scholarly journals Regulation of monkey liver serine hydroxymethyltransferase by nicotinamide nucleotide

1978 ◽  
Vol 174 (3) ◽  
pp. 1055-1058 ◽  
Author(s):  
K S Ramesh ◽  
N A Rao
Keyword(s):  
Serine Hydroxymethyltransferase ◽  
Monkey Liver ◽  
First Time ◽  
Metabolic Interconversion ◽  
Time Lead

The positive homotropic binding of tetrahydrofolate to monkey liver serine hydroxymethyltransferase was abolished on preincubating the enzyme with NADH and NADPH. NAD+ was a negative heterotropic effector, whereas NADP+ was without effect. The allosteric effects of nicotinamide nucleotides on the serine hydroxymethyltransferase, reported for the first time, lead to a better understanding of the regulation of the metabolic interconversion of folate coenzymes.

Upcoming Computing System Challenges – The HiPEAC Vision Anstehende Herausforderungen der Computer Industrie – Die HiPEAC Vision

2008 ◽  
Vol 50 (5) ◽  
Author(s):  
Koen De Bosschere
Keyword(s):  
Economic Growth ◽  
Computing System ◽  
Major Research ◽  
Slowing Down ◽  
Research Challenges ◽  
Exponential Increase ◽  
Computing Industry ◽  
Computing Performance ◽  
First Time ◽  
Time Lead

AbstractOver the last decades, we have witnessed an exponential increase in sequential computing performance, but since few years this progress is slowing down. This paper describes the current evolutions in technology and architecture that cause this slowdown, and lists the major research challenges that need to be tackled in the coming years to further continue this exponential performance growth. If the computing industry fails to solve these challenges soon, this will for the first time lead to a stop of the exponential performance growth, which might eventually impact the economic growth of western economies.

scholarly journals Bacterial catabolism of threonine. Threonine degradation initiated by L-threonine-NAD+ oxidoreductase

1976 ◽  
Vol 156 (2) ◽  
pp. 449-458 ◽  
Author(s):  
S C Bell ◽  
J M Turner
Keyword(s):  
Specific Activity ◽  
Maximum Activity ◽  
Serine Hydroxymethyltransferase ◽  
Enzyme Preparations ◽  
Coa Ligase ◽  
Nad Oxidoreductase ◽  
Glycine Cleavage ◽  
The Hill ◽  
First Time ◽  
Corynebacterium Sp

1. Isolates representing seven bacterial genera capable of growth on L-threonine medium, and possessing high L-threonine 3-dehydrogenase activity, were examined to elucidate the catabolic route. 2. The results of growth, manometric and enzymic experiments indicated the catabolism of L-threonine by cleavage to acetyl-CoA plus glycine, the glycine being further metabolized via L-serine to pyruvate, in all cases. No evidence was obtained of a role for aminoacetone in threonine catabolism or for the metabolism of glycine by the glycerate pathway. 3. The properties of a number of key enzymes in L-threonine catabolism were investigated. The inducibly formed L-threonine 3-dehydrogenase, purified from Corynebacterium sp. B6 to a specific activity of about 30-35 mumol of product formed/min per mg of protein, exhibited a sigmoid kinetic response to substrate concentration. The half-saturating concentration of substrate, [S]0.5, was 20mM and the Hill constant (h) was 1.50. The Km for NAD+ was 0.8mM. The properties of the enzyme were studied in cell-free extracts of other bacteria. 4. New assays for 2-amino-3-oxobutyrate-CoA ligase were devised. The Km for CoA was determined for the first time and found to be 0.14mM at pH8, for the enzyme from Corynebacterium sp. B6. Evidence was obtained for the efficient linkage of the dehydrogenase and ligase enzymes. Cell-free extracts all possessed high activities of the inducibly formed ligase. 5. L-Serine hydroxymethyltransferase was formed constitutively by all isolates, whereas formation of the ‘glycine-cleavage system’ was generally induced by growth on L-threonine or glycine. The coenzyme requirements of both enzymes were established, and their linked activity in the production of L-serine from glycine was demonstrated by using extracts of Corynebacterium sp. B6. 6. L-Serine dehydratase, purified from Corynebacterium sp. B6 to a specific activity of about 4mumol of product formed/min per mg of protein, was found to exhibit sigmoid kinetics with an [S]0.5 of about 20mM and h identical to 1.4. Similar results were obtained with enzyme preparations from all isolates. The enzyme required Mg2+ for maximum activity, was different from the L-threonine dehydratase also detectable in extracts, and was induced by growth on L-threonine or glycine.

