1
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Knorr J, Sülzner N, Geissler B, Spies C, Grandjean A, Kutta RJ, Jung G, Nuernberger P. Ultrafast transient absorption and solvation of a super-photoacid in acetoneous environments. PHOTOCHEMICAL & PHOTOBIOLOGICAL SCIENCES : OFFICIAL JOURNAL OF THE EUROPEAN PHOTOCHEMISTRY ASSOCIATION AND THE EUROPEAN SOCIETY FOR PHOTOBIOLOGY 2022; 21:2179-2192. [PMID: 36178669 DOI: 10.1007/s43630-022-00287-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/11/2022] [Accepted: 08/08/2022] [Indexed: 12/13/2022]
Abstract
The phenomenon of photoacidity, i.e., an increase in acidity by several orders of magnitude upon electronic excitation, is frequently encountered in aromatic alcohols capable of transferring a proton to a suitable acceptor. A promising new class of neutral super-photoacids based on pyranine derivatives has been shown to exhibit pronounced solvatochromic effects. To disclose the underlying mechanisms contributing to excited-state proton transfer (ESPT) and the temporal characteristics of solvation and ESPT, we scrutinize the associated ultrafast dynamics of the strongest photoacid of this class, namely tris(1,1,1,3,3,3-hexafluoropropan-2-yl)8-hydroxypyrene-1,3,6-trisulfonate, in acetoneous environment, thereby finding experimental evidence for ESPT even under these adverse conditions for proton transfer. Juxtaposing results from time-correlated single-photon counting and femtosecond transient absorption measurements combined with a complete decomposition of all signal components, i.e., absorption of ground and excited states as well as stimulated emission, we disclose dynamics of solvation, rotational diffusion, and radiative relaxation processes in acetone and identify the relevant steps of ESPT along with the associated time scales.
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Affiliation(s)
- Johannes Knorr
- Physikalische Chemie II, Ruhr-Universität Bochum, 44780, Bochum, Germany.,Erlangen Graduate School in Advanced Optical Technologies (SAOT), Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Paul-Gordan-Straße 6, 91052, Erlangen, Germany
| | - Niklas Sülzner
- Lehrstuhl für Theoretische Chemie, Ruhr-Universität Bochum, 44780, Bochum, Germany.,Physikalische Chemie II, Ruhr-Universität Bochum, 44780, Bochum, Germany
| | - Bastian Geissler
- Institut für Physikalische und Theoretische Chemie, Universität Regensburg, Universitätsstraße 31, 95053, Regensburg, Germany.,Physikalische Chemie II, Ruhr-Universität Bochum, 44780, Bochum, Germany
| | - Christian Spies
- Biophysikalische Chemie, Universität des Saarlandes, 66123, Saarbrücken, Germany.,Physikalische Chemie II, Ruhr-Universität Bochum, 44780, Bochum, Germany
| | - Alexander Grandjean
- Biophysikalische Chemie, Universität des Saarlandes, 66123, Saarbrücken, Germany
| | - Roger Jan Kutta
- Institut für Physikalische und Theoretische Chemie, Universität Regensburg, Universitätsstraße 31, 95053, Regensburg, Germany
| | - Gregor Jung
- Biophysikalische Chemie, Universität des Saarlandes, 66123, Saarbrücken, Germany
| | - Patrick Nuernberger
- Institut für Physikalische und Theoretische Chemie, Universität Regensburg, Universitätsstraße 31, 95053, Regensburg, Germany. .,Physikalische Chemie II, Ruhr-Universität Bochum, 44780, Bochum, Germany.
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Study on Hydrolysis Properties and Mechanism of Poly(3-Methacrylamido Propyl Trimethyl Ammonium Chloride) Solution. Polymers (Basel) 2022; 14:polym14142811. [PMID: 35890587 PMCID: PMC9318009 DOI: 10.3390/polym14142811] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Revised: 07/06/2022] [Accepted: 07/07/2022] [Indexed: 02/01/2023] Open
Abstract
Poly(3-methacrylamido propyl trimethyl ammonium chloride) (PMAPTAC) is a typical cationic water-soluble polyelectrolyte, which has been widely used in petroleum, papermaking, daily cosmetics and other fields in the form of an aqueous solution. However, the acid–base and thermal stability of PMAPTAC in aqueous solution have not been reported yet, which hinders its further application in high-temperature and acid–base environments. To address these deficiencies, the effects of temperature and pH of PMAPTAC with different intrinsic viscosities on its hydrolysis stability were investigated qualitatively and quantitatively, and the hydrolysis mechanism was studied. Firstly, the qualitative analysis showed that the apparent viscosity of the PMAPTAC solution decreased with hydrolysis time at different temperatures and pH. The higher the temperature and the lower the pH, the greater the viscosity loss of PMAPTAC. The quantitative analysis showed that the hydrolysis rate of the PMAPTAC sample solution increased with the increase in temperature and pH. In addition, the intrinsic viscosity of PMAPTAC samples had little effect on the hydrolytic stability of PMAPTAC. Secondly, by analyzing the viscosity curves at different pH and temperatures by Arrhenius analysis, the Arrhenius equations were found to be 1/τ = 200.34e^((−25.04)/RT), 1/τ = 9127.07e^((−38.90)/RT) and 1/τ = 4683.03e^((−39.89)/RT) for pH 3, pH 7 and pH 11, respectively. Thirdly, the hydrolysis rate of PDMC was the fastest under alkaline conditions. In addition, compared with PDMC, PMAPTAC had better hydrolysis stability under the same conditions. Finally, the mechanism of the hydrolyzed polymer was studied by FTIR and 13CNMR, which showed that the carbonyl group of PMAPTAC was hydrolyzed into a carboxyl group, and the small molecule (3-aminopropyl) trimethylammonium chloride was generated, while the ester group of PDMC was hydrolyzed into a carboxyl group, and choline chloride was released. The above results can provide a theoretical basis for the application of PMAPTAC in some high-temperature and acid–base environments.
