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Poudel H, Wales DJ, Leitner DM. Vibrational Energy Landscapes and Energy Flow in GPCRs. J Phys Chem B 2024; 128:7568-7576. [PMID: 39058920 DOI: 10.1021/acs.jpcb.4c04513] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/28/2024]
Abstract
We construct and analyze disconnectivity graphs to provide the first graphical representation of the vibrational energy landscape of a protein, in this study β2AR, a G-protein coupled receptor (GPCR), in active and inactive states. The graphs, which indicate the relative free energy of each residue and the minimum free energy barriers for energy transfer between them, reveal important composition, structural and dynamic properties that mediate the flow of energy. Prolines and glycines, which contribute to GPCR plasticity and function, are identified as bottlenecks to energy transport along the backbone from which alternative pathways for energy transport via nearby noncovalent contacts emerge, seen also in the analysis of first passage time (FPT) distributions presented here. Striking differences between the disconnectivity graphs and FPT distributions for the inactive and active states of β2AR are found where structural and dynamic changes occur upon activation, contributing to allosteric regulation.
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Affiliation(s)
- Humanath Poudel
- Department of Chemistry, University of Nevada, Reno, Nevada 89557, United States
| | - David J Wales
- Yusuf Hamied Department of Chemistry, Cambridge University, Cambridge CB2 1EW, U.K
| | - David M Leitner
- Department of Chemistry, University of Nevada, Reno, Nevada 89557, United States
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Poudel H, Reid KM, Yamato T, Leitner DM. Energy Transfer across Nonpolar and Polar Contacts in Proteins: Role of Contact Fluctuations. J Phys Chem B 2020; 124:9852-9861. [PMID: 33107736 DOI: 10.1021/acs.jpcb.0c08091] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Molecular dynamics simulations of the villin headpiece subdomain HP36 have been carried out to examine relations between rates of vibrational energy transfer across non-covalently bonded contacts and equilibrium structural fluctuations, with focus on van der Waals contacts. Rates of energy transfer across van der Waals contacts vary inversely with the variance of the contact length, with the same constant of proportionality for all nonpolar contacts of HP36. A similar relation is observed for hydrogen bonds, but the proportionality depends on contact pairs, with hydrogen bonds stabilizing the α-helices all exhibiting the same constant of proportionality, one that is distinct from those computed for other polar contacts. Rates of energy transfer across van der Waals contacts are found to be up to 2 orders of magnitude smaller than rates of energy transfer across polar contacts.
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Affiliation(s)
- Humanath Poudel
- Department of Chemistry, University of Nevada, Reno, Nevada 89557, United States
| | - Korey M Reid
- Department of Chemistry, University of Nevada, Reno, Nevada 89557, United States
| | - Takahisa Yamato
- Graduate School of Science, Division of Material Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya 464-8602, Japan
| | - David M Leitner
- Department of Chemistry, University of Nevada, Reno, Nevada 89557, United States
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Harder-Viddal C, Roshko RM, Stetefeld J. Energy flow and intersubunit signalling in GSAM: A non-equilibrium molecular dynamics study. Comput Struct Biotechnol J 2020; 18:1651-1663. [PMID: 32670505 PMCID: PMC7338781 DOI: 10.1016/j.csbj.2020.06.025] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Revised: 06/14/2020] [Accepted: 06/16/2020] [Indexed: 12/11/2022] Open
Abstract
Non-equilibrium molecular dynamics simulations of vibrational energy flow induced by the imposition of a thermal gradient have been performed on the μ2-dimeric enzyme glutamate-1-semialdehyde aminomutase (GSAM), the key enzyme in the biosynthesis of chlorophyll, in order to identify energy transport pathways and to elucidate their role as potential allosteric communication networks for coordinating functional dynamics, specifically the negative cooperativity observed in the motion of the two active site gating loops. Fully atomistic MD simulations of thermal diffusion were executed with a GROMACS simulation package on a fully solvated GSAM enzyme by heating various active site target ligands (initially, catalytic intermediates and cofactors) to 300K while holding the remainder of the protein and the solvent bath at 10K and monitoring the temperature T(t) of all the enzyme residues as a function of time over a 1ns observation window. Energy is observed to be deposited in a relatively small number of discrete chains of residues most of which contribute to specific structural or biochemical functionality. Thermal linkages between all thermally active chains were established by isolating a specific pair of chains and performing a thermal diffusion simulation on the pair, one held at 300K and the other at 10K, with the rest of the protein frozen in its initial atomic configuration and thus thermally unresponsive. Proceeding in this way, it was possible to map out multiple pathways of vibrational energy flow leading from one of the active sites through a network of contiguous residues, many of which were evolutionarily conserved and linked by hydrogen bonds, into the other active site and ultimately to the other gating loop.
