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M D Fayer - One of the best experts on this subject based on the ideXlab platform.
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hydrogen bond migration between molecular sites observed with ultrafast 2d ir chemical Exchange Spectroscopy
Journal of Physical Chemistry B, 2010Co-Authors: Daniel E Rosenfeld, Kyungwon Kwak, Zsolt Gengeliczki, M D FayerAbstract:Hydrogen-bonded complexes between phenol and phenylacetylene are studied using ultrafast two-dimensional infrared (2D IR) chemical Exchange Spectroscopy. Phenylacetylene has two possible π hydrogen bonding acceptor sites (phenyl or acetylene) that compete for hydrogen bond donors in solution at room temperature. The OD stretch frequency of deuterated phenol is sensitive to which acceptor site it is bound. The appearance of off-diagonal peaks between the two vibrational frequencies in the 2D IR spectrum reports on the Exchange process between the two competitive hydrogen-bonding sites of phenol−phenylacetylene complexes in the neat phenylacetylene solvent. The chemical Exchange process occurs in ∼5 ps and is assigned to direct hydrogen bond migration along the phenylacetylene molecule. Other nonmigration mechanisms are ruled out by performing 2D IR experiments on phenol dissolved in the phenylacetylene/carbon tetrachloride mixed solvent. The observation of direct hydrogen bond migration can have implicatio...
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dynamics of liquids molecules and proteins measured with ultrafast 2d ir vibrational echo chemical Exchange Spectroscopy
Annual Review of Physical Chemistry, 2009Co-Authors: M D FayerAbstract:A wide variety of molecular systems undergo fast structural changes under thermal equilibrium conditions. Such transformations are involved in a vast array of chemical problems. Experimentally measuring equilibrium dynamics is a challenging problem that is at the forefront of chemical research. This review describes ultrafast 2D IR vibrational echo chemical Exchange experiments and applies them to several types of molecular systems. The formation and dissociation of organic solute-solvent complexes are directly observed. The dissociation times of 13 complexes, ranging from 4 ps to 140 ps, are shown to obey a relationship that depends on the complex's formation enthalpy. The rate of rotational gauche-trans isomerization around a carbon-carbon single bond is determined for a substituted ethane at room temperature in a low viscosity solvent. The results are used to obtain an approximate isomerization rate for ethane. Finally, the time dependence of a well-defined single structural transformation of a protein is measured.
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ion water hydrogen bond switching observed with 2d ir vibrational echo chemical Exchange Spectroscopy
Proceedings of the National Academy of Sciences of the United States of America, 2009Co-Authors: David E Moilanen, Daryl B Wong, Daniel E Rosenfeld, Emily E Fenn, M D FayerAbstract:The Exchange of water hydroxyl hydrogen bonds between anions and water oxygens is observed directly with ultrafast 2D IR vibrational echo chemical Exchange Spectroscopy (CES). The OD hydroxyl stretch of dilute HOD in H2O in concentrated (5.5 M) aqueous solutions of sodium tetrafluoroborate (NaBF4) displays a spectrum with a broad water-like band (hydroxyl bound to water oxygen) and a resolved, blue shifted band (hydroxyl bound to BF4−). At short time (200 fs), the 2D IR vibrational echo spectrum has 4 peaks, 2 on the diagonal and 2 off-diagonal. The 2 diagonal peaks are the 0–1 transitions of the water-like band and the hydroxyl-anion band. Vibrational echo emissions at the 1–2 transition frequencies give rise to 2 off-diagonal peaks. On a picosecond time scale, additional off-diagonal peaks grow in. These new peaks arise from chemical Exchange between water hydroxyls bound to anions and hydroxyls bound to water oxygens. The growth of the chemical Exchange peaks yields the time dependence of anion–water hydroxyl hydrogen bond switching under thermal equilibrium conditions as Taw = 7 ± 1 ps. Pump-probe measurements of the orientational relaxation rates and vibrational lifetimes are used in the CES data analysis. The pump-probe measurements are shown to have the correct functional form for a system undergoing Exchange.
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solute solvent complex kinetics and thermodynamics probed by 2d ir vibrational echo chemical Exchange Spectroscopy
Journal of Physical Chemistry B, 2008Co-Authors: Junrong Zheng, M D FayerAbstract:The formation and dissociation kinetics of a series of triethylsilanol/solvent weakly hydrogen bonding complexes with enthalpies of formation ranging from −1.4 to −3.3 kcal/mol are measured with ultrafast two-dimensional infrared (2D IR) chemical Exchange Spectroscopy in liquid solutions at room temperature. The correlation between the complex enthalpies of formation and dissociation rate constants can be expressed with an equation similar to the Arrhenius equation. The experimental results are in accord with previous observations on eight phenol/solvent complexes with enthalpies of formation from −0.6 to −2.5 kcal/mol. It was found that the inverse of the solute−solvent complex dissociation rate constant is linearly related to exp(−ΔH0/RT) where ΔH0 is the complex enthalpy of formation. It is shown here, that the triethylsilanol−solvent complexes obey the same relationship with the identical proportionality constant, that is, all 13 points, five silanol complexes and eight phenol complexes, fall on the s...