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Zadok I, Long H, Pivovar B, Roznowska A, Michalak A, Dekel DR, Srebnik S. Unexpected hydroxide ion structure and properties at low hydration. J Mol Liq 2020. [DOI: 10.1016/j.molliq.2020.113485] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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4
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Slanina T, Ayub R, Toldo J, Sundell J, Rabten W, Nicaso M, Alabugin I, Fdez Galván I, Gupta AK, Lindh R, Orthaber A, Lewis RJ, Grönberg G, Bergman J, Ottosson H. Impact of Excited-State Antiaromaticity Relief in a Fundamental Benzene Photoreaction Leading to Substituted Bicyclo[3.1.0]hexenes. J Am Chem Soc 2020; 142:10942-10954. [PMID: 32456426 PMCID: PMC7497645 DOI: 10.1021/jacs.9b13769] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
![]()
Benzene exhibits a rich photochemistry
which can provide access
to complex molecular scaffolds that are difficult to access with reactions
in the electronic ground state. While benzene is aromatic in its ground
state, it is antiaromatic in its lowest ππ* excited
states. Herein, we clarify to what extent relief of excited-state
antiaromaticity (ESAA) triggers a fundamental benzene photoreaction:
the photoinitiated nucleophilic addition of solvent to benzene in
acidic media leading to substituted bicyclo[3.1.0]hex-2-enes. The
reaction scope was probed experimentally, and it was found that silyl-substituted
benzenes provide the most rapid access to bicyclo[3.1.0]hexene derivatives,
formed as single isomers with three stereogenic centers in yields
up to 75% in one step. Two major mechanism hypotheses, both involving
ESAA relief, were explored through quantum chemical calculations and
experiments. The first mechanism involves protonation of excited-state
benzene and subsequent rearrangement to bicyclo[3.1.0]hexenium cation,
trapped by a nucleophile, while the second involves photorearrangement
of benzene to benzvalene followed by protonation and nucleophilic
addition. Our studies reveal that the second mechanism is operative.
We also clarify that similar ESAA relief leads to puckering of S1-state silabenzene and pyridinium ion, where the photorearrangement
of the latter is of established synthetic utility. Finally, we identified
causes for the limitations of the reaction, information that should
be valuable in explorations of similar photoreactions. Taken together,
we reveal how the ESAA in benzene and 6π-electron heterocycles
trigger photochemical distortions that provide access to complex three-dimensional
molecular scaffolds from simple reactants.
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Affiliation(s)
- Tomáš Slanina
- Department of Chemistry - Ångström Laboratory, Uppsala University, SE-751 20, Uppsala, Sweden.,Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, Flemingovo námĕstí 2, 16610 Prague 6, Czech Republic
| | - Rabia Ayub
- Department of Chemistry - Ångström Laboratory, Uppsala University, SE-751 20, Uppsala, Sweden
| | - Josene Toldo
- Department of Chemistry - Ångström Laboratory, Uppsala University, SE-751 20, Uppsala, Sweden
| | - Johan Sundell
- Medicinal Chemistry, Research and Early Development Cardiovascular, Renal and Metabolism, BioPharmaceuticals R&D, AstraZeneca, Gothenburg, Sweden
| | - Wangchuk Rabten
- Department of Chemistry - Ångström Laboratory, Uppsala University, SE-751 20, Uppsala, Sweden
| | - Marco Nicaso
- Department of Chemistry - Ångström Laboratory, Uppsala University, SE-751 20, Uppsala, Sweden
| | - Igor Alabugin
- Department of Chemistry and Biochemistry, Florida State University, Tallahassee, Florida 32306-4390, United States
| | - Ignacio Fdez Galván
- Department of Chemistry - BMC, Uppsala University, SE-751 23 Uppsala, Sweden
| | - Arvind K Gupta
- Department of Chemistry - Ångström Laboratory, Uppsala University, SE-751 20, Uppsala, Sweden
| | - Roland Lindh
- Department of Chemistry - BMC, Uppsala University, SE-751 23 Uppsala, Sweden.,Uppsala Center for Computational Chemistry - UC3, Uppsala University, SE-751 23 Uppsala Sweden
| | - Andreas Orthaber
- Department of Chemistry - Ångström Laboratory, Uppsala University, SE-751 20, Uppsala, Sweden
| | - Richard J Lewis
- Medicinal Chemistry, Research and Early Development Respiratory, Inflammation and Autoimmune, BioPharmaceuticals R&D, AstraZeneca, Gothenburg, Sweden
| | - Gunnar Grönberg
- Medicinal Chemistry, Research and Early Development Respiratory, Inflammation and Autoimmune, BioPharmaceuticals R&D, AstraZeneca, Gothenburg, Sweden
| | - Joakim Bergman
- Medicinal Chemistry, Research and Early Development Cardiovascular, Renal and Metabolism, BioPharmaceuticals R&D, AstraZeneca, Gothenburg, Sweden
| | - Henrik Ottosson
- Department of Chemistry - Ångström Laboratory, Uppsala University, SE-751 20, Uppsala, Sweden
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5
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Hwang J, Chang J. Understanding the mass-transfer of Br species in an aqueous and quaternary ammonium polybromide biphasic system via particle-impact electrochemical analysis. J IND ENG CHEM 2019. [DOI: 10.1016/j.jiec.2019.08.028] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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6
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Suwannakham P, Chaiwongwattana S, Sagarik K. Mechanisms of photoexcitation and photoionization in small water clusters. RSC Adv 2018; 8:36731-36744. [PMID: 35558945 PMCID: PMC9089274 DOI: 10.1039/c8ra06095a] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2018] [Accepted: 10/23/2018] [Indexed: 11/21/2022] Open
Abstract
The S0 → S1 excitation leads to strong polarization and formation of [(H2O)2]+˙ from which both photoexcited and photoionized products are generated.
