1
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Roh S, Nam Y, Nguyen MTN, Han JH, Lee JS. Dynamic Covalent Bond-Based Polymer Chains Operating Reversibly with Temperature Changes. Molecules 2024; 29:3261. [PMID: 39064840 PMCID: PMC11279090 DOI: 10.3390/molecules29143261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2024] [Revised: 07/04/2024] [Accepted: 07/08/2024] [Indexed: 07/28/2024] Open
Abstract
Dynamic bonds can facilitate reversible formation and dissociation of connections in response to external stimuli, endowing materials with shape memory and self-healing capabilities. Temperature is an external stimulus that can be easily controlled through heat. Dynamic covalent bonds in response to temperature can reversibly connect, exchange, and convert chains in the polymer. In this review, we introduce dynamic covalent bonds that operate without catalysts in various temperature ranges. The basic bonding mechanism and the kinetics are examined to understand dynamic covalent chemistry reversibly performed by equilibrium control. Furthermore, a recent synthesis method that implements dynamic covalent coupling based on various polymers is introduced. Dynamic covalent bonds that operate depending on temperature can be applied and expand the use of polymers, providing predictions for the development of future smart materials.
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Affiliation(s)
| | | | | | | | - Jun Seop Lee
- Department of Materials Science and Engineering, Gachon University, 1342 Seongnam-daero, Sujeong-gu, Seongnam-si 13120, Gyeonggi-do, Republic of Korea; (S.R.); (Y.N.); (M.T.N.N.); (J.-H.H.)
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2
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Li X, Sun X. 1,3-Proton Transfer of Pyridoxal 5'-Phosphate Schiff Base in the Branched-Chain Aminotransferase: Concerted or Stepwise Mechanism? J Phys Chem B 2024; 128:77-85. [PMID: 38131279 DOI: 10.1021/acs.jpcb.3c05875] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2023]
Abstract
The branched-chain aminotransferase from Mycobacterium tuberculosis (MtIlvE) is a pyridoxal 5'-phosphate (PLP) dependent enzyme, and it is essential for the synthesis of the branched-chain amino acids. Ketimine is an important intermediate in the catalytic process. We have investigated the mechanism of ketimine formation and the energy landscape using the multiple computational methods. It is found that the 1,3-proton transfer involved in ketimine formation occurs through a stepwise process rather than a one-step process. Lys204 is identified as a key residue for ligand binding and as a base that abstracts the Cα proton from the PLP-Glu Schiff base, yielding a carbanionic intermediate. The first proton transfer is the rate-limiting step with an energy barrier of 17.8 kcal mol-1. Our study disclosed the detailed pathway of the proton transfer from external aldimine to ketimine, providing novel insights into the catalytic mechanism of other PLP-dependent enzymes.
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Affiliation(s)
- Xue Li
- School of Life Sciences, Changchun Normal University, Changchun 130023, People's Republic of China
| | - Xiaoli Sun
- Institute of Theoretical Chemistry, Jilin University, Changchun 130023, People's Republic of China
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3
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Acharya A, Jana K, Kleinekathöfer U. Antibiotic Charge Profile Determines the Extent of L3 Dynamics in OmpF: An Expedited Passage for Molecules with a Positive Charge. J Phys Chem B 2023; 127:10766-10777. [PMID: 38064341 DOI: 10.1021/acs.jpcb.3c04557] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2023]
Abstract
Efficient permeation into Gram-negative bacterial cells is a much-desired property in the design of antibacterial agents. The goal is to arrive at one or more chemical modifications of molecules that improve their uptake into the cell while maintaining a good binding affinity to the intracellular target. Previously, we proposed a mechanistic rationale for the fast permeation of bulky antibiotics that involves induced conformational dynamics in the constriction loop L3 of the OmpF channel. This flexibility is caused by the perturbation of a hydrogen bond network stabilizing the L3 loop due to the strong interactions of the positively charged moiety on the antibiotic with the residues of the L3 loop. In the present work, we examine how differences in the charge profile of antibiotic molecules can affect the permeation process, in particular, the L3 dynamics. To this end, we have performed all-atom molecular dynamics simulations to study the permeation process of molecules with differences in the net charge through the Escherichia coli OmpF channel. The results from these simulations suggest that a positively charged moiety on the antibiotic is responsible for strong interactions with the negatively charged residues of the L3 loop, promoting conformational dynamics in the L3 loop. In contrast, antibiotics without a positively charged moiety are unable to initiate such a dynamic response in the L3 loop. This distinct behavior of the L3 loop in the presence of molecules with different charge characteristics provides a plausible mechanism whereby large molecules with an appropriate charge distribution can leverage an L3 dynamic-dependent pathway to permeate efficiently. The results are relevant to the structure-based design of molecules with improved uptake properties achieved through systematic chemical modifications that effectively engage the L3 loop.
