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Seung-Pyo Lee,
Yong-Jin Kim,
Joo Myung Lee,
Ho-Young Hwang,
Hyung-Kwan Kim, Kyung-Hwan Kim,
Ki-Bong Kim,
Dae-Won Sohn,
Hyuk Ahn,
Byung-Hee Oh,
Young-Bae Park
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ABSTRACT: Although atrial fibrillation (AF) and decreased exercise capacity are common in chronic mitral regurgitation patients, the relationship between rhythm status and exercise capacity after corrective surgery is largely unknown.
Seventy-one patients undergoing repair or replacement of mitral valve for chronic severe mitral regurgitation were examined with preoperative and 6 months' postoperative cardiopulmonary exercise test and two-dimensional echocardiography. Patients were divided into three groups according to preoperative versus postoperative rhythm (sinus/sinus, SS [n=42]; AF/sinus, AS [n=17]; AF/AF, AA group [n=12]).
Preoperative maximal oxygen consumption was lower and ventilatory efficiency was higher in the AS and AA groups compared with the SS group. However, maximal oxygen consumption improved only in the AS group at 6 months' postoperative cardiopulmonary exercise test (24.0±6.9 versus 24.6±6.1 mL·kg(-1)·min(-1) in the SS group, 19.3±5.9 versus 23.2±6.4 mL·kg(-1)·min(-1) in the AS group, 19.8±5.4 versus 18.8±5.1 mL·kg(-1)·min(-1) in the AA group; p=0.016 for maximal oxygen consumption by analysis of covariance) as well as ventilatory efficiency. Echocardiography verified more significant reduction of left atrial volume in the SS and AS groups than in the AA group (172.2±68.0 versus 96.7±31.0 mL in the SS group, 247.5±77.8 versus 129.2±25.7 mL in the AS group, 316.7±210.0 versus 192.0±95.0 mL in the AA group; p=0.001 for left atrial volume by analysis of covariance) as well as pulmonary artery systolic pressure. When analyzed for significant predictors of postoperative maximal oxygen consumption, being in the AS group but not the SS group was a significant positive predictor when compared with the AA group (β=5.475; p=0.006).
Successful sinus conversion of AF, preferably by maze operation, in patients undergoing surgical correction of chronic severe mitral regurgitation confers improved exercise capacity. Reduction of left atrial volume and pulmonary artery pressure may contribute to this improvement.
The Annals of thoracic surgery 04/2012; 93(6):1888-95. · 3.74 Impact Factor
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Tae Wu Kim,
Jae Hyuk Lee,
Jungkweon Choi, Kyung Hwan Kim,
Luuk J. van Wilderen,
Laurent Guerin,
Youngmin Kim,
Yang Ouk Jung,
Cheolhee Yang,
Jeongho Kim,
Michael Wulff,
Jasper J. van Thor,
Hyotcherl Ihee
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ABSTRACT: Photoreceptor proteins play crucial roles in receiving light stimuli that give rise to the responses required for biological function. However, structural characterization of conformational transition of the photoreceptors has been elusive in their native aqueous environment, even for a prototype photoreceptor, photoactive yellow protein (PYP). We employ pump-probe X-ray solution scattering to probe the structural changes that occur during the photocycle of PYP in a wide time range from 3.16 μs to 300 ms. By the analysis of both kinetics and structures of the intermediates, the structural progression of the protein in the solution phase is vividly visualized. We identify four structurally distinct intermediates and their associated five time constants and reconstructed the molecular shapes of the four intermediates from time-independent, species-associated difference scattering curves. The reconstructed structures of the intermediates show the large conformational changes such as the protrusion of N-terminus, which is restricted in the crystalline phase due to the crystal contact and thus could not be clearly observed by X-ray crystallography. The protrusion of the N-terminus and the protein volume gradually increase with the progress of the photocycle and becomes maximal in the final intermediate, which is proposed to be the signalling state. The data not only reveal that a common kinetic mechanism is applicable to both the crystalline and solution phases, but also provide direct evidence for how the sample environment influences structural dynamics and the reaction rates of the PYP photocycle.
