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Schindl A, Hagen ML, Cooley I, Jäger CM, Warden AC, Zelzer M, Allers T, Croft AK. Ion-combination specific effects driving the enzymatic activity of halophilic alcohol dehydrogenase 2 from Haloferax volcanii in aqueous ionic liquid solvent mixtures. RSC SUSTAINABILITY 2024; 2:2559-2580. [PMID: 39211508 PMCID: PMC11353702 DOI: 10.1039/d3su00412k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Accepted: 06/30/2024] [Indexed: 09/04/2024]
Abstract
Biocatalysis in ionic liquids enables novel routes for bioprocessing. Enzymes derived from extremophiles promise greater stability and activity under ionic liquid (IL) influence. Here, we probe the enzyme alcohol dehydrogenase 2 from the halophilic archaeon Haloferax volcanii in thirteen different ion combinations for relative activity and analyse the results against molecular dynamics (MD) simulations of the same IL systems. We probe the ionic liquid property space based on ion polarizability and molecular electrostatic potential. Using the radial distribution functions, survival probabilities and spatial distribution functions of ions, we show that cooperative ion-ion interactions determine ion-protein interactions, and specifically, strong ion-ion interactions equate to higher enzymatic activity if neither of the ions interact strongly with the protein surface. We further demonstrate a tendency for cations interacting with the protein surface to be least detrimental to enzymatic activity if they show a low polarizability when combined with small hydrophilic anions. We also find that the IL ion influence is not mitigated by the surplus of negatively charged residues of the halophilic enzyme. This is shown by free energy landscape analysis in root mean square deviation and distance variation plots of active site gating residues (Trp43 and His273) demonstrating no protection of specific structural elements relevant to preserving enzymatic activity. On the other hand, we observe a general effect across all IL systems that a tight binding of water at acidic residues is preferentially interrupted at these residues through the increased presence of potassium ions. Overall, this study demonstrates a co-ion interaction dependent influence on allosteric surface residues controlling the active/inactive conformation of halophilic alcohol dehydrogenase 2 and the necessity to engineer ionic liquid systems for enzymes that rely on the integrity of functional surface residues regardless of their halophilicity or thermophilicity for use in bioprocessing.
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Affiliation(s)
- Alexandra Schindl
- Sustainable Process Technologies Group, Department of Chemical and Environmental Engineering, University of Nottingham Nottingham NG7 2RD UK
- School of Pharmacy, University of Nottingham, University Park Campus Nottingham NG7 2RD UK
- School of Life Sciences, University of Nottingham, Queen's Medical Centre Nottingham NG7 2UH UK
- School of Molecular and Cellular Biology, University of Leeds Leeds LS2 9JT UK
- Astbury Centre for Structural Molecular Biology, Faculty of Biological Sciences, University of Leeds Leeds LS2 9JT UK
| | - M Lawrence Hagen
- Sustainable Process Technologies Group, Department of Chemical and Environmental Engineering, University of Nottingham Nottingham NG7 2RD UK
| | - Isabel Cooley
- Department of Chemical Engineering, Loughborough University LE11 3TU UK
| | - Christof M Jäger
- Sustainable Process Technologies Group, Department of Chemical and Environmental Engineering, University of Nottingham Nottingham NG7 2RD UK
- Data Science and Modelling, Pharmaceutical Sciences, R&D, AstraZeneca Gothenburg Pepparedsleden 1 SE-431 83 Mölndal Sweden
| | - Andrew C Warden
- CSIRO Environment, Commonwealth Scientific and Industrial Research Organization (CSIRO), Research and Innovation Park Acton Canberra ACT 2600 Australia
- Advanced Engineering Biology Future Science Platform, Commonwealth Scientific and Industrial Research Organisation (CSIRO), Research and Innovation Park Acton Canberra ACT 2600 Australia
| | - Mischa Zelzer
- School of Pharmacy, University of Nottingham, University Park Campus Nottingham NG7 2RD UK
| | - Thorsten Allers
- School of Life Sciences, University of Nottingham, Queen's Medical Centre Nottingham NG7 2UH UK
| | - Anna K Croft
- Department of Chemical Engineering, Loughborough University LE11 3TU UK
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2
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Hsieh AY, Haines RS, Harper JB. Effects of Ionic Liquids on the Nucleofugality of Bromide. J Org Chem 2024; 89:6247-6256. [PMID: 38655582 DOI: 10.1021/acs.joc.4c00249] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/26/2024]
Abstract
The nucleofugality of bromide was measured in solvent mixtures containing ionic liquids. The solvolysis rate constants of the bromides of well-defined electrofuges were determined in mixtures containing different proportions of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide in ethanol. Temperature-dependent kinetic studies allowed an explanation of the observed solvent effects in different mixtures in terms of interactions in solution. Using the solvolysis data, the nucleofugality of bromide in these systems was determined. Likewise, nucleofugality data for bromide were determined in mixtures containing high proportions of seven further ionic liquids. These data allowed quantification of the effects of both varying the amount of ionic liquid and the nature of ionic liquid components on the nucleofugality of bromide. Importantly, ionic liquid mixtures were shown to affect the nucleofugality in a manner similar to chloride, providing a method for predicting the effects of ionic liquids on other electrofuges. Further, the ionic liquids were shown to move the transition state earlier along the reaction coordinate, meaning that there is less charge development in the transition state.
