Oxidative sulphitolysis of the disulphide groups in insulin and cystine

1962 ◽  
Vol 15 (2) ◽  
pp. 365 ◽  
Author(s):  
SJ Leach ◽  
JM Swan
Keyword(s):  
Metal Ions ◽  
Room Temperature ◽  
Air Oxidation ◽  
Large Excess ◽  
Reaction Proceeding ◽  
Disulphide Bonds ◽  
Combined Action ◽  
A Chain ◽  
Oxidative Sulphitolysis ◽  
Two Stages

All three disulphide bonds in insulin are broken by the combined action of sulphite and oxygen, the reaction proceeding at a reasonable rate at room temperature, pH 8-10. This " oxidative sulphitolysis " (RSSR'+RSSO< +RISSO<) is strongly catalysed by metal ions, particularly Cu(11). For a 1% solution of insulin at pH 10 containing 2x 10-4iu CU(II), reaction is complete in about 24 hr at 20 OC, and acidification then gives a precipitate of the S-sulpho B-chain, the S-sulpho A-chain remaining in solution. Catalysis of the air-oxidative sulphitolysis of cystine to S-sulphocysteine (Clarke 1932 ; Kolthoff and Stricks 1951a, 1951b) is confirmed, CU(II), M~(II), CO(IIL), and F~(III) being most effective in that order. In these reactions the binding of metal ions by intermediate thiols prevents or retards the usual metal-catalysed air oxidation of sulphite to sulphate, so that a large excess of sulphite is not required. When a mixture of insulin and sulphite is oxidized with CU(II) with exclusion of oxygen, two end-points are readily detected (cf. cystine ; Kolthoff and Stricks 1951a, 1951b), corresponding to the reactions In addition there is evidence for the formation, in the early stages, of cupric mercaptide according to the equation Cupric sulphitolysis can also be carried out in two stages by &st titrating the insulin with CU(I) to the end-point of the reaction and then with CU(II) to complete the reaction according to RSCU+SO;- +2Cu2++RSS0c +3Cu+.

Formation of Dislocation Channels in Neutron Irradiated Molybdenum

1972 ◽  
Vol 30 ◽  
pp. 672-673
Author(s):  
S. Mahajan
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ambient Temperature ◽  
Room Temperature ◽  
Channel Formation ◽  
Early Stages ◽  
Transmission Electron ◽  
Three Stages ◽  
Two Stages ◽  
Polycrystalline Molybdenum

The evolution of dislocation channels in irradiated metals during deformation can be envisaged to occur in three stages: (i) formation of embryonic cluster free regions, (ii) growth of these regions into microscopically observable channels and (iii) termination of their growth due to the accumulation of dislocation damage. The first two stages are particularly intriguing, and we have attempted to follow the early stages of channel formation in polycrystalline molybdenum, irradiated to 5×1019 n. cm−2 (E > 1 Mev) at the reactor ambient temperature (∼ 60°C), using transmission electron microscopy. The irradiated samples were strained, at room temperature, up to the macroscopic yield point.Figure 1 illustrates the early stages of channel formation. The observations suggest that the cluster free regions, such as A, B and C, form in isolated packets, which could subsequently link-up to evolve a channel.

scholarly journals Recyclable Self-Healing Polyurethane Cross-Linked by Alkyl Diselenide with Enhanced Mechanical Properties

Polymers ◽  
2019 ◽  
Vol 11 (5) ◽  
pp. 773 ◽  
Author(s):  
Yuqing Qian ◽  
Xiaowei An ◽  
Xiaofei Huang ◽  
Xiangqiang Pan ◽  
Jian Zhu ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Room Temperature ◽  
Amide Bond ◽  
Self Healing ◽  
Healing Efficiency ◽  
Polyurethane Networks ◽  
Combined Action ◽  
Cross Linker ◽  
Dynamic Structures ◽  
External Interventions

Dynamic structures containing polymers can behave as thermosets at room temperature while maintaining good mechanical properties, showing good reprocessability, repairability, and recyclability. In this work, alkyl diselenide is effectively used as a dynamic cross-linker for the design of self-healing poly(urea–urethane) elastomers, which show quantitative healing efficiency at room temperature, without the need for any catalysts or external interventions. Due to the combined action of the urea bond and amide bond, the material has better mechanical properties. We also compared the self-healing effect of alkyl diselenide-based polyurethanes and alkyl disulfide-based polyurethanes. The alkyl diselenide has been incorporated into polyurethane networks using a para-substituted amine diphenyl alkyl diselenide. The resulting materials not only exhibit faster self-healing properties than the corresponding disulfide-based materials, but also show the ability to be processed at temperatures as low as 60 °C.

