The Experts below are selected from a list of 471 Experts worldwide ranked by ideXlab platform
Yuji Goto - One of the best experts on this subject based on the ideXlab platform.
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structural characterization of the molten globule of alpha lactalbumin by solution x ray scattering
Protein Science, 1997Co-Authors: Mikio Kataoka, Kunihiro Kuwajima, Fumio Tokunaga, Yuji GotoAbstract:A compact denatured state is often observed under a mild denaturation condition for various proteins. A typical example is the alpha-lactalbumin molten globule. Although the molecular compactness and shape are the essential properties for defining the molten globule, there have been ambiguities of these properties for the molten globule of alpha-lactalbumin. Using solution X-ray scattering, we have examined the structural properties of two types of molten globule of alpha-lactalbumin, the apo-protein at neutral pH and the acid molten globule. The radius of gyration for the native holo-protein was 15.7 A, but the two different molten globules both had a radius of gyration of 17.2 A. The maximum dimension of the molecule was also increased from 50 A for the native state to 60 A for the molten globule. These values clearly indicate that the molten globule is not as compact as the native state. The increment in the radius of gyration was less than 10% for the alpha-lactalbumin molten globule, compared with up to 30% for the molten globules of other globular proteins. Intramolecular disulfide bonds restrict the molecular expansion of the molten globule. The distance distribution function of the alpha-lactalbumin molten globule is composed of a single peak suggesting a globular shape, which is simply swollen from the native state. The scattering profile in the high Q region of the molten globule indicates the presence of a significant amount of tertiary fold. Based on the structural properties obtained by solution X-ray scattering, general and conceptual structural images for the molten globules of various proteins are described and compared with the individual, detailed structural model obtained by nuclear magnetic resonance.
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Thermodynamic stability of the molten globule states of apomyoglobin.
Journal of Molecular Biology, 1995Co-Authors: Ichiro Nishii, Mikio Kataoka, Yuji GotoAbstract:Abstract Whereas horse apomyoglobin is fully unfolded at pH 2 in the absence of salt, addition of a salt such as sodium chloride or sodium trichloroacetate stabilizes the molten globule state. Thermal unfolding of the salt-stabilized molten globule states of horse apomyoglobin at pH 2 measured by far-UV circular dichroism occurs not only on heating (i.e. heat-denaturation) but also on cooling (i.e. cold-denaturation). This demonstrates that a hydrophobic interaction contributes to the stability of the molten globule state and suggests that the unfolding transition can be represented by a cooperative two-state mechanism. To clarify the mechanism of conformational transition, we investigated the thermal unfolding of the chloride-stabilized molten globule state by differential scanning calorimetry. We observed a broad but distinct excess heat capacity peak, which is consistent with the unfolding transition measured by circular dichroism. To further characterize the molten globule states, we examined by far-UV circular dichroism the denaturant-induced unfolding transitions of the molten globule states stabilized by sodium chloride or sodium trichloroacetate. The urea-induced unfolding transitions of the molten globule states were explained by the two-state mechanism. The guanidine-hydrochloride-induced unfolding experiments clarified that the trichloroacetate-stabilized molten globule state is distinct from the chloride-stabilized one and that the former involves additional helical segment(s). These results support a view that the thermal unfolding of the molten globule states at pH 2 can be approximated by a two-state transition. However, several results suggested that a combined mechanism incorporating the two-state transition and a gradual structural change would be more general in describing the conformational transition of the molten globule states. f2
Akimasa Tasaka - One of the best experts on this subject based on the ideXlab platform.
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new iodide based molten salt systems for high temperature molten salt batteries
Journal of Power Sources, 2009Co-Authors: Syozo Fujiwara, Fumio Kato, Syouichiro Watanabe, Minoru Inaba, Akimasa TasakaAbstract:Abstract Novel multi-component molten salt systems containing iodides, LiF–LiBr–LiI, LiF–NaBr–LiI, and LiF–LiCl–LiBr–LiI, were investigated for use as electrolytes in high temperature molten salt batteries to improve the discharge rate-capability. The iodide-based molten salts showed higher ionic conductivity (∼3 S cm −1 at 500 °C) than conventional LiCl–KCl, and had low enough melting points (below 400 °C) that can be used in practical high temperature molten salt batteries. The iodide-based salts showed instability at temperatures higher than 280 °C in dried air. The decomposition mechanism of iodide-based molten salts was discussed, and it was found that elimination of oxygen from the environment is effective to stabilize the iodide-based molten salts at high temperatures.
Y Tamaura - One of the best experts on this subject based on the ideXlab platform.