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Affiliation(s)
- Andrew Y Hsieh
- School of Chemistry, University of New South Wales, UNSW, Sydney, NSW 2052, Australia
| | - Ronald S Haines
- School of Chemistry, University of New South Wales, UNSW, Sydney, NSW 2052, Australia
| | - Jason B Harper
- School of Chemistry, University of New South Wales, UNSW, Sydney, NSW 2052, Australia
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3
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Resende LF, Pliego JR. Modeling the alkylation of amines with alkyl bromides: explaining the low selectivity due to multiple alkylation. J Mol Model 2024; 30:107. [PMID: 38492112 DOI: 10.1007/s00894-024-05902-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2023] [Accepted: 03/12/2024] [Indexed: 03/18/2024]
Abstract
CONTEXT Nucleophilic substitution reactions of aliphatic amines with alkyl halides represent a simple and direct mechanism for obtaining higher-order aliphatic amines. However, it is well known that these reactions suffer from low selectivity due to multiple alkylations, which is attributed to the higher reactivity of the newly formed amine. In order to provide a detailed explanation for this kind of system, we have investigated the reactivity of primary and secondary amines with 1-bromopropane and 2-bromopropane. The free energy profile in acetonitrile solution was obtained and a detailed microkinetic analysis was needed to analyze this complex reaction system. We have found that the product of the first alkylation is an ion pair corresponding to the protonated secondary amine and the bromide ion, which can transfer the proton to the reactant primary amine. Then, the newly formed secondary amine can also react, leading to a second alkylation to produce a tertiary protonated amine. Our modeling points out that both the proton transfer equilibria and the similar reactivity of the primary and secondary amines produce reduced selectivity. The proton transfer equilibria also contribute to slowing down the kinetics of the first alkylation. METHODS The exploration of the mechanism was done by geometry optimization using the CPCM/X3LYP/ma-def2-SVP method, followed by harmonic frequency calculation at this same level of theory. A composite approach was used to obtain the free energy profile, using the more accurate ωB97X-D3/ma-def2-TZVPP level of theory for electronic energy and the SMD model for the solvation free energy. These calculations were performed with the ORCA 4 program. The detailed microkinetic analysis was done using the Kintecus program.
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Affiliation(s)
- Luis F Resende
- Departamento de Ciências Naturais, Universidade Federal de São João del Rei, São João del Rei, MG, 36301-160, Brazil
| | - Josefredo R Pliego
- Departamento de Ciências Naturais, Universidade Federal de São João del Rei, São João del Rei, MG, 36301-160, Brazil.
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Hsieh AY, Haines RS, Harper JB. The effects of ionic liquids on the ethanolysis of a chloroacenaphthene. Evaluation of the effectiveness of nucleofugality data to predict reaction outcome. RSC Adv 2023; 13:21036-21043. [PMID: 37448642 PMCID: PMC10336772 DOI: 10.1039/d3ra04302a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 06/30/2023] [Indexed: 07/15/2023] Open
Abstract
The reaction of a chlorobenzene in mixtures containing ethanol and eight different ionic liquids was investigated in order to understand the effects of varying proportions and constituent ions of an ionic liquid on the rate constant of the process. The results were found to be generally consistent with previously studied reactions of the same type, with small proportions of an ionic liquid resulting in a rate constant increase compared to ethanol and large proportions causing a rate constant decrease. Temperature dependent kinetic studies were used to interpret the changes in reaction outcome, particularly noting an entropic cost on moving to high proportions of ionic liquid, consistent with organisation of solvent around the transition state. While attempts to use empirical solvent parameters to correlate outcome with the ionic liquid used were unsuccessful, use of recently acquired nucleofugality data for chloride and estimations for the electrofuge allowed for excellent prediction of the effects of ionic liquids, with rate constants quantitatively predicted in systems containing both different proportions of ionic liquid (mean absolute error (MAE) log(k1) = 0.11) and different ionic liquids (MAE log(k1) = 0.33). Importantly, this demonstrates the ready application of these quantitative reactivity parameters.