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Affiliation(s)
- Parichart Suwannakham
- School of Chemistry
- Institute of Science
- Suranaree University of Technology
- Nakhon Ratchasima 30000
- Thailand
| | - Sermsiri Chaiwongwattana
- School of Chemistry
- Institute of Science
- Suranaree University of Technology
- Nakhon Ratchasima 30000
- Thailand
| | - Kritsana Sagarik
- School of Chemistry
- Institute of Science
- Suranaree University of Technology
- Nakhon Ratchasima 30000
- Thailand
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7
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Loupe N, Nasirova N, Doan J, Valdez D, Furlani M, Dimakis N, Smotkin ES. DFT - experimental IR spectroscopy of lithiated single ion conducting perfluorinated sulfonated ionomers: Ion induced polarization band broadening. J Electroanal Chem (Lausanne) 2017. [DOI: 10.1016/j.jelechem.2017.02.041] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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8
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9
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Asthana A, Wheeler DR. A polarizable reactive force field for water to enable molecular dynamics simulations of proton transport. J Chem Phys 2013; 138:174502. [DOI: 10.1063/1.4798457] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
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10
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Greisch JF, Harding ME, Kordel M, Klopper W, Kappes MM, Schooss D. Intrinsic fluorescence properties of rhodamine cations in gas-phase: triplet lifetimes and dispersed fluorescence spectra. Phys Chem Chem Phys 2013; 15:8162-70. [DOI: 10.1039/c3cp44362k] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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11
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Kale S, Herzfeld J. Proton Defect Solvation and Dynamics in Aqueous Acid and Base. Angew Chem Int Ed Engl 2012. [DOI: 10.1002/ange.201203568] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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12
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Kale S, Herzfeld J. Proton defect solvation and dynamics in aqueous acid and base. Angew Chem Int Ed Engl 2012; 51:11029-32. [PMID: 23037880 DOI: 10.1002/anie.201203568] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2012] [Revised: 07/18/2012] [Indexed: 11/11/2022]
Abstract
Easy come, easy go: LEWIS, a new model of reactive and polarizable water that enables the simulation of a statistically reliable number of proton hopping events in aqueous acid and base at concentrations of practical interest, is used to evaluate proton transfer intermediates in aqueous acid and base (picture, left and right, respectively).
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Affiliation(s)
- Seyit Kale
- Graduate Program in Biophysics and Structural Biology, Brandeis University, MS 009, 415 South Street, Waltham, MA, USA
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13
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Bankura A, Chandra A. Hydroxide ion can move faster than an excess proton through one-dimensional water chains in hydrophobic narrow pores. J Phys Chem B 2012; 116:9744-57. [PMID: 22793519 DOI: 10.1021/jp301466e] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Carbon nanotubes (CNT) are known to provide a hydrophobic, confined environment for water where its structure and dynamics can be very different from those of bulk water. In particular, narrow CNTs of the type (6,6) allow only a single one-dimensional (1D) chain of water molecules inside them, thus providing an idealized scenario to study motion in 1D along water chains. In the present study, we have investigated structural and dynamic behavior of water and also of an excess proton and hydroxide ion in water-filled narrow CNTs by means of ab initio molecular dynamics and combined quantum-classical simulations. The main focus of the present work is on the molecular mechanism and kinetics of hydronium and hydroxide ion migration along 1D water chains of different lengths in confinement. It is found that the hydrogen-bonded structures of water and the excess proton and hydroxide ion in CNTs can be very different from those in bulk, and these altered solvation structures play critical roles in determining the proton-transfer (PT) rates along water chains. For the present 1D chain systems, the hydroxide ion is found to migrate at a slightly faster rate than the excess proton, unlike their relative mobilities in bulk water. This faster migration of the hydroxide ion is found not only in CNTs with periodicity along the tube axis but also in isolated CNTs where the excess proton and the hydroxide ion are allowed to move under the influence of an electric field of an oppositely charged ion. The roles of rotational jumps and hydrogen-bond fluctuations in the PT events are discussed. In addition, the significance of hydrogen-bonding defects on the dynamics of an excess proton and hydroxide ion is also discussed for varying chain lengths.
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Affiliation(s)
- Arindam Bankura
- Department of Chemistry, Indian Institute of Technology, Kanpur, India 208016
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14
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Kale S, Herzfeld J, Dai S, Blank M. Lewis-inspired representation of dissociable water in clusters and Grotthuss chains. J Biol Phys 2012; 38:49-59. [PMID: 23277669 PMCID: PMC3285721 DOI: 10.1007/s10867-011-9229-5] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2011] [Accepted: 05/08/2011] [Indexed: 10/18/2022] Open
Abstract
Proton transfer to and from water is critical to the function of water in many settings. However, it has been challenging to model. Here, we present proof-of-principle for an efficient yet robust model based on Lewis-inspired submolecular particles with interactions that deviate from Coulombic at short distances to take quantum effects into account. This "LEWIS" model provides excellent correspondence with experimental structures for water molecules and water clusters in their neutral, protonated and deprotonated forms; reasonable values for the proton affinities of water and hydroxide; a good value for the strength of the hydrogen bond in the water dimer; the correct order of magnitude for the stretch and bend force constants of water; and the expected time course for Grotthuss transport in water chains.
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Affiliation(s)
- Seyit Kale
- Graduate Program in Biophysics and Structural Biology, Brandeis University, Waltham, MA 02454 USA
| | - Judith Herzfeld
- Department of Chemistry, Brandeis University, Waltham, MA 02454 USA
| | - Stacy Dai
- Department of Chemistry, Brandeis University, Waltham, MA 02454 USA
| | - Michael Blank
- Department of Chemistry, Brandeis University, Waltham, MA 02454 USA
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15
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Lee SH, Rasaiah JC. Proton transfer and the mobilities of the H+ and OH− ions from studies of a dissociating model for water. J Chem Phys 2011; 135:124505. [DOI: 10.1063/1.3632990] [Citation(s) in RCA: 138] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023] Open
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16
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Goyal P, Elstner M, Cui Q. Application of the SCC-DFTB method to neutral and protonated water clusters and bulk water. J Phys Chem B 2011; 115:6790-805. [PMID: 21526802 DOI: 10.1021/jp202259c] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
The self-consistent charge density functional tight-binding (SCC-DFTB) method has been actively employed to study proton-transfer processes in biological systems. Recent studies in the literature employing SCC-DFTB reported that the method favors the Zundel form of the hydrated proton over the Eigen form, both in gas-phase water clusters and in bulk water, in disagreement with both higher-level calculations and experimental data. In this work, we explore the performance of SCC-DFTB for protonated gas-phase water clusters and bulk water (the latter both with and without an excess proton) with a modified O-H repulsive potential reported in our earlier work and with on-site third-order expansion of the DFT energy. Our results show that, with the proper set of published parameters, SCC-DFTB does correctly favor the Eigen form of the hydrated proton as compared to the Zundel form, both in gas-phase clusters and in the bulk; the amphiphilic character of the hydrated proton discussed in the literature has also been observed. The analyses do, however, bring forth remaining limitations in terms of the solvation structure around the hydrated proton as well as the structure of bulk water, which can guide future improvements of the method.