John L. Markley - One of the best experts on this subject based on the ideXlab platform.
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two dimensional magnetization Exchange Spectroscopy of anabaena 7120 ferredoxin nuclear overhauser effect and electron self Exchange cross peaks from amino acid residues surrounding the 2fe 2s cluster
Biochemistry, 1991Co-Authors: Lars Skjeldal, William M. Westler, Hazel M. Holden, Bruce L. Jacobson, Andrzej M Krezel, Ivan Rayment, John L. MarkleyAbstract:Hyperfine {sup 1}H NMR signals of the 2 Fe-2S* vegetative ferredoxin from Anabaena 7,120 have been studied by two-dimensional (2D) magnetization Exchange Spectroscopy. The rapid longitudinal relaxation rates of these signals required the use of very short nuclear Overhauser effect (NOE) mixing times (0.5-20 ms). The resulting pattern of NOE cross-relaxation peaks when combined with previous 1D NOE results led to elucidation of the carbon-bound proton spin systems from each of the four cysteines ligated to the 2Fe-2S* cluster in the reduced ferredoxin. Additional NOE cross peaks were observed that provide information about other amino acid residues that interact with the iron-sulfur cluster. NOE cross peaks were assigned tentatively to Leu{sup 27}, Arg{sup 42}, and Ala{sup 43} on the basis of the X-ray coordinates of oxidized Anabaena 7,120 ferredoxin. Three chemical Exchange cross peaks were detected in magnetization Exchange spectra of half-reduced ferredoxin and assigned to the {sup 1}H{sup {alpha}} protons of Cys{sup 49} and Cys{sup 79} (both of whose sulfur atoms are ligated to Fe(III)) and Arg{sup 42} (whose amide nitrogen is hydrogen-bonded to one of the inorganic sulfurs of the 2Fe-2S* cluster). The chemical Exchange cross peaks provide a means of extending assignments in the spectrum of reducedmore » ferredoxin to assignments in the spectrum of the oxidized protein. The results suggest that 2D magnetization Exchange Spectroscopy employing short mixing times will be useful for the assignment and characterization of hyperfine {sup 1}H peaks in a variety of paramagnetic proteins.« less
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two dimensional magnetization Exchange Spectroscopy of anabaena 7120 ferredoxin nuclear overhauser effect and electron self Exchange cross peaks from amino acid residues surrounding the 2fe 2s cluster
Biochemistry, 1991Co-Authors: Lars Skjeldal, William M. Westler, Hazel M. Holden, Bruce L. Jacobson, Andrzej M Krezel, Ivan Rayment, John L. MarkleyAbstract:Hyperfine 1H NMR signals of the 2Fe-2S* vegetative ferredoxin from Anabaena 7120 have been studied by two-dimensional (2D) magnetization Exchange Spectroscopy. The rapid longitudinal relaxation rates of these signals required the use of very short nuclear Overhauser effect (NOE) mixing times (0.5-20 ms). The resulting pattern of NOE cross-relaxation peaks when combined with previous 1D NOE results [Dugad, L. B., La Mar, G. N., Banci, L., & Bertini, I. (1990) Biochemistry 29, 2263-2271] led to elucidation of the carbon-bound proton spin systems from each of the four cysteines ligated to the 2Fe-2S* cluster in the reduced ferredoxin. Additional NOE cross peaks were observed that provide information about other amino acid residues that interact with the iron-sulfur cluster. NOE cross peaks were assigned tentatively to Leu27, Arg42, and Ala43 on the basis of the X-ray coordinates of oxidized Anabaena 7120 ferredoxin [Rypniewski, W.R., Breiter, D.R., Benning, M.M., Wesenberg, G., Oh, B.-H., Markley, J.L., Rayment, I., & Holden, H. M. (1991) Biochemistry 30, 4126-4131]. Three chemical Exchange cross peaks were detected in magnetization Exchange spectra of half-reduced ferredoxin and assigned to the 1H alpha protons of Cys49 and Cys79 [both of whose sulfur atoms are ligated to Fe(III)] and Arg42 (whose amide nitrogen is hydrogen-bonded to one of the inorganic sulfurs of the 2Fe-2S* cluster). The chemical Exchange cross peaks provide a means of extending assignments in the spectrum of reduced ferredoxin to assignments in the spectrum of the oxidized protein.(ABSTRACT TRUNCATED AT 250 WORDS)
Lars Skjeldal - One of the best experts on this subject based on the ideXlab platform.
