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Barone V, Crisci L, Di Grande S. Accurate Thermochemical and Kinetic Parameters at Affordable Cost by Means of the Pisa Composite Scheme (PCS). J Chem Theory Comput 2023; 19:7273-7286. [PMID: 37774410 PMCID: PMC10601482 DOI: 10.1021/acs.jctc.3c00817] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2023] [Indexed: 10/01/2023]
Abstract
A new strategy for the computation at an affordable cost of geometrical structures, thermochemical parameters, and rate constants for medium-sized molecules in the gas phase is proposed. The most distinctive features of the new model are the systematic use of cc-pVnZ-F12 basis sets, the addition of MP2 core-valence correlation in geometry optimizations by a double-hybrid functional, the separate extrapolation of MP2 and post-MP2 contributions, and the inclusion of anharmonic contributions in zero-point energies and thermodynamic functions. A thorough benchmark based on a wide range of prototypical systems shows that the new scheme outperforms the most well-known model chemistries without the need for any empirical parameter. Additional tests show that the computed zero-point energies and thermal contributions can be confidently used for obtaining accurate thermochemical and kinetic parameters. Since the whole computational workflow is translated in a black-box procedure, which can be followed with standard electronic structure codes, the way is paved for the accurate yet not prohibitively expensive study of medium- to large-sized molecules also by nonspecialists.
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Affiliation(s)
- Vincenzo Barone
- Scuola
Normale Superiore di Pisa, Piazza dei Cavalieri 7, 56125 Pisa, Italy
| | - Luigi Crisci
- Scuola
Normale Superiore di Pisa, Piazza dei Cavalieri 7, 56125 Pisa, Italy
| | - Silvia Di Grande
- Scuola
Normale Superiore di Pisa, Piazza dei Cavalieri 7, 56125 Pisa, Italy
- Scuola
Superiore Meridionale, Largo San Marcellino 10, 80138 Napoli, Italy
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2
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Di Grande S, Kállay M, Barone V. Accurate thermochemistry at affordable cost by means of an improved version of the JunChS-F12 model chemistry. J Comput Chem 2023; 44:2149-2157. [PMID: 37432050 DOI: 10.1002/jcc.27187] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2023] [Accepted: 06/23/2023] [Indexed: 07/12/2023]
Abstract
The junChS-F12 composite method has been improved by means of the latest implementation of the CCSD(F12*)(T+) ansatz and validated for the thermochemistry of molecules containing atoms of the first three rows of the periodic table. A thorough benchmark showed that this model, in conjunction with cost-effective revDSD-PBEP86-D3(BJ) reference geometries, offers an optimal compromise between accuracy and computational cost. If improved geometries are sought, the most effective option is to add MP2-F12 core-valence correlation corrections to CCSD(T)-F12b/jun-cc-pVTZ geometries without the need of performing any extrapolation to the complete basis set limit. In the same vein, CCSD(T)-F12b/jun-cc-pVTZ harmonic frequencies are remarkably accurate without any additional contribution. Pilot applications to noncovalent intermolecular interactions, conformational landscapes, and tautomeric equilibria confirm the effectiveness and reliability of the model.
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Affiliation(s)
- S Di Grande
- Classe di Scienze, Scuola Normale Superiore di Pisa, Pisa, Italy
- Scuola Superiore Meridionale, Napoli, Italy
| | - M Kállay
- Department of Physical Chemistry and Materials Science, Faculty of Chemical Technology and Biotechnology, Budapest University of Technology and Economics, Budapest, Hungary
- ELKH-BME Quantum Chemistry Research Group, Budapest, Hungary
- MTA-BME Lendület Quantum Chemistry Research Group, Budapest, Hungary
| | - V Barone
- Classe di Scienze, Scuola Normale Superiore di Pisa, Pisa, Italy
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3
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Lemler PM, Craft CL, Pollok CH, Regan TP, Vaccaro PH. Isolated and solvated chiroptical behavior in conformationally flexible butanamines. Chirality 2023; 35:586-618. [PMID: 37550220 DOI: 10.1002/chir.23570] [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: 03/15/2023] [Revised: 04/15/2023] [Accepted: 04/17/2023] [Indexed: 08/09/2023]
Abstract
The nonresonant optical activity of two highly flexible aliphatic amines, (2R)-3-methyl-2-butanamine (R-MBA) and (2R)-(3,3)-dimethyl-2-butanamine (R-DMBA), has been probed under isolated and solvated conditions to examine the roles of conformational isomerism and to explore the influence of extrinsic perturbations. The optical rotatory dispersion (ORD) measured in six solvents presented uniformly negative rotatory powers over the 320-590 nm region, with the long-wavelength magnitude of chiroptical response growing nearly monotonically as the dielectric constant of the surroundings diminished. The intrinsic specific optical rotation,α λ T (in deg dm-1 [g/mL]-1 ), extracted for ambient vapor-phase samples of R-MBA [-11.031(98) and -2.29 (11)] and R-DMBA [-9.434 (72) and -1.350 (48)] at 355 and 633 nm were best reproduced by counterintuitive solvents of high polarity (yet low polarizability) like acetonitrile and methanol. Attempts to interpret observed spectral signatures quantitatively relied on the linear-response frameworks of density-functional