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Affiliation(s)
- Abhishek Acharya
- School of Science, Constructor University, Campus Ring 1, 28759 Bremen, Germany
| | - Kalyanashis Jana
- School of Science, Constructor University, Campus Ring 1, 28759 Bremen, Germany
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4
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Moldovan OL, Vari CE, Tero-Vescan A, Cotoi OS, Cocuz IG, Tabaran FA, Pop R, Fülöp I, Chis RF, Lungu IA, Rusu A. Potential Defence Mechanisms Triggered by Monosodium Glutamate Sub-Chronic Consumption in Two-Year-Old Wistar Rats. Nutrients 2023; 15:4436. [PMID: 37892513 PMCID: PMC10610236 DOI: 10.3390/nu15204436] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2023] [Revised: 10/15/2023] [Accepted: 10/17/2023] [Indexed: 10/29/2023] Open
Abstract
Monosodium glutamate (MSG) is the sodium salt of glutamic acid (GLA), used as a flavour enhancer. MSG is considered a controversial substance. It is incriminated in disturbing the antioxidant system, but also has beneficial effects, as GLA metabolism plays a crucial role in homeostasis. This study highlights which positive or negative aspects of MSG sub-chronic consumption are better reflected in subjects potentially affected by advanced age. Daily doses of MSG were administered to four groups of two-year-old Wistar rats for 90 days: (I) 185 mg/kg bw, (II) 1500 mg/kg bw, (III) 3000 mg/kg bw and (IV) 6000 mg/kg bw, compared to a MSG non-consumer group. Aspartate aminotransferase, alanine aminotransferase, alkaline phosphatase, direct and total bilirubin, total cholesterol, triglycerides, creatinine and urea levels were analysed; stomach, liver and kidney samples were subjected to histopathological analysis. Although, in most cases, there were no statistical differences, interesting aspects of the dose-effect relationship were observed. After MSG sub-chronic consumption, the positive aspects of GLA seem to be reflected better than the negative ones. The hormesis effect, with low-level reactive oxygen species' protective effects and GLA metabolism, may represent the hypothesis of a potential defence mechanism triggered by MSG sub-chronic consumption in ageing rats.
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Affiliation(s)
- Octavia-Laura Moldovan
- Medicine and Pharmacy Doctoral School, George Emil Palade University of Medicine, Pharmacy, Science, and Technology of Targu Mures, 540142 Targu Mures, Romania;
| | - Camil-Eugen Vari
- Pharmacology and Clinical Pharmacy Department, Faculty of Pharmacy, George Emil Palade University of Medicine, Pharmacy, Science, and Technology of Targu Mures, 540142 Targu Mures, Romania;
| | - Amelia Tero-Vescan
- Medical Chemistry and Biochemistry Department, Faculty of Medicine in English, George Emil Palade University of Medicine, Pharmacy, Science, and Technology of Targu Mures, 540142 Targu Mures, Romania;
| | - Ovidiu Simion Cotoi
- Pathophysiology Department, Faculty of Medicine, George Emil Palade University of Medicine, Pharmacy, Science, and Technology of Targu Mures, 540142 Targu Mures, Romania; (O.S.C.); (I.G.C.)
- Pathology Department, Mures Clinical County Hospital, 540011 Targu Mures, Romania
| | - Iuliu Gabriel Cocuz
- Pathophysiology Department, Faculty of Medicine, George Emil Palade University of Medicine, Pharmacy, Science, and Technology of Targu Mures, 540142 Targu Mures, Romania; (O.S.C.); (I.G.C.)
- Pathology Department, Mures Clinical County Hospital, 540011 Targu Mures, Romania
| | - Flaviu Alexandru Tabaran
- Department of Pathology, Faculty of Veterinary Medicine, University of Agricultural Sciences and Veterinary Medicine of Cluj-Napoca, 400372 Cluj-Napoca, Romania; (F.A.T.); (R.P.)
| | - Romelia Pop
- Department of Pathology, Faculty of Veterinary Medicine, University of Agricultural Sciences and Veterinary Medicine of Cluj-Napoca, 400372 Cluj-Napoca, Romania; (F.A.T.); (R.P.)
