Formation of Thioamide Derivatives from Reactions of Isothiocyanates with Oxazol-2-amines

1985 ◽  
Vol 38 (3) ◽  
pp. 447 ◽  
Author(s):  
G Crank ◽  
HR Khan
Keyword(s):  
Chemical Properties ◽  
Amino Group ◽  
Usual Reaction

4-Substituted oxazol-2-amines react with isothiocyanates to give products having a thioamide function at C5. The reaction is considered to be an electrophilic process in competition with the usual reaction of the amino group with the isothiocyanate . The nature of the isothiocyanate and the type of substituent at C4 affect the amount of the thioamide product formed. Some chemical properties of the thioamides are also investigated.

scholarly journals A reaction of glucose with peptides

1972 ◽  
Vol 129 (1) ◽  
pp. 203-208 ◽  
Author(s):  
Henry B. F. Dixon
Keyword(s):  
Aqueous Solution ◽  
Acetic Acid ◽  
Blood Glucose ◽  
Dissociation Constant ◽  
Electrophoretic Mobility ◽  
Chemical Properties ◽  
Amino Group ◽  
Half Time ◽  
N Terminus ◽  
And Chemical Properties

Valylhistidine (Val-His) reacts with glucose (Glc) in a mixture of pyridine and acetic acid to form glucosylvalylhistidine (Glc-Val-His). The pK of the α-amino group is thereby lowered to about 5.6 as judged by electrophoretic mobility. The reaction: [Formula: see text] also occurs in an aqueous solution of pyridine and acetic acid of pH6.2 at 50°C, in which it exhibits a half-time of about 30h and a dissociation constant of about 0.3m. Isoleucyltyrosine and glucose react similarly in aqueous solution. The Glc-Val-His has the chromatographic, electrophoretic and chemical properties reported by Holmquist & Schroeder (1966a) for the substance released by proteolysis from the N-terminus of the β-chains of haemoglobin AIc; the value of the dissociation constant means that the concentration of haemoglobin AIc found naturally could be explained by reaction of haemoglobin A with the blood glucose.

scholarly journals Chemical properties of the functional groups of insulin

1981 ◽  
Vol 193 (2) ◽  
pp. 419-425 ◽  
Author(s):  
Y K Chan ◽  
G Oda ◽  
H Kaplan
Keyword(s):  
Functional Groups ◽  
Chemical Properties ◽  
Amino Group ◽  
Histidine Residues ◽  
Tyrosine Residues ◽  
Order Of Magnitude ◽  
Phenolic Group ◽  
Dimeric Form ◽  
A Chain ◽  
Phenylalanine Residue

The method of competitive binding [Kaplan, Stevenson & Hartley (1971) Biochem. J. 124, 289-299] with 1-fluoro-2,4-dinitrobenzene as the labelling reagent [Duggleby & Kaplan (1975) Biochemistry 14, 5168-5175] was used to determine the chemical properties, namely pK and reactivity, of the amino groups, the histidine residues and the tyrosine residues of the dimeric form of pig zinc-free insulin at 20.0 degrees C. The N-terminal glycine residue of the A-chain has a pK of 7.7 and a slightly higher than normal reactivity. The N-terminal phenylalanine residue of the B-chain has a pK of 6.9 and is approximately an order of magnitude more reactive than a corresponding amino group with the same pK value. The lysine epsilon-amino group has an unusually low pK of 7.0 but has approximately the expected reactivity of such a group. In the case of the two histidine and four tyrosine residues only the average properties of each class were determined. The histidine residues have a pK value of approx. 6.6, but, however, their reactivity is at least an order of magnitude greater than that of a free imidazole group. The tyrosine residues have a pK value of approx. 10, but their average reactivities are substantially less than for a free phenolic group. At alkaline pH values above 8 the reactivity of all the functional groups show sharp discontinuities, indicating that insulin is undergoing a structural change that alters the properties of these groups.

scholarly journals SYNTHESIS AND REACTIVITY OF 4-NITRO-3-(TETRAZOL-5-YL) FURAZAN WITH N- AND O-NUCLEOPHILES

2017 ◽  
Vol 60 (5) ◽  
pp. 21
Author(s):  
Elena V. Stepanova ◽  
Andrei I. Stepanov
Keyword(s):  
Hydrogen Peroxide ◽  
Sulfuric Acid ◽  
Carboxylic Acid ◽  
Total Yield ◽  
Cycloaddition Reaction ◽  
Chemical Properties ◽  
Amino Group ◽  
Nuclear Magnetic Resonance Spectra ◽  
13C Nuclear Magnetic Resonance ◽  
Partial Neutralization

