active for n-butane oxidation to 1-butanol, with Cu3Pd additionally exhibiting high selectivity for 1-butanol. Achieving high activity and selectivity toward 1-butanol is found to require a precise balance of the catalyst affinity for OH* and O*, with catalysts that bind these species too strongly garnering large coverages of O*, which block active sites and inhibit the rate of n-butane conversion, and catalysts that bind these species too weakly promoting dehydrogenation of C4 species, as this process supplies H atoms that can convert OH* and O* to the more-stable H2O*. Catalytic affinity for C* is also found to have a significant impact on selectivity toward 1-butanol, since the formation energy of C* on catalyst surfaces is found to correlate to catalytic ability to break C–H bonds, with catalysts that bind C* too strongly tending to overdehydrogenate C4 species. The reaction C4H9* + O* ↔ C4H9O* + * is found to be rate-controlling on those catalysts that are most active for 1-butanol production.

Medium effect (water versus MeCN) on reactivity and reaction pathways for the SNAr reaction of 1-aryloxy-2,4-dinitrobenzenes with cyclic secondary amines

A kinetic study on SNAr reactions of 1-aryloxy-2,4-dinitrobenzenes (1a–1h) with a series of cyclic secondary amines in 80 mol% water – 20 mol% DMSO at 25.0 ± 0.1 °C is reported. The plots of kobsd versus amine concentration curve upward except for the reactions of substrates possessing a strong electron-withdrawing group in the leaving aryloxide with strongly basic piperidine. The curved plots indicate that the reactions proceed through both uncatalytic and catalytic routes. Linear Brønsted-type plots have been obtained for the uncatalyzed and catalyzed reactions of 1-(4-nitrophenoxy)-2,4-dinitrobenzene (1a) with βnuc = 0.84 and 0.78, respectively. The Yukawa–Tsuno plot for the uncatalyzed reactions of 1a–1h with piperidine results in an excellent linear correlation with ρ = 1.66 and r = 0.31. In contrast, rate constants for catalyzed reactions are independent of the electronic nature of the substituent in the leaving group. The current SNAr reactions have been proposed to proceed via a zwitterionic intermediate (MC±) that partitions to products through uncatalytic and catalytic routes. The catalyzed reaction from MC± has been concluded to proceed through a concerted mechanism with a six-membered cyclic transition state (TScycl) rather than via a stepwise pathway with a discrete anionic intermediate (MC−), the traditionally accepted mechanism. Medium effects on the reactivity and reaction mechanism are discussed. Particularly, hydrogen bonding of the amines to water precludes formation of kinetically significant dimers found in some aprotic solvents; no explicit role for water in the catalytic transition state is required or proposed. The specific stabilization of the leaving aryloxides substituted with strong electron-withdrawing groups accounts for the lack of the catalytic pathway in these systems (1a–1c) with piperidine nucleophile.

Binding of the Microbial Cyclic Tetrapeptide Trapoxin A to the Class I Histone Deacetylase HDAC8.

Trapoxin A is a microbial cyclic tetrapeptide that is an essentially irreversible inhibitor of class I histone deacetylases (HDACs). The inhibitory warhead is the α,β-epoxyketone side-chain of (2S,9S)-2-amino-8-oxo-9,10-epoxydecanoic acid (l-Aoe), which mimics the side-chain of the HDAC substrate acetyl-l-lysine. We now report the crystal structure of the HDAC8-trapoxin A complex at 1.24 Å resolution, revealing that the ketone moiety of l-Aoe undergoes nucleophilic attack to form a zinc-bound tetrahedral gem-diolate that mimics the tetrahedral intermediate and its flanking transition states in catalysis. Mass spectrometry, activity measurements, and isothermal titration calorimetry confirm that trapoxin A binds tightly (Kd = 3 ± 1 nM) and does not covalently modify the enzyme, so the epoxide moiety of l-Aoe remains intact. Comparison of the HDAC8-trapoxin A complex with the HDAC6-HC toxin complex provides new insight regarding the inhibitory potency of l-Aoe-containing natural products against class I and class II HDACs.

Insights into the Catalytic Mechanism and Transition State Stabilization of 5′‐Methylthioadenosine Nucleosidase using Neutron Crystallography