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Affiliation(s)
- Puja Goyal
- Department of Chemistry, University of Wisconsin, Madison, Madison, Wisconsin 53706, United States
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17
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Kuno M, Ando H, Morihata H, Sakai H, Mori H, Sawada M, Oiki S. Temperature dependence of proton permeation through a voltage-gated proton channel. ACTA ACUST UNITED AC 2009; 134:191-205. [PMID: 19720960 PMCID: PMC2740922 DOI: 10.1085/jgp.200910213] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Voltage-gated proton channels are found in many different types of cells, where they facilitate proton movement through the membrane. The mechanism of proton permeation through the channel is an issue of long-term interest, but it remains an open question. To address this issue, we examined the temperature dependence of proton permeation. Under whole cell recordings, rapid temperature changes within a few milliseconds were imposed. This method allowed for the measurement of current amplitudes immediately before and after a temperature jump, from which the ratios of these currents (Iratio) were determined. The use of Iratio for evaluating the temperature dependence minimized the contributions of factors other than permeation. Temperature jumps of various degrees (DeltaT, -15 to 15 degrees C) were applied over a wide temperature range (4-49 degrees C), and the Q10s for the proton currents were evaluated from the Iratios. Q10 exhibited a high temperature dependence, varying from 2.2 at 10 degrees C to 1.3 at 40 degrees C. This implies that processes with different temperature dependencies underlie the observed Q10. A novel resistivity pulse method revealed that the access resistance with its low temperature dependence predominated in high temperature ranges. The measured temperature dependence of Q10 was decomposed into Q10 of the channel and of the access resistances. Finally, the Q10 for proton permeation through the voltage-gated proton channel itself was calculated and found to vary from 2.8 at 5 degrees C to 2.2 at 45 degrees C, as expected for an activation enthalpy of 64 kJ/mol. The thermodynamic features for proton permeation through proton-selective channels were discussed for the underlying mechanism.
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Affiliation(s)
- Miyuki Kuno
- Department of Physiology, Osaka City University Graduate School of Medicine, Abeno-ku, Osaka 545-8585, Japan
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18
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Ufimtsev IS, Kalinichev AG, Martinez TJ, Kirkpatrick RJ. A multistate empirical valence bond model for solvation and transport simulations of OH- in aqueous solutions. Phys Chem Chem Phys 2009; 11:9420-30. [PMID: 19830325 DOI: 10.1039/b907859b] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
We describe a new multistate empirical valence bond (MS-EVB) model of OH(-) in aqueous solutions. This model is based on the recently proposed "charged ring" parameterization for the intermolecular interaction of hydroxyl ion with water [Ufimtsev, et al., Chem. Phys. Lett., 2007, 442, 128] and is suitable for classical molecular simulations of OH(-) solvation and transport. The model reproduces the hydration structure of OH(-)(aq) in good agreement with experimental data and the results of ab initio molecular dynamics simulations. It also accurately captures the major structural, energetic, and dynamic aspects of the proton transfer processes involving OH(-) (aq). The model predicts an approximately two-fold increase of the OH(-) mobility due to proton exchange reactions.
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Affiliation(s)
- Ivan S Ufimtsev
- Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA
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19
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Nunes RMD, Pineiro M, Arnaut LG. Photoacid for Extremely Long-Lived and Reversible pH-Jumps. J Am Chem Soc 2009; 131:9456-62. [DOI: 10.1021/ja901930c] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Rui M. D. Nunes
- Chemistry Department, University of Coimbra, 3000 Coimbra, Portugal
| | - Marta Pineiro
- Chemistry Department, University of Coimbra, 3000 Coimbra, Portugal
| | - Luis G. Arnaut
- Chemistry Department, University of Coimbra, 3000 Coimbra, Portugal
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20
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Coskuner O, Allison TC. Dynamic and Structural Properties of Aqueous Arsenic Solutions. Chemphyschem 2009; 10:1187-9. [DOI: 10.1002/cphc.200800650] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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21
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Brunklaus G, Schauff S, Markova D, Klapper M, Müllen K, Spiess HW. Proton Mobilities in Phosphonic Acid-Based Proton Exchange Membranes Probed by 1H and 2H Solid-State NMR Spectroscopy. J Phys Chem B 2009; 113:6674-81. [DOI: 10.1021/jp901714f] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Gunther Brunklaus
- Max-Planck-Institut für Polymerforschung, Postfach 3148, D-55021 Mainz, Germany
| | - Siri Schauff
- Max-Planck-Institut für Polymerforschung, Postfach 3148, D-55021 Mainz, Germany
| | - Dilyana Markova
- Max-Planck-Institut für Polymerforschung, Postfach 3148, D-55021 Mainz, Germany
| | - Markus Klapper
- Max-Planck-Institut für Polymerforschung, Postfach 3148, D-55021 Mainz, Germany
| | - Klaus Müllen
- Max-Planck-Institut für Polymerforschung, Postfach 3148, D-55021 Mainz, Germany
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22
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Markovitch O, Chen H, Izvekov S, Paesani F, Voth GA, Agmon N. Special pair dance and partner selection: elementary steps in proton transport in liquid water. J Phys Chem B 2008; 112:9456-66. [PMID: 18630857 DOI: 10.1021/jp804018y] [Citation(s) in RCA: 241] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Conditional and time-dependent radial distribution functions reveal the details of the water structure surrounding the hydronium during the proton mobility process. Using this methodology for classical multistate empirical valence bond (MS-EVB) and ab initio molecular dynamics trajectories, as well as quantal MS-EVB trajectories, we supply statistical proof that proton hops in liquid water occur by a transition from the H3O+[3H2O] Eigen-complex, via the H5O2+ Zundel-complex, to a H3O+[3H2O] centered on a neighboring water molecule. In the "resting period" before a transition, there is a distorted hydronium with one of its water ligands at a shorter distance and another at a longer distance than average. The identity of this "special partner" interchanges rapidly within the three first-shell water ligands. This is coupled to cleavage of an acceptor-type hydrogen bond. Just before the transition, a partner is selected by an additional translation of the H3O+ moiety in its direction, possibly enabled by loosening of donor-type hydrogen bonds on the opposite side. We monitor the transition in real time, showing how the average structure is converted to a distorted H5O2+ cation constituting the transitional complex for proton hopping between water molecules.