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Affiliation(s)
- C Harder-Viddal
- Department of Chemistry and Physics, Canadian Mennonite University, 500 Shaftesbury Blvd, Winnipeg, Manitoba, Canada
| | - R M Roshko
- Department of Physics and Astronomy, University of Manitoba, 30A Sifton Rd, Winnipeg, Manitoba, Canada
| | - J Stetefeld
- Department of Chemistry, University of Manitoba, 144 Dysart Rd, Winnipeg, Manitoba, Canada.,Center for Oil and Gas Research and Development (COGRAD), Canada.,Department of Biochemistry and Medical Genetics, University of Manitoba, Canada.,Department of Human Anatomy and Cell Science, University of Manitoba, Canada
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4
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Leitner DM, Yamato T. Recent developments in the computational study of protein structural and vibrational energy dynamics. Biophys Rev 2020; 12:317-322. [PMID: 32124240 DOI: 10.1007/s12551-020-00661-0] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2020] [Accepted: 02/23/2020] [Indexed: 12/11/2022] Open
Abstract
Recent developments in the computational study of energy transport in proteins are reviewed, including advances in both methodology and applications. The concept of energy exchange network (EEN) is discussed, and a recent calculation of EENs for the allosteric protein FixL is reviewed, which illustrates how residues and protein regions involved in the allosteric transition can be identified. Recent work has examined relations between EENs and protein dynamics as well as structure. We review some of the computational studies carried out on several proteins that explore connections between energy conductivity across polar contacts in proteins and between proteins and water and equilibrium dynamics of the contacts, and we discuss some of the recent experimental work that addresses this topic.
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Affiliation(s)
- David M Leitner
- Department of Chemistry and Chemical Physics Program, University of Nevada, Reno, NV, 89557, USA.
- Graduate School of Science, Division of Material Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan.
| | - Takahisa Yamato
- Graduate School of Science, Division of Material Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, 464-8602, Japan.
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Abstract
Direct visualization of electronic and molecular events during biochemical reactions is essential to mechanistic insights. This Letter presents an in-depth analysis of the serial crystallographic data sets collected by Barends and Schlichting et al. ( Science 2015 , 350 , 445 ) that probe the ligand photodissociation in carbonmonoxy myoglobin. This analysis reveals electron density changes caused by the formation of high-spin 3d atomic orbitals of the heme iron upon photolysis and their dynamic behaviors within the first few picoseconds. The heme iron is found popping out of and recoiling back into the heme plane in succession. These findings provide long-awaited visual validations for previous works using ultrafast spectroscopy and molecular dynamics simulations. Electron density variations are also found largely in the solvent during the first period of a low-frequency oscillation. This work demonstrates the importance of the analytical methods in detecting and isolating weak, transient signals of electronic changes arising from chemical reactions.