| | - Ibolya Fülöp
- Toxicology and Biopharmacy Department, Faculty of Pharmacy, George Emil Palade University of Medicine, Pharmacy, Science, and Technology of Targu Mures, 540142 Targu Mures, Romania;
| | - Rafael Florin Chis
- Faculty of Medicine, George Emil Palade University of Medicine, Pharmacy, Science, and Technology of Targu Mures, 540142 Targu Mures, Romania;
| | - Ioana-Andreea Lungu
- Medicine and Pharmacy Doctoral School, George Emil Palade University of Medicine, Pharmacy, Science, and Technology of Targu Mures, 540142 Targu Mures, Romania;
| | - Aura Rusu
- Pharmaceutical and Therapeutic Chemistry Department, Faculty of Pharmacy, George Emil Palade University of Medicine, Pharmacy, Science, and Technology of Targu Mures, 540142 Targu Mures, Romania;
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5
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Rastogi S, Chandra A. Free Energy Landscapes of the Tautomeric Interconversion of Pyridoxal 5'-Phosphate Aldimines at the Active Site of Ornithine Decarboxylase in Aqueous Media. J Phys Chem B 2023; 127:8139-8149. [PMID: 37721415 DOI: 10.1021/acs.jpcb.3c04142] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/19/2023]
Abstract
The pyridoxal 5'-phosphate (PLP) acts as a coenzyme for a large number of biochemical reactions. It exists in mainly two bound forms at the active site of the concerned enzyme: the internal aldimine, in which the PLP is bound with the ϵ-amino group of lysine at the active site, and the external aldimine, where the PLP is bound to the substrate amino acid. Both the internal and external aldimines have Schiff base linkage (N-H-O) and can exist in two tautomeric structures of ketoenamine and enolimine forms. In this work, we have investigated the free energy landscape for the tautomeric proton transfer in the internal and external aldimines at the active site of the ornithine decarboxylase enzyme in an aqueous medium. We performed hybrid quantum-classical metadynamics and force field-based molecular dynamics simulations, which revealed that the ketoenamine tautomer is more stable than the enolimine form. The QM/MM metadynamics calculations show that the free energy difference between the ketoenamine and enolimine forms for the internal aldimine is 3.9 kcal/mol, and it is found to be 5.8 kcal/mol for the external aldimine, with the ketoenamine form being more stable in both cases. The results are further supported by calculations of the binding free energies from classical simulations and static quantum chemical calculations in different environments. We have also analyzed the configurational structure of the microenvironment at the active site in order to have better insights into the interactions of the active site residues with the PLP in its two tautomeric forms.
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Affiliation(s)
- Shreya Rastogi
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh 208016, India
| | - Amalendu Chandra
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh 208016, India
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6
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Tripathi S, Nair NN. Temperature Accelerated Sliced Sampling to Probe Ligand Dissociation from Protein. J Chem Inf Model 2023; 63:5182-5191. [PMID: 37540828 DOI: 10.1021/acs.jcim.3c00376] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/06/2023]
Abstract
Modeling ligand unbinding in proteins to estimate the free energy of binding and probing the mechanism presents several challenges. They primarily pertain to the entropic bottlenecks resulting from protein and solvent conformations. While exploring the unbinding processes using enhanced sampling techniques, very long simulations are required to sample all of the conformational states as the system gets trapped in local free energy minima along transverse coordinates. Here, we demonstrate that temperature accelerated sliced sampling (TASS) is an ideal approach to overcome some of the difficulties faced by conventional sampling methods in studying ligand unbinding. Using TASS, we study the unbinding of avibactam inhibitor molecules from the Class C β-lactamase (CBL) active site. Extracting CBL-avibactam unbinding free energetics, unbinding pathways, and identifying critical interactions from the TASS simulations are demonstrated.
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Affiliation(s)
- Shubhandra Tripathi
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India
| | - Nisanth N Nair
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur 208016, India
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7
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Acharya A, Jana K, Gurvic D, Zachariae U, Kleinekathöfer U. Fast prediction of antibiotic permeability through membrane channels using Brownian dynamics. Biophys J 2023; 122:2996-3007. [PMID: 36992560 PMCID: PMC10398345 DOI: 10.1016/j.bpj.2023.03.035] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2022] [Revised: 03/02/2023] [Accepted: 03/23/2023] [Indexed: 03/30/2023] Open
Abstract
The efficient permeation across the Gram-negative bacterial membrane is an important step in the overall process of antibacterial action of a molecule and the one that has posed a significant hurdle on the way toward approved antibiotics. Predicting the permeability for a large library of molecules and assessing the effect of different molecular transformations on permeation rates of a given molecule is critical to the development of effective antibiotics. We present a computational approach for obtaining estimates of molecular permeability through a porin channel in a matter of hours using a Brownian dynamics approach. The fast sampling using a temperature acceleration scheme enables the approximate estimation of permeability using the inhomogeneous solubility diffusion model. Although the method is a significant approximation to similar all-atom approaches tested previously, we show that the present approach predicts permeabilities that correlate fairly well with the respective experimental permeation rates from liposome swelling experiments and accumulation rates from antibiotic accumulation assays, and is significantly, i.e., about 14 times, faster compared with a previously reported approach. The possible applications of the scheme in high-throughput screening for fast permeators are discussed.
