Active Site Model Research Articles

Computational Investigation of the Role of Metal Center Identity in Cytochrome P450 Enzyme Model Reactivity.

Mononuclear Fe enzymes such as heme-containing cytochrome P450 enzymes catalyze a variety of C-H activation reactions under ambient conditions, and they represent an attractive platform for engineering reactivity through changes to the native enzyme. Using density functional theory, we study both native Fe and non-native group 8 (Ru, Os) and group 9 (Ir) metal centers in an active site model of P450. We quantify how changing the metal changes spin state preferences throughout the catalytic cycle. Our calculations reveal an intermediate-spin ground state for all Fe intermediates while the heavier metals prefer low-spin ground states across most intermediates in the reaction cycle. We also study the rate-determining hydrogen atom transfer (HAT) step and the subsequent rebound step. We observe comparable HAT barriers for Fe and Ru, a much higher barrier for Os, and the lowest HAT barrier for Ir. Rebound steps are barrierless for all metals, and the rebound intermediate for Fe is most significantly stabilized. Examination of ground spin states of all intermediates in the reaction cycle reveals spin-allowed pathways for the group 8 metals and spin-forbidden energetics for the group 9 Ir with potential two-state reactivity. Our work highlights the differences between the group 8 metals and the group 9 Ir, and it suggests that engineered P450 enzymes with Ru in particular result in improved enzyme reactivity toward C-H hydroxylation.

The Effect of Chalcogen-Chalcogen Bond Formation in the New Delhi Metallo-β-Lactamase 1 Enzyme to Counteract Antibiotic Resistance.

New Delhi metallo-β-lactamase 1 (NDM-1) is an enzyme involved in the drug resistance of many bacteria against most of the widely adopted antibiotics, such as penicillins, cephalosporins, and carbapenems. Consequently, inhibiting NDM-1 swiftly has gained significant interest as a strategy to counteract this bacterial defense mechanism, thereby restoring the effectiveness of antibiotics. Among the inhibitors tested against the enzyme, ebselen (EbSe) showed particularly promising results. This molecule, renowned for its numerous benefits to the human body, targets the enzyme's active site at Cys208 with its selenium atom, facilitating the expulsion of the catalytic zinc ion from the active pocket. Since the inhibitory mechanism of EbSe remains poorly understood, gaining detailed information about it is highly desirable. In the present work, density functional theory calculations and μs-long molecular dynamics simulations are carried out to investigate the reaction mechanism of EbSe with NDM-1, unveiling the structural implications of the inhibition. A large model of the NDM-1 active site is built to investigate the different mechanistic proposals for the SeEbSe-SCys208 bond formation. Deeper insights into Lys211 are also provided to consolidate its role during the inhibition process. Furthermore, the chemical reaction with the ebsulfur (EbS) molecule is also investigated to compare its behavior with that of the periodic relative selenium. Molecular dynamics simulations, besides evidencing the role of the L3 and L10 loops in the occurrence of the inhibition, corroborate the Zn ion release from the active site as a result of the complete disruption of its coordination sphere caused by the creation of the SeEbSe-SCys208 covalent bond.

Computational screening of transition metal-nitrogen-carbon materials as electrocatalysts for CO2 reduction

Atomically dispersed M-N-C catalysts are a promising, cost-effective class of materials for reducing CO2 to value-added products through the CO2 reduction reaction (CO2RR). However, complex multi-objective optimization of several properties including catalyst stability, activity, and selectivity for target products are necessary to make CO2RR more efficient with this class of catalysts. We systematically investigate activity and selectivity for carbon monoxide, formic acid, and hydrogen evolution pathways on model M-N4C10 active sites for 26 transition metal species. Our work shows that under acidic conditions, all the considered M-N4C10 sites except M=Fe, Co, Cr, Cd, and Pt should have CO2RR onset potentials lower than the hydrogen evolution reaction. We identify the transition metal active sites that should catalyze the CO pathway, leading to gaseous CO production, CO poisoning, or reduction to further products. To understand the reasons for predicted activity and selectivity, we furthermore correlate atomic features for the transition metals with the calculated onset potential of each pathway, showing moderate correlation between both electronegativity and atomic radii with the CO2RR onset potentials. The high-throughput and feature-based approach in this work not only serves as a guide for present experimental efforts but can also serve as a starting point for machine learning efforts to accelerate active site modeling and catalyst discovery.

