scholarly journals FACTORS WHICH INFLUENCE THE STABILITY OF TRYPTOPHAN DURING THE HYDROLYSIS OF PROTEINS IN ALKALINE SOLUTION

1947 ◽  
Vol 171 (2) ◽  
pp. 551-560 ◽  
Author(s):  
K.A. Kuiken ◽  
Carl M. Lyman ◽  
Fred Hale
Keyword(s):  
Alkaline Solution ◽  
The Stability ◽  
Hydrolysis Of

Schiff base equilibria. II. Beryllium complexes of N-n-butylsalicylideneimine and the hydrolysis of the Be2+ ion

1965 ◽  
Vol 18 (5) ◽  
pp. 651 ◽  
Author(s):  
RW Green ◽  
PW Alexander
Keyword(s):  
Aqueous Solution ◽  
Schiff Base ◽  
Complex Formation ◽  
Distribution Coefficient ◽  
Dilute Aqueous Solution ◽  
The Stability ◽  
Ph Range ◽  
Hydrolysis Of ◽  
Beryllium Complexes ◽  
Equilibria In Aqueous Solution

The Schiff base, N-n-butylsalicylideneimine, extracts more than 99.8% beryllium into toluene from dilute aqueous solution. The distribution of beryllium has been studied in the pH range 5-13 and is discussed in terms of the several complex equilibria in aqueous solution. The stability constants of the complexes formed between beryllium and the Schiff base are log β1 11.1 and log β2 20.4, and the distribution coefficient of the bis complex is 550. Over most of the pH range, hydrolysis of the Be2+ ion competes with complex formation and provides a means of measuring the hydrolysis constants. They are for the reactions: Be(H2O)42+ ↔ 2H+ + Be(H2O)2(OH)2, log*β2 - 13.65; Be(H2O)42+ ↔ 3H+ + Be(H2O)(OH)3-, log*β3 -24.11.

scholarly journals Stability of Methylphenidate under Various pH Conditions in the Presence or Absence of Gut Microbiota

2021 ◽  
Vol 14 (8) ◽  
pp. 733
Author(s):  
Julia Aresti-Sanz ◽  
Markus Schwalbe ◽  
Rob Rodrigues Pereira ◽  
Hjalmar Permentier ◽  
Sahar El Aidy
Keyword(s):  
Gut Microbiota ◽  
In Silico Analysis ◽  
Intestinal Bacteria ◽  
Inactive Form ◽  
High Interindividual Variability ◽  
Ritalinic Acid ◽  
Ph Conditions ◽  
Small Intestinal ◽  
The Stability ◽  
Hydrolysis Of

Methylphenidate is one of the most widely used oral treatments for attention-deficit/hyperactivity disorder (ADHD). The drug is mainly absorbed in the small intestine and has low bioavailability. Accordingly, a high interindividual variability in terms of response to the treatment is known among ADHD patients treated with methylphenidate. Nonetheless, very little is known about the factors that influence the drug’s absorption and bioavailability. Gut microbiota has been shown to reduce the bioavailability of a wide variety of orally administered drugs. Here, we tested the ability of small intestinal bacteria to metabolize methylphenidate. In silico analysis identified several small intestinal bacteria to harbor homologues of the human carboxylesterase 1 enzyme responsible for the hydrolysis of methylphenidate in the liver into the inactive form, ritalinic acid. Despite our initial results hinting towards possible bacterial hydrolysis of the drug, up to 60% of methylphenidate is spontaneously hydrolyzed in the absence of bacteria and this hydrolysis is pH-dependent. Overall, our results indicate that the stability of methylphenidate is compromised under certain pH conditions in the presence or absence of gut microbiota.

VIII.—The Stability of Suspensions. I. The Rate of Sedimentation of Kaolin Suspensions by Salts at Varying Hydrogen Ion Concentrations

1926 ◽  
Vol 45 (1) ◽  
pp. 59-70 ◽  
Author(s):  
William Ogilvy Kermack ◽  
William Turner Horace Williamson
Keyword(s):  
Sodium Chloride ◽  
Acid Solution ◽  
Alkaline Solution ◽  
Calcium Sulphate ◽  
Sodium Sulphate ◽  
Aluminium Chloride ◽  
Monocalcium Phosphate ◽  
Sodium Hydrogen Phosphate ◽  
Rate Of Sedimentation ◽  
The Stability

Summary1. The rates of sedimentation of a kaolin suspension in presence of varying concentrations of a salt (sodium chloride, potassium chloride, sodium sulphate, di-sodium hydrogen phosphate, sodium citrate, calcium chloride, calcium sulphate, monocalcium phosphate, “superphosphate”, aluminium chloride, ferric chloride or lanthanum chloride) have been compared at various pH values. Abnormal results are obtained with sodium chloride, monocalcium phosphate, aluminium, ferric and lanthanum chlorides.2. Sodium chloride increases the rate of sedimentation in alkaline solution, but actually inhibits it in acid solution.3. In concentrations of monocalcium phosphate above 0·06 per cent, abnormal sedimentation in alkaline solution takes place, with the result that it is much more complete than at the corresponding concentrations in acid solution.4. In acid solution the tervalent ions, aluminium, ferric and lanthanum have little effect, but a zone of very marked flocculation occurs at pH 7–8. This zone separates a region within which the unsedimented particles are negatively charged from a region within which they are positively charged.