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Leitner DM, Pandey HD, Reid KM. Energy Transport across Interfaces in Biomolecular Systems. J Phys Chem B 2019; 123:9507-9524. [DOI: 10.1021/acs.jpcb.9b07086] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- David M. Leitner
- Department of Chemistry, University of Nevada, Reno, Nevada 89557, United States
| | - Hari Datt Pandey
- Department of Chemistry, University of Nevada, Reno, Nevada 89557, United States
| | - Korey M. Reid
- Department of Chemistry, University of Nevada, Reno, Nevada 89557, United States
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Affiliation(s)
- Masahide Terazima
- Department of Chemistry, Graduate School of Science, Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
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Leitner DM, Yamato T. MAPPING ENERGY TRANSPORT NETWORKS IN PROTEINS. REVIEWS IN COMPUTATIONAL CHEMISTRY 2018. [DOI: 10.1002/9781119518068.ch2] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Haddadian EJ, Zhang H, Freed KF, Douglas JF. Comparative Study of the Collective Dynamics of Proteins and Inorganic Nanoparticles. Sci Rep 2017; 7:41671. [PMID: 28176808 PMCID: PMC5296861 DOI: 10.1038/srep41671] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2015] [Accepted: 12/14/2016] [Indexed: 12/16/2022] Open
Abstract
Molecular dynamics simulations of ubiquitin in water/glycerol solutions are used to test the suggestion by Karplus and coworkers that proteins in their biologically active state should exhibit a dynamics similar to 'surface-melted' inorganic nanoparticles (NPs). Motivated by recent studies indicating that surface-melted inorganic NPs are in a 'glassy' state that is an intermediate dynamical state between a solid and liquid, we probe the validity and significance of this proposed analogy. In particular, atomistic simulations of ubiquitin in solution based on CHARMM36 force field and pre-melted Ni NPs (Voter-Chen Embedded Atom Method potential) indicate a common dynamic heterogeneity, along with other features of glass-forming (GF) liquids such as collective atomic motion in the form of string-like atomic displacements, potential energy fluctuations and particle displacements with long range correlations ('colored' or 'pink' noise), and particle displacement events having a power law scaling in magnitude, as found in earthquakes. On the other hand, we find the dynamics of ubiquitin to be even more like a polycrystalline material in which the α-helix and β-sheet regions of the protein are similar to crystal grains so that the string-like collective atomic motion is concentrated in regions between the α-helix and β-sheet domains.
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Affiliation(s)
- Esmael J Haddadian
- Biological Sciences Collegiate Division, University of Chicago, Chicago, IL 60637, USA
| | - Hao Zhang
- Department of Chemical and Materials Engineering, University of Alberta, Alberta, T6G 1H9 Canada
| | - Karl F Freed
- Department of Chemistry, James Franck Institute, and Computation Institute, University of Chicago, Chicago, IL 60637, USA
| | - Jack F Douglas
- Materials Science and Engineering Division, Materials Measurement Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA
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Gnanasekaran R. Probing the communication of deoxythymidine triphosphate in HIV-1 reverse transcriptase by communication maps and interaction energy studies. Phys Chem Chem Phys 2017; 19:29608-29616. [DOI: 10.1039/c7cp06386e] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
We calculate communication maps for HIV-1 Reverse Transcriptase (RT) to elucidate energy transfer pathways between deoxythymidine triphosphate (dTTP) and other parts of the protein.
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Barends TRM, Foucar L, Ardevol A, Nass K, Aquila A, Botha S, Doak RB, Falahati K, Hartmann E, Hilpert M, Heinz M, Hoffmann MC, Köfinger J, Koglin JE, Kovacsova G, Liang M, Milathianaki D, Lemke HT, Reinstein J, Roome CM, Shoeman RL, Williams GJ, Burghardt I, Hummer G, Boutet S, Schlichting I. Direct observation of ultrafast collective motions in CO myoglobin upon ligand dissociation. Science 2015; 350:445-50. [PMID: 26359336 DOI: 10.1126/science.aac5492] [Citation(s) in RCA: 269] [Impact Index Per Article: 29.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Accepted: 08/26/2015] [Indexed: 11/02/2022]
Abstract
The hemoprotein myoglobin is a model system for the study of protein dynamics. We used time-resolved serial femtosecond crystallography at an x-ray free-electron laser to resolve the ultrafast structural changes in the carbonmonoxy myoglobin complex upon photolysis of the Fe-CO bond. Structural changes appear throughout the protein within 500 femtoseconds, with the C, F, and H helices moving away from the heme cofactor and the E and A helices moving toward it. These collective movements are predicted by hybrid quantum mechanics/molecular mechanics simulations. Together with the observed oscillations of residues contacting the heme, our calculations support the prediction that an immediate collective response of the protein occurs upon ligand dissociation, as a result of heme vibrational modes coupling to global modes of the protein.