A rational four-stages scheme for the synthesis of 4-nitro-3-(tetrazol-5-yl)furazane is proposed. The synthesis starts from the stage of 3-amino-4-(1,2,4-oxadiazol-3-yl)-furazan preparation by condensation of amidoxime of 4-aminofurazan-3-carboxylic acid with triethyl orthoformate, further reductive ring opening of 1,2,4-oxadiazole cycle. The action of hydrazine results in amidrazone of 4-aminofurazan-3-carboxylic acid formation. On the next step the diazotization of the resulting compound with sodium nitrite in acetic acid gives 3-amino-4-(tetrazol-5-yl)furazane. At last stage the titled 4-nitro-3-(tetrazol-5-yl)furazan was synthesized by oxidation of the amino group of 3-amino-4-(tetrazol-5-yl)furazan by a solution of 30% hydrogen peroxide in concentrated sulfuric acid with 85% yield. The increase in the oxidative activity of the H2O2/H2SO4 system by carrying out the oxidation stage at an elevated temperature made possible to substantially reduce the consumption of hydrogen peroxide and sulfuric acid. The desired 4-nitro-3-(tetrazol-5-yl)furazan was isolated by partial neutralization of the reaction mixture with sodium orthophosphate, followed by extraction with ethyl acetate. The total yield of 4-nitro-3-(tetrazol-5-yl)furazane in terms of the starting amidoxime of 4-aminofurazan-3-carboxylic acid was 42-48%. It was shown that the reaction of 4-nitro-3-(tetrazol-5-yl)furazan with a number of N- and O-nucleophilic agents (sodium azide, high-basic amines, hydrazine, sodium hydroxide, methanol in the presence of potassium carbonate) resulted in the substitution of the nitro group of the selected compound by a nucleophile and formation of corresponding 4-R-3-(tetrazol-5-yl)furazane derivatives (R = N3, substituted amino group, NHNH2, OH, OMe). Some chemical properties of thereby obtained compounds are considered. Thus [3 + 2] cycloaddition reaction of 4-azido-3-(tetrazol-5-yl)furazane (R = N3) with propargyl alcohol was used at the synthesis of 4- (4-hydroxy-methyl-1,2,3-triazol-1-yl)-3-(tetrazol-5-yl)furazane. The condensation of 3-hydrazino-4-(tetrazol-5-yl)furazane (R = NHNH2) with carbonyl compounds in the case of reaction with benzaldehyde leads to the corresponding hydrazone, with β-dicarbonyl compounds (malonaldehyde, acetylacetone) pyrazole derivatives were obtained. The synthesized compounds are characterized by 1H and 13C nuclear magnetic resonance spectra, by IR and mass spectroscopy. For citation:Stepanova E.V., Stepanov A.I. Obtaining and Reactivity of 4-nitro-3-(tetrazol-5-yl) furazan with N- and O-nucleophiles. Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol. 2017. V. 60. N 5. P. 21-29

Unusual chemical properties of the amino groups of insulin: implications for structure–function relationship

1979 ◽  
Vol 57 (6) ◽  
pp. 489-496 ◽  
Author(s):  
Marla G. Sheffer ◽  
Harvey Kaplan
Keyword(s):  
Carbon Dioxide ◽  
Acetic Anhydride ◽  
Chemical Properties ◽  
Amino Terminus ◽  
Amino Group ◽  
Amino Groups ◽  
Ph Values ◽  
Function Relationship ◽  
Ph Range ◽  
Association State

The chemical properties of the three amino groups of insulin were obtained at 10 and 37 °C using the competitive labelling technique with acetic anhydride as the labelling reagent. At 10 °C, pK values of 7.9, 7.2, and 7.8 were found for the glycyl A1, phenylalanyl B1, and lysyl B29 amino groups. When compared with standard amino compounds by means of a Brønsted plot, the two amino-termini were found to be 'super-reactive' and the lysyl ε-amino group buried. In the presence of carbon dioxide at physiological pH values, all three amino groups became much less reactive indicating that they had reacted to form carbamino derivatives. Above pH 8 the reactivities of the glycyl amino terminus and ε-amino group increase sharply indicating that insulin is undergoing a conformational change which is most likely a change in its association state. At 37 °C the amino groups do not titrate normally but exhibit sharp increases in reactivity over the physiological pH range with the midpoints in the pH reactivity profiles between pH values of 7.0 and 7.3. This behaviour is interpreted as a rapid disaggregation of insulin to form monomers as a result of the ionization of the amino groups. It is concluded that at physiological pH and temperature all three amino groups are deprotonated.

scholarly journals Structure-function relationships in the free insulin monomer

1986 ◽  
Vol 237 (3) ◽  
pp. 663-668 ◽  
Author(s):  
M A Hefford ◽  
G Oda ◽  
H Kaplan
Keyword(s):  
Chemical Properties ◽  
The Other ◽  
Monomeric Unit ◽  
Crystallographic Structure ◽  
Amino Group ◽  
Ph Profile ◽  
X Ray ◽  
Predominant Species ◽  
N Terminus ◽  
Free Insulin

The chemical properties of the functional groups of insulin were determined at a concentration (0.5 microM) where the predominant species of insulin is the free (unassociated) monomeric unit. The glycine N-terminus and the four tyrosine phenolic groups had the same properties as in the associated forms of insulin. On the other hand the lysine epsilon-amino group and the two histidine imidazole groups had substantially altered properties. Some alteration in the properties of the phenylalanine N-terminus was also observed. The reactivity-pH profile for the imidazole groups showed a second ionization with a pKa of 10.1 in addition to an ionization with a pKa of 6.8. On the basis of the X-ray-crystallographic structure of hexameric insulin the observed changes can be accounted for by disruption of monomer-monomer or dimer-dimer interactions in the associated states of insulin. It is concluded that the conformation of the monomeric unit of insulin is essentially the same in its free and associated states in solution.

