Reduction of Folate and Dihydrofolate by Dithionite

1972 ◽  
Vol 50 (11) ◽  
pp. 1191-1198 ◽  
Author(s):  
M. Kawai ◽  
K. G. Scrimgeour
Keyword(s):  
Free Radical ◽  
Low Temperatures ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Kinetic Method ◽  
Sodium Dithionite ◽  
Nucleophilic Attack ◽  
Stopped Flow ◽  
Reduction Processes ◽  
Radical Reduction

Sodium dithionite reduces folate to 7,8-dihydrofolate at room temperature, but further reduction to the tetrahydro level can be obtained at elevated temperatures (11). Both folate and dihydrofolate form adducts with dithionite (presumably sulfinates), and these adducts appear to be intermediates in the reduction processes. The adduct of dihydrofolate is not converted to tetrahydrofolate at low temperatures, and is thus more amenable to examination. The mechanism of reduction of the folate compounds and of the nicotinamide ring by dithionite involves nucleophilic attack by the dithionite, not a free radical reduction as with p-nitrophenol. The rate of addition of bisulfite to folate and dihydrofolate has been measured by the stopped-flow kinetic method, and the nonenzymic and enzyme-catalyzed addition of nucleophiles to folate compounds is discussed.

Substantiation of a Technique of Determining Stress in Thin Films at Very Low Temperatures

2015 ◽  
Vol 14 ◽  
pp. 28-36
Author(s):  
C.C. Chama
Keyword(s):  
Thin Film ◽  
Thin Films ◽  
Low Temperatures ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
High Temperature Stress ◽  
Hysteresis Curves ◽  
Stress Hysteresis

Substantiation of a technique earlier employed in determining stress in Copper-Silver thin films at very low temperatures is presented. It is shown that the stress measured at elevated temperatures using Stoney’s equation can be utilized in the determination of stress at very low temperatures. To demonstrate the application of this technique, a case study has been conducted by utilizing stress hysteresis curves obtained from the Cu-6at%Ag thin film heated from room temperature to 400°C and cooled back to room temperature in two cycles. The stresses in the Cu-6at%Ag thin film at various low temperatures up to-197°C have been determined by utilizing data from high temperature stress hysteresis curves.

Effect of Sodium Exposure On the Mechanical Properties of Zirconium

CORROSION ◽  
1961 ◽  
Vol 17 (1) ◽  
pp. 31t-34t ◽  
Author(s):  
J. C. BOKROS
Keyword(s):  
Mechanical Properties ◽  
Fatigue Life ◽  
Tensile Properties ◽  
High Temperatures ◽  
Low Temperatures ◽  
Hydrogen Absorption ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Surface Oxide ◽  
The Other

Abstract It was found that surface oxide which developed on zirconium in impure sodium significantly lowered the fatigue life at elevated temperatures. Hydrogen absorption, on the other hand, had little effect on the fatigue life at elevated temperatures but lowered the fatigue life at room temperature. Also, critical recrystallization which occurred above 950 F in zirconium (a phenomenon unrelated to the presence of sodium) reduced the fatigue life at elevated as well as low temperatures. The effects attributable to sodium (i.e., the formation of surface oxide and absorption of reasonable amounts of hydrogen), did not significantly alter the tensile properties of zirconium at high temperatures. 6.3.20, 4.7, 3.5.8, 3.2.3

scholarly journals Thermocontrolled Reversible Enzyme Complexation-Inactivation-Protection by Poly(N-acryloyl glycinamide)

Polymers ◽  
2021 ◽  
Vol 13 (20) ◽  
pp. 3601
Author(s):  
Pavel I. Semenyuk ◽  
Lidia P. Kurochkina ◽  
Lauri Mäkinen ◽  
Vladimir I. Muronetz ◽  
Sami Hietala
Keyword(s):  
Low Temperatures ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Proteinase K ◽  
Solution Temperature ◽  
Proteolytic Degradation ◽  
Biotechnological Applications ◽  
Thermoresponsive Polymer ◽  
Critical Solution Temperature ◽  
Upper Critical Solution Temperature

A prospective technology for reversible enzyme complexation accompanied with its inactivation and protection followed by reactivation after a fast thermocontrolled release has been demonstrated. A thermoresponsive polymer with upper critical solution temperature, poly(N-acryloyl glycinamide) (PNAGA), which is soluble in water at elevated temperatures but phase separates at low temperatures, has been shown to bind lysozyme, chosen as a model enzyme, at a low temperature (10 °C and lower) but not at room temperature (around 25 °C). The cooling of the mixture of PNAGA and lysozyme solutions from room temperature resulted in the capturing of the protein and the formation of stable complexes; heating it back up was accompanied by dissolving the complexes and the release of the bound lysozyme. Captured by the polymer, lysozyme was inactive, but a temperature-mediated release from the complexes was accompanied by its reactivation. Complexation also partially protected lysozyme from proteolytic degradation by proteinase K, which is useful for biotechnological applications. The obtained results are relevant for important medicinal tasks associated with drug delivery such as the delivery and controlled release of enzyme-based drugs.

scholarly journals Pengaruh Waktu Aging dan Metode Ekstraksi terhadap Aktivitas Antioksidan Black Garlic yang Dibandingkan dengan Bawang Putih (Allium sativum L.)

