The journal of physical chemistry. B, Jan 15, 2008
Globular proteins undergo structural transitions to denatured states when sufficient thermodynami... more Globular proteins undergo structural transitions to denatured states when sufficient thermodynamic state or chemical perturbations are introduced to their native environment. Cold denaturation is a somewhat counterintuitive phenomenon whereby proteins lose their compact folded structure as a result of a temperature drop. The currently accepted explanation for cold denaturation is based on an associated favorable change in the contact free energy between water and nonpolar groups at colder temperatures which would weaken the hydrophobic interaction and is thought to eventually allow polymer entropy to disrupt protein tertiary structure. In this paper we explore how this environmental perturbation leads to changes in the protein hydration and local motions in apomyoglobin. We do this by analyzing changes in protein hydration and protein motion from molecular dynamics simulation trajectories initially at 310 K, followed by a temperature drop to 278 K. We observe an increase in the number of solvent contacts around the protein and, in particular, distinctly around nonpolar atoms. Further analysis shows that the fluctuations of some protein atoms increase with decreasing temperature. This is accompanied by an observed increase in the isothermal compressibility of the protein, indicating an increase in the protein interior interstitial space. Closer inspection reveals that atoms with increased compressibility and larger-than-expected fluctuations are localized within the protein core regions. These results provide insight into a description of the mechanism of cold denaturation. That is, the lower temperature leads to solvent-induced packing defects at the protein surface, and this more favorable water-protein interaction in turn destabilizes the overall protein structure.
We discuss the kinematics of these clusters and of three additional bulge clusters -- NGC 6522, N... more We discuss the kinematics of these clusters and of three additional bulge clusters -- NGC 6522, NGC 6528 and NFC 6553 -- whose proper motions with respect to bulge stars had been determined previously. We find that all of the clusters have velocities that confine them to the bulge region. Of the three metal poor clusters ([Fe/H] < -1.0), NGC 6522, and NGC 6723 have kinematics consistent with halo membership. The third cluster, NGC 6266 however, appears to belong to a rotationally-supported system. Of the four metal rich clusters ([Fe/H] >= -1.0), NGC 6304 and NGC 6553 also have kinematics consistent with membership to a rotationally-supported system. NGC 6528 has kinematics, metallicity and mass that argue in favor of a genuine Milky-Way bar cluster. NGC 6316's kinematics indicate membership to a hotter system than the bar.
Currently the entanglement of formation can be calculated analytically for mixed states in a $(2\... more Currently the entanglement of formation can be calculated analytically for mixed states in a $(2\otimes2)$-dimensional Hilbert space. For states in higher dimensional Hilbert space a closed formula for quantifying entanglement does not exist. In this regard only entanglement bounds has been found for estimating it. In this work, we find an analytical expression for evaluating the entanglement of formation for bipartite ($2\otimes d$)-dimensional mixed states.
The Guide Star Photometric Catalog (GSPC) is an all-sky set of 1477 photoelectrically determined ... more The Guide Star Photometric Catalog (GSPC) is an all-sky set of 1477 photoelectrically determined BV sequences covering the magnitude range from 9 to 15. The GSPC was created to provide photometric calibrators for the HST Guide Star Catalog (GSC). Each sequence nominally contains (at least) six stars, each with a photometric precision of 0.05 mag. In practice, a small number of sequences contain fewer stars; and the precisions achieved for the faintest stars are more nearly 0.1 mag. For declinations greater than +3 degrees the sequences generally lie near the centers of the original Palomar Observatory - National Geographic Society Sky Atlas. Other sequences lie near the centers of the ESO/SERC Southern Sky Atlas. The catalog also includes a list of suspected variable stars, a bibliography of literature sequences, and additional information which was useful in the data reduction and for quality control of the final catalog. The full catalog is made of 7 FITS files: tables 1 to 5, references (table 6 of the paper) and the actual catalogue (table 7 of the paper). The ascii versions of Tables 1 to 5 are included in this file; the ascii version of the references (refs.dat) and of the actual catalogue (catalog.dat) are described here. The updated version 1 was created by replacing photometric sequences P040, P421, S335 and S742 in GSPC version 1. The updated sequences have improved photometry and/or positions. In addition the sigma's in V and B-V (here eV and eB-V) were replaced with the values provided by the authors when we noted a discrepancy with the published values. (2 data files).