Statistical criteria of stellar population types

1966 ◽  
Vol 24 ◽  
pp. 101-110
Author(s):  
W. Iwanowska
Keyword(s):  
Stellar Population ◽  
Chemical Properties ◽  
Spectrophotometric Study ◽  
Physical And Chemical Properties ◽  
Population Type ◽  
The Galaxy ◽  
Distribution Parameters ◽  
Physical And Chemical ◽  
Statistical Criteria ◽  
And Chemical Properties

In connection with the spectrophotometric study of population-type characteristics of various kinds of stars, a statistical analysis of kinematical and distribution parameters of the same stars is performed at the Toruń Observatory. This has a twofold purpose: first, to provide a practical guide in selecting stars for observing programmes, second, to contribute to the understanding of relations existing between the physical and chemical properties of stars and their kinematics and distribution in the Galaxy.

Biophysical Measurement of Molecular Weight of Foot-and-Mouth Disease RNA Fragments

1974 ◽  
Vol 32 ◽  
pp. 262-263
Author(s):  
Sydney S. Breese ◽  
Howard L. Bachrach
Keyword(s):  
Chemical Properties ◽  
Foot And Mouth Disease ◽  
Mouth Disease ◽  
Distilled Water ◽  
Bovine Plasma ◽  
Mouth Disease Virus ◽  
Foot And Mouth ◽  
Carbon Coated ◽  
Rna Fragments ◽  
Physical And Chemical

Continuing studies on the physical and chemical properties of foot-and-mouth disease virus (FMDV) have included electron microscopy of RNA strands released when highly purified virus (1) was dialyzed against demlneralized distilled water. The RNA strands were dried on formvar-carbon coated electron microscope screens pretreated with 0.1% bovine plasma albumin in distilled water. At this low salt concentration the RNA strands were extended and were stained with 1% phosphotungstic acid. Random dispersions of strands were recorded on electron micrographs, enlarged to 30,000 or 40,000 X and the lengths measured with a map-measuring wheel. Figure 1 is a typical micrograph and Fig. 2 shows the distributions of strand lengths for the three major types of FMDV (A119 of 6/9/72; C3-Rezende of 1/5/73; and O1-Brugge of 8/24/73.

Decoration of specific sites on freeze-fractured membranes

1978 ◽  
Vol 36 (2) ◽  
pp. 140-141
Author(s):  
H. Gross ◽  
H. Moor
Keyword(s):  
Pure Water ◽  
Freeze Fracture ◽  
Chemical Properties ◽  
Surface Forces ◽  
Sulfate Pentahydrate ◽  
Copper Sulfate Pentahydrate ◽  
Physico Chemical ◽  
Water Of Hydration ◽  
Small Container ◽  
Binding Forces

Fracturing under ultrahigh vacuum (UHV, p ≤ 10-9 Torr) produces membrane fracture faces devoid of contamination. Such clean surfaces are a prerequisite foe studies of interactions between condensing molecules is possible and surface forces are unequally distributed, the condensate will accumulate at places with high binding forces; crystallites will arise which may be useful a probes for surface sites with specific physico-chemical properties. Specific “decoration” with crystallites can be achieved nby exposing membrane fracture faces to water vopour. A device was developed which enables the production of pure water vapour and the controlled variation of its partial pressure in an UHV freeze-fracture apparatus (Fig.1a). Under vaccum (≤ 10-3 Torr), small container filled with copper-sulfate-pentahydrate is heated with a heating coil, with the temperature controlled by means of a thermocouple. The water of hydration thereby released enters a storage vessel.

Cathodoluminescence of Catalyst Crystallites

1982 ◽  
Vol 40 ◽  
pp. 664-665
Author(s):  
E.D. Boyes ◽  
P.L. Gai ◽  
D.B. Darby ◽  
C. Warwick
Keyword(s):  
Defect Density ◽  
Chemical Properties ◽  
Operating Conditions ◽  
Semiconductor Materials ◽  
Environmental Cell ◽  
High Resolution Structure ◽  
Commercially Important ◽  
Crystallographic Defects ◽  
Resolution Structure

The extended crystallographic defects introduced into some oxide catalysts under operating conditions may be a consequence and accommodation of the changes produced by the catalytic activity, rather than always being the origin of the reactivity. Operation without such defects has been established for the commercially important tellurium molybdate system. in addition it is clear that the point defect density and the electronic structure can both have a significant influence on the chemical properties and hence on the effectiveness (activity and selectivity) of the material as a catalyst. SEM/probe techniques more commonly applied to semiconductor materials, have been investigated to supplement the information obtained from in-situ environmental cell HVEM, ultra-high resolution structure imaging and more conventional AEM and EPMA chemical microanalysis.

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