High performance fiber-shaped perovskite solar cells based on lead acetate precursor

2018 ◽  
Vol 2 (1) ◽  
pp. 79-84 ◽  
Author(s):  
Hsienwei Hu ◽  
Bin Dong ◽  
Buxin Chen ◽  
Xue Gao ◽  
Dechun Zou
Keyword(s):  
Solar Cells ◽  
Lead Acetate ◽  
High Performance ◽  
Perovskite Solar Cells ◽  
Curved Surfaces ◽  
Film Morphology ◽  
High Performance Fiber ◽  
Lead Source ◽  
First Time ◽  
Time Lead

For the first time, lead acetate was introduced as the lead source to improve the perovskite film morphology on highly curved surfaces. The resulting fiber-shaped perovskite solar cells achieved a PCE of 7.53%.

scholarly journals Inhibition of monkey liver serine hydroxymethyltransferase by Cibacron Blue 3G-A

1980 ◽  
Vol 187 (1) ◽  
pp. 249-252 ◽  
Author(s):  
K S Ramesh ◽  
N Appaji Rao
Keyword(s):  
Absorption Spectrum ◽  
Binding Domain ◽  
Serine Hydroxymethyltransferase ◽  
Free Enzyme ◽  
Cibacron Blue ◽  
Monkey Liver ◽  
Dye Absorption ◽  
Blue Sepharose

Cibacron Blue 3G-A inhibited monkey liver serine hydroxymethyltransferase competitively with respect to tetrahydrofolate and non-competitively with respect to L-serine. NADH, a positive heterotropic effector, failed to protect the enzymes against inhibition by the dye and was unable to desorb the enzyme from Blue Sepharose CL-6B gel matrix. The binding of the dye to the free enzyme was confirmed by changes in the dye absorption spectrum. The results indicate that the dye probably binds at the tetrahydrofolate-binding domain of the enzyme, rather than at the ‘dinucleotide fold’.

scholarly journals Purification and physicochemical, kinetic and immunological properties of allosteric serine hydroxymethyltransferase from monkey liver

1980 ◽  
Vol 187 (3) ◽  
pp. 623-636 ◽  
Author(s):  
K S Ramesh ◽  
N Appaji Rao
Keyword(s):  
Liver Enzyme ◽  
Thermal Inactivation ◽  
Heat Stability ◽  
Serine Hydroxymethyltransferase ◽  
Heat Denaturation ◽  
Monkey Liver ◽  
Catalytically Active ◽  
Antibody Complex ◽  
Bacterial Sources ◽  
Blue Sepharose

The homogeneous serine hydroxymethyltransferase purified from monkey liver, by the use of Blue Sepharose affinity chromatography, exhibited positive homotropic co-operative interactions (h = 2.5) with tetrahydrofolate and heterotropic interactions with L-serine and nicotinamide nucleotides. The enzyme had an unusually high temperature optimum of 60 degrees C and was protected against thermal inactivation by L-serine. The allosteric effects were abolished when the monkey liver enzyme was purified by using a heat-denaturation step in the presence of L-serine, a procedure adopted by earlier workers for the purification of this enzyme from mammalian and bacterial sources. The enzyme activity was inhibited completely by N5-methyltetrahydrofolate, N5-formyltetrahydrofolate, dichloromethotrexate, aminopterin and D-cycloserine, whereas methotrexate and dihydrofolate were partial inhibitors. The insoluble monkey liver enzyme-antibody complex was catalytically active and failed to show positive homotropic co-operative interactions with tetrahydrofolate (h = 1) and heterotropic interactions with NAD+. The enzyme showed a higher heat-stability in a complex with its antibody than as the free enzyme. These results highlight the pitfalls in using a heat-denaturation step in the purification of allosteric enzymes.