Electric fields imbue enzyme reactivity by aligning active site fragment orbitals

It is broadly recognized that intramolecular electric fields, produced by the protein scaffold and acting on the active site, facilitate enzymatic catalysis. This field effect can be described by several theoretical models, each of which is intuitive to varying degrees. In this contribution, we show that a fundamental effect of electric fields is to generate electrostatic potentials that facilitate the energetic alignment of reactant frontier orbitals. We apply this model to demystify the impact of electric fields on high-valent iron-oxo heme proteins: catalases, peroxidases, and peroxygenases/monooxygenases. Specifically, we show that this model easily accounts for the observed field-induced changes to the spin distribution within peroxidase active sites and explains the transition between epoxidation and hydroxylation pathways seen in Cytochrome P450 active site models. Thus, for the intuitive interpretation of the chemical effect of the field, the strategy involves analyzing the response of the orbitals of active site fragments, and their energetic alignment. We note that the energy difference between fragment orbitals involved in charge redistribution acts as a measure for the chemical hardness/softness of the reactive complex. This measure, and its sensitivity to electric fields, offers a single parameter model from which to quantitatively assess the effects of electric fields on reactivity and selectivity. Thus, the model provides an additional perspective to describe electrostatic preorganization and offers ways for its manipulation.

An innovative guanidinium-based ionic covalent organic frameworks with abundant aromatic rings for high-efficiency naproxen removal: Adsorption behavior, mechanisms, and density functional theory calculations

In recent years, naproxen (NPX) has raised significant environmental concerns requiring urgent attention. This study presents an innovative guanidinium-based ionic covalent organic framework (TFPB-TgCl), containing abundant aromatic rings, which was successfully synthesized via Schiff base reaction for the efficient and selective removal of NPX. Remarkably, TFPB-TgCl manifested a maximal NPX adsorption capacity of 308 mg/g at pH = 5. The adsorption on the active site (AOAS) model highlighted the simultaneous occurrence of both physical and chemical adsorption during the NPX uptake. The coefficients of the physical adsorption rates (5.6479, 1.9224, and 1.9224 min−1 for NPX concentrations of 20, 50, and 100 mg/L, respectively) were significantly higher than those of the chemical adsorption rates (0.1759, 0.0681, and 0.0567 g·mg−1·min−1 for the same concentrations), indicating the predominance of physical adsorption. Furthermore, the multilayer adsorption (MLA) model suggested that an adsorption site can interact with more NPX molecules, benefiting from various electrostatic and π-π interactions. The negative values of enthalpy change (ΔH° = −11.956 kJ/mol) and Gibbs free energy (ΔG < 0) confirmed the exothermic and spontaneous nature of the adsorption process. Additionally, in the optimal adsorption configuration (−131.57 kcal/mol), the Independent Gradient Model based on Hirshfeld partition (IGMH) was utilized to identify interaction sites between the guanidinium group of TFPB-TgCl and the carboxyl group of NPX, with subsequent electrostatic potential (ESP) analysis emphasizing their crucial role in electrostatic adsorption. Overall, the adsorption mechanism of electrostatic and π-π interactions in TFPB-TgCl highlights the significant contribution of its guanidinium and aromatic rings in facilitating NPX adsorption.

