The kinetics of cholesterol oxidase synthesis byNocardia rhodocrous

1976 ◽  
Vol 18 (5) ◽  
pp. 601-621 ◽  
Author(s):  
B. C. Buckland ◽  
M. D. Lilly ◽  
P. Dunnill
Keyword(s):  
Cholesterol Oxidase ◽  
Kinetics Of

scholarly journals Localization of cholesterol in sphingomyelinase-treated fibroblasts

1995 ◽  
Vol 308 (1) ◽  
pp. 269-274 ◽  
Author(s):  
M I Pörn ◽  
J P Slotte
Keyword(s):  
Plasma Membrane ◽  
Cell Surface ◽  
Staining Pattern ◽  
Cholesterol Oxidase ◽  
Cholesterol Oxidation ◽  
Cellular Cholesterol ◽  
Hypotonic Buffer ◽  
Induced Changes ◽  
Kinetics Of

The distribution of cellular unesterified cholesterol was studied in fibroblasts, which had been depleted of plasma membrane sphingomyelin by exposure to exogenous sphingomyelinase. This treatment has previously been shown to induce an increase in cholesterol esterification, a decrease in the biosynthesis of cholesterol, and a decreased susceptibility of cell cholesterol to oxidation with cholesterol oxidase. When the cellular localization of cholesterol was studied with fluorescent filipin staining, sphingomyelin depletion did not cause any visible changes in the filipin-cholesterol staining pattern, suggesting that the major part of cellular cholesterol was retained in the plasma membrane after sphingomyelinase treatment. After the oxidation of cell-surface cholesterol with cholesterol oxidase, the plasma membrane was no longer stained by filipin, but the plasma membrane cholesterol of sphingomyelin-depleted cells appeared to be resistant to oxidation with cholesterol oxidase when sphingomyelinase was used as an oxidation-promoting agent. However, the use of hypotonic buffer or phosphatidylcholine-specific phospholipase C together with cholesterol oxidase resulted in a complete oxidation of the cell-surface cholesterol in sphingomyelin-depleted cells, as evidenced by the filipin-cholesterol staining pattern. Similar results were obtained when [3H]cholesterol-labelled fibroblasts were used for determination of the susceptibility to cholesterol oxidation. The kinetics of [3H]cholesterol oxidation in sphingomyelin-depleted cells with cholesterol oxidase in hypotonic buffer indicated that approximately 85% of the cellular cholesterol still resided in the plasma membrane after sphingomyelin depletion. These results are contradictory to earlier reports on sphingomyelinase-induced changes in cellular cholesterol distribution and suggest that minor changes in the kinetics of cholesterol transport from the plasma membrane to the endoplasmic reticulum may be responsible for the sphingomyelinase-induced changes in the rates of cholesterol metabolism. Whereas the use of phospholipases to promote the oxidation of cholesterol in some instances might lead to misinterpretations, the use of hypotonic buffer together with cholesterol oxidase proved to be a more reliable method for the determination of cellular cholesterol distribution.

Kinetics of cholesterol oxidation by cholesterol oxidase

1996 ◽  
Vol 60 (1) ◽  
pp. 63-72 ◽  
Author(s):  
Palligarnai T. Vasudevan ◽  
Tao Zhou
Keyword(s):  
Cholesterol Oxidase ◽  
Cholesterol Oxidation ◽  
Kinetics Of

Direct observations of radiation-enhanced transformations in glass

1983 ◽  
Vol 41 ◽  
pp. 354-355
Author(s):  
J. F. DeNatale ◽  
D. G. Howitt
Keyword(s):  
Glass Matrix ◽  
Diffusion Mechanism ◽  
Bubble Formation ◽  
Silicate Glasses ◽  
Phase Decomposition ◽  
Direct Observations ◽  
Thin Foils ◽  
Oxygen Bubble ◽  
Electron Energy Loss ◽  
Kinetics Of

The electron irradiation of silicate glasses containing metal cations produces various types of phase separation and decomposition which includes oxygen bubble formation at intermediate temperatures figure I. The kinetics of bubble formation are too rapid to be accounted for by oxygen diffusion but the behavior is consistent with a cation diffusion mechanism if the amount of oxygen in the bubble is not significantly different from that in the same volume of silicate glass. The formation of oxygen bubbles is often accompanied by precipitation of crystalline phases and/or amorphous phase decomposition in the regions between the bubbles and the detection of differences in oxygen concentration between the bubble and matrix by electron energy loss spectroscopy cannot be discerned (figure 2) even when the bubble occupies the majority of the foil depth.The oxygen bubbles are stable, even in the thin foils, months after irradiation and if van der Waals behavior of the interior gas is assumed an oxygen pressure of about 4000 atmospheres must be sustained for a 100 bubble if the surface tension with the glass matrix is to balance against it at intermediate temperatures.