Chemistry (Weinheim an der Bergstrasse, Germany), Jan 4, 2005
The ellipticity of the electron density is proposed as a convenient tool to characterize electroc... more The ellipticity of the electron density is proposed as a convenient tool to characterize electrocyclic reactions. The study of the electron density offers several advantages since it is an experimental observable. This simple topological index has proven powerful and robust for the characterization of a wide variety of electrocyclic and pseudoelectrocyclic processes. This property is sensitive to changes in the anisotropy of the electron density in the bond-forming region and provides an insightful description of the events occurring along the reaction coordinate.
In the systems of reconstruction 3D of structured light or interferometric, the spatial phase unw... more In the systems of reconstruction 3D of structured light or interferometric, the spatial phase unwrapping by traditional methods constitutes a difficult problem to solve. The inherent noise to the surface, low visibility of the fringes patterns or the computational method for fringe pattern analysis can affect the discontinuous phase map, producing errors affect the quality of the demodulation of the fringes pattern. In this work, two methods are implemented: a first method for filtering the discontinuous phase maps based on windowed Fourier transform (WFT) and a second method for phase unwrapping based on a parameter of reliability-guided. The WFT is implemented by mean of a windowed function of Gauss, which controls the extension and quality of the filtrate. On the other hand, the spatial phase unwrapping takes as parameter of reliability-guided the matrix of intensity modulation (MIM). The elements of this MIM are used to identify the direction of phase unwrapping over the filtered phase map. It means that the pixel with higher parameter value in the parameter map will be phase unwrapped earlier. The efficiency of the methods and the influences of the WFT on the phase spatial unwrapping are proved in discontinuous maps, which were obtained by mean of Fourier transform and phase shifting.
The two metal rich clusters NGC 6388 and NGC 6441 have velocities incompatibile with membership i... more The two metal rich clusters NGC 6388 and NGC 6441 have velocities incompatibile with membership in the thick disk or the bar of the Milky Way. They can be though of as members of a kinematically hot system in the inner Galaxy. Curiously, both clusters have similar velocity components. Together with their similar Galactic location and peculiar but similar stellar-population characteristics, these two clusters may share a common origin. Their velocities are also very low indicating that the two clusters are now at/near apocenter, and they will not leave the inner ~4 kpc of the Galaxy.
These are the first results of the Southern Proper-Motion Program (SPM) where the second-epoch ob... more These are the first results of the Southern Proper-Motion Program (SPM) where the second-epoch observations are taken with the CCD camera system recently installed on the double astrograph at El Leoncito, Argentina.
The journal of physical chemistry. B, Jan 15, 2008
Globular proteins undergo structural transitions to denatured states when sufficient thermodynami... more Globular proteins undergo structural transitions to denatured states when sufficient thermodynamic state or chemical perturbations are introduced to their native environment. Cold denaturation is a somewhat counterintuitive phenomenon whereby proteins lose their compact folded structure as a result of a temperature drop. The currently accepted explanation for cold denaturation is based on an associated favorable change in the contact free energy between water and nonpolar groups at colder temperatures which would weaken the hydrophobic interaction and is thought to eventually allow polymer entropy to disrupt protein tertiary structure. In this paper we explore how this environmental perturbation leads to changes in the protein hydration and local motions in apomyoglobin. We do this by analyzing changes in protein hydration and protein motion from molecular dynamics simulation trajectories initially at 310 K, followed by a temperature drop to 278 K. We observe an increase in the number of solvent contacts around the protein and, in particular, distinctly around nonpolar atoms. Further analysis shows that the fluctuations of some protein atoms increase with decreasing temperature. This is accompanied by an observed increase in the isothermal compressibility of the protein, indicating an increase in the protein interior interstitial space. Closer inspection reveals that atoms with increased compressibility and larger-than-expected fluctuations are localized within the protein core regions. These results provide insight into a description of the mechanism of cold denaturation. That is, the lower temperature leads to solvent-induced packing defects at the protein surface, and this more favorable water-protein interaction in turn destabilizes the overall protein structure.
We discuss the kinematics of these clusters and of three additional bulge clusters -- NGC 6522, N... more We discuss the kinematics of these clusters and of three additional bulge clusters -- NGC 6522, NGC 6528 and NFC 6553 -- whose proper motions with respect to bulge stars had been determined previously. We find that all of the clusters have velocities that confine them to the bulge region. Of the three metal poor clusters ([Fe/H] < -1.0), NGC 6522, and NGC 6723 have kinematics consistent with halo membership. The third cluster, NGC 6266 however, appears to belong to a rotationally-supported system. Of the four metal rich clusters ([Fe/H] >= -1.0), NGC 6304 and NGC 6553 also have kinematics consistent with membership to a rotationally-supported system. NGC 6528 has kinematics, metallicity and mass that argue in favor of a genuine Milky-Way bar cluster. NGC 6316's kinematics indicate membership to a hotter system than the bar.