Journal of the American Chemical Society 01/2012; 134(6):3145-3153. · 9.91 Impact Factor
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Kyung Hwan Kim,
Srinivasan Muniyappan,
Key Young Oang,
Jong Goo Kim,
Shunsuke Nozawa,
Tokushi Sato,
Shin-ya Koshihara,
Robert Henning,
Irina Kosheleva,
Hosung Ki,
Youngmin Kim,
Tae Wu Kim,
Jeongho Kim,
Shin-ichi Adachi,
Hyotcherl Ihee
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ABSTRACT: Proteins serve as molecular machines in performing their biological functions, but the detailed structural transitions are difficult to observe in their native aqueous environments in real time. For example, despite extensive studies, the solution-phase structures of the intermediates along the allosteric pathways for the transitions between the relaxed (R) and tense (T) forms have been elusive. In this work, we employed picosecond X-ray solution scattering and novel structural analysis to track the details of the structural dynamics of wild-type homodimeric hemoglobin (HbI) from the clam Scapharca inaequivalvis and its F97Y mutant over a wide time range from 100 ps to 56.2 ms. From kinetic analysis of the measured time-resolved X-ray solution scattering data, we identified three structurally distinct intermediates (I1, I2, and I3) and their kinetic pathways common for both the wild type and the mutant. The data revealed that the singly liganded and unliganded forms of each intermediate share the same structure, providing direct evidence that the ligand photolysis of only a single subunit induces the same structural change as the complete photolysis of both subunits does. In addition, by applying novel structural analysis to the scattering data, we elucidated the detailed structural changes in the protein, including changes in the heme–heme distance, the quaternary rotation angle of subunits, and interfacial water gain/loss. The earliest, R-like I1 intermediate is generated within 100 ps and transforms to the R-like I2 intermediate with a time constant of 3.2 ± 0.2 ns. Subsequently, the late, T-like I3 intermediate is formed via subunit rotation, a decrease in the heme–heme distance, and substantial gain of interfacial water and exhibits ligation-dependent formation kinetics with time constants of 730 ± 120 ns for the fully photolyzed form and 5.6 ± 0.8 μs for the partially photolyzed form. For the mutant, the overall kinetics are accelerated, and the formation of the T-like I3 intermediate involves interfacial water loss (instead of water entry) and lacks the contraction of the heme–heme distance, thus underscoring the dramatic effect of the F97Y mutation. The ability to keep track of the detailed movements of the protein in aqueous solution in real time provides new insights into the protein structural dynamics.
Journal of the American Chemical Society. 01/2012;
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ABSTRACT: We investigate the structural dynamics of iodine elimination reaction of 1,2-diiodoethane (C(2)H(4)I(2)) in cyclohexane by applying time-resolved X-ray liquidography (TRXL). The TRXL technique combines structural sensitivity of X-ray diffraction and 100 ps time resolution of X-ray pulses from synchrotron and allows direct probing of transient structure of reacting molecules. From the analysis of time-dependent X-ray solution scattering patterns using global fitting based on DFT calculation and MD simulation, we elucidate the kinetics and structure of transient intermediates resulting from photodissociation of C(2)H(4)I(2). In particular, the effect of solvent on the reaction kinetics and pathways is examined by comparison with an earlier TRXL study on the same reaction in methanol. In cyclohexane, the C(2)H(4)I radical intermediate undergoes two branched reaction pathways, formation of C(2)H(4)I-I isomer and direct dissociation into C(2)H(4) and I, while only isomer formation occurs in methanol. Also, the C(2)H(4)I-I isomer has a shorter lifetime in cyclohexane by an order of magnitude than in methanol. The difference in the reaction dynamics in the two solvents is accounted for by the difference in solvent polarity. In addition, we determine that the C(2)H(4)I radical has a bridged structure, not a classical structure, in cyclohexane.