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Affiliation(s)
- Omer Markovitch
- Institute of Chemistry and the Fritz Haber Research Center, The Hebrew University of Jerusalem, Jerusalem, Israel
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23
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Bosisio C, Quercioli V, Collini M, D'Alfonso L, Baldini G, Bettati S, Campanini B, Raboni S, Chirico G. Protonation and conformational dynamics of GFP mutants by two-photon excitation fluorescence correlation spectroscopy. J Phys Chem B 2008; 112:8806-14. [PMID: 18582099 DOI: 10.1021/jp801164n] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
GFP mutants are known to display fluorescence flickering, a process that occurs in a wide time range. Because serine 65, threonine 203, glutamate 222, and histidine 148 have been indicated as key residues in determining the GFP fluorescence photodynamics, we have focused here on the role of histidine 148 and glutamate 222 by studying the fluorescence dynamics of GFPmut2 (S65A, V68L, and S72A GFP) and its H148G (Mut2G) and E222Q (Mut2Q) mutants. Two relaxation components are found in the fluorescence autocorrelation functions of GFPmut2: a 10-100 micros pH-dependent component and a 100-500 micros laser-power-dependent component. The comparison of these three mutants shows that the mutation of histidine 148 to glycine induces a 3-fold increase in the protonation rate, thereby indicating that the protonation-deprotonation of the chromophore occurs via a proton exchange with the solution mediated by the histidine 148 residue. The power-dependent but pH-independent relaxation mode, which is not affected by the E222Q and H148G mutations, is due to an excited-state process that is probably related to conformational rearrangements of the chromophore after the photoexcitation, more than to the chromophore excited-state proton transfer.
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Affiliation(s)
- C Bosisio
- Dipartimento G. Occhialini, Universita di Milano Bicocca
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24
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Vendrell O, Meyer HD. A proton between two waters: insight from full-dimensional quantum-dynamics simulations of the [H2O–H–OH2]+ cluster. Phys Chem Chem Phys 2008; 10:4692-703. [DOI: 10.1039/b807317a] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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25
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Vendrell O, Gatti F, Meyer HD. Full dimensional (15-dimensional) quantum-dynamical simulation of the protonated water dimer. II. Infrared spectrum and vibrational dynamics. J Chem Phys 2007; 127:184303. [DOI: 10.1063/1.2787596] [Citation(s) in RCA: 191] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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26
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Wu Y, Chen H, Wang F, Paesani F, Voth GA. An improved multistate empirical valence bond model for aqueous proton solvation and transport. J Phys Chem B 2007; 112:467-82. [PMID: 17999484 DOI: 10.1021/jp076658h] [Citation(s) in RCA: 208] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
A new multistate empirical valence bond model (MS-EVB3) is developed for proton solvation and transport in aqueous solutions. The new model and its quantum version (qMS-EVB3) are based on the MS-EVB2 model [Day et al., J. Chem. Phys. 2002, 117, 5839] and recently developed flexible water models-the SPC/Fw model [Wu et al. J. Chem. Phys. 2006, 124, 24503] and the qSPC/Fw model [Paesani et al. J. Chem. Phys. 2006, 125, 184507]-for classical and quantum simulations, respectively. Using ab initio data as benchmarks, the binding energies and optimized geometries calculated with the new model for protonated water clusters, as well as the potential energy surface for proton shuttling between water molecules in a cluster environment, are improved in comparison to the MS-EVB2 model. For aqueous solutions, classical and quantum molecular dynamics simulations with the MS-EVB3 model yield a more accurate description of the solvation structure and diffusive dynamics of the excess proton. New insight is also provided into the proton solvation and hopping dynamics in water, as well as the "amphiphilic" nature of the hydrated proton that has been predicted to give rise to its enhanced concentration at aqueous interfaces and an effectively lower pH of the air-water interface [Petersen et al. J. Phys. Chem. B 2004, 108, 14804].
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Affiliation(s)
- Yujie Wu
- Department of Chemistry and Center for Biophysical Modeling and Simulation, University of Utah, 315 South 1400 East, Room 2020, Salt Lake City, Utah 84112-0850, USA
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27
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Vendrell O, Gatti F, Meyer HD. Dynamics and Infrared Spectroscopy of the Protonated Water Dimer. Angew Chem Int Ed Engl 2007; 46:6918-21. [PMID: 17676569 DOI: 10.1002/anie.200702201] [Citation(s) in RCA: 147] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Affiliation(s)
- Oriol Vendrell
- Theoretische Chemie, Physikalisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 229, 69120 Heidelberg, Germany
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28
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Vendrell O, Gatti F, Meyer HD. Dynamik und Infrarotspektroskopie des protonierten Wasser-Dimers. Angew Chem Int Ed Engl 2007. [DOI: 10.1002/ange.200702201] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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29
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Markovitch O, Agmon N. Structure and Energetics of the Hydronium Hydration Shells. J Phys Chem A 2007; 111:2253-6. [PMID: 17388314 DOI: 10.1021/jp068960g] [Citation(s) in RCA: 148] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Proton solvation and proton mobility are both subjects of great interest in chemistry and biology. Here we have studied the hydration shells of H3O+ at temperatures ranging from 260 to 340 K using the multistate empirical valence-bond methodology (MS-EVB2). We have calculated the radial distribution functions for the protonium and its solvation shells. Furthermore, we have determined the Gibbs energy and the enthalpy for hydrogen bonds donated or accepted by the first two solvation shells, in comparison to bulk water. We find systematic bond-energy differences that appear to agree with a recent IR study on proton hydration. Implications of our results to various proton mobility mechanisms are discussed.