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Affiliation(s)
| | | | - Dominik Gurvic
- School of Life Sciences, University of Dundee, Dundee, United Kingdom
| | - Ulrich Zachariae
- School of Life Sciences, University of Dundee, Dundee, United Kingdom
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8
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Dutta S, Chandra A. A Multiple Proton Transfer Mechanism for the Charging Step of the Aminoacylation Reaction at the Active Site of Aspartyl tRNA Synthetase. J Chem Inf Model 2023; 63:1819-1832. [PMID: 36893463 DOI: 10.1021/acs.jcim.2c01332] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/11/2023]
Abstract
Aspartyl-tRNA synthetase catalyzes the attachment of aspartic acid to its cognate tRNA by the aminoacylation reaction during the initiation of the protein biosynthesis process. In the second step of the aminoacylation reaction, known as the charging step, the aspartate moiety is transferred from aspartyl-adenylate to the 3'-OH of A76 of tRNA through a proton transfer process. We have investigated different pathways for the charging step through three separate QM/MM simulations combined with the enhanced sampling method of well-sliced metadynamics and found out the most feasible pathway for the reaction at the active site of the enzyme. In the charging reaction, both the phosphate group and the ammonium group after deprotonation can potentially act as a base for proton transfer in the substrate-assisted mechanism. We have considered three possible mechanisms involving different pathways of proton transfer, and only one of them is determined to be enzymatically feasible. The free energy landscape along reaction coordinates where the phosphate group acts as the general base showed that, in the absence of water, the barrier height is 52.6 kcal/mol. The free energy barrier is reduced to 39.7 kcal/mol when the active site water molecules are also treated quantum mechanically, thus allowing a water mediated proton transfer. The charging reaction involving the ammonium group of the aspartyl adenylate is found to follow a path where first a proton from the ammonium group moves to a water in the vicinity forming a hydronium ion (H3O+) and NH2 group. The hydronium ion subsequently passes the proton to the Asp233 residue, thus minimizing the chance of back proton transfer from hydronium to the NH2 group. The neutral NH2 group subsequently takes the proton from the O3' of A76 with a free energy barrier of 10.7 kcal/mol. In the next step, the deprotonated O3' makes a nucleophilic attack to the carbonyl carbon forming a tetrahedral transition state with a free energy barrier of 24.8 kcal/mol. Thus, the present work shows that the charging step proceeds through a multiple proton transfer mechanism where the amino group formed after deprotonation acts as the base to capture a proton from O3' of A76 rather than the phosphate group. The current study also shows the important role played by Asp233 in the proton transfer process.
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Affiliation(s)
- Saheb Dutta
- Department of Chemistry, Institute of Technology Kanpur, Kanpur, Uttar Pradesh 208016, India
| | - Amalendu Chandra
- Department of Chemistry, Institute of Technology Kanpur, Kanpur, Uttar Pradesh 208016, India
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9
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Dutta S, Chandra A. Free Energy Landscape of the Adenylation Reaction of the Aminoacylation Process at the Active Site of Aspartyl tRNA Synthetase. J Phys Chem B 2022; 126:5821-5831. [PMID: 35895864 DOI: 10.1021/acs.jpcb.2c03843] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The process of protein biosynthesis is initiated by the aminoacylation process where a transfer ribonucleic acid (tRNA) is charged by the attachment of its cognate amino acid at the active site of the corresponding aminoacyl tRNA synthetase enzyme. The first step of the aminoacylation process, known as the adenylation reaction, involves activation of the cognate amino acid where it reacts with a molecule of adenosine triphosphate (ATP) at the active site of the enzyme to form the aminoacyl adenylate and inorganic pyrophosphate. In the current work, we have investigated the adenylation reaction between aspartic acid and ATP at the active site of the fully solvated aspartyl tRNA synthetase (AspRS) from Escherichia coli in aqueous medium at room temperature through hybrid quantum mechanical/molecular mechanical (QM/MM) simulations combined with enhanced sampling methods of well-tempered and well-sliced metadynamics. The objective of the present work is to study the associated free energy landscape and reaction barrier and also to explore the effects of active site mutation on the free energy surface of the reaction. The current calculations include finite temperature effects on free energy profiles. In particular, apart from contributions of interaction energies, the current calculations also include contributions of conformational, vibrational, and translational entropy of active site residues, substrates, and also the rest of the solvated protein and surrounding water into the free energy calculations. The present QM/MM metadynamics simulations predict a free energy barrier of 23.35 and 23.5 kcal/mol for two different metadynamics methods used to perform the reaction at the active site of the wild type enzyme. The free energy barrier increases to 30.6 kcal/mol when Arg217, which is an important conserved residue of the wild type enzyme at its active site, is mutated by alanine. These free energy results including the effect of mutation compare reasonably well with those of kinetic experiments that are available in the literature. The current work also provides molecular details of structural changes of the reactants and surroundings as the system dynamically evolves along the reaction pathway from reactant to the product state through QM/MM metadynamics simulations.