theory (B3LYP, cam-B3LYP, and dispersion-corrected analogs) and coupled-cluster theory (CCSD), with variants of the polarizable continuum model (PCM) deployed to account for the effects of implicit solvation. Building on the identification of several low-lying equilibrium geometries (nine for R-MBA and three for R-DMBA), ensemble-averaged ORD profiles were calculated at T = 300 K by means of the independent-conformer ansatz, which enabled response properties predicted for the optimized structure of each isomer to be combined through Boltzmann-weighted population fractions derived from corresponding relative internal-energy or free-energy values, the latter of which stemmed from composite CBS-APNO and G4 analyses. Although reasonable accord between theory and experiment was realized for the isolated (vapor-phase) species, the solution-phase results were less satisfactory and tended to degrade progressively as the solvent polarity increased. These trends were attributed to solvent-mediated changes in structural parameters and energy metrics for the transition states that separate and putatively isolate the equilibrium conformations supported by the ground electronic potential-energy surface, with the resulting displacement of barrier locations and/or decrease of barrier heights compromising the underlying premise of the independent-conformer ansatz.
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Affiliation(s)
- Paul M Lemler
- Department of Chemistry, Yale University, New Haven, Connecticut, USA
- Intel Corporation, Hillsboro, Oregon, USA
| | - Clayton L Craft
- Department of Chemistry, Yale University, New Haven, Connecticut, USA
- United States Air Force Research Laboratory, Rome, New York, USA
| | - Corina H Pollok
- Department of Chemistry, Yale University, New Haven, Connecticut, USA
- Organische Chemie II, Ruhr-Universität Bochum, Bochum, Germany
| | - Thomas P Regan
- Department of Chemistry, Yale University, New Haven, Connecticut, USA
| | - Patrick H Vaccaro
- Department of Chemistry, Yale University, New Haven, Connecticut, USA
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Barone V, Di Grande S, Lazzari F, Mendolicchio M. Accurate Structures and Spectroscopic Parameters of Guanine Tautomers in the Gas Phase by the Pisa Conventional and Explicitly Correlated Composite Schemes (PCS and PCS-F12). J Phys Chem A 2023; 127:6771-6778. [PMID: 37535450 PMCID: PMC10440789 DOI: 10.1021/acs.jpca.3c03999] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Revised: 07/21/2023] [Indexed: 08/05/2023]
Abstract
A general strategy for the accurate computation of structural and spectroscopic properties of biomolecule building blocks in the gas phase is proposed and validated for tautomeric equilibria. The main features of the new model are the inclusion of core-valence correlation in geometry optimizations by a double hybrid functional and the systematic use of wave-function composite methods in conjunction with cc-pVnZ-F12 basis sets with separate extrapolation of MP2 and post-MP2 contributions. The resulting Pisa composite scheme employing conventional (PCS) or explicitly correlated (PCS-F12) approaches is applied to the challenging problem of guanine tautomers in the gas phase. The results are in remarkable agreement with the experimental structures, relative stabilities, and spectroscopic signatures of different tautomers. The accuracy of the results obtained at reasonable cost by means of black-box parameter-free approaches paves the way toward systematic investigations of other molecular bricks of life also by non-specialists.
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Affiliation(s)
- Vincenzo Barone
- Scuola
Normale Superiore, Piazza dei Cavalieri 7, Pisa 56126, Italy
| | - Silvia Di Grande
- Scuola
Normale Superiore, Piazza dei Cavalieri 7, Pisa 56126, Italy
- Scuola
Superiore Meridionale, Largo San Marcellino 10, Napoli 80138, Italy
| | - Federico Lazzari
- Scuola
Normale Superiore, Piazza dei Cavalieri 7, Pisa 56126, Italy
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Barone V. DFT Meets Wave-Function Composite Methods for Characterizing Cytosine Tautomers in the Gas Phase. J Chem Theory Comput 2023; 19:4970-4981. [PMID: 37479680 PMCID: PMC10413851 DOI: 10.1021/acs.jctc.3c00465] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Indexed: 07/23/2023]
Abstract
A general strategy for the accurate computation of structural and spectroscopic properties of biomolecule building blocks in the gas phase has been further improved and validated with a special reference to tautomeric equilibria. The main improvements concern the use of the cc-pVTZ-F12 basis set in both DFT and CCSD(T)-F12 computations, the inclusion of core-valence correlation in geometry optimizations by double hybrid functionals, and the use of the cc-pVQZ-F12 basis set for complete basis set extrapolation at the MP2-F12 level. The resulting model chemistry is applied to the challenging problem of cytosine tautomers in the gas phase. The results are in remarkable agreement with experiment concerning both rotational and vibrational spectroscopic parameters and permit their unbiased interpretation in terms of structural and thermochemical features. Together with the intrinsic interest of the studied molecule, the accuracy of the results obtained at reasonable cost without any empirical parameter suggests that the proposed composite method can be profitably employed for accurate investigations of other molecular bricks of life.