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J: Phys. ZV France 9 (1 999) Pr3-373 Solar gasification of coal using carbonate molten salt reactor
2016Co-Authors: Y Tamaura, M. Tsuji, S. Yoshida, T. SanoAbstract:Abstract. The gasification of coal with CO, in the molten salt (K,CO,/Na,CO,) (CG-CO,/molten salt system) has been studied at 1123K. The gasification rate of the cola into CO was enhanced in the molten salt by 3.3 times, compared with that without the molten salt. The reason for the enhancement was discussed. Main factor would be the enhancement of the coal charring owing to the efficient heat flow from the molten salt tot the coal through the solid/liquid interface between the coal surface and the molten salt. Another reason would be the catalytic effect of the alkaline cations (Kf, Na') on the Boudouard reaction (C + CO, = 2CO). This coal gasification process (CG-CO,/molten salt) is an endothermic process (coal charring and Boudouard reactions), and can be applied for the solar thermochemical process to convert solar energy into chemical energy and store it. Since the CG-CO,/molten salt system can be operated at 1123K, which is fairly lower than that for the conventional coal gasification with H,O. We have proposed an solar hybrid fuel production system, where the solar energy and the coal energy can be hybridized using the CG-CO,/molten salt system. 1
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study on design of molten salt solar receivers for beam down solar concentrator
Solar Energy, 2006Co-Authors: Hiroshi Hasuike, Yoshio Yoshizawa, Akio Suzuki, Y TamauraAbstract:Systems using molten salt as thermal media have been proposed for solar thermal power generation and for synthetic fuel production. We have been developing molten salt solar receivers, in which molten salt is heated by concentrated solar radiation, in the Solar Hybrid Fuel Project of Japan. A cavity shaped receiver, which is suitable for a beam-down type solar concentration system, was considered. In order to design molten salt solar receivers, a numerical simulation program for the prediction of characteristics of receivers was developed. The simulation program presents temperature distributions of a receiver and molten salt with the use of heat flux distribution of solar radiation and properties of composing materials as input data. Radiation to heat conversion efficiency is calculated from input solar power and heat transferred to molten salt. The thermal resistance of molten salt and the maximum discharge pressure of molten salt pumps were taken into account as restrictions for the design of receivers. These restrictions require control of maximum receiver temperature and pressure drop in the molten salt channel. Based on the incident heat flux distribution formed with a 100 MWth class beam-down type solar concentration system, we proposed a shape of solar receiver that satisfies the requirements. The radiation to heat conversion efficiency of the designed receiver was calculated to be about 90%.
Rob Slotow - One of the best experts on this subject based on the ideXlab platform.
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the african golden cat caracal aurata africa s least known felid
Mammal Review, 2015Co-Authors: Laila Bahaaeldin, Philipp Henschel, Thomas M Butynski, David W Macdonald, David Mills, Rob SlotowAbstract:The African golden cat Caracal aurata is endemic to tropical Africa. It is one of the world's least-studied felids and is considered rare in most of its geographic range. The status of the African golden cat in the wild has never been rigorously assessed, but the species is increasingly threatened by habitat degradation, loss and fragmentation, and by unsustainable hunting. We describe the African golden cat and review its taxonomy, distribution, ecology, behaviour, threats and conservation status. The information presented here is based on the literature and on new data from the first two intensive field studies on the species (underway in Gabon and Uganda). The golden cat is phenotypically variable. Within the two main colour morphs, golden/reddish-brown and grey, there is wide variation and intergradation. Both of these morphs occur throughout the species' range. Melanistic and chocolate-brown morphs also occur but are uncommon. Recent genetic analysis indicates that the golden cat is closely related to the caracal Caracal caracal, and it has, therefore, been changed from the genus Profelis to Caracal. The golden cat is predominantly terrestrial and cathemeral. Its diet consists mainly of rodents and small ungulates. Field studies in Gabon and Uganda have established that golden cats can be locally common. They are prone to capture by wire snares, however, and are absent in forests hunted at commercial scales. Species-focused camera trap surveys are effective for collecting distribution, abundance, population structure, ecological and behavioural data on golden cats.
Laila Bahaaeldin - One of the best experts on this subject based on the ideXlab platform.
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the african golden cat caracal aurata africa s least known felid
Mammal Review, 2015Co-Authors: Laila Bahaaeldin, Philipp Henschel, Thomas M Butynski, David W Macdonald, David Mills, Rob SlotowAbstract:The African golden cat Caracal aurata is endemic to tropical Africa. It is one of the world's least-studied felids and is considered rare in most of its geographic range. The status of the African golden cat in the wild has never been rigorously assessed, but the species is increasingly threatened by habitat degradation, loss and fragmentation, and by unsustainable hunting. We describe the African golden cat and review its taxonomy, distribution, ecology, behaviour, threats and conservation status. The information presented here is based on the literature and on new data from the first two intensive field studies on the species (underway in Gabon and Uganda). The golden cat is phenotypically variable. Within the two main colour morphs, golden/reddish-brown and grey, there is wide variation and intergradation. Both of these morphs occur throughout the species' range. Melanistic and chocolate-brown morphs also occur but are uncommon. Recent genetic analysis indicates that the golden cat is closely related to the caracal Caracal caracal, and it has, therefore, been changed from the genus Profelis to Caracal. The golden cat is predominantly terrestrial and cathemeral. Its diet consists mainly of rodents and small ungulates. Field studies in Gabon and Uganda have established that golden cats can be locally common. They are prone to capture by wire snares, however, and are absent in forests hunted at commercial scales. Species-focused camera trap surveys are effective for collecting distribution, abundance, population structure, ecological and behavioural data on golden cats.