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Affiliation(s)
- Andrew Y Hsieh
- School of Chemistry, University of New South Wales UNSW Sydney NSW 2052 Australia +61 2 9385 6141 +61 2 9385 4692
| | - Ronald S Haines
- School of Chemistry, University of New South Wales UNSW Sydney NSW 2052 Australia +61 2 9385 6141 +61 2 9385 4692
| | - Jason B Harper
- School of Chemistry, University of New South Wales UNSW Sydney NSW 2052 Australia +61 2 9385 6141 +61 2 9385 4692
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Matthewman EL, Kapila B, Grant ML, Weber CC. The amphiphilic nanostructure of ionic liquids affects the dehydration of alcohols. Chem Commun (Camb) 2022; 58:13572-13575. [PMID: 36412193 DOI: 10.1039/d2cc04854j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The effect of the amphiphilic nanostructure of ionic liquids on the dehydration of secondary alcohols to alkenes has been investigated. The influence of these nanostructures was inverted when an acid catalyst was added to the reaction. This phenomenon was ascribed to a balance between ion-solute interactions and the formation of solute-catalyst hydrogen bonds, highlighting the complex interplay between interactions and reaction outcomes in these nanostructured solvent systems.
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Affiliation(s)
- Emma L Matthewman
- School of Chemical Sciences, The University of Auckland, Auckland, New Zealand. .,MacDiarmid Institute for Advanced Materials and Nanotechnology, New Zealand
| | - Bhavana Kapila
- School of Science, Auckland University of Technology, Auckland, New Zealand
| | - Mason L Grant
- School of Chemical Sciences, The University of Auckland, Auckland, New Zealand. .,MacDiarmid Institute for Advanced Materials and Nanotechnology, New Zealand
| | - Cameron C Weber
- School of Chemical Sciences, The University of Auckland, Auckland, New Zealand. .,MacDiarmid Institute for Advanced Materials and Nanotechnology, New Zealand
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Coney MD, Morris DC, Gilbert A, Prescott SW, Haines RS, Harper JB. Effects of Ionic Liquids on the Nucleofugality of Chloride. J Org Chem 2021; 87:1767-1779. [PMID: 34756050 DOI: 10.1021/acs.joc.1c02043] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The nucleofugality of chloride has been measured in solvent mixtures containing ionic liquids for the first time, allowing reactivity in these solvents to be put in context with molecular solvents. Using well-described electrofuges, solvolysis rate constants were determined in mixtures containing different proportions of ethanol and the ionic liquid 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide; the different solvent effects observed as the mixture changed could be explained using interactions of the ionic liquid with species along the reaction coordinate, determined using temperature dependent kinetic studies. The solvolysis data allowed determination of the nucleofugality of chloride in these mixtures, which varied with the proportion of salt in the reaction mixture, demonstrating quantitatively the importance of the amount of ionic liquid in the reaction mixture in determining reaction outcome. Nucleofugality data for chloride were determined in seven further ionic liquids, with the reactivity shown to vary over more than an order of magnitude. This outcome illustrates that the components of the ionic liquid are critical in determining reaction outcome. Overall, this work quantitatively extends the understanding of solvent effects in ionic liquids and demonstrates the potential for such information to be used to rationally select an ionic liquid to control reaction outcome.
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Koutsoukos S, Philippi F, Malaret F, Welton T. A review on machine learning algorithms for the ionic liquid chemical space. Chem Sci 2021; 12:6820-6843. [PMID: 34123314 PMCID: PMC8153233 DOI: 10.1039/d1sc01000j] [Citation(s) in RCA: 47] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2021] [Accepted: 04/28/2021] [Indexed: 01/05/2023] Open
Abstract
There are thousands of papers published every year investigating the properties and possible applications of ionic liquids. Industrial use of these exceptional fluids requires adequate understanding of their physical properties, in order to create the ionic liquid that will optimally suit the application. Computational property prediction arose from the urgent need to minimise the time and cost that would be required to experimentally test different combinations of ions. This review discusses the use of machine learning algorithms as property prediction tools for ionic liquids (either as standalone methods or in conjunction with molecular dynamics simulations), presents common problems of training datasets and proposes ways that could lead to more accurate and efficient models.