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Affiliation(s)
- Saheb Dutta
- Department of Chemistry, Indian Institute of Technology Kanpur, Uttar Pradesh, India 208016
| | - Amalendu Chandra
- Department of Chemistry, Indian Institute of Technology Kanpur, Uttar Pradesh, India 208016
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10
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Ji R, Shen J. Chirality Transformation in Metathesis Reactions of Salicylaldehyde/Pyridoxal‐Based Imines. ChemistrySelect 2022. [DOI: 10.1002/slct.202201332] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Rui‐Xue Ji
- Xiamen Key Laboratory of Optoelectronic Materials and Advanced Manufacturing College of Materials Science and Engineering Huaqiao University Xiamen 361021 China
| | - Jiang‐Shan Shen
- Xiamen Key Laboratory of Optoelectronic Materials and Advanced Manufacturing College of Materials Science and Engineering Huaqiao University Xiamen 361021 China
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11
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Gupta A, Verma S, Javed R, Sudhakar S, Srivastava S, Nair NN. Exploration of high dimensional free energy landscapes by a combination of temperature-accelerated sliced sampling and parallel biasing. J Comput Chem 2022; 43:1186-1200. [PMID: 35510789 DOI: 10.1002/jcc.26882] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2021] [Revised: 03/27/2022] [Accepted: 04/11/2022] [Indexed: 12/22/2022]
Abstract
Temperature-accelerated sliced sampling (TASS) is an enhanced sampling method for achieving accelerated and controlled exploration of high-dimensional free energy landscapes in molecular dynamics simulations. With the aid of umbrella bias potentials, the TASS method realizes a controlled exploration and divide-and-conquer strategy for computing high-dimensional free energy surfaces. In TASS, diffusion of the system in the collective variable (CV) space is enhanced with the help of metadynamics bias and elevated-temperature of the auxiliary degrees of freedom (DOF) that are coupled to the CVs. Usually, a low-dimensional metadynamics bias is applied in TASS. In order to further improve the performance of TASS, we propose here to use a highdimensional metadynamics bias, in the same form as in a parallel bias metadynamics scheme. Here, a modified reweighting scheme, in combination with artificial neural network is used for computing unbiased probability distribution of CVs and projections of high-dimensional free energy surfaces. We first validate the accuracy and efficiency of our method in computing the four-dimensional free energy landscape for alanine tripeptide in vacuo. Subsequently, we employ the approach to calculate the eight-dimensional free energy landscape of alanine pentapeptide in vacuo. Finally, the method is applied to a more realistic problem wherein we compute the broad four-dimensional free energy surface corresponding to the deacylation of a drug molecule which is covalently complexed with a β-lactamase enzyme. We demonstrate that using parallel bias in TASS improves the efficiency of exploration of high-dimensional free energy landscapes.