Annulate lamellae in the Sertoli cells of guinea pig testis after unilateral torsion of the spermatic cord

1984 ◽  
Vol 42 ◽  
pp. 196-197
Author(s):  
J. Chakraborty ◽  
A. P. Sinha Hikim ◽  
J. S. Jhunjhunwala
Keyword(s):  
Sertoli Cells ◽  
Guinea Pigs ◽  
Spermatic Cord ◽  
Present Report ◽  
Cell Types ◽  
Annulate Lamellae ◽  
Spermatogenic Cells ◽  
Electron Microscopic ◽  
Structural Details ◽  
First Time

Although the presence of annulate lamellae was noted in many cell types, including the rat spermatogenic cells, this structure was never reported in the Sertoli cells of any rodent species. The present report is based on a part of our project on the effect of torsion of the spermatic cord to the contralateral testis. This paper describes for the first time, the fine structural details of the annulate lamellae in the Sertoli cells of damaged testis from guinea pigs.One side of the spermatic cord of each of six Hartly strain adult guinea pigs was surgically twisted (540°) under pentobarbital anesthesia (1). Four months after induction of torsion, animals were sacrificed, testes were excised and processed for the light and electron microscopic investigations. In the damaged testis, the majority of seminiferous tubule contained a layer of Sertoli cells with occasional spermatogonia (Fig. 1). Nuclei of these Sertoli cells were highly pleomorphic and contained small chromatinic clumps adjacent to the inner aspect of the nuclear envelope (Fig. 2).

Electron spectroscopic imaging and diffraction

1991 ◽  
Vol 49 ◽  
pp. 706-707
Author(s):  
M. Rühle ◽  
J. Mayer ◽  
J.C.H. Spence ◽  
J. Bihr ◽  
W. Probst ◽  
...  
Keyword(s):  
Materials Science ◽  
Electron Spectroscopic Imaging ◽  
Magnetic Filter ◽  
Magnetic Imaging ◽  
Illumination System ◽  
Probe Size ◽  
Diffraction Patterns ◽  
Fritz Haber ◽  
Koehler Illumination ◽  
First Time

A new Zeiss TEM with an imaging Omega filter is a fully digitized, side-entry, 120 kV TEM/STEM instrument for materials science. The machine possesses an Omega magnetic imaging energy filter (see Fig. 1) placed between the third and fourth projector lens. Lanio designed the filter and a prototype was built at the Fritz-Haber-Institut in Berlin, Germany. The imaging magnetic filter allows energy-filtered images or diffraction patterns to be recorded without scanning using efficient area detection. The energy dispersion at the exit slit (Fig. 1) results in ∼ 1.5 μm/eV which allows imaging with energy windows of ≤ 10 eV. The smallest probe size of the microscope is 1.6 nm and the Koehler illumination system is used for the first time in a TEM. Serial recording of EELS spectra with a resolution < 1 eV is possible. The digital control allows X,Y,Z coordinates and tilt settings to be stored and later recalled.

A Novel TEM Technique for Characterizing As-Grown CVD Diamond Films

1991 ◽  
Vol 49 ◽  
pp. 956-957 ◽  
Author(s):  
Z.L. Wang ◽  
J. Bentley ◽  
R.E. Clausing ◽  
L. Heatherly ◽  
L.L. Horton
Keyword(s):  
Diamond Films ◽  
Chemical Vapor ◽  
Growth Direction ◽  
Dark Field ◽  
Growth Surface ◽  
Specimen Preparation ◽  
Transmission Electron ◽  
Diffraction Patterns ◽  
First Time ◽  
Microstructural Studies

Microstructural studies by transmission electron microscopy (TEM) of diamond films grown by chemical vapor deposition (CVD) usually involve tedious specimen preparation. This process has been avoided with a technique that is described in this paper. For the first time, thick as-grown diamond films have been examined directly in a conventional TEM without thinning. With this technique, the important microstructures near the growth surface have been characterized. An as-grown diamond film was fractured on a plane containing the growth direction. It took about 5 min to prepare a sample. For TEM examination, the film was tilted about 30-45° (see Fig. 1). Microstructures of the diamond grains on the top edge of the growth face can be characterized directly by transmitted electron bright-field (BF) and dark-field (DF) images and diffraction patterns.

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