Development of Potential Slip Surface Identification Model for Active Deep-Seated Landslide Sites: A Case Study in Taiwan

Identifying locations of landslide slip surfaces provides critical information for understanding the volume of landslides and the scale of disasters, both of which are essential for formulating disaster preparedness and mitigation strategies. Based on hydrogeological survey data from 24 deep-seated landslide-prone sites in Taiwan’s mountainous regions, this study developed the hydraulic conductivity potential index (HCPI) using principal component analysis to quantify the hydraulic properties of disturbed rock formations with six geological factors. Then, regression analysis was performed to construct a permeability estimation model for the geological environment of landslides. Finally, the established model was utilized to develop an identification method for potential slip depths in landslide-prone sites. Results indicated a strong relation between HCPI and hydraulic conductivity with a determination coefficient of 0.895. The relation equation confirmed that the data it generated concerning the depths of significant changes in hydraulic conductivity could be used to identify potential slip surfaces. Additionally, this study successfully established a rule for identifying potential slip zones by summarizing data concerning the generated hydraulic conductivity profiles, stratigraphic lithology, existing inclinometer slip depth records, and groundwater level of landslide sites. This identification method was then applied to predict potential slip depths for ten landslide sites where slip surfaces have not yet occurred. These findings offer a new alternative to having early information on potential sliding depths for timely disaster management and control implementation.

On the Nature of HOPG-Supported Pt1Ti2O7 and its Decomposition of a Nerve Agent Simulant: A Cluster Model of a Single Atom Catalyst Active Site.

Chemical weapons, including hyper lethal nerve agents, are a persistently looming threat across the modern geopolitical landscape. There is a pressing need for the design and development of improved protective materials, which can be substantially aided by the cultivation of a fundamental molecular-level understanding of candidate systems and the corresponding decomposition chemistry. The emergence of the exciting new class of single atom catalyst (SAC) materials has enhanced the prospect of subnanoscale design tailoring in the hopes of optimizing activity and selectivity for a variety of chemical applications. Here, we apply our recently developed experimental technique for modeling the active sites of such SAC materials through the preparation of surface supported size-selected single metal-atom doped metal oxide clusters. The propensity for an SAC cluster model system for Pt1/TiO2 materials, Pt1Ti2O7 supported on highly oriented pyrolytic graphite (HOPG), to adsorb and decompose nerve agent simulant dimethyl methylphosphonate (DMMP) was investigated through a combination of temperature-programmed desorption/reaction (TPD/R) and X-ray photoelectron spectroscopy (XPS). XPS measurements of the as-prepared Pt1Ti2O7 clusters supported the successful isolation of single Pt atoms in clusters monodispersed across the HOPG surface. TPD/R experiments showed that the reactivity exhibited by the Pt1Ti2O7 clusters was distinct from that of Ti2O7 clusters lacking the single Pt atom. It was found that DMMP decomposed over Pt1Ti2O7 upon heating to as low as room temperature, and higher temperature treatments evolved exclusively H2O, CO, and H2, while decomposition over Ti2O7 evolved only methanol and formaldehyde at elevated temperatures. This indicated the promotion of C-H and PO-C bond cleavage within DMMP due to the presence of single Pt atoms in the clusters. Further, the Pt1Ti2O7 clusters were found to desorb P-containing decomposition species, preventing active site poisoning; however, a change of reactivity reflecting that of Ti2O7 was observed following a single TPD/R cycle. This suggested the encapsulation of active Pt sites by titanium oxide during high temperature treatment and is thus an issue deserving of serious attention in the study of Pt1/Ti2O7 SAC materials.

Discussing the Terms Biomimetic and Bioinspired within Bioinorganic Chemistry.

The terms biomimetic and bioinspired are very relevant in the field of bioinorganic chemistry and have been widely applied. Although they were defined by the International Organization for Standardization in 2015, these terms have at times been used rather ambiguously in the literature. This may be due to the inherent complexity of bioinorganic systems where, for example, a structural model of an enzyme active site may not replicate its function. Conversely, the function of an enzyme may be reproduced in a system where the structure does not resemble the enzyme's active site. To address this, we suggest definitions for the terms biomimetic and bioinspired wherein structure and function have been decoupled. With the help of some representative case studies we have outlined the challenges that may arise and make suggestions on how to apply terminology with careful intention.