5′‐Methylthioadenosine nucleosidase (MTAN) is an obligatory homodimeric protein that catalyzes the hydrolysis of the N‐ribosidic bond of a variety of adenosine‐containing metabolites. The proposed catalytic mechanism of MTAN is initiated by D198 protonating the N7 position of the adenyl moiety, which consequently causes elongation and ultimate breaking of the N‐ribosidic bond, resulting in the formation of an oxocarbenium ion intermediate. Of particular interest is the pKa elevation of D198 that was proposed to have a value of 8.2, which is significantly higher than the theoretical pKa for an aspartic acid side chain. In this study we present the first joint X‐ray/neutron crystal structures of Helicobacter pylori MTAN (HpMTAN) in complex with a substrate (S‐adenosylhomocysteine), early (Formycin A) and late (p‐ClPh‐Thio‐DADMe‐ImmA) dissociative transition state analogues, as well as with the catalytic products (adenine and S‐ribosylhomocysteine). The solved X‐ray/neutron crystal structures provide the positions of exchangeable hydrogen atoms and protonation states of ionizable groups that further our understanding of the catalytic mechanism as well as the stabilization of the transition state for HpMTAN. These results confirm that the catalytic reaction is initiated by D198 functioning as a general acid through the observation of a shared deuterium atom with unconventional hydrogen bond geometry between the carboxylate group of D198 and the N7 position of adenine. Additionally, the transition state analogues neutron structures illustrate the minor differences in the hydrogen bond interactions resulting in the DADMe‐ImmA analogues being extremely potent inhibitors with Kd values in the picomolar range, despite HpMTAN shown to contain an early dissociative transition state structure.Support or Funding InformationThis work was supported by the Center for the Advancement of Science in Space via a cooperative agreement with National Aeronautics and Space Administration Grant N‐123528‐01 (to D.R.R) and by National Institute of Allergy and Infectious Disease/NIH Grant AI105084 (to D.R.R.).

In Silico Studies of Small Molecule Interactions with Enzymes Reveal Aspects of Catalytic Function.

Small molecules, such as solvent, substrate, and cofactor molecules, are key players in enzyme catalysis. Computational methods are powerful tools for exploring the dynamics and thermodynamics of these small molecules as they participate in or contribute to enzymatic processes. In-depth knowledge of how small molecule interactions and dynamics influence protein conformational dynamics and function is critical for progress in the field of enzyme catalysis. Although numerous computational studies have focused on enzyme–substrate complexes to gain insight into catalytic mechanisms, transition states and reaction rates, the dynamics of solvents, substrates, and cofactors are generally less well studied. Also, solvent dynamics within the biomolecular solvation layer play an important part in enzyme catalysis, but a full understanding of its role is hampered by its complexity. Moreover, passive substrate transport has been identified in certain enzymes, and the underlying principles of molecular recognition are an area of active investigation. Enzymes are highly dynamic entities that undergo different conformational changes, which range from side chain rearrangement of a residue to larger-scale conformational dynamics involving domains. These events may happen nearby or far away from the catalytic site, and may occur on different time scales, yet many are related to biological and catalytic function. Computational studies, primarily molecular dynamics (MD) simulations, provide atomistic-level insight and site-specific information on small molecule interactions, and their role in conformational pre-reorganization and dynamics in enzyme catalysis. The review is focused on MD simulation studies of small molecule interactions and dynamics to characterize and comprehend protein dynamics and function in catalyzed reactions. Experimental and theoretical methods available to complement and expand insight from MD simulations are discussed briefly.

Structure of protein O-mannose kinase reveals a unique active site architecture.

The 'pseudokinase' SgK196 is a protein O-mannose kinase (POMK) that catalyzes an essential phosphorylation step during biosynthesis of the laminin-binding glycan on α-dystroglycan. However, the catalytic mechanism underlying this activity remains elusive. Here we present the crystal structure of Danio rerio POMK in complex with Mg2+ ions, ADP, aluminum fluoride, and the GalNAc-β3-GlcNAc-β4-Man trisaccharide substrate, thereby providing a snapshot of the catalytic transition state of this unusual kinase. The active site of POMK is established by residues located in non-canonical positions and is stabilized by a disulfide bridge. GalNAc-β3-GlcNAc-β4-Man is recognized by a surface groove, and the GalNAc-β3-GlcNAc moiety mediates the majority of interactions with POMK. Expression of various POMK mutants in POMK knockout cells further validated the functional requirements of critical residues. Our results provide important insights into the ability of POMK to function specifically as a glycan kinase, and highlight the structural diversity of the human kinome.

Effective cleavage of phosphodiester promoted by the zinc(II) and copper(II) inclusion complexes of β-cyclodextrin

To construct the model of metallohydrolase, two inclusion complexes [MLCl2(β-CD)] (1, M=Zn(II); 2, M=Cu(II); L=N,N′-bis(2-pyridylmethyl)amantadine; β-CD=β-cyclodextrin) were synthesized by mixing β-CDs with the pre-synthesized complexes G1, [ZnLCl2] and G2, [CuLCl2]. Structures of G1, G2, 1 and 2 were characterized by X-ray crystallography, respectively. In solution, two chloride anions of G1 and G2 underwent ligand exchange with solvent molecules according to ESI-MS analysis. The chemical equilibrium constants were determined by potentiometric pH titration. The kinetics of bis(4-nitrophenyl) phosphate (BNPP) hydrolysis catalyzed by G1, G2, 1 and 2 were examined at pHs ranging from 7.50 to 10.50 at 308±0.1K. The pH profile of rate constant of BNPP hydrolysis catalyzed by 1 exhibited an exponential increase with the second-order rate constant of 2.68×10−3M−1s−1 assigned to the di-hydroxo species, which was approximately an order of magnitude higher than those of reported mono-Zn(II)-hydroxo species. The high reactivity was presumably hydroxyl-rich microenvironment provided by β-CDs, which might effect in stabilizing either the labile zinc-hydroxo species or the catalytic transition state.