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Affiliation(s)
- Abhinav Gupta
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, India
| | - Shivani Verma
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, India
| | - Ramsha Javed
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, India
| | - Suraj Sudhakar
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, India
| | - Saurabh Srivastava
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, India.,Department of Chemistry, Manipal University Jaipur, Jaipur, Rajasthan, India
| | - Nisanth N Nair
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, India
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12
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Soniya K, Chandra A. Free Energy Landscape and Proton Transfer Pathways of the Transimination Reaction at the Active site of the Serine Hydroxymethyltransferase Enzyme in Aqueous Medium. J Phys Chem B 2021; 125:11848-11856. [PMID: 34696588 DOI: 10.1021/acs.jpcb.1c05864] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Serine hydroxymethyltransferase (SHMT) is a ubiquitous enzyme belonging to the fold type I or aspartate aminotransferase (AspAT) family of the pyridoxal 5'-phosphate (PLP)-dependent enzymes. Like other PLP-dependent enzymes, SHMT also undergoes the so-called transimination reaction before exhibiting its enzymatic activity. The transimination process constitutes an important pre-step for all PLP-dependent enzymes, where an internal aldimine of the PLP-enzyme complex gets converted to an external aldimine of the substrate-PLP complex at the active site of the enzyme. In case of the transimination reaction involving SHMT, the PLP molecule bound to the active site lysine residue of SHMT (internal aldimine) gets detached from the enzyme by a serine substrate to produce an external aldimine complex, where the PLP is now bound to the serine substrate. In the current study, the free energy surfaces and reaction pathways of different steps of the transimination reaction at the active site of SHMT are investigated by employing hybrid quantum mechanical/molecular mechanical (QM/MM) simulations combined with metadynamics methods of rare event sampling. It is found that the process of transimination involving serine and PLP at the active site of the SHMT enzyme takes place through different elementary steps such as the formation of the first geminal diamine intermediate (GDI1), transfer of a proton from the substrate serine to the phenolic oxygen of PLP, followed by another proton transfer from PLP to the amine nitrogen of lysine with the formation of the second geminal diamine intermediate (GDI2), and finally, detachment of the active site lysine residue from PLP to produce the external aldimine.
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Affiliation(s)
- Kumari Soniya
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh 208016, India
| | - Amalendu Chandra
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh 208016, India
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13
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Abstract
Although dynamic reactions of imines have been extensively studied, the dynamic behaviors manipulated by chirality remain nearly unexplored. In this work, enantioselective amine exchange reactions were demonstrated as a first example via the reaction of enantiomeric chiral amines such as natural amino acids with a series of innovative axially chiral 1,1'-binaphthyl-2,2'-diamine (BNDA)-based imines that were prepared from the condensation reactions between BNDA and salicylaldehyde (SA) or its derivatives. This enantioselective dynamic behavior can be directly indicated by the degree of the fluorescence response of the R-configuration of imines to the d-enantiomer of chiral amine, because the released BNDA can serve as the fluorescence signal output when the amine exchange reaction occurs, which is far higher than the response to its l-enantiomer under identical experimental conditions. For the S-configuration of chiral imines, the fluorescence response is the opposite. The enantioselective exchange reaction can be tuned by altering the electron-withdrawing or electron-donating capability of the substituent at position 4 or 5 of the SA part of chiral imines. Not only o-OH groups in SA-based imines but also protic solvents used as reaction media were found to be important to the dynamic behavior at high rates.
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Affiliation(s)
- Rui-Xue Ji
- Xiamen Key Laboratory of Optoelectronic Materials and Advanced Manufacturing, College of Materials Science and Engineering, Huaqiao University, Xiamen 361021, China
| | - Ning Liu
- Xiamen Key Laboratory of Optoelectronic Materials and Advanced Manufacturing, College of Materials Science and Engineering, Huaqiao University, Xiamen 361021, China
| | - Jiang-Shan Shen
- Xiamen Key Laboratory of Optoelectronic Materials and Advanced Manufacturing, College of Materials Science and Engineering, Huaqiao University, Xiamen 361021, China
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14
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Acharya A, Prajapati JD, Kleinekathöfer U. Improved Sampling and Free Energy Estimates for Antibiotic Permeation through Bacterial Porins. J Chem Theory Comput 2021; 17:4564-4577. [PMID: 34138557 DOI: 10.1021/acs.jctc.1c00369] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Antibiotics enter into bacterial cells via protein channels that serve as low-energy pathways through the outer membrane, which is otherwise impenetrable. Insights into the molecular mechanisms underlying the transport processes are vital for the development of effective antibacterials. A much-desired prerequisite is an accurate and reproducible determination of free energy surfaces for antibiotic translocation, enabling quantitative and meaningful comparisons of permeation mechanisms for different classes of antibiotics. Inefficient sampling along the orthogonal degrees of freedom, for example, in umbrella sampling and metadynamics approaches, is however a key limitation affecting the accuracy and the convergence of free energy estimates. To overcome this limitation, two sampling methods have been employed in the present study that, respectively, combine umbrella sampling and metadynamics-style biasing schemes with temperature acceleration for improved sampling along orthogonal degrees of freedom. As a model for the transport of bulky solutes, the ciprofloxacin-OmpF system has been selected. The well-tempered metadynamics approach with multiple walkers is compared with its "temperature-accelerated" variant in terms of improvements in sampling and convergence of free energy estimates. We find that the inclusion of collective variables governing solute degrees of freedom and solute-water interactions within the sampling scheme largely alleviates sampling issues. Concerning improved sampling and convergence of free energy estimates from independent simulations, the temperature-accelerated sliced sampling approach that combines umbrella sampling with temperature-accelerated molecular dynamics performs even better as shown for the ciprofloxacin-OmpF system.