Bidentate Substrate Binding Mode in Oxalate Decarboxylase.

Oxalate decarboxylase is an Mn- and O2-dependent enzyme in the bicupin superfamily that catalyzes the redox-neutral disproportionation of the oxalate monoanion to form carbon dioxide and formate. Its best-studied isozyme is from Bacillus subtilis where it is stress-induced under low pH conditions. Current mechanistic schemes assume a monodentate binding mode of the substrate to the N-terminal active site Mn ion to make space for a presumed O2 molecule, despite the fact that oxalate generally prefers to bind bidentate to Mn. We report on X-band 13C-electron nuclear double resonance (ENDOR) experiments on 13C-labeled oxalate bound to the active-site Mn(II) in wild-type oxalate decarboxylase at high pH, the catalytically impaired W96F mutant enzyme at low pH, and Mn(II) in aqueous solution. The ENDOR spectra of these samples are practically identical, which shows that the substrate binds bidentate (κO, κO') to the active site Mn(II) ion. Domain-based local pair natural orbital coupled cluster singles and doubles (DLPNO-CCSD) calculations of the expected 13C hyperfine coupling constants for bidentate bound oxalate predict ENDOR spectra in good agreement with the experiment, supporting bidentate bound substrate. Geometry optimization of a substrate-bound minimal active site model by density functional theory shows two possible substrate coordination geometries, bidentate and monodentate. The bidentate structure is energetically preferred by ~4.7 kcal/mol. Our results revise a long-standing hypothesis regarding substrate binding in the enzyme and suggest that dioxygen does not bind to the active site Mn ion after substrate binds. The results are in agreement with our recent mechanistic hypothesis of substrate activation via a long-range electron transfer process involving the C-terminal Mn ion.

Mol-ecular structure of tris-[(6-bromo-pyridin-2-yl)meth-yl]amine.

Coordination compounds of polydentate nitro-gen ligands with metals are used extensively in research areas such as catalysis, and as models of complex active sites of enzymes in bioinorganic chemistry. Tris(2-pyridyl-meth-yl)amine (TPA) is a tripodal tetra-dentate ligand that is known to form coordination compounds with metals, including copper, iron and zinc. The related compound, tris-[(6-bromo-pyridin-2-yl)meth-yl]amine (TPABr3), C18H15Br3N4, which possesses a bromine atom on the 6-position of each of the three pyridyl moieties, is also known but has not been heavily investigated. The mol-ecular structure of TPABr3 as determined by X-ray diffraction is reported here. The TPABr3 molecule belongs to the triclinic, P space group and displays interesting intermolecular Br⋯Br interactions that provide a stabilizing influence within the molecule.

Modeling of Active Sites and Mechanism of Oxidative Coupling of Methane over Alkali Tungstate Catalysts

Modeling of Active Sites and Mechanism of Oxidative Coupling of Methane over Alkali Tungstate Catalysts

Performant automatic differentiation of local coupled cluster theories: Response properties and ab initio molecular dynamics

In this work, we introduce a differentiable implementation of the local natural orbital coupled cluster (LNO-CC) method within the automatic differentiation framework of the PySCFAD package. The implementation is comprehensively tuned for enhanced performance, which enables the calculation of first-order static response properties on medium-sized molecular systems using coupled cluster theory with single, double, and perturbative triple excitations [CCSD(T)]. We evaluate the accuracy of our method by benchmarking it against the canonical CCSD(T) reference for nuclear gradients, dipole moments, and geometry optimizations. In addition, we demonstrate the possibility of property calculations for chemically interesting systems through the computation of bond orders and Mössbauer spectroscopy parameters for a [NiFe]-hydrogenase active site model, along with the simulation of infrared spectra via ab initio LNO-CC molecular dynamics for a protonated water hexamer.