Growth mechanism and characterization of ZnO nano-tubes synthesized using the hydrothermal-etching method

2009 ◽  
Vol 63 (6) ◽  
Author(s):  
Yan Li ◽  
Chuan-Sheng Liu ◽  
Yun-Ling Zou
Keyword(s):  
Room Temperature ◽  
Morphological Analysis ◽  
Diffraction Field ◽  
X Ray Diffraction ◽  
X Ray ◽  
Room Temperature Photoluminescence ◽  
Etching Method ◽  
Nano Rods ◽  
Two Stages

AbstractZnO nano-tubes (ZNTs) have been successfully synthesized via a simple hydrothermal-etching method, and characterized by X-ray diffraction, field emission scanning electron microscopy and room temperature photoluminescence measurement. The as-synthesized ZNTs have a diameter of 500 nm, wall thickness of 20–30 nm, and length of 5 µm. Intensity of the plane (0002) diffraction peak, compared with that of plane (10$$ \bar 1 $$0) of ZNTs, is obviously lower than that of ZnO nano-rods. This phenomenon can be caused by the smaller cross section of plane (0002) of the nano-tubes compared with that of other morphologies. On basis of the morphological analysis, the formation process of nano-tubes can be proposed in two stages: hydrothermal growth and reaction etching process.

The Influence of Heat and Two Stages Precipitation in the Process of Natural Polymer Purification from the Byproduct of Bioethanol Process Base on Empty Palm Fruit Bunch

2015 ◽  
Vol 1123 ◽  
pp. 177-181
Author(s):  
Achmad Hanafi ◽  
Harry Budiman ◽  
Fauzan Aulia
Keyword(s):  
Sulfuric Acid ◽  
Sodium Hydroxide ◽  
Room Temperature ◽  
Black Liquor ◽  
Ash Content ◽  
Natural Polymer ◽  
Palm Fruit ◽  
Second Stage ◽  
Direct Precipitation ◽  
Two Stages

The biopolymer material, lignin, was recovered from the black liquor by acidification of the black liquor using sulfuric acid. Several purification techniques were carried out to produce the high purity of lignin such as gradual precipitation of lignin from black liquor (first stage: precipitation at pH 7, second stage: precipitation at pH 2) and the diluting of crude lignin by sodium hydroxide then followed by re-precipitation at different temperature. Subsequently, the impurities of lignin product resulted from each purification techniques was determined as ash content that analyzed using temperature program furnace; and the content of lignin was investigated using spectrophotometer UV-Vis. The result showed that the content of lignin of material produced from gradual precipitation was approximately 77.6%. It was higher than the content of lignin about 3.4% of material produced from direct precipitation to pH 2. In addition, the elevating of temperature from 40 to 60°C was no considerably affect to the content of lignin in precipitate produced from re-precipitation of crude lignin solution in sodium hydroxide. Nonetheless, the content of lignin of precipitate improved 15% when the temperature of re-precipitation of crude lignin solution in sodium hydroxide was raised from room temperature to 40-60°C.

A Novel Alkali-Metal Hydrido-tris(pyrazolyl)borate (Tp*) Complex. Isolation and Crystal Structure of [(Me2CO)3(NaTp*)2]

2014 ◽  
Vol 69 (7) ◽  
pp. 793-798
Author(s):  
Laurent Plasseraud ◽  
Hélène Cattey
Keyword(s):  
Crystal Structure ◽  
Alkali Metal ◽  
Sodium Hydroxide ◽  
Title Compound ◽  
Room Temperature ◽  
Crystallographic Analysis ◽  
Monoclinic Space Group ◽  
Large Excess ◽  
X Ray ◽  
Acetone Water

The title compound was isolated from the treatment of Tp*Sn(Cl)2Bu (1) with a large excess of sodium hydroxide in a mixture of acetone-water at room temperature. [(Me2CO)3(NaTp*)2] (2) crystallizes at 4 °C as prismatic colorless crystals, in the monoclinic space group P21/c with Z = 4, a = 12.2837(6), b = 24.3197(12), c = 16.9547(8) Å, β = 110.017(1)°, and V = 4759.0(4) Å3. The X-ray crystallographic analysis revealed a dinuclear unit in which two Tp*Na moieties are held together by three bridging acetone molecules acting as oxygen-based donors.

ChemInform Abstract: A Mild CuCl-Catalyzed Glaser-Type Homocoupling Reaction: Air Oxidation and Room Temperature.