Industrial Wastewaters of the Feed Industry: use of Sodium Ferrate in the Phenol Purification Process

2021 ◽  
Vol 25 (1) ◽  
pp. 829-839
Author(s):  
Gulnara Altynbayeva ◽  
Olga Kadnikova ◽  
Arman Aydarhanov ◽  
Medet Toretayev
Keyword(s):  
Alkaline Solution ◽  
Organic Substances ◽  
Purification Process ◽  
Industrial Wastewaters ◽  
Feed Industry ◽  
Feed Production ◽  
The Stability ◽  
Combined Feed

Abstract The article presents the results of studies of the possibility of using sodium ferrate in the treatment of wastewater from organic substances on the example of phenol in the production of combined feed. This research has shown the technology of obtaining encapsulated ferrate using hexane, ethylcellulose and paraffin; it has also established the stability of encapsulated sodium ferrate in air and in an alkaline solution. Furthermore, the evaluation of the efficiency of using encapsulated sodium ferrate in the purification of the simulated solution from phenol in the technology of combined feed production.

Study and modeling of mechanisms of cholinesterasis reactions in order to improve their catalytic properties in the neutralization reactions of organophosphorous compounds

2020 ◽  
pp. 134-174
Author(s):  
Sergey Varfolomeev ◽  
Bella Grigorenko ◽  
Sofya Lushchekina ◽  
Patrick Masson ◽  
Galina Mahaeva ◽  
...  
Keyword(s):  
First Generation ◽  
Organophosphorus Compounds ◽  
Protein Molecule ◽  
Catalytic Antibodies ◽  
High Rate ◽  
Biological Targets ◽  
Organophosphorous Compounds ◽  
Rate Of Hydrolysis ◽  
The Stability ◽  
Hydrolysis Of

“Biocleaners” or “bioscavengers” are biological objects (enzymes, catalytic antibodies) that are capable of binding and/or hydrolyzing organophosphorus compounds (OPC). Their use seems to be the most effective alternative to traditional antidotes to neutralize or detoxify OPC. The introduction of bioscavengers allows neutralizing toxicant molecules in the bloodstream before they reach their biological targets, thereby providing protection against poisoning. Bioscavengers of the first-generation neutralized OPC molecules by stoichiometrically binding to them. The safety and efficacy of human butyrylcholinesterase (BChE) for protecting against OPC poisoning has been shown. However, the stoichiometric neutralization of OPC requires the introduction of a huge amount of expensive biopharmaceuticals. Catalytic bioscavengers that hydrolytically neutralize OPC were introduced at a much lower dose to achieve the same degree of effectiveness. The most effective catalytic bioscavengers are enzymes. The most promising enzymes are artificial mammalian paraoxonase mutants and bacterial phosphotriesterases. However, studies of other enzymes, such as prolidases, oxidases, artificial mutants of cholinesterases and carboxyl esterases and catalytic antibodies are actively ongoing. Since OPC are pseudosubstrates of cholinesterases (ChEs), a detailed description of the mechanisms of inhibition, dealkylation, and spontaneous reactivation of phosphorylated ChEs is critical for the development of ChEs mutants with a high rate of hydrolysis of OPC. The review presents an analysis of different views on the mechanisms of interaction of ChEs with OPC, discusses the possible directions of creating effective catalytic biological traps based on BChE and changes in their mechanism of action as compared to the native enzyme. A separate section is devoted to the effect of mutations, both polymorphic and artificial, on the stability of the protein molecule of BChE.

Human cholinesterases

2020 ◽  
pp. 63-120
Author(s):  
Sergey Varfolomeev ◽  
Bella Grigorenko ◽  
Sofya Lushchekina ◽  
Alexander Nemuchin
Keyword(s):  
Active Site ◽  
The Body ◽  
Polymorphic Modification ◽  
Substrate Complex ◽  
Enzyme Substrate ◽  
Mechanism Of Hydrolysis ◽  
The Central Nervous System ◽  
The Stability ◽  
Hydrolysis Of ◽  
Enzyme Reactivity

The work is devoted to modeling the elementary stages of the hydrolysis reaction in the active site of enzymes belonging to the class of cholinesterases — acetylcholinesterase (AChE) and butyrylcholinesterase (BChE). The study allowed to describe at the molecular level the effect of the polymorphic modification of BChE, causing serious physiolog ical consequences. Cholinesterase plays a crucial role in the human body. AChE is one of the key enzymes of the central nervous system, and BChE performs protective functions in the body. According to the results of calculations using the combined method of quantum and molecular mechanics (KM/MM), the mechanism of the hydrolysis of the native acetylcholine substrate in the AChE active center was detailed. For a series of ester substrates, a method for estimation of dependence of the enzyme reactivity on the structure of the substrate has been developed. The mechanism of hydrolysis of the muscle relaxant of succininylcholine BChE and the effect of the Asp70Gly polymorph on it were studied. Using various computer simulation methods, the stability of the enzyme-substrate complex of two enzyme variants with succinylcholine was studied.

The hydrolysis of maleimide in alkaline solution

1976 ◽  
Vol 54 (9) ◽  
pp. 1400-1404 ◽  
Author(s):  
Remigio Germano Barradas ◽  
Stephen Fletcher ◽  
John Douglas Porter
Keyword(s):  
Alkaline Solution ◽  
Reaction Scheme ◽  
Rate Equations ◽  
Bulk Concentration ◽  
Rate Of Reaction ◽  
Ph Range ◽  
Derived Data ◽  
Hydrolysis