Structure Activity of β-Amidomethyl Vinyl Sulfones as Covalent Inhibitors of Chikungunya nsP2 Cysteine Protease with Anti-alphavirus Activity.

Despite their widespread impact on human health there are no approved drugs for combating alphavirus infections. The heterocyclic β-aminomethyl vinyl sulfone RA-0002034 (1a) is a potent irreversible covalent inhibitor of the alphavirus nsP2 cysteine protease with broad spectrum antiviral activity. Analogs of 1a that varied each of three regions of the molecule were synthesized to establish structure-activity relationships for inhibition of Chikungunya (CHIKV) nsP2 protease and viral replication. The covalent warhead was highly sensitive to modifications of the sulfone or vinyl substituents. However, numerous alterations to the core 5-membered heterocycle and its aryl substituent were well tolerated and several analogs were identified that enhanced CHIKV nsP2 binding. For example, the 4-cyanopyrazole analog 8d exhibited a kinact /Ki ratio >10,000 M-1s-1. 3-Arylisoxazole was identified an isosteric replacement for the 5-membered heterocycle, which circumvented the intramolecular cyclization that complicated the synthesis of pyrazole-based inhibitors like 1a. The accumulated structure-activity data was used to build a ligand-based model of the enzyme active site, which can be used to guide the design of covalent nsP2 protease inhibitors as potential therapeutics against alphaviruses.

Active Sites of Mixed-Metal Core-Shell Oxygen Evolution Reaction Catalysts: FeO4 Sites on Ni Cores or NiN4 Sites in C Shells?

Water electrolysis for clean hydrogen production requires high-activity, high-stability, and low-cost catalysts for its particularly sluggish half-reaction, the oxygen evolution reaction (OER). Currently, the most promising of such catalysts working in alkaline conditions is a core-shell nanostructure, NiFe@NC, whose Fe-doped Ni (NiFe) nanoparticles are encapsulated and interconnected by N-doped graphitic carbon (NC) layers, but the exact OER mechanism of these catalysts is still unclear, and even the location of the OER active site, either on the core side or on the shell side, is still debated. Therefore, we herein derive a plausible active-site model for each side based on various experimental evidence and density functional theory calculations and then build OER free-energy diagrams on both sides to determine the active-site location. The core-side model is an FeO4-type (rather than NiO4-type) active site where an Fe atom sits on Ni oxide layers grown on top of the core surface during catalyst activation, whose facile dissolution provides an explanation for the activity loss of such catalysts directly exposed to the electrolyte. The shell-side model is a NiN4-type (rather than FeN4-type) active site where a Ni atom is intercalated into the porphyrin-like N4C site of the NC shell during catalyst synthesis. Their OER free-energy diagrams indicate that both sites require similar amounts of overpotentials, despite a complete shift in their potential-determining steps, i.e., the final O2 evolution from the oxophilic Fe on the core and the initial OH adsorption to the hydrophobic shell. We conclude that the major active sites are located on the core, but the NC shell not only protects the vulnerable FeO4 active sites on the core from the electrolyte but also provides independent active sites, owing to the N doping.

HPLC with chiral stationary phase for separation and kinetics study of aspartic acid epimerization in Peroxiredoxin 2 active site peptide

Amino acid epimerization, a process of converting L-amino acids to D-amino acids, will lead to modification in the protein structure and, subsequently, its biological function. This modification causes no change in protein m/z and may be overlooked during protein analysis. Aspartic Acid Epimerization (AAE) is faster than other amino acids and could be accelerated by free radicals and peroxides. In this work, a novel and site-specific HPLC method using a chiral stationary phase for determining the AAE in the active site model peptide (AP) of Peroxiredoxin 2 has been developed and validated. The developed method showed good linearity (1 – 200 μg/mL) and recoveries of the limit of quantification (LOQ), low, medium, and high concentrations were between 85% and 115%. The Kinetics of AAE in AP were studied using the developed method, and the results showed that when ascorbic acid and Cu2+ coexisted, the AP epimerized rapidly. The AAE extent increased with time and was positively correlated with hydrogen peroxide generation.