The Journal of Physical Chemistry A 11/2011; 116(11):2713-22. · 2.95 Impact Factor
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ABSTRACT: Anisotropic X-ray scattering patterns of transiently aligned protein molecules in solution are measured by using pump-probe X-ray solution scattering. When a linearly polarized laser pulse interacts with an ensemble of molecules, the population of excited molecules is created with their transition dipoles preferentially aligned along the laser polarization direction. We measured the X-ray scattering from the myoglobin protein molecules excited by a linearly polarized, short laser pulse and obtained anisotropic scattering patterns on 100 ps time scale. An anisotropic scattering pattern contains higher structural information content than a typical isotropic pattern available from randomly oriented molecules. In addition, multiple independent diffraction patterns measured by using various laser polarization orientations will give substantially increased amount of structural information compared with a single isotropic pattern. By monitoring the temporal change of the anisotropic scattering pattern from 100 ps to 1 μs, we observed the orientational dynamics of photo-generated myoglobin with the rotational diffusion time of ∼15 ns.
Journal of Physical Chemistry Letters 02/2011; 2(5):350-356. · 6.21 Impact Factor
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ABSTRACT: Here we report structural dynamics of equine myoglobin (Mb) in response to the CO photodissociation visualized by picosecond time-resolved X-ray solution scattering. The data clearly reveal new structural dynamics that occur in the timescale of ∼360 picoseconds (ps) and ∼9 nanoseconds (ns), which have not been clearly detected in previous studies.
Chemical Communications 01/2011; 47(1):289-91. · 6.17 Impact Factor
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ABSTRACT: Anisotropic X-ray scattering patterns of transiently aligned protein molecules in solution are measured by using pump-probe X-ray solution scattering. When a linearly polarized laser pulse interacts with an ensemble of molecules, the population of excited molecules is created with their transition dipoles preferentially aligned along the laser polarization direction. We measured the X-ray scattering from the myoglobin protein mole-cules excited by a linearly polarized, short laser pulse and obtained anisotropic scattering patterns on a 100 ps time scale. An an-isotropic scattering pattern contains higher structural information content than a typical isotropic pattern available from randomly oriented molecules. In addition, multiple independent diffraction patterns measured by using various laser polarization orientations will give a substantially increased amount of structural information compared with that from a single isotropic pattern. By monitoring the temporal change of the anisotropic scattering pattern from 100 ps to 1 μs, we observed the orientational dynamics of photo-generated myoglobin with the rotational diffusion time of ∼15 ns. SECTION: Kinetics, Spectroscopy T ime-resolved X-ray solution scattering (liquidography) offers a means of directly accessing the transient molecular structure in the solution phase, for example, the time dependence of bond lengths and angles. Structural dynamics of various molecular systems in solution including diatomic molecules, haloalkanes, organometallic complexes, protein molecules, and nanoparticles have been elucidated using this technique. 1-15 Due to the lack of long-range order and random orientation of molecules in solution, a solution scattering pattern generally exhibits an isotropic, smooth oscillation profile, containing much less information content compared with diffraction patterns from crystalline samples. Enhancing information content would allow extraction of more accurate structures and dynamics. As one of the first steps toward this goal, here, we investigate the possibility of increasing the information content by manipulating the polarization orientation of the pump laser pulse relative to the X-ray propagation direction. As a result, the excited molecules are photoselectively aligned and generate anisotropic X-ray scattering patterns. To some extent, this approach is similar to time domain spectroscopy using polarized light, which has been a powerful tool for selectively probing molecular orientational dynamics in isotropic media. 16-20 One of the most representative polariza-tion spectroscopic techniques is pump-probe transient anisot-ropy, which can measure the depolarization rate. When a linearly polarized laser pulse interacts with an ensemble of molecules, the population of excited molecules is created with their transition dipoles preferentially aligned along the laser polarization direc-tion. By using another linearly polarized light propagating in the same direction as the first laser beam as a probe, the evolution of a transition dipole direction over time can be probed in real time. The transient anisotropy has been mainly used for measuring rotational diffusion of molecules 21,22 as well as energy transfer dynamics in multichromophore systems such as conjugated poly-mers 23,24 and photosynthetic light-harvesting complexes. 25,26 In addition, important insight has been gained from polarization anisotropy studies of aqueous systems in the infrared region. 27-29 With the advance in time-resolved diffraction techniques, the potential of probing the molecular orientational dynamics using electron diffraction has been investigated. 30-33 Especially, when applied to time-resolved diffraction techniques, it has been anticipated that linearly polarized excitation can help to char-acterize the molecular structure and dynamics more clearly because it has the effect of freezing the molecular orientation along the polarization direction. Conversely, the anisotropy effect manifested in the diffraction pattern could mislead the interpretation of the diffraction pattern. Therefore, more careful treatment is needed in the analysis of the anisotropic diffraction pattern.