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Affiliation(s)
- Omer Markovitch
- Department of Physical Chemistry and the Fritz Haber Research Center, The Hebrew University, Jerusalem 91904, Israel
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30
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Marx D. Proton Transfer 200 Years after von Grotthuss: Insights from Ab Initio Simulations. Chemphyschem 2007. [DOI: 10.1002/cphc.200790002] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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31
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Lapid H, Agmon N, Petersen MK, Voth GA. A bond-order analysis of the mechanism for hydrated proton mobility in liquid water. J Chem Phys 2007; 122:14506. [PMID: 15638673 DOI: 10.1063/1.1814973] [Citation(s) in RCA: 212] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Bond-order analysis is introduced to facilitate the study of cooperative many-molecule effects on proton mobility in liquid water, as simulated using the multistate empirical valence-bond methodology. We calculate the temperature dependence for proton mobility and the total effective bond orders in the first two solvation shells surrounding the H(5)O(2) (+) proton-transferring complex. We find that proton-hopping between adjacent water molecules proceeds via this intermediate, but couples to hydrogen-bond dynamics in larger water clusters than previously anticipated. A two-color classification of these hydrogen bonds leads to an extended mechanism for proton mobility.
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Affiliation(s)
- Hadas Lapid
- Department of Physical Chemistry and Fritz Haber Research Center, The Hebrew University, Jerusalem 91904, Israel
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32
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Dellago C, Hummer G. Kinetics and mechanism of proton transport across membrane nanopores. PHYSICAL REVIEW LETTERS 2006; 97:245901. [PMID: 17280300 DOI: 10.1103/physrevlett.97.245901] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/19/2006] [Indexed: 05/07/2023]
Abstract
We use computer simulations to study the kinetics and mechanism of proton passage through a narrow-pore carbon-nanotube membrane separating reservoirs of liquid water. Free energy and rate constant calculations show that protons move across the membrane diffusively along single-file chains of hydrogen-bonded water molecules. Proton passage through the membrane is opposed by a high barrier in the effective potential, reflecting the large electrostatic penalty for desolvation and reminiscent of charge exclusion in biological water channels. At neutral pH, we estimate a translocation rate of about 1 proton per hour and tube.
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Affiliation(s)
- Christoph Dellago
- Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria
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33
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Hassan SA, Hummer G, Lee YS. Effects of electric fields on proton transport through water chains. J Chem Phys 2006; 124:204510. [PMID: 16774356 PMCID: PMC1808339 DOI: 10.1063/1.2198820] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Molecular dynamics simulations on quantum energy surfaces are carried out to study the effects of perturbing electric fields on proton transport (PT) in protonated water chains. As an idealized model of a hydrophobic cavity in the interior of a protein the water molecules are confined into a carbon nanotube (CNT). The water chain connects a hydrated hydronium ion (H3O+) at one end of the CNT and an imidazole molecule at the other end. Without perturbing electric fields PT from the hydronium proton donor to the imidazole acceptor occurs on a picosecond time scale. External perturbations to PT are created by electric fields of varying intensities, normal to the CNT axis, generated by a neutral pair of charges on the nanotube wall. For fields above approximately 0.5 VA, the hydronium ion is effectively trapped at the CNT center, and PT blocked. Fields of comparable strength are generated inside proteins by nearby polar/charged amino acids. At lower fields the system displays a rich dynamic behavior, where the excess charge shuttles back and forth along the water chain before reaching the acceptor group on the picosecond time scale. The effects of the perturbing field on the proton movement are analyzed in terms of structural and dynamic properties of the water chain. The implications of these observations on PT in biomolecular systems and its control by external perturbing fields are discussed.
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Affiliation(s)
- Sergio A Hassan
- Center for Molecular Modeling, DCB/CIT, National Institutes of Health, U.S. DHHS, Bethesda, Maryland 20892, USA.
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34
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Labile supramolecular structures and their dynamics in associated liquids based on NMR data. Russ Chem Bull 2006. [DOI: 10.1007/s11172-006-0302-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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35
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Yan L, Balbuena PB, Seminario JM. Perfluorobutane Sulfonic Acid Hydration and Interactions with O2Adsorbed on Pt3. J Phys Chem A 2006; 110:4574-81. [PMID: 16571065 DOI: 10.1021/jp056748r] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The side chain of NAFION, a proton conductive membrane used as electrolyte in low-temperature fuel cells, is modeled with perfluorobutane sulfonic acid. Density functional theory is used to characterize structures and energetics of hydration of the model system interacting with a proton solvated with up to 24 water molecules and analyze interactions of some of these hydrated complexes with O(2) adsorbed on Pt(3). It is found that at least three water molecules are needed to ionize the sulfonic acid, and higher degrees of hydration induce the formation of cages where the water molecules are held together via complex hydrogen-bond networks. The interaction between the complex formed by the ionized acid and the hydrated proton, in contact with a bridge-adsorbed O(2)-Pt(3), promotes the protonation of the adsorbed O(2). Upon protonation, the O(2)-Pt(3) system evolves from hydrophobic to hydrophilic behavior, which may facilitate further interfacial contact.