A novel loofah-like chitosan/alginate composite aerogels prepared for efficient removal of perchlorate: Experimental and DFT study

Perchlorate, an emerging contaminant in drinking water, has attracted global attention. In this study, a novel loofah-like porous chitosan/alginate composite aerogel (CTS/SA-m) was fabricated using ionotropic pregelation and freeze-dried technology to effectively adsorb perchlorate. The performance, isotherms, thermodynamics, and kinetics of perchlorate adsorption by CTS/SA-m were systematically discussed. The results showed that the loofah-like CTS/SA-m with high hydrophilicity exhibited excellent adsorption properties. Over 95 % of the removal rate in 10 min can be achieved, with initial concentration of perchlorate and CTS/SA-m dosage of 10 mg/L and 2 g/L, respectively. And 70.15 mg/g of equilibrium adsorption capacity of perchlorate could be reached at pH 5 and 298 K. pH had little effect on the removal rate of perchlorate, the removal rate surpassed 85 % over a wide pH range of 3.0–11.0. Multilayer adsorption (MLA), intraparticle diffusion (IPD), and adsorption on the active site (AOAS) models were employed to discuss the adsorption mechanism of perchlorate. It was confirmed that double-layer chemisorption played a dominant role. Density functional theory (DFT) analysis of binding energy revealed the effect of functional groups on the ClO4− adsorption strength in the order of –NH3+ > –COOH > –NH2 > –OH. Furthermore, electrostatic potential and the independent gradient model confirmed that electrostatic interactions, hydrogen bonding, and van der Waals forces contributed to the highly efficient adsorption of perchlorate. These findings have a vital promoting effect on perchlorate removal technology in water treatment. Moreover, the loofah-like CTS/SA-m aerogel material, exhibiting outstanding performance, shows great potential in effectively in trapping perchlorate anions from aquatic systems.

Continuous kinetics of 2-hydroxyisobutryic acid esterification using solid acid granular and monolithic activated carbon catalysts

Kinetics of 2-hydroxyisobutyric acid (2-HIBA) esterification with ethanol was studied using sulfonated carbon catalysts in granular (sGAC) and monolith (sACM) forms in a continuous flow packed bed reactor. 2-HIBA is a potential biobased carboxylic acid and its ester a sustainably produced industrial solvent. The catalyst monolith form, made from renewable carbon, offers significantly higher space time yields and conversions, yet little kinetic data or models are available for its use, especially under non-ideal conditions. The effect of ethanol/2-HIBA molar ratio (44, 10, 3.6 and 1.5) at different liquid residence times (3–9 min) was investigated using sGAC. Kinetics of sACM esterifications were investigated at a molar ratio of 3.6 by varying the residence time (2–7 min) and compared with the sGAC. The sACM displayed higher ester yields, acid conversions, and significantly higher reaction rates and space–time-yields (2.1–2.8 ×) compared to the sGAC due to higher surface area to volume ratio. The sACM reaction rates and turnover frequency were comparable to solid acid resins and sulfated silica and zirconia. Pseudo-homogeneous, Eley-Rideal and Langmuir-Hinshelwood models were applied to fit the kinetic data, and the reaction system parameters were obtained through regression analysis. The LH dual active site model resulted in the lowest mean relative error for both 2-HIBA and ester concentration residuals. Adsorption/desorption equilibrium constants for 2-HIBA, ethanol, and ester, were higher compared to water suggesting hydrophobic regions in the sGAC/sACM. Estimation of the external and internal mass transfer criteria indicated negligible effects of mass transfer. With further development sACM and the kinetic model can be used for reactor design of continuous esterification processes using solid acid monolith catalysts.