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Affiliation(s)
- Spyridon Koutsoukos
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London White City Campus London W12 0BZ UK
| | - Frederik Philippi
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London White City Campus London W12 0BZ UK
| | - Francisco Malaret
- Department of Chemical Engineering, Imperial College London South Kensington Campus London SW7 2AZ UK
| | - Tom Welton
- Department of Chemistry, Molecular Sciences Research Hub, Imperial College London White City Campus London W12 0BZ UK
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Morris DC, Prescott SW, Harper JB. Rapid relaxation NMR measurements to predict rate coefficients in ionic liquid mixtures. An examination of reaction outcome changes in a homologous series of ionic liquids. Phys Chem Chem Phys 2021; 23:9878-9888. [PMID: 33908419 DOI: 10.1039/d0cp06066f] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A series of ionic liquids based on the 1-alkyl-3-methylimidazolium cations were examined as components of the solvent mixture for a bimolecular substitution process. The effects on both the rate coefficient of the process and the NMR spin-spin relaxation of the solvent components of changing either the alkyl chain length or the amount of ionic liquid in the reaction mixture were determined. At a constant mole fraction, a shorter alkyl chain length resulted in a greater rate coefficient enhancement and a longer relaxation time, with the opposite effects for a longer alkyl chain length. For a given ionic liquid, increasing the proportion of salt in the reaction mixture resulted in a greater rate coefficient and a shorter relaxation time. The microscopic origins of the rate coefficient enhancement were determined and a step change found in the activation parameters on increasing the alkyl chain length from hexyl to octyl, suggesting notable structuring in solution. Across a range of ionic liquids and solvent compositions, the relaxation time from NMR measurements was shown to relate to the reaction rate coefficient. The approach of using fast and simple NMR relaxation measurements to predict reaction outcomes was exemplified using a morpholinium-based ionic liquid.
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Affiliation(s)
- Daniel C Morris
- School of Chemical Engineering, University of New South Wales, Sydney, NSW 2052, Australia.
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Gilbert A, Haines RS, Harper JB. The effects of using an ionic liquid as a solvent for a reaction that proceeds through a phenonium ion. J PHYS ORG CHEM 2021. [DOI: 10.1002/poc.4217] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Affiliation(s)
- Alyssa Gilbert
- School of Chemistry University of New South Wales, UNSW Sydney Sydney New South Wales Australia
| | - Ronald S. Haines
- School of Chemistry University of New South Wales, UNSW Sydney Sydney New South Wales Australia
| | - Jason B. Harper
- School of Chemistry University of New South Wales, UNSW Sydney Sydney New South Wales Australia
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Greaves TL, Schaffarczyk McHale KS, Burkart-Radke RF, Harper JB, Le TC. Machine learning approaches to understand and predict rate constants for organic processes in mixtures containing ionic liquids. Phys Chem Chem Phys 2021; 23:2742-2752. [PMID: 33496292 DOI: 10.1039/d0cp04227g] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
The ability to tailor the constituent ions in ionic liquids (ILs) is highly advantageous as it provides access to solvents with a range of physicochemical properties. However, this benefit also leads to large compositional spaces that need to be explored to optimise systems, often involving time consuming experimental work. The use of machine learning methods is an effective way to gain insight based on existing data, to develop structure-property relationships and to allow the prediction of ionic liquid properties. Here we have applied machine learning models to experimentally determined rate constants of a representative organic process (the reaction of pyridine with benzyl bromide) in IL-acetonitrile mixtures. Multiple linear regression (MLREM) and artificial neural networks (BRANNLP) were both able to model the data well. The MLREM model was able to identify the structural features on the cations and anions that had the greatest effect on the rate constant. Secondly, predictive MLREM and BRANNLP models were developed from the full initial set of rate constant data. From these models, a large number of predictions (>9000) of rate constant were made for mixtures of different ionic liquids, at different proportions of ionic liquid and molecular solvent, at different temperatures. A selection of these predictions were tested experimentally, including through the preparation of novel ionic liquids, with overall good agreement between the predicted and experimental data. This study highlights the benefits of using machine learning methods on kinetic data in ionic liquid mixtures to enable the development of rigorous structure-property relationships across multiple variables simultaneously, and to predict properties of new ILs and experimental conditions.
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Affiliation(s)
- Tamar L Greaves
- College of Science Engineering and Health, RMIT University, Melbourne, VIC 3001, Australia.
| | | | | | - Jason B Harper
- School of Chemistry, University of New South Wales, Sydney, NSW 2052, Australia.
| | - Tu C Le
- College of Science Engineering and Health, RMIT University, Melbourne, VIC 3001, Australia.
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Kahlon NK, Weber CC. Micellar Catalysis and Reactivity in Nanostructured Ionic Liquids: Two Sides of the Same Coin? Aust J Chem 2021. [DOI: 10.1071/ch21109] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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