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Affiliation(s)
- Vincenzo Barone
- Scuola Normale Superiore
di Pisa, Piazza dei Cavalieri 7, 56126 Pisa, Italy
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6
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Stochastic dynamic quantitative and 3D structural matrix assisted laser desorption/ionization mass spectrometric analyses of mixture of nucleosides. J Mol Struct 2022. [DOI: 10.1016/j.molstruc.2022.132701] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Huang SR, Tureček F. Noncanonical Isomers of Nucleoside Cation Radicals: An Ab Initio Study of the Dark Matter of DNA Ionization. J Phys Chem A 2022; 126:2480-2497. [PMID: 35439003 DOI: 10.1021/acs.jpca.2c00894] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Cation radicals of DNA nucleosides, 2'-deoxyadenosine, 2'-deoxyguanosine, 2'-deoxycytidine, and 2'-deoxythymidine, can exist in standard canonical forms or as noncanonical isomers in which the charge is introduced by protonation of the nucleobase, whereas the radical predominantly resides in the deoxyribose moiety. Density functional theory as well as correlated ab initio calculations with coupled clusters (CCSD(T)) that were extrapolated to the complete basis set limit showed that noncanonical nucleoside ion isomers were thermodynamically more stable than their canonical forms in both the gas phase and as water-solvated ions. This indicated the possibility of exothermic conversion of canonical to noncanonical forms. The noncanonical isomers were calculated to have very low adiabatic ion-electron recombination energies (REad) for the lowest-energy isomers 2'-deoxy-(N-3H)adenos-1'-yl (4.74 eV), 2'-deoxy-(N-7H)guanos-1'-yl (4.66 eV), 2'-deoxy-(N-3H)cytid-1'-yl (5.12 eV), and 2'-deoxy-5-methylene-(O-2H)uridine (5.24 eV). These were substantially lower than the REad value calculated for the canonical 2'-deoxyadenosine, 2'-deoxy guanosine, 2'-deoxy cytidine, and 2'-deoxy thymidine cation radicals, which were 7.82, 7.46, 8.14, and 8.20 eV, respectively, for the lowest-energy ion conformers of each type. Charge and spin distributions in noncovalent cation-radical dA⊂dT and dG⊂dC nucleoside pairs and dAT, dCT, dTC, and dGC dinucleotides were analyzed to elucidate the electronic structure of the cation radicals. Born-Oppenheimer molecular dynamics trajectory calculations of the dinucleotides and nucleoside pairs indicated rapid exothermic proton transfer from noncanonical T+· to A in both dAT+· and dA⊂dT+·, leading to charge and radical separation. Noncanonical T+· in dCT+· and dTC+· initiated rapid proton transfer to cytosine, whereas the canonical dCT+· dinucleotide ion retained the cation radical structure without isomerization. No spontaneous proton transfer was found in dGC+· and dG⊂dC+· containing canonical neutral and noncanonical ionized deoxycytidine.