Eliminating Imaginary Vibrational Frequencies in Quantum-Chemical Cluster Models of Enzymatic Active Sites.

In constructing finite models of enzyme active sites for quantum-chemical calculations, atoms at the periphery of the model must be constrained to prevent unphysical rearrangements during geometry relaxation. A simple fixed-atom or "coordinate-lock" approach is commonly employed but leads to undesirable artifacts in the form of small imaginary frequencies. These preclude evaluation of finite-temperature free-energy corrections, limiting thermochemical calculations to enthalpies only. Full-dimensional vibrational frequency calculations are possible by replacing the fixed-atom constraints with harmonic confining potentials. Here, we compare that approach to an alternative strategy in which fixed-atom contributions to the Hessian are simply omitted. While the latter strategy does eliminate imaginary frequencies, it tends to underestimate both the zero-point energy and the vibrational entropy while introducing artificial rigidity. Harmonic confining potentials eliminate imaginary frequencies and provide a flexible means to construct active-site models that can be used in unconstrained geometry relaxations, affording better convergence of reaction energies and barrier heights with respect to the model size, as compared to models with fixed-atom constraints.

How Do Differences in Electronic Structure Affect the Use of Vanadium Intermediates as Mimics in Nonheme Iron Hydroxylases?

We study active-site models of nonheme iron hydroxylases and their vanadium-based mimics using density functional theory to determine if vanadyl is a faithful structural mimic. We identify crucial structural and energetic differences between ferryl and vanadyl isomers owing to the differences in their ground electronic states, i.e., high spin (HS) for Fe and low spin (LS) for V. For the succinate cofactor bound to the ferryl intermediate, we predict facile interconversion between monodentate and bidentate coordination isomers for ferryl species but difficult rearrangement for vanadyl mimics. We study isomerization of the oxo intermediate between axial and equatorial positions and find the ferryl potential energy surface to be characterized by a large barrier of ca. 10 kcal/mol that is completely absent for the vanadyl mimic. This analysis reveals even starker contrasts between Fe and V in hydroxylases than those observed for this metal substitution in nonheme halogenases. Analysis of the relative bond strengths of coordinating carboxylate ligands for Fe and V reveals that all of the ligands show stronger binding to V than Fe owing to the LS ground state of V in contrast to the HS ground state of Fe, highlighting the limitations of vanadyl mimics of native nonheme iron hydroxylases.

Synthesis and Application of a Near-Infrared Light-Emitting Fluorescent Probe for Specific Imaging of Cancer Cells with High Sensitivity and Selectivity.

The preclinical diagnosis of tumors is of great significance to cancer treatment. Near-infrared fluorescence imaging technology is promising for the in-situ detection of tumors with high sensitivity. Here, a fluorescent probe was synthesized on the basis of Au nanoclusters with near-infrared light emission and applied to fluorescent cancer cell labeling. Near-infrared methionine-N-Hydroxy succinimide Au nanoclusters (Met-NHs-AuNCs) were prepared successfully by one-pot synthesis using Au nanoclusters, methionine, and N-Hydroxy succinimide as frameworks, reductants, and stabilizers, respectively. The specific fluorescence imaging of tumor cells or tissues by fluorescent probe was studied on the basis of SYBYL Surflex-DOCK simulation model of LAT1 active site of overexpressed receptor on cancer cell surface. The results showed that Met-NHs-AuNCs interacted with the surface of LAT1, and C_Score scored the conformation of the probe and LAT1 as five. Characterization and in vitro experiments were conducted to explore the Met-NHs-AuNCs targeted uptake of cancer cells. The prepared near-infrared fluorescent probe (Met-NHs-AuNCs) can specifically recognize the overexpression of L-type amino acid transporter 1 (LAT1) in cancer cells so that it can show red fluorescence in cancer cells. Meanwhile, normal cells (H9c2) have no fluorescence. The fluorescent probe demonstrates the power of targeting and imaging cancer cells.