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Affiliation(s)
- Thomas R M Barends
- Max-Planck-Institut für Medizinische Forschung, Jahnstraße 29, 69120 Heidelberg, Germany.
| | - Lutz Foucar
- Max-Planck-Institut für Medizinische Forschung, Jahnstraße 29, 69120 Heidelberg, Germany
| | - Albert Ardevol
- Max-Planck-Institut für Biophysik, Max-von-Laue-Straße 3, 60438 Frankfurt am Main, Germany
| | - Karol Nass
- Max-Planck-Institut für Medizinische Forschung, Jahnstraße 29, 69120 Heidelberg, Germany
| | - Andrew Aquila
- European XFEL GmbH, Albert-Einstein-Ring 19, 22761 Hamburg, Germany
| | - Sabine Botha
- Max-Planck-Institut für Medizinische Forschung, Jahnstraße 29, 69120 Heidelberg, Germany
| | - R Bruce Doak
- Max-Planck-Institut für Medizinische Forschung, Jahnstraße 29, 69120 Heidelberg, Germany
| | - Konstantin Falahati
- Institut für Physikalische und Theoretische Chemie, Goethe-Universität, Max-von-Laue-Straße 7, 60438 Frankfurt am Main, Germany
| | - Elisabeth Hartmann
- Max-Planck-Institut für Medizinische Forschung, Jahnstraße 29, 69120 Heidelberg, Germany
| | - Mario Hilpert
- Max-Planck-Institut für Medizinische Forschung, Jahnstraße 29, 69120 Heidelberg, Germany
| | - Marcel Heinz
- Max-Planck-Institut für Biophysik, Max-von-Laue-Straße 3, 60438 Frankfurt am Main, Germany. Institut für Physikalische und Theoretische Chemie, Goethe-Universität, Max-von-Laue-Straße 7, 60438 Frankfurt am Main, Germany
| | - Matthias C Hoffmann
- Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
| | - Jürgen Köfinger
- Max-Planck-Institut für Biophysik, Max-von-Laue-Straße 3, 60438 Frankfurt am Main, Germany
| | - Jason E Koglin
- Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
| | - Gabriela Kovacsova
- Max-Planck-Institut für Medizinische Forschung, Jahnstraße 29, 69120 Heidelberg, Germany
| | - Mengning Liang
- Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
| | - Despina Milathianaki
- Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
| | - Henrik T Lemke
- Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
| | - Jochen Reinstein
- Max-Planck-Institut für Medizinische Forschung, Jahnstraße 29, 69120 Heidelberg, Germany
| | - Christopher M Roome
- Max-Planck-Institut für Medizinische Forschung, Jahnstraße 29, 69120 Heidelberg, Germany
| | - Robert L Shoeman
- Max-Planck-Institut für Medizinische Forschung, Jahnstraße 29, 69120 Heidelberg, Germany
| | - Garth J Williams
- Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
| | - Irene Burghardt
- Institut für Physikalische und Theoretische Chemie, Goethe-Universität, Max-von-Laue-Straße 7, 60438 Frankfurt am Main, Germany
| | - Gerhard Hummer
- Max-Planck-Institut für Biophysik, Max-von-Laue-Straße 3, 60438 Frankfurt am Main, Germany
| | - Sébastien Boutet
- Linac Coherent Light Source (LCLS), SLAC National Accelerator Laboratory, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
| | - Ilme Schlichting
- Max-Planck-Institut für Medizinische Forschung, Jahnstraße 29, 69120 Heidelberg, Germany.
