Preferential Hydrolysis of Kynurenine Peptides

1969 ◽  
Vol 24 (3) ◽  
pp. 294-300 ◽  
Author(s):  
F. M. Veronese ◽  
E. Boccu ◽  
C. A. Benassi ◽  
E. Scoffone
Keyword(s):  
Alkaline Hydrolysis ◽  
Alkaline Media ◽  
Amino Group ◽  
Acidic Media ◽  
Model Compounds ◽  
Preferential Cleavage ◽  
Controlled Potential Electrolysis ◽  
Mechanism Of Hydrolysis ◽  
Controlled Potential ◽  
Hydrolysis Of

The preferential cleavage of kynurenine peptides bonds was studied through reduction to γ- (o- aminophenyl) -homoserine derivatives followed by mild acidic as well as mild alkaline hydrolysis. The reduction of keto group of kynurenine to hydroxy one was achieved by controlled potential electrolysis at -1.05 Volts. In order to understand the mechanism of hydrolysis some model compounds related to kynurenine peptides were also synthesized and studied. Hydrolysis of γ- (o-aminophenyl)-homoserine peptides in acidic media is related only to the assistance of γ-hydroxy function, whereas in alkaline media also aromatic amino group is involved.

The Chemical Evolution of a Nitrogenase Model, 20 Alkyl Molybdates(VI) and the Mechanism of Hydrocarbon Production by Nitrogenase [1]

1982 ◽  
Vol 37 (3) ◽  
pp. 380-385 ◽  
Author(s):  
G. N. Schrauzer ◽  
Laura A. Hughes ◽  
Norman Strampach
Keyword(s):  
Aqueous Solution ◽  
Alkaline Hydrolysis ◽  
Room Temperature ◽  
Bond Cleavage ◽  
Model Compounds ◽  
Hydrocarbon Production ◽  
Acidic Solutions ◽  
Reducing Conditions ◽  
Hydrolysis Of ◽  
Derivatives Of

Abstract Colorless alkylmolybdates(VI) of composition R-MoO3-are generated in aqueous solutions by the alkaline hydrolysis of complexes R-Mo(Bpy)(0)2Br(Bpy = 2,2′-bipyridyl, R = CH3 and higher alkyl). At room temperature in alkaline aqueous solution, the new organometallic derivatives of oxomolybdate(VI) are remarkably resistant against Mo-C bond hydrolysis. Decomposition occurs more rapidly on heating, affording unrearranged alkanes according to the eq.: R-MoO3- + OH-→RH + Mo04=. In acidic solutions, the methylmolybdate(VI) species decomposes with the formation of a mixture of methane and ethane while higher alkylmolybdates carrying hydrogen in the β-position relative to molybdenum undergo Mo-C bond heterolysis by way of β-elimina-tion: R-CH2CH2-MoO3 → Mo+4 (aq) + H+ + R-CH = CH2. The Mo-C bond of alkylmolybdates is resistant to oxidants but is very sensitive to cleavage under reducing conditions. Reductive Mo-C bond cleavage occurs particularly rapidly in the presence of thiols and reduced ferredoxin model compounds. The latter reactions simulate the terminal steps of hydrocarbon producing reactions of nitrogenase with alternate substrates such as CN-, R-CN or R-NC, confirming previous mechanistic conclusions concerning the mechanism of nitrogenase action.

scholarly journals Novel insight in carbohydrate degradation during alkaline treatment

Holzforschung ◽  
2015 ◽  
Vol 69 (6) ◽  
pp. 667-675 ◽  
Author(s):  
Kaarlo Nieminen ◽  
Lidia Testova ◽  
Markus Paananen ◽  
Herbert Sixta
Keyword(s):  
Chain Length ◽  
Alkaline Hydrolysis ◽  
Alkaline Treatment ◽  
Polymer Chains ◽  
Alkaline Media ◽  
Parameter Estimates ◽  
Reaction Rate Constants ◽  
Carbohydrate Degradation ◽  
The Impact ◽  
Hydrolysis Of

Abstract A mathematical model is presented, in which the yield loss (YL) and the decline in polymerization of carbohydrates is comprehended. The model is applicable to the treatment of cellulose and hemicelluloses in alkaline media, and it features the actions of peeling, stopping, and alkaline hydrolysis of the polymer chains. The peeling reaction is further subdivided into primary and secondary peeling depending on whether it originates from an initial reducing end-group (REG) or from an REG created by alkaline hydrolysis. Fitting the model to experimental data provides estimates of the various reaction rate constants. When available, simultaneous observations of the YL and the decrease in chain length contribute to the evaluation of the parameters. Alternatively, if the data are limited to the YL, the obtained parameter estimates allow for a projection of the time development of chain length. The model has been applied on data from two types of experiments: soda-anthraquinone treatment of cotton linters and kraft treatment of Scots pine. It was possible to evaluate the impact of the different processes on degradation as well as the portions of polymer chains possessing active or stabilized REGs.