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Affiliation(s)
- Liuming Yan
- Department of Chemical Engineering, Texas A&M University, College Station, Texas 77843, USA
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36
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Abstract
Topological defects in aqueous solution in the form of H(+)(aq) and OH(-)(aq) ions undergo anomalously fast transport via the structural Grotthuss diffusion mechanism. However, while the microscopic details of this process are well understood for H(+)(aq), the corresponding picture for OH(-)(aq) remains unresolved. Mechanistic scenarios proposed previously are critically reviewed with the help of the presolvation concept, which provides a unifying framework for understanding charge migration mechanisms in hydrogen-bonded networks. It is argued that OH(-)(aq) features a nonclassical, in the Lewis sense, hypercoordinated solvation structure. The resulting mechanism deviates substantially from the traditional "mirror image" picture. Within the presolvation concept, it can also be suggested why alternative scenarios are inconsistent with experimental data.
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Affiliation(s)
- Mark E Tuckerman
- Department of Chemistry and Courant Institute of Mathematical Sciences, 100 Washington Square East, New York University, New York, New York 10003, USA
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37
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Lignell A, Khriachtchev L, Lignell H, Räsänen M. Protons solvated in noble-gas matrices: Interaction with nitrogen. Phys Chem Chem Phys 2006; 8:2457-63. [PMID: 16721429 DOI: 10.1039/b603822k] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
Abstract
The interaction of a (NgHNg)(+) cation (Ng = Ar and Kr) with a nitrogen molecule is studied. The structure, energetics, and vibrational properties of these complexed systems are computationally studied at the MP2/6-311++G(2d,2p) level of theory. The computations reveal two stable structures, linear and T-shaped configurations, with BSSE corrected interaction energies of the order of -1000 cm(-1). The (NgHNg)(+)[dot dot dot]N(2) complexes are characterized experimentally by IR absorption spectroscopy in solid Ar and Kr matrices. The spectra show that only one complex structure is present, as evidenced by the single nitrogen-induced nu(3) band. According to the computational results, the linear structure is more probable in the experiments. However, our results show that the one-to-one complex at the present computational level does not accurately agree with the matrix-isolation experiments, the differences originating possibly from the influence of the surrounding matrix. Based on the current data, the mechanism of cation decay in noble-gas matrices is discussed. The observed similar decay of (NgHNg)(+) and its N(2) complex indicates that the solvated proton is unable to tunnel and is therefore immobile in noble-gas matrices. The observations for the cation decay are consistent with the electron neutralization mechanism.
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Affiliation(s)
- Antti Lignell
- Laboratory of Physical Chemistry, University of Helsinki, Finland.
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38
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39
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Tachikawa M, Shiga M. Geometrical H/D Isotope Effect on Hydrogen Bonds in Charged Water Clusters. J Am Chem Soc 2005; 127:11908-9. [PMID: 16117507 DOI: 10.1021/ja053135j] [Citation(s) in RCA: 80] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
To investigate the proton/deuteron geometrical isotope effect of positively and negatively charged water complexes, H5O2+ and H3O2-, we have carried out accurate ab initio path integral simulations considering the electron correlation effect. It has been found that the isotope effect on the hydrogen bond is different between these two species in that the oxygen separation becomes shorter in H5O2+ while longer in H3O2- by deuteron substitution. This behavior is ascribed to the change in the quantum effect of hydrogen bonds whether the shared hydrogen is on a single or double well potential surface.
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Affiliation(s)
- Masanori Tachikawa
- Quantum Chemical Physics Division, Graduate School of Science, Yokohama-City University, Japan.
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40
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Ren Y, Li M, Wong NB. Prototropic tautomerism of imidazolone in aqueous solution: a density functional approach using the combined discrete/self-consistent reaction field (SCRF) models. J Mol Model 2005; 11:167-73. [PMID: 15744506 DOI: 10.1007/s00894-005-0242-0] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2004] [Accepted: 01/05/2005] [Indexed: 10/25/2022]
Abstract
A systematic investigation of the proton transfer in the keto-amino/enol tautomerization of imidazolone was undertaken. Calculations in aqueous solution were performed using both combined discrete/self-consistent reaction field (SCRF) and SCRF methods. Complexes containing one to three water molecules around the hydrophilic site of imidazolone were used for the combined discrete/SCRF calculations. The DFT results predict that the barrier height for non-water-assisted intramolecular proton transfer is very high (214.8 kJmol(-1)). Hydrogen bonding between imidazolone and the water molecule(s) will dramatically lower the barrier by a concerted multiple proton transfer mechanism. The proton transfer process through a eight-member ring formed by imidazolone and two water molecules is found to be more efficient and the calculated barrier height is ca. 61 kJmol(-1).
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Affiliation(s)
- Yi Ren
- School of chemistry of chemical engineering, Southwest China Normal University, Chongqing, 400715, People's Republic of China.
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41
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Abstract
The absorption of a photon by a hydroxy-aromatic photoacid triggers a cascade of events contributing to the overall phenomenon of intermolecular excited-state proton transfer. The fundamental steps involved were studied over the last 20 years using a combination of theoretical and experimental techniques. They are surveyed in this sequel in sequential order, from fast to slow. The excitation triggers an intramolecular charge transfer to the ring system, which is more prominent for the anionic base than the acid. The charge redistribution, in turn, triggers changes in hydrogen-bond strengths that set the stage for the proton-transfer step itself. This step is strongly influenced by the solvent, resulting in unusual dependence of the dissociation rate coefficient on water content, temperature, and isotopic substitution. The photolyzed proton can diffuse in the aqueous solution in a mechanism that involves collective changes in hydrogen-bonding. On longer times, it may recombine adiabatically with the excited base or quench it. The theory for these diffusion-influenced geminate reactions has been developed, showing nice agreement with experiment. Finally, the effect of inert salts, bases, and acids on these reactions is analyzed.
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Affiliation(s)
- Noam Agmon
- Department of Physical Chemistry and the Fritz Haber Research Center, The Hebrew University, Jerusalem 91904, Israel.