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two dimensional magnetization Exchange Spectroscopy of anabaena 7120 ferredoxin nuclear overhauser effect and electron self Exchange cross peaks from amino acid residues surrounding the 2fe 2s cluster
Biochemistry, 1991Co-Authors: Lars Skjeldal, William M. Westler, Hazel M. Holden, Bruce L. Jacobson, Andrzej M Krezel, Ivan Rayment, John L. MarkleyAbstract:Hyperfine {sup 1}H NMR signals of the 2 Fe-2S* vegetative ferredoxin from Anabaena 7,120 have been studied by two-dimensional (2D) magnetization Exchange Spectroscopy. The rapid longitudinal relaxation rates of these signals required the use of very short nuclear Overhauser effect (NOE) mixing times (0.5-20 ms). The resulting pattern of NOE cross-relaxation peaks when combined with previous 1D NOE results led to elucidation of the carbon-bound proton spin systems from each of the four cysteines ligated to the 2Fe-2S* cluster in the reduced ferredoxin. Additional NOE cross peaks were observed that provide information about other amino acid residues that interact with the iron-sulfur cluster. NOE cross peaks were assigned tentatively to Leu{sup 27}, Arg{sup 42}, and Ala{sup 43} on the basis of the X-ray coordinates of oxidized Anabaena 7,120 ferredoxin. Three chemical Exchange cross peaks were detected in magnetization Exchange spectra of half-reduced ferredoxin and assigned to the {sup 1}H{sup {alpha}} protons of Cys{sup 49} and Cys{sup 79} (both of whose sulfur atoms are ligated to Fe(III)) and Arg{sup 42} (whose amide nitrogen is hydrogen-bonded to one of the inorganic sulfurs of the 2Fe-2S* cluster). The chemical Exchange cross peaks provide a means of extending assignments in the spectrum of reducedmore » ferredoxin to assignments in the spectrum of the oxidized protein. The results suggest that 2D magnetization Exchange Spectroscopy employing short mixing times will be useful for the assignment and characterization of hyperfine {sup 1}H peaks in a variety of paramagnetic proteins.« less
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two dimensional magnetization Exchange Spectroscopy of anabaena 7120 ferredoxin nuclear overhauser effect and electron self Exchange cross peaks from amino acid residues surrounding the 2fe 2s cluster
Biochemistry, 1991Co-Authors: Lars Skjeldal, William M. Westler, Hazel M. Holden, Bruce L. Jacobson, Andrzej M Krezel, Ivan Rayment, John L. MarkleyAbstract:Hyperfine 1H NMR signals of the 2Fe-2S* vegetative ferredoxin from Anabaena 7120 have been studied by two-dimensional (2D) magnetization Exchange Spectroscopy. The rapid longitudinal relaxation rates of these signals required the use of very short nuclear Overhauser effect (NOE) mixing times (0.5-20 ms). The resulting pattern of NOE cross-relaxation peaks when combined with previous 1D NOE results [Dugad, L. B., La Mar, G. N., Banci, L., & Bertini, I. (1990) Biochemistry 29, 2263-2271] led to elucidation of the carbon-bound proton spin systems from each of the four cysteines ligated to the 2Fe-2S* cluster in the reduced ferredoxin. Additional NOE cross peaks were observed that provide information about other amino acid residues that interact with the iron-sulfur cluster. NOE cross peaks were assigned tentatively to Leu27, Arg42, and Ala43 on the basis of the X-ray coordinates of oxidized Anabaena 7120 ferredoxin [Rypniewski, W.R., Breiter, D.R., Benning, M.M., Wesenberg, G., Oh, B.-H., Markley, J.L., Rayment, I., & Holden, H. M. (1991) Biochemistry 30, 4126-4131]. Three chemical Exchange cross peaks were detected in magnetization Exchange spectra of half-reduced ferredoxin and assigned to the 1H alpha protons of Cys49 and Cys79 [both of whose sulfur atoms are ligated to Fe(III)] and Arg42 (whose amide nitrogen is hydrogen-bonded to one of the inorganic sulfurs of the 2Fe-2S* cluster). The chemical Exchange cross peaks provide a means of extending assignments in the spectrum of reduced ferredoxin to assignments in the spectrum of the oxidized protein.(ABSTRACT TRUNCATED AT 250 WORDS)
Daniel E Rosenfeld - One of the best experts on this subject based on the ideXlab platform.