J. Phys. Chem. Lett. 01/2011; 2:350-356.
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ABSTRACT: We investigate the photoinduced dissociation of HgBr(2) in methanol and the ensuring structural dynamics of the photo-products over a time span from 100 ps to 1 μs after photolysis at 267 nm by using time-resolved X-ray liquidography (TRXL). By making use of the atomic-level structural sensitivity of X-ray scattering and the superb 100 ps time resolution of X-ray pulses from a 3rd-generation synchrotron, the structural dynamics of a chemical reaction in solution can be directly monitored. The measured time-dependent X-ray solution scattering signals, analyzed using global-fitting based on DFT calculations and MD simulations, show that photoexcited HgBr(2) dissociates via both two-body (HgBr + Br) and three-body (Hg + Br + Br) dissociation pathways with a ∼2 : 1 branching ratio. Following dissociation, the photoproducts recombine via three reactions involving Br species: (1) Hg + Br, (2) HgBr + Br, and (3) Br + Br. The associated rate constants and branching ratios are determined from the global-fitting analysis. Also, we examine the energy dissipation from reacting solute molecules and relaxation of excited molecules to solvent bath accompanying the temperature rise of 0.54 K. Compared to a previous TRXL study of the photodissociation of HgI(2), the results of this work suggest that the photodissociation pathway of HgBr(2) is different from that of HgI(2), which dissociates predominantly via two-body dissociation, at least to within the currently available time resolution of ∼100 ps. In addition, the error analysis of the fit parameters used in the global-fitting are discussed in detail with a comparison of various error estimation algorithms.
Physical Chemistry Chemical Physics 10/2010; 12(37):11536-47. · 3.57 Impact Factor
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ABSTRACT: In recent years, the time-resolved X-ray diffraction technique has been established as an excellent tool for studying reaction dynamics and protein structural transitions with the aid of 100 ps X-ray pulses generated from third-generation synchrotrons. The forthcoming advent of the X-ray free-electron laser (XFEL) will bring a substantial improvement in pulse duration, photon flux and coherence of X-ray pulses, making time-resolved X-ray diffraction even more powerful. This technical breakthrough is envisioned to revolutionize the field of reaction dynamics associated with time-resolved diffraction methods. Examples of candidates for the first femtosecond X-ray diffraction experiments using highly coherent sub-100 fs pulses generated from XFELs are presented in this paper. They include the chemical reactions of small molecules in the gas and solution phases, solvation dynamics and protein structural transitions. In these potential experiments, ultrafast reaction dynamics and motions of coherent rovibrational wave packets will be monitored in real time. In addition, high photon flux and coherence of XFEL-generated X-ray pulses give the prospect of single-molecule diffraction experiments.
Acta crystallographica. Section A, Foundations of crystallography 03/2010; 66(Pt 2):270-80. · 49.93 Impact Factor
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ABSTRACT: We obtained a solution structural model of myoglobin (Mb) formed upon the CO photolysis of MbCO by analyzing time-resolved X-ray solution scattering data. An experiment-restrained rigid-body molecular dynamics simulation was used to find the best model whose theoretical difference scattering curve gives a satisfactory agreement with the experimental data at the time delay of 10 ns. The obtained solution model shows structural changes similar to crystallographic models for MbCO --> Mb but also displays a noticeable difference in that the N-terminus and F helix show larger structural changes.
The Journal of Physical Chemistry B 09/2009; 113(40):13131-3. · 3.70 Impact Factor