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Affiliation(s)
- Shu R Huang
- Department of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, Washington 98195-1700, United States
| | - František Tureček
- Department of Chemistry, University of Washington, Bagley Hall, Box 351700, Seattle, Washington 98195-1700, United States
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Wieder M, Fass J, Chodera JD. Fitting quantum machine learning potentials to experimental free energy data: predicting tautomer ratios in solution. Chem Sci 2021; 12:11364-11381. [PMID: 34567495 PMCID: PMC8409483 DOI: 10.1039/d1sc01185e] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2021] [Accepted: 07/05/2021] [Indexed: 11/21/2022] Open
Abstract
The computation of tautomer ratios of druglike molecules is enormously important in computer-aided drug discovery, as over a quarter of all approved drugs can populate multiple tautomeric species in solution. Unfortunately, accurate calculations of aqueous tautomer ratios—the degree to which these species must be penalized in order to correctly account for tautomers in modeling binding for computer-aided drug discovery—is surprisingly difficult. While quantum chemical approaches to computing aqueous tautomer ratios using continuum solvent models and rigid-rotor harmonic-oscillator thermochemistry are currently state of the art, these methods are still surprisingly inaccurate despite their enormous computational expense. Here, we show that a major source of this inaccuracy lies in the breakdown of the standard approach to accounting for quantum chemical thermochemistry using rigid rotor harmonic oscillator (RRHO) approximations, which are frustrated by the complex conformational landscape introduced by the migration of double bonds, creation of stereocenters, and introduction of multiple conformations separated by low energetic barriers induced by migration of a single proton. Using quantum machine learning (QML) methods that allow us to compute potential energies with quantum chemical accuracy at a fraction of the cost, we show how rigorous relative alchemical free energy calculations can be used to compute tautomer ratios in vacuum free from the limitations introduced by RRHO approximations. Furthermore, since the parameters of QML methods are tunable, we show how we can train these models to correct limitations in the underlying learned quantum chemical potential energy surface using free energies, enabling these methods to learn to generalize tautomer free energies across a broader range of predictions. We show how alchemical free energies can be calculated with QML potentials to identify deficiencies in RRHO approximations for computing tautomeric free energies, and how these potentials can be learned from experiment to improve prediction accuracy.![]()
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Affiliation(s)
- Marcus Wieder
- Computational and Systems Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center New York NY 10065 USA
| | - Josh Fass
- Computational and Systems Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center New York NY 10065 USA .,Tri-Institutional PhD Program in Computational Biology and Medicine, Weill Cornell Graduate School of Medical Sciences New York NY 10065 USA
| | - John D Chodera
- Computational and Systems Biology Program, Sloan Kettering Institute, Memorial Sloan Kettering Cancer Center New York NY 10065 USA
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Liu Y, Ma C, Leonen CJA, Chatterjee C, Nováková G, Marek A, Tureček F. Tackling a Curious Case: Generation of Charge-Tagged Guanosine Radicals by Gas-Phase Electron Transfer and Their Characterization by UV-vis Photodissociation Action Spectroscopy and Theory. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2021; 32:772-785. [PMID: 33567214 PMCID: PMC8579407 DOI: 10.1021/jasms.0c00459] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
We report the generation of gas-phase riboguanosine radicals that were tagged at ribose with a fixed-charge 6-(trimethylammonium)hexane-1-aminocarbonyl group. The radical generation relied on electron transfer from fluoranthene anion to noncovalent dibenzocrown-ether dication complexes which formed nucleoside cation radicals upon one-electron reduction and crown-ether ligand loss. The cation radicals were characterized by collision-induced dissociation (CID), photodissociation (UVPD), and UV-vis action spectroscopy. Identification of charge-tagged guanosine radicals was challenging because of spontaneous dissociations by loss of a hydrogen atom and guanine that occurred upon storing the ions in the ion trap without further excitation. The loss of H proceeded from an exchangeable position on N-7 in guanine that was established by deuterium labeling and was the lowest energy dissociation of the guanosine radicals according to transition-state energy calculations. Rate constant measurements revealed an inverse isotope effect on the loss of either hydrogen or deuterium with rate constants kH = 0.25-0.26 s-1 and kD = 0.39-0.54 s-1. We used time-dependent density functional theory calculations, including thermal vibronic effects, to predict the absorption spectra of several protomeric radical isomers. The calculated spectra of low-energy N-7-H guanine-radical tautomers closely matched the action spectra. Transition-state-theory calculations of the rate constants for the loss of H-7 and guanine agreed with the experimental rate constants for a narrow range of ion effective temperatures. Our calculations suggest that the observed inverse isotope effect does not arise from the isotope-dependent differences in the transition-state energies. Instead, it may be caused by the dynamics of post-transition-state complexes preceding the product separation.
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Affiliation(s)
- Yue Liu
- Department of Chemistry, Bagley Hall, Box 351700, University of Washington, Seattle, Washington 98195-1700, United States
| | - Congcong Ma
- Department of Chemistry, Bagley Hall, Box 351700, University of Washington, Seattle, Washington 98195-1700, United States
| | - Calvin J A Leonen
- Department of Chemistry, Bagley Hall, Box 351700, University of Washington, Seattle, Washington 98195-1700, United States
| | - Champak Chatterjee
- Department of Chemistry, Bagley Hall, Box 351700, University of Washington, Seattle, Washington 98195-1700, United States
| | - Gabriela Nováková
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 16610 Prague 6, Czech Republic
| | - Aleš Marek
- Institute of Organic Chemistry and Biochemistry, Czech Academy of Sciences, Flemingovo nám. 2, 16610 Prague 6, Czech Republic
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Wentrup C. RACI Awards 2017–19. Aust J Chem 2019. [DOI: 10.1071/chv72n8_fo] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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