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Affiliation(s)
- Abhishek Acharya
- Department of Physics and Earth Sciences, Jacobs University Bremen, 28759 Bremen, Germany
| | | | - Ulrich Kleinekathöfer
- Department of Physics and Earth Sciences, Jacobs University Bremen, 28759 Bremen, Germany
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15
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Shen S, Butrin A, Doubleday PF, Melani RD, Beaupre BA, Tavares MT, Ferreira GM, Kelleher NL, Moran GR, Liu D, Silverman RB. Turnover and Inactivation Mechanisms for ( S)-3-Amino-4,4-difluorocyclopent-1-enecarboxylic Acid, a Selective Mechanism-Based Inactivator of Human Ornithine Aminotransferase. J Am Chem Soc 2021; 143:8689-8703. [PMID: 34097381 PMCID: PMC8367020 DOI: 10.1021/jacs.1c02456] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The inhibition of human ornithine δ-aminotransferase (hOAT) is a potential therapeutic approach to treat hepatocellular carcinoma. In this work, (S)-3-amino-4,4-difluorocyclopent-1-enecarboxylic acid (SS-1-148, 6) was identified as a potent mechanism-based inactivator of hOAT while showing excellent selectivity over other related aminotransferases (e.g., GABA-AT). An integrated mechanistic study was performed to investigate the turnover and inactivation mechanisms of 6. A monofluorinated ketone (M10) was identified as the primary metabolite of 6 in hOAT. By soaking hOAT holoenzyme crystals with 6, a precursor to M10 was successfully captured. This gem-diamine intermediate, covalently bound to Lys292, observed for the first time in hOAT/ligand crystals, validates the turnover mechanism proposed for 6. Co-crystallization yielded hOAT in complex with 6 and revealed a novel noncovalent inactivation mechanism in hOAT. Native protein mass spectrometry was utilized for the first time in a study of an aminotransferase inactivator to validate the noncovalent interactions between the ligand and the enzyme; a covalently bonded complex was also identified as a minor form observed in the denaturing intact protein mass spectrum. Spectral and stopped-flow kinetic experiments supported a lysine-assisted E2 fluoride ion elimination, which has never been observed experimentally in other studies of related aminotransferase inactivators. This elimination generated the second external aldimine directly from the initial external aldimine, rather than the typical E1cB elimination mechanism, forming a quinonoid transient state between the two external aldimines. The use of native protein mass spectrometry, X-ray crystallography employing both soaking and co-crystallization methods, and stopped-flow kinetics allowed for the detailed elucidation of unusual turnover and inactivation pathways.