Irradiation behavior of pyrolytic silicon carbide

1983 ◽  
Vol 41 ◽  
pp. 72-73
Author(s):  
R. J. Lauf
Keyword(s):  
Silicon Carbide ◽  
Fission Products ◽  
Thermodynamics And Kinetics ◽  
Neutron Fluences ◽  
Fuel Particles ◽  
Sic Coatings ◽  
Irradiation Behavior ◽  
Kinetics Of ◽  
Htgr Fuel

Fuel particles for the High-Temperature Gas-Cooled Reactor (HTGR) contain a layer of pyrolytic silicon carbide to act as a miniature pressure vessel and primary fission product barrier. Optimization of the SiC with respect to fuel performance involves four areas of study: (a) characterization of as-deposited SiC coatings; (b) thermodynamics and kinetics of chemical reactions between SiC and fission products; (c) irradiation behavior of SiC in the absence of fission products; and (d) combined effects of irradiation and fission products. This paper reports the behavior of SiC deposited on inert microspheres and irradiated to fast neutron fluences typical of HTGR fuel at end-of-life.

The Ordered Phase Formation in Ti-Al-Ga Alloys

1970 ◽  
Vol 28 ◽  
pp. 440-441
Author(s):  
Shiro Fujishiro ◽  
Harold L. Gegel
Keyword(s):  
Thermal Stability ◽  
High Temperature ◽  
Titanium Alloys ◽  
Growth Kinetics ◽  
Stoichiometric Composition ◽  
Good Potential ◽  
Alpha Titanium ◽  
Cold Rolled ◽  
Kinetics Of ◽  
Thermal Stability Of

Ordered-alpha titanium alloys having a DO19 type structure have good potential for high temperature (600°C) applications, due to the thermal stability of the ordered phase and the inherent resistance to recrystallization of these alloys. Five different Ti-Al-Ga alloys consisting of equal atomic percents of aluminum and gallium solute additions up to the stoichiometric composition, Ti3(Al, Ga), were used to study the growth kinetics of the ordered phase and the nature of its interface.The alloys were homogenized in the beta region in a vacuum of about 5×10-7 torr, furnace cooled; reheated in air to 50°C below the alpha transus for hot working. The alloys were subsequently acid cleaned, annealed in vacuo, and cold rolled to about. 050 inch prior to additional homogenization

Ion Beam Induced Interfacial Reactions in Molybdenum Thin Films on Silicon

1981 ◽  
Vol 39 ◽  
pp. 162-163
Author(s):  
L. J. Chen ◽  
L. S. Hung ◽  
J. W. Mayer
Keyword(s):  
Ion Beam ◽  
Chemical Vapor ◽  
Interfacial Reactions ◽  
Practical Applications ◽  
Microelectronic Devices ◽  
Recent Emergence ◽  
Chemical Vapor Deposited ◽  
Atomic Mixing ◽  
Silicon Interface ◽  
Kinetics Of

When an energetic ion penetrates through an interface between a thin film (of species A) and a substrate (of species B), ion induced atomic mixing may result in an intermixed region (which contains A and B) near the interface. Most ion beam mixing experiments have been directed toward metal-silicon systems, silicide phases are generally obtained, and they are the same as those formed by thermal treatment.Recent emergence of silicide compound as contact material in silicon microelectronic devices is mainly due to the superiority of the silicide-silicon interface in terms of uniformity and thermal stability. It is of great interest to understand the kinetics of the interfacial reactions to provide insights into the nature of ion beam-solid interactions as well as to explore its practical applications in device technology.About 500 Å thick molybdenum was chemical vapor deposited in hydrogen ambient on (001) n-type silicon wafer with substrate temperature maintained at 650-700°C. Samples were supplied by D. M. Brown of General Electric Research & Development Laboratory, Schenectady, NY.

In situ study of electron beam-induced chemical vapor deposition of Au in an environmental TEM

1995 ◽  
Vol 53 ◽  
pp. 256-257
Author(s):  
J. Drucker ◽  
R. Sharma ◽  
J. Kouvetakis ◽  
K.H.J. Weiss
Keyword(s):  
Electron Beam ◽  
Chemical Vapor Deposition ◽  
Vapor Deposition ◽  
Quantum Effect ◽  
Line Drawing ◽  
Chemical Vapor ◽  
Environmental Cell ◽  
Engineering Changes ◽  
Kinetics Of

Patterning of metals is a key element in the fabrication of integrated microelectronics. For circuit repair and engineering changes constructive lithography, writing techniques, based on electron, ion or photon beam-induced decomposition of precursor molecule and its deposition on top of a structure have gained wide acceptance Recently, scanning probe techniques have been used for line drawing and wire growth of W on a silicon substrate for quantum effect devices. The kinetics of electron beam induced W deposition from WF6 gas has been studied by adsorbing the gas on SiO2 surface and measuring the growth in a TEM for various exposure times. Our environmental cell allows us to control not only electron exposure time but also the gas pressure flow and the temperature. We have studied the growth kinetics of Au Chemical vapor deposition (CVD), in situ, at different temperatures with/without the electron beam on highly clean Si surfaces in an environmental cell fitted inside a TEM column.

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