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Agbo JK, Xu Y, Zhang P, Straub JE, Leitner DM. Vibrational energy flow across heme–cytochrome c and cytochrome c–water interfaces. Theor Chem Acc 2014. [DOI: 10.1007/s00214-014-1504-7] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
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13
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Matsunaga Y, Baba A, Li CB, Straub JE, Toda M, Komatsuzaki T, Berry RS. Spatio-temporal hierarchy in the dynamics of a minimalist protein model. J Chem Phys 2013; 139:215101. [DOI: 10.1063/1.4834415] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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14
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15
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Zhang Y, Straub JE. Direct evidence for mode-specific vibrational energy relaxation from quantum time-dependent perturbation theory. III. The nu(4) and nu(7) modes of nonplanar nickel porphyrin models. J Chem Phys 2009; 130:215101. [PMID: 19508100 DOI: 10.1063/1.3147704] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The time scales and pathways of vibrational energy relaxation (VER) of the nu(4) and nu(7) modes of three nickel porphyrin models, nickel porphine (NiP), nickel protoporphyrin IX (Ni-heme), and nickel octaethylporphyrin (NiOEP), were studied using a non-Markovian time-dependent perturbation theory at the B3LYP/6-31G(d) level. When NiP is calculated with D(4h) symmetry, it has the planar structure and the same VER properties as ferrous iron porphine (FeP). The porphine cores of both Ni-heme and NiOEP were distorted from a planar geometry, assuming a nonplanar structure, similar to that of the heme structure in cytochrome c. The VER time scales of Ni-heme are found to be similar to those predicted for a planar iron heme, but the derived pathways have distinctly different features. In particular, the strong coupling between the nu(7) mode and the overtone of the approximately 350 cm(-1) gamma(7) mode, observed for planar porphyrins, is absent in both nonplanar nickel porphyrins. Direct energy exchange between the nu(4) and nu(7) modes is not observed in NiOEP, but is found to play an essential role in the VER of the nu(4) mode in Ni-heme. The Ni-heme isopropionate groups are involved in the dominant VER pathways of both the nu(4) and nu(7) modes of Ni-heme. However, in contrast with VER pathways derived in planar iron heme, the isopropionate groups are not observed to play an essential role relative to other side chains in spatially directing the vibrational energy flow.
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Affiliation(s)
- Yong Zhang
- Department of Chemistry, Boston University, Boston, Massachusetts 02215, USA.
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16
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Zhang Y, Fujisaki H, Straub JE. Mode-Specific Vibrational Energy Relaxation of Amide I′ and II′ Modes in N-Methylacetamide/Water Clusters: Intra- and Intermolecular Energy Transfer Mechanisms. J Phys Chem A 2009; 113:3051-60. [DOI: 10.1021/jp8109995] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Yong Zhang
- Department of Chemistry, Boston University, Boston, Massachusetts 02215
| | - Hiroshi Fujisaki
- Department of Chemistry, Boston University, Boston, Massachusetts 02215
| | - John E. Straub
- Department of Chemistry, Boston University, Boston, Massachusetts 02215
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17
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Zhang Y, Straub JE. Direct evidence for mode-specific vibrational energy relaxation from quantum time-dependent perturbation theory. II. The ν4 and ν7 modes of iron-protoporphyrin IX and iron porphine. J Chem Phys 2009; 130:095102. [DOI: 10.1063/1.3086080] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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18
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Zhang Y, Fujisaki H, Straub JE. Direct evidence for mode-specific vibrational energy relaxation from quantum time-dependent perturbation theory. I. Five-coordinate ferrous iron porphyrin model. J Chem Phys 2009; 130:025102. [DOI: 10.1063/1.3055277] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
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19
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Affiliation(s)
- David M. Leitner