Currently the entanglement of formation can be calculated analytically for mixed states in a $(2\... more Currently the entanglement of formation can be calculated analytically for mixed states in a $(2\otimes2)$-dimensional Hilbert space. For states in higher dimensional Hilbert space a closed formula for quantifying entanglement does not exist. In this regard only entanglement bounds has been found for estimating it. In this work, we find an analytical expression for evaluating the entanglement of formation for bipartite ($2\otimes d$)-dimensional mixed states.
The Guide Star Photometric Catalog (GSPC) is an all-sky set of 1477 photoelectrically determined ... more The Guide Star Photometric Catalog (GSPC) is an all-sky set of 1477 photoelectrically determined BV sequences covering the magnitude range from 9 to 15. The GSPC was created to provide photometric calibrators for the HST Guide Star Catalog (GSC). Each sequence nominally contains (at least) six stars, each with a photometric precision of 0.05 mag. In practice, a small number of sequences contain fewer stars; and the precisions achieved for the faintest stars are more nearly 0.1 mag. For declinations greater than +3 degrees the sequences generally lie near the centers of the original Palomar Observatory - National Geographic Society Sky Atlas. Other sequences lie near the centers of the ESO/SERC Southern Sky Atlas. The catalog also includes a list of suspected variable stars, a bibliography of literature sequences, and additional information which was useful in the data reduction and for quality control of the final catalog. The full catalog is made of 7 FITS files: tables 1 to 5, references (table 6 of the paper) and the actual catalogue (table 7 of the paper). The ascii versions of Tables 1 to 5 are included in this file; the ascii version of the references (refs.dat) and of the actual catalogue (catalog.dat) are described here. The updated version 1 was created by replacing photometric sequences P040, P421, S335 and S742 in GSPC version 1. The updated sequences have improved photometry and/or positions. In addition the sigma's in V and B-V (here eV and eB-V) were replaced with the values provided by the authors when we noted a discrepancy with the published values. (2 data files).
Chemistry (Weinheim an der Bergstrasse, Germany), Jan 4, 2005
The ellipticity of the electron density is proposed as a convenient tool to characterize electroc... more The ellipticity of the electron density is proposed as a convenient tool to characterize electrocyclic reactions. The study of the electron density offers several advantages since it is an experimental observable. This simple topological index has proven powerful and robust for the characterization of a wide variety of electrocyclic and pseudoelectrocyclic processes. This property is sensitive to changes in the anisotropy of the electron density in the bond-forming region and provides an insightful description of the events occurring along the reaction coordinate.
In the systems of reconstruction 3D of structured light or interferometric, the spatial phase unw... more In the systems of reconstruction 3D of structured light or interferometric, the spatial phase unwrapping by traditional methods constitutes a difficult problem to solve. The inherent noise to the surface, low visibility of the fringes patterns or the computational method for fringe pattern analysis can affect the discontinuous phase map, producing errors affect the quality of the demodulation of the fringes pattern. In this work, two methods are implemented: a first method for filtering the discontinuous phase maps based on windowed Fourier transform (WFT) and a second method for phase unwrapping based on a parameter of reliability-guided. The WFT is implemented by mean of a windowed function of Gauss, which controls the extension and quality of the filtrate. On the other hand, the spatial phase unwrapping takes as parameter of reliability-guided the matrix of intensity modulation (MIM). The elements of this MIM are used to identify the direction of phase unwrapping over the filtered phase map. It means that the pixel with higher parameter value in the parameter map will be phase unwrapped earlier. The efficiency of the methods and the influences of the WFT on the phase spatial unwrapping are proved in discontinuous maps, which were obtained by mean of Fourier transform and phase shifting.
The two metal rich clusters NGC 6388 and NGC 6441 have velocities incompatibile with membership i... more The two metal rich clusters NGC 6388 and NGC 6441 have velocities incompatibile with membership in the thick disk or the bar of the Milky Way. They can be though of as members of a kinematically hot system in the inner Galaxy. Curiously, both clusters have similar velocity components. Together with their similar Galactic location and peculiar but similar stellar-population characteristics, these two clusters may share a common origin. Their velocities are also very low indicating that the two clusters are now at/near apocenter, and they will not leave the inner ~4 kpc of the Galaxy.
These are the first results of the Southern Proper-Motion Program (SPM) where the second-epoch ob... more These are the first results of the Southern Proper-Motion Program (SPM) where the second-epoch observations are taken with the CCD camera system recently installed on the double astrograph at El Leoncito, Argentina.
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