2021 ◽  
Vol 1 (1) ◽  
pp. 16-23
Author(s):  
Salma Fadhilah Azhar ◽  
Kiki Mulkiya Y ◽  
Reza Abdul Kodir
Keyword(s):  
Free Radical ◽  
Chemical Reactions ◽  
Maillard Reaction ◽  
Oxidation Reaction ◽  
Aging Process ◽  
Room Temperature ◽  
Allium Sativum ◽  
Absorbance Measurement ◽  
Activity Test ◽  
Radical Reduction

Abstract. Antioxidant is a compound that could obstruct oxidation reaction through free radical binding. Garlic (Allium sativum L.) is a plant which has many benefits that could be used for traditional medication. Some of pharmacology effects which was discovered are antioxidant, anti-hypertensive, anti-cholesterol, and antimicrobial. Black garlic is the heating aging process which induces many chemical reactions of garlic such as non-enzymatically discoloration to be brown, Maillard reaction which produces antibacterial compound, caramelization, and phenol formation as antioxidant that causes discoloration from cream to dark brown or black. White and Black garlic were extracted through two methods, namely maceration (room temperature) and digestion (± 40°C) by using 96% ethanol solvent. The activity test of extract antioxidant is done using DPPH free radical reduction (2,2-difenil-1-pikrilhidrazil) with absorbance measurement uses UV-Vis spectrophotometry with DPPH maximum wavelength is 515 mm. Garlic maceration has value IC50 in the amount of 28.422 ppm, two weeks maceration of black garlic in the amount of 27.129 ppm and four weeks maceration of black garlic in the amount of 13.041 ppm. While garlic digestion in the amount of 28.524 ppm, two weeks digestion of black garlic in the amount of 28.086 ppm and four weeks digestion of black garlic in the amount of 15.160 ppm. Abstrak. Antioksidan merupakan senyawa yang dapat menghambat reaksi oksidasi, dengan cara mengikat radikal bebas. Bawang putih (Allium sativum L.) merupakan salah satu tanaman yang mempunyai banyak khasiat yang digunakan untuk pengobatan tradisional. Efek farmakologi yang telah diketahui salah satunya adalah antioksidan, anti-hipertensi, anti-kolesterol, anti-mikroba. Bawang hitam merupakan proses aging dengan pemanasan yang menginduksi banyak reaksi kimia pada bawang putih seperti perubahan warna menjadi coklat secara non-enzimatik, reaksi Maillard yang menghasilkan senyawa antibakteri, karamelisasi, dan pembentukan fenol sebagai antioksidan yang menyebabkan warnanya berubah dari putih kekuningan menjadi coklat tua atau hitam. Bawang putih dan bawang hitam diekstraksi menggunakan dua metode yaitu maserasi (suhu kamar) dan digesti (suhu ±40°C) dengan menggunakan pelarut etanol 96%. Uji aktivitas antioksidan ekstrak dilakukan dengan menggunakan metode peredaman radikal bebas DPPH (2,2-difenil-1-pikrilhidrazil) dengan pengukuran absorbansi menggunakan spektrofotometri UV–Vis pada panjang gelombang maksimal DPPH yaitu 515 nm. Pada bawang putih maserasi memiliki nilai IC50 sebesar 28,422 ppm, bawang hitam 2 minggu maserasi 27,129 ppm dan bawang hitam 4 minggu maserasi 13,041 ppm. Sedangkan pada bawang putih digesti 28,524 ppm, bawang hitam 2 minggu digesti 28,086 ppm dan bawang hitam 4 minggu digesti 15,160 ppm.

Creep of a niobium beryllide, Nb2Be17

1993 ◽  
Vol 8 (4) ◽  
pp. 757-763 ◽  
Author(s):  
T.G. Nieh ◽  
J. Wadsworth ◽  
T.C. Chou ◽  
D. Owen ◽  
A.H. Chokshi
Keyword(s):  
Low Temperatures ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Hardness Test ◽  
Transient Creep ◽  
Test Results ◽  
Creep Properties ◽  
Dislocation Glide ◽  
Applied Stresses ◽  
Hot Hardness

A niobium beryllide, Nb2Be17, has been prepared by powder-metallurgy techniques and the mechanical properties characterized both at room and elevated temperatures. Microhardness and fracture toughness were measured at room temperature. Hardness and hot-hardness test results indicated that, although the material was brittle at low temperatures, it became plastic at elevated temperatures (>1000 °C). Creep properties of Nb2Be17 were studied at temperatures from 1250 to 1350 °C and applied stresses from 10 to 90 MPa. The stress exponent, determined from stress-change tests, was about 3, and the activation energy, determined from temperature-change tests, was about 575 kJ/mol. The creep of Nb2Be17 at high temperature is apparently controlled by dislocation glide; this proposal was supported by transient creep experiments. Comparisons have been made between the creep properties of Nb2Be17 and other intermetallics.