- Department of Chemistry and Chemical Physics Program, University of Nevada, Reno, Nevada 89557;
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Tan ML, Bizzarri AR, Xiao Y, Cannistraro S, Ichiye T, Manzoni C, Cerullo G, Adams MWW, Jenney FE, Cramer SP. Observation of terahertz vibrations in Pyrococcus furiosus rubredoxin via impulsive coherent vibrational spectroscopy and nuclear resonance vibrational spectroscopy – interpretation by molecular mechanics. J Inorg Biochem 2007; 101:375-84. [PMID: 17204331 DOI: 10.1016/j.jinorgbio.2006.09.031] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2006] [Revised: 09/28/2006] [Accepted: 09/29/2006] [Indexed: 10/24/2022]
Abstract
We have used impulsive coherent vibrational spectroscopy (ICVS) to study the Fe(S-Cys)(4) site in oxidized rubredoxin (Rd) from Pyrococcus furiosus (Pf). In this experiment, a 15 fs visible laser pulse is used to coherently pump the sample to an excited electronic state, and a second <10 fs pulse is used to probe the change in transmission as a function of the time delay. PfRd was observed to relax to the ground state by a single exponential decay with time constants of approximately 255-275 fs. Superimposed on this relaxation are oscillations caused by coherent excitation of vibrational modes in both excited and ground electronic states. Fourier transformation reveals the frequencies of these modes. The strongest ICV mode with 570 nm excitation is the symmetric Fe-S stretching mode near 310 cm(-1), compared to 313 cm(-1) in the low temperature resonance Raman. If the rubredoxin is pumped at 520 nm, a set of strong bands occurs between 20 and 110 cm(-1). Finally, there is a mode at approximately 500 cm(-1) which is similar to features near 508 cm(-1) in blue Cu proteins that have been attributed to excited state vibrations. Normal mode analysis using 488 protein atoms and 558 waters gave calculated spectra that are in good agreement with previous nuclear resonance vibrational spectra (NRVS) results. The lowest frequency normal modes are identified as collective motions of the entire protein or large segments of polypeptide. Motion in these modes may affect the polar environment of the redox site and thus tune the electron transfer functions in rubredoxins.
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Affiliation(s)
- Ming-Liang Tan
- Department of Applied Science, University of California, Davis, CA 95616, USA
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Dwyer JR, Hebeisen CT, Ernstorfer R, Harb M, Deyirmenjian VB, Jordan RE, Miller RJD. Femtosecond electron diffraction: 'making the molecular movie'. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2006; 364:741-78. [PMID: 16483961 DOI: 10.1098/rsta.2005.1735] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Femtosecond electron diffraction (FED) has the potential to directly observe transition state processes. The relevant motions for this barrier-crossing event occur on the hundred femtosecond time-scale. Recent advances in the development of high-flux electron pulse sources with the required time resolution and sensitivity to capture barrier-crossing processes are described in the context of attaining atomic level details of such structural dynamics-seeing chemical events as they occur. Initial work focused on the ordered-to-disordered phase transition of Al under strong driving conditions for which melting takes on nm or molecular scale dimensions. This work has been extended to Au, which clearly shows a separation in time-scales for lattice heating and melting. It also demonstrates that superheated face-centred cubic (FCC) metals melt through thermal mechanisms involving homogeneous nucleation to propagate the disordering process. A new concept exploiting electron-electron correlation is introduced for pulse characterization and determination of t=0 to within 100fs as well as for spatial manipulation of the electron beam. Laser-based methods are shown to provide further improvements in time resolution with respect to pulse characterization, absolute t=0 determination, and the potential for electron acceleration to energies optimal for time-resolved diffraction.
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Affiliation(s)
- Jason R Dwyer
- University of Toronto Institute for Optical Sciences and Departments of Chemistry and Physics Toronto, Ontario M5S 3H6, Canada
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