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42
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Abbruzzetti S, Grandi E, Viappiani C, Bologna S, Campanini B, Raboni S, Bettati S, Mozzarelli A. Kinetics of Acid-Induced Spectral Changes in the GFPmut2 Chromophore. J Am Chem Soc 2004; 127:626-35. [PMID: 15643887 DOI: 10.1021/ja045400r] [Citation(s) in RCA: 48] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We have used a nanosecond pH-jump technique, coupled with simultaneous transient absorption and fluorescence emission detection, to characterize the dynamics of the acid-induced spectral changes in the GFPmut2 chromophore. Disappearance of the absorbance at 488 nm and the green fluorescence emission occurs with a thermally activated, double exponential relaxation. To understand the source of the two transients we have introduced mutations in amino acid residues that interact with the chromophore (H148G, T203V, and E222Q). Results indicate that the faster transient is associated with proton binding from the solution, while the second process, smaller in amplitude, is attributed to structural rearrangement of the amino acids surrounding the chromophore. The protonation rate shows a 3-fold increase for the H148G mutant, demonstrating that His148 plays a key role in protecting the chromophore from the solvent. The deprotonation rate for T203V is an order of magnitude smaller, showing that the hydrogen bond with the hydroxyl of Thr203 is important in stabilizing the deprotonated form of the chromophore. A kinetic model suggests that, in addition to protecting the chromophore from the solvent, His148 may act as the primary acceptor for the protons on the way to the chromophore.
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Affiliation(s)
- Stefania Abbruzzetti
- Dipartimento di Fisica, Università di Parma, Parco Area delle Scienze 7/A, 43100 Parma, Italy
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43
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Zhuang W, Dellago C. Dissociation of Hydrogen Chloride and Proton Transfer in Liquid Glycerol: An Ab Initio Molecular Dynamics Study. J Phys Chem B 2004. [DOI: 10.1021/jp047676r] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Affiliation(s)
- Wei Zhuang
- Department of Chemistry, University of California at Irvine, Irvine, California 92697, and Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria
| | - Christoph Dellago
- Department of Chemistry, University of California at Irvine, Irvine, California 92697, and Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria
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44
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Tachikawa M, Shiga M. Theoretical study on isotope and temperature effect in hydronium ion using ab initio path integral simulation. J Chem Phys 2004; 121:5985-91. [PMID: 15367026 DOI: 10.1063/1.1785779] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
We have applied the ab initio path integral molecular dynamics simulation to study hydronium ion and its isotopes, which are the simplest systems for hydrated proton and deuteron. In this simulation, all the rotational and vibrational degrees of freedom are treated fully quantum mechanically, while the potential energies of the respective atomic configurations are calculated "on the fly" using ab initio quantum chemical approach. With the careful treatment of the ab initio electronic structure calculation by relevant choices in electron correlation level and basis set, this scheme is theoretically quite rigorous except for Born-Oppenheimer approximation. This accurate calculation allows a close insight into the structural shifts for the isotopes of hydronium ion by taking account of both quantum mechanical and thermal effects. In fact, the calculation is shown to be successful to quantitatively extract the geometrical isotope effect with respect to the Walden inversion. It is also shown that this leads to the isotope effect on the electronic structure as well as the thermochemical properties.
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Affiliation(s)
- Masanori Tachikawa
- Quantum Chemistry Division, Graduate School of Science, Yokohama-city University, Seto 22-2, Kanazawa-ku, Yokohama 236-0027, Japan.
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45
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Kreuer KD, Paddison SJ, Spohr E, Schuster M. Transport in Proton Conductors for Fuel-Cell Applications: Simulations, Elementary Reactions, and Phenomenology. Chem Rev 2004; 104:4637-78. [PMID: 15669165 DOI: 10.1021/cr020715f] [Citation(s) in RCA: 1105] [Impact Index Per Article: 55.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Affiliation(s)
- Klaus-Dieter Kreuer
- Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, D-70569 Stuttgart, Germany.
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46
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Zahn D. Investigation of the complex reaction coordinate of acid catalyzed amide hydrolysis from molecular dynamics simulations. Chem Phys 2004. [DOI: 10.1016/j.chemphys.2004.01.016] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
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47
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Zahn D. Theoretical Study of the Mechanisms of Acid-Catalyzed Amide Hydrolysis in Aqueous Solution. J Phys Chem B 2003. [DOI: 10.1021/jp034175h] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Dirk Zahn
- Max Planck Institute for Chemical Physics of Solids, Noethnitzer Strasse 40, 01087 Dresden, Germany
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48
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49
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Casadesús R, Moreno M, Lluch JM. A theoretical study of the ground and first excited singlet state proton transfer reaction in isolated 7-azaindole–water complexes. Chem Phys 2003. [DOI: 10.1016/s0301-0104(03)00173-3] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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50
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Abstract
Proton channels exist in a wide variety of membrane proteins where they transport protons rapidly and efficiently. Usually the proton pathway is formed mainly by water molecules present in the protein, but its function is regulated by titratable groups on critical amino acid residues in the pathway. All proton channels conduct protons by a hydrogen-bonded chain mechanism in which the proton hops from one water or titratable group to the next. Voltage-gated proton channels represent a specific subset of proton channels that have voltage- and time-dependent gating like other ion channels. However, they differ from most ion channels in their extraordinarily high selectivity, tiny conductance, strong temperature and deuterium isotope effects on conductance and gating kinetics, and insensitivity to block by steric occlusion. Gating of H(+) channels is regulated tightly by pH and voltage, ensuring that they open only when the electrochemical gradient is outward. Thus they function to extrude acid from cells. H(+) channels are expressed in many cells. During the respiratory burst in phagocytes, H(+) current compensates for electron extrusion by NADPH oxidase. Most evidence indicates that the H(+) channel is not part of the NADPH oxidase complex, but rather is a distinct and as yet unidentified molecule.
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Affiliation(s)
- Thomas E Decoursey
- Department of Molecular Biophysics and Physiology, Rush Presbyterian St. Luke's Medical Center, Chicago, Illinois 60612, USA.
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