Mechanical Properties and Dislocation Structure of Single Crystal Cdte Deformed in Compression at 300°C

1976 ◽  
Vol 34 ◽  
pp. 592-593
Author(s):  
Ernest L. Hall ◽  
J. B. Vander Sande
Keyword(s):  
Mechanical Properties ◽  
Single Crystal ◽  
Dislocation Structure ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Strain Curve ◽  
Optical Devices ◽  
Semiconductor Compound ◽  
Wide Range ◽  
Sample Orientation

The present paper describes research on the mechanical properties and related dislocation structure of CdTe, a II-VI semiconductor compound with a wide range of uses in electrical and optical devices. At room temperature CdTe exhibits little plasticity and at the same time relatively low strength and hardness. The mechanical behavior of CdTe was examined at elevated temperatures with the goal of understanding plastic flow in this material and eventually improving the room temperature properties. Several samples of single crystal CdTe of identical size and crystallographic orientation were deformed in compression at 300°C to various levels of total strain. A resolved shear stress vs. compressive glide strain curve (Figure la) was derived from the results of the tests and the knowledge of the sample orientation.

Spherulite Structures in a Melt Spun Fe-Ni Austenitic Steel

1985 ◽  
Vol 43 ◽  
pp. 52-53
Author(s):  
G. M. Michal ◽  
T. K. Glasgow ◽  
T. J. Moore
Keyword(s):  
Austenitic Steel ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Large Range ◽  
Amorphous Structure ◽  
Nucleation And Growth ◽  
Ni Alloys ◽  
Melt Spun ◽  
Crystal Fibers ◽  
Rapidly Solidified

Large additions of B to Fe-Ni alloys can lead to the formation of an amorphous structure, if the alloy is rapidly cooled from the liquid state to room temperature. Isothermal aging of such structures at elevated temperatures causes crystallization to occur. Commonly such crystallization pro ceeds by the nucleation and growth of spherulites which are spherical crystalline bodies of radiating crystal fibers. Spherulite features were found in the present study in a rapidly solidified alloy that was fully crysstalline as-cast. This alloy was part of a program to develop an austenitic steel for elevated temperature applications by strengthening it with TiB2. The alloy contained a relatively large percentage of B, not to induce an amorphous structure, but only as a consequence of trying to obtain a large volume fracture of TiB2 in the completely processed alloy. The observation of spherulitic features in this alloy is described herein. Utilization of the large range of useful magnifications obtainable in a modern TEM, when a suitably thinned foil is available, was a key element in this analysis.

FANSTEEL 85 METAL

Alloy Digest ◽  
1981 ◽  
Vol 30 (6) ◽  
Keyword(s):  
High Temperature ◽  
Physical Properties ◽  
Creep Strength ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Base Alloy ◽  
Heat Treating ◽  
Good Combination ◽  
Bend Strength ◽  
Temperature Performance

Abstract FANSTEEL 85 METAL is a columbium-base alloy characterized by good fabricability at room temperature, good weldability and a good combination of creep strength and oxidation resistance at elevated temperatures. Its applications include missile and rocket components and many other high-temperature parts. This datasheet provides information on composition, physical properties, microstructure, hardness, elasticity, tensile properties, and bend strength as well as creep. It also includes information on low and high temperature performance as well as forming, heat treating, machining, joining, and surface treatment. Filing Code: Cb-7. Producer or source: Fansteel Metallurgical Corporation. Originally published December 1963, revised June 1981.

TECHALLOY NICKEL 200

Alloy Digest ◽  
1977 ◽  
Vol 26 (6) ◽  
Keyword(s):  
Physical Properties ◽  
Surface Treatment ◽  
Low Temperatures ◽  
Nickel Alloys ◽  
Elevated Temperatures ◽  
Heat Treating ◽  
General Purpose ◽  
Commercially Pure ◽  
Electrical Components ◽  
Nickel 200

Abstract TECHALLOY Nickel 200 is commercially pure wrought nickel. It maintains good strength at elevated temperatures and is tough and ductile at low temperatures. It is a general-purpose material when the properties of nickel alloys are not needed. Its many uses include spun and cold-formed parts, electrical components, transducers and nickel-cadmium batteries. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on forming, heat treating, machining, joining, and surface treatment. Filing Code: Ni-246. Producer or source: Techalloy Company Inc..

Strong Coupling: Polariton Bose Condensation

2017 ◽  
Author(s):  
Alexey V. Kavokin ◽  
Jeremy J. Baumberg ◽  
Guillaume Malpuech ◽  
Fabrice P. Laussy
Keyword(s):  
Strong Coupling ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Dissipative System ◽  
Bose Condensation ◽  
Einstein Condensation ◽  
Strong Coupling Regime ◽  
Stimulated Scattering ◽  
Exciton Polaritons ◽  
Bose Einstein

In this Chapter we address the physics of Bose-Einstein condensation and its implications to a driven-dissipative system such as the polariton laser. We discuss the dynamics of exciton-polaritons non-resonantly pumped within a microcavity in the strong coupling regime. It is shown how the stimulated scattering of exciton-polaritons leads to formation of bosonic condensates that may be stable at elevated temperatures, including room temperature.

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