ChemInform ◽  
2015 ◽  
Vol 46 (33) ◽  
pp. no-no
Author(s):  
Xi Chen ◽  
Hailong Zhang ◽  
Jinping Chen ◽  
Hang Gong
Keyword(s):  
Room Temperature ◽  
Air Oxidation ◽  
Homocoupling Reaction

Reactions of Thiyl Radicals. XI. Further Investigations of Thiol–Disulfide Photolyses in the Liquid Phase

1973 ◽  
Vol 51 (9) ◽  
pp. 1410-1415 ◽  
Author(s):  
Donna D. Carlson ◽  
Arthur R. Knight
Keyword(s):  
Liquid Phase ◽  
Room Temperature ◽  
Liquid Mixtures ◽  
Quantum Yields ◽  
Chain Reaction ◽  
Photochemical Process ◽  
High Quantum Efficiency ◽  
Thiyl Radicals ◽  
Exchange Processes ◽  
A Chain

The photolysis of C2H5SH liquid at 2537 Å has been shown to give H2 and C2H5SSC2H5 at equal rates with a quantum yield of 0.25. The photolysis of ethanethiol – methyl disulfide liquid mixtures leads, via a chain reaction involving propagation by attack of thiyl radicals on the disulfide S—S bond, to the formation with high quantum efficiency of CH3SH, C2H5SSC2H5 and, as an intermediate that is consumed after long exposures, CH3SSC2H5. The net result of the sequence of exchange processes is the essentially irreversible conversion of the methyl disulfide into methanethiol. The same overall reaction occurs thermally at room temperature, but the rate is appreciably less than that of the photochemical process. The quantum yields of formation of the unsymmetrical disulfides arising from the photochemically initiated exchange reaction in equimolar mixtures of CH3SSCH3 + n-C3H7SSC3H7 and C2H5SSC2H5 + n-C3H7SSC3H7 have been shown to be 6.9 and 4.4, compared to 355 for CH3-SSCH3 + C2H5SSC2H5 mixtures. In all three types of system examined in this investigation all thiyl radicals can be accounted for stoichiometrically on the basis of exchange and combination reactions alone, indicating negligible disproportionation of these species in condensed phase.

scholarly journals Metal-organic magnets with large coercivity and ordering temperatures up to 242°C

Science ◽  
2020 ◽  
Vol 370 (6516) ◽  
pp. 587-592 ◽  
Author(s):  
Panagiota Perlepe ◽  
Itziar Oyarzabal ◽  
Aaron Mailman ◽  
Morgane Yquel ◽  
Mikhail Platunov ◽  
...  
Keyword(s):  
Metal Ions ◽  
Room Temperature ◽  
Building Blocks ◽  
Inorganic Materials ◽  
Coordination Networks ◽  
Critical Temperatures ◽  
Considerable Success ◽  
Organic Magnets ◽  
Metal Organic ◽  
Constituent Elements

Magnets derived from inorganic materials (e.g., oxides, rare-earth–based, and intermetallic compounds) are key components of modern technological applications. Despite considerable success in a broad range of applications, these inorganic magnets suffer several drawbacks, including energetically expensive fabrication, limited availability of certain constituent elements, high density, and poor scope for chemical tunability. A promising design strategy for next-generation magnets relies on the versatile coordination chemistry of abundant metal ions and inexpensive organic ligands. Following this approach, we report the general, simple, and efficient synthesis of lightweight, molecule-based magnets by postsynthetic reduction of preassembled coordination networks that incorporate chromium metal ions and pyrazine building blocks. The resulting metal-organic ferrimagnets feature critical temperatures up to 242°C and a 7500-oersted room-temperature coercivity.

Electron-Nuclear Hyperfine Interactions of 53Cr 3+ in Mg2SiO4 (Forsterite)

1980 ◽  
Vol 35 (12) ◽  
pp. 1296-1303 ◽  
Author(s):  
H. Rager
Keyword(s):  
Transition Metal ◽  
Hyperfine Interaction ◽  
Metal Ions ◽  
Room Temperature ◽  
Hyperfine Interactions ◽  
Small Variation ◽  
Transition Metal Ions ◽  
Oxygen Sublattice ◽  
Oxygen Coordination ◽  
Nuclear Spin System

Abstract The magnetic hyperfine interaction between the electron and nuclear spin system of 53Cr3+ was studied at the Mg sites, M1 and M2, in Mg2SiO4. The study was undertaken at room temperature and 9.52 GHz. The hyperfine structure data exhibit a covalent Cr-O bonding of approximately 10% indicating a mainly but not purely ionic bonding. Including the corresponding results obtained for 57Fe 3+ [1] and 55Mn2+ [2] in Mg2SiO4, this is interpreted such that the bonding of transition metal ions is mainly dominated by the oxygen sublattice in Mg2SiO4 and less by the properties of the transition metal ions themselves. The small variation of the hyperfine splitting parameters found for 53Cr3+ at M1 and M2, and also for 57Fe3+ at these positions indicates that the hyperfine interaction varies also with varying average metal oxygen distances as well as with changes in the oxygen coordination size.

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