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Affiliation(s)
- Sida Shen
- Department of Chemistry, Center for Molecular Innovation and Drug Discovery, and Center for Developmental Therapeutics, Northwestern University, Evanston, Illinois 60208, United States
| | - Arseniy Butrin
- Department of Chemistry and Biochemistry, Loyola University Chicago, Chicago, Illinois 60660, United States
| | - Peter F. Doubleday
- Department of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, United States
| | - Rafael D. Melani
- Department of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, United States
| | - Brett A. Beaupre
- Department of Chemistry and Biochemistry, Loyola University Chicago, Chicago, Illinois 60660, United States
| | - Mauricio T. Tavares
- Department of Molecular Medicine, Scripps Research, Jupiter, Florida 33458, United States
| | - Glaucio M. Ferreira
- Department of Clinical and Toxicological Analyses, School of Pharmaceutical Sciences, University of São Paulo, São Paulo, SP, 05508-000, Brazil
| | - Neil L. Kelleher
- Department of Chemistry, Center for Molecular Innovation and Drug Discovery, and Center for Developmental Therapeutics, Northwestern University, Evanston, Illinois 60208, United States,Department of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, United States
| | - Graham R. Moran
- Department of Chemistry and Biochemistry, Loyola University Chicago, Chicago, Illinois 60660, United States
| | - Dali Liu
- Department of Chemistry and Biochemistry, Loyola University Chicago, Chicago, Illinois 60660, United States,Corresponding authors: (R.B.S.) . Phone: +1-847-491-5653; (D.L.) . Phone: +1-773-508-3093
| | - Richard B. Silverman
- Department of Chemistry, Center for Molecular Innovation and Drug Discovery, and Center for Developmental Therapeutics, Northwestern University, Evanston, Illinois 60208, United States,Department of Molecular Biosciences, Northwestern University, Evanston, Illinois 60208, United States,Department of Pharmacology, Northwestern University, Chicago, Illinois, 60611, United States,Corresponding authors: (R.B.S.) . Phone: +1-847-491-5653; (D.L.) . Phone: +1-773-508-3093
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16
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Dutta Banik S, Bankura A, Chandra A. A QM/MM simulation study of transamination reaction at the active site of aspartate aminotransferase: Free energy landscape and proton transfer pathways. J Comput Chem 2020; 41:2684-2694. [PMID: 32932551 DOI: 10.1002/jcc.26422] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2020] [Revised: 08/08/2020] [Accepted: 09/03/2020] [Indexed: 11/10/2022]
Abstract
Transaminase is a key enzyme for amino acid metabolism, which reversibly catalyzes the transamination reaction with the help of PLP (pyridoxal 5' -phosphate) as its cofactor. Here we have investigated the mechanism and free energy landscape of the transamination reaction involving the aspartate transaminase (AspTase) enzyme and aspartate-PLP (Asp-PLP) complex using QM/MM simulation and metadynamics methods. The reaction is found to follow a stepwise mechanism where the active site residue Lys258 acts as a base to shuttle a proton from α-carbon (CA) to imine carbon (C4A) of the PLP-Asp Schiff base. In the first step, the Lys258 abstracts the CA proton of the substrate leading to the formation of a carbanionic intermediate which is followed by the reprotonation of the Asp-PLP Schiff base at C4A atom by Lys258. It is found that the free energy barrier for the proton abstraction by Lys258 and that for the reprotonation are 17.85 and 3.57 kcal/mol, respectively. The carbanionic intermediate is 7.14 kcal/mol higher in energy than the reactant. Hence, the first step acts as the rate limiting step. The present calculations also show that the Lys258 residue undergoes a conformational change after the first step of transamination reaction and becomes proximal to C4A atom of the Asp-PLP Schiff base to favor the second step. The active site residues Tyr70* and Gly38 anchor the Lys258 in proper position and orientation during the first step of the reaction and stabilize the positive charge over Lys258 generated at the intermediate step.
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Affiliation(s)
- Sindrila Dutta Banik
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh, India
| | - Arindam Bankura
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh, India
| | - Amalendu Chandra
- Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur, Uttar Pradesh, India
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17
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Schaufelberger F, Seigel K, Ramström O. Hydrogen-Bond Catalysis of Imine Exchange in Dynamic Covalent Systems. Chemistry 2020; 26:15581-15588. [PMID: 32427370 DOI: 10.1002/chem.202001666] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2020] [Indexed: 12/28/2022]
Abstract
The reversibility of imine bonds has been exploited to great effect in the field of dynamic covalent chemistry, with applications such as preparation of functional systems, dynamic materials, molecular machines, and covalent organic frameworks. However, acid catalysis is commonly needed for efficient equilibration of imine mixtures. Herein, it is demonstrated that hydrogen bond donors such as thioureas and squaramides can catalyze the equilibration of dynamic imine systems under unprecedentedly mild conditions. Catalysis occurs in a range of solvents and in the presence of many sensitive additives, showing moderate to good rate accelerations for both imine metathesis and transimination with amines, hydrazines, and hydroxylamines. Furthermore, the catalyst proved simple to immobilize, introducing both reusability and extended control of the equilibration process.
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Affiliation(s)
- Fredrik Schaufelberger
- Department of Chemistry, KTH-Royal Institute of Technology, Teknikringen 36, 10044, Stockholm, Sweden
| | - Karolina Seigel
- Department of Chemistry, KTH-Royal Institute of Technology, Teknikringen 36, 10044, Stockholm, Sweden
| | - Olof Ramström
- Department of Chemistry, KTH-Royal Institute of Technology, Teknikringen 36, 10044, Stockholm, Sweden.,Department of Chemistry, University of Massachusetts Lowell, One University Ave., Lowell, MA, 01854, USA.,Department of Chemistry and Biomedical Sciences, Linnaeus University, 39182, Kalmar, Sweden
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