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hydrogen bond migration between molecular sites observed with ultrafast 2d ir chemical Exchange Spectroscopy
Journal of Physical Chemistry B, 2010Co-Authors: Daniel E Rosenfeld, Kyungwon Kwak, Zsolt Gengeliczki, M D FayerAbstract:Hydrogen-bonded complexes between phenol and phenylacetylene are studied using ultrafast two-dimensional infrared (2D IR) chemical Exchange Spectroscopy. Phenylacetylene has two possible π hydrogen bonding acceptor sites (phenyl or acetylene) that compete for hydrogen bond donors in solution at room temperature. The OD stretch frequency of deuterated phenol is sensitive to which acceptor site it is bound. The appearance of off-diagonal peaks between the two vibrational frequencies in the 2D IR spectrum reports on the Exchange process between the two competitive hydrogen-bonding sites of phenol−phenylacetylene complexes in the neat phenylacetylene solvent. The chemical Exchange process occurs in ∼5 ps and is assigned to direct hydrogen bond migration along the phenylacetylene molecule. Other nonmigration mechanisms are ruled out by performing 2D IR experiments on phenol dissolved in the phenylacetylene/carbon tetrachloride mixed solvent. The observation of direct hydrogen bond migration can have implicatio...
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ion water hydrogen bond switching observed with 2d ir vibrational echo chemical Exchange Spectroscopy
Proceedings of the National Academy of Sciences of the United States of America, 2009Co-Authors: David E Moilanen, Daryl B Wong, Daniel E Rosenfeld, Emily E Fenn, M D FayerAbstract:The Exchange of water hydroxyl hydrogen bonds between anions and water oxygens is observed directly with ultrafast 2D IR vibrational echo chemical Exchange Spectroscopy (CES). The OD hydroxyl stretch of dilute HOD in H2O in concentrated (5.5 M) aqueous solutions of sodium tetrafluoroborate (NaBF4) displays a spectrum with a broad water-like band (hydroxyl bound to water oxygen) and a resolved, blue shifted band (hydroxyl bound to BF4−). At short time (200 fs), the 2D IR vibrational echo spectrum has 4 peaks, 2 on the diagonal and 2 off-diagonal. The 2 diagonal peaks are the 0–1 transitions of the water-like band and the hydroxyl-anion band. Vibrational echo emissions at the 1–2 transition frequencies give rise to 2 off-diagonal peaks. On a picosecond time scale, additional off-diagonal peaks grow in. These new peaks arise from chemical Exchange between water hydroxyls bound to anions and hydroxyls bound to water oxygens. The growth of the chemical Exchange peaks yields the time dependence of anion–water hydroxyl hydrogen bond switching under thermal equilibrium conditions as Taw = 7 ± 1 ps. Pump-probe measurements of the orientational relaxation rates and vibrational lifetimes are used in the CES data analysis. The pump-probe measurements are shown to have the correct functional form for a system undergoing Exchange.
Peter Hamm - One of the best experts on this subject based on the ideXlab platform.
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protein ligand migration mapped by nonequilibrium 2d ir Exchange Spectroscopy
Proceedings of the National Academy of Sciences of the United States of America, 2007Co-Authors: Jens Bredenbeck, Jan Helbing, Karin Nienhaus, Ulrich G Nienhaus, Peter HammAbstract:2D-IR Exchange Spectroscopy has been introduced recently to map chemical Exchange networks in equilibrium with subpicosecond time resolution. Here, we demonstrate the generalization of 2D-IR Exchange Spectroscopy to nonequilibrium systems and its application to map light-triggered migration of ligands between different sites in a protein. Within picoseconds after a photodissociating laser pulse, carbon monoxide ligands relocate from their binding site A at the heme prosthetic group of myoglobin to a primary docking site B in the distal heme pocket. Multiple CO stretching bands are observed for the CO ligand in sites A and B, indicating that several distinct conformational substates of the myoglobin:ligand complex coexist in solution. Exchange cross-peaks between the bands associated with substates of heme-bound CO and photodissociated CO in the primary docking site reveal the substate connectivity at physiological temperature.
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nonequilibrium 2d ir Exchange Spectroscopy ligand migration in proteins
15th International Conference on Ultrafast Phenomena (2006) paper MI3, 2006Co-Authors: Jens Bredenbeck, Jan Helbing, Karin Nienhaus, Ulrich G Nienhaus, Peter HammAbstract:Two-dimensional Exchange Spectroscopy maps networks of interconverting chemical species in dynamic equilibrium. We present the extension of ultrafast 2D-IR Exchange Spectroscopy to the nonequilibrium regime and its application to ligand migration in proteins.