Quaternary salts of N,N-dimethylaminoethyl esters of pivalic and 2-methyl-3-methoxypropionic acid and their hydrolysis

1986 ◽  
Vol 51 (1) ◽  
pp. 206-214 ◽  
Author(s):  
Stanislav Ševčík ◽  
Martin Přádný
Keyword(s):  
Methyl Iodide ◽  
Alkaline Hydrolysis ◽  
Structural Unit ◽  
Model Compounds ◽  
Dimethylaminoethyl Methacrylate ◽  
Quaternary Salts ◽  
Terminal Unit ◽  
Kinetics Of ◽  
Hydrolysis Of

The synthesis and kinetics of quaternization of model compounds of poly(N,N-dimethylaminoethyl methacrylate) in water-alcoholic solutions brought about by methyl iodide and the alkaline hydrolysis of products in water have been investigated. N,N-Dimethylaminoethyl pivalate was selected as a model of the structural unit of the reported polymer; N,N-dimethylaminoethyl-2-methyl-3-methoxypropionate was the model of the terminal unit of the anionically prepared polymer.

Sulfenyl Halides as Modifying Reagents for Polypeptides and Proteins

1968 ◽  
Vol 23 (10) ◽  
pp. 1319-1325 ◽  
Author(s):  
F. M. Veronese ◽  
A. Fontana ◽  
E. Boccu ◽  
C. A. Benassi
Keyword(s):  
Polypeptide Chain ◽  
Peptide Bond ◽  
Tryptophan Residue ◽  
Amino Group ◽  
Model Compounds ◽  
Mild Conditions ◽  
Selective Reaction ◽  
Hydrolysis Of ◽  
Related Compounds ◽  
Sulfenyl Halides

The conversion of 2-thio-aryl-tryptophan and related derivatives to the corresponding 2-hydroxycompounds by acidic hydrolysis was investigated. The thioether function is introduced into the tryptophan residue by the selective reaction of sulfenyl halides with the indole nucleus. The substitution occurs under mild conditions only when the amino group of the tryptophan residue is free. The assistance of the amino group was confirmed using model compounds. Thus 2-thio-(2-nitrophenyl) -tryptamine is smoothly converted to 2-hydroxy-tryptamine whereas 2-thio- (2-nitrophenyl) -β-indolyl-propionic acid is completely stable under the same conditions. The conversion of 2-thio-aryl-tryptophan units linked in a polypeptide chain to the corresponding 2-hydroxy-tryptophan occurs only under conditions during which hydrolysis of the peptide bond occurs. It was also observed that the 2-nitro-thiophenols which are released during the hydrolysis of 2-thio- (2-nitrophenyl) -tryptophan and related compounds are converted under the conditions of the reaction to 2-aminobenzene sulfonic acids.

scholarly journals Decomposition of Dimethoate and Omethoate in Aqueous Solutions – Half-Life, Neurotoxicity and Mechanism of Hydrolysis

2021 ◽  
Author(s):  
Vladan J. Anićijević ◽  
Milena Petković ◽  
Igor A Pašti ◽  
Tamara Lazarević-Pašti
Keyword(s):  
Aqueous Solutions ◽  
Alkaline Hydrolysis ◽  
Quantum Chemical ◽  
Contaminated Water ◽  
Organophosphate Pesticides ◽  
Chemical Transformations ◽  
Acidic Solutions ◽  
Mechanism Of Hydrolysis ◽  
Hydrolysis Of ◽  
Over Time

Organophosphate pesticides are used in large quantities. However, they exhibit toxic effects on non-target organisms. Dimethoate and its oxo-analog omethoate inhibit acetylcholinesterase and are toxic for mammals. Moreover, they show extreme toxicity for bees. Once in the environment, they undergo chemical transformations and decomposition. We show that dime-thoate and omethoate decompose rapidly in alkaline aqueous solutions (half-lives 5.7 and 0.89 days) but are highly stable in acidic solutions (half-lives 124 and 104 days). These differences are explained using quantum chemical calculations, indicating that a weaker P–S bond in omethoate is more susceptible to hydrolysis, particularly at a high pH. The toxicity of these pesticides solutions decreases over time, indicating that no or very little highly toxic omethoate is formed during hydrolysis. Presented data can be used to predict dimethoate and omethoate concentrations in contaminated water depending on pH. Presented results suggest that alkaline hydrolysis of organophosphates has an advantage over other techniques for their removal since there is no risk of omethoate accumulation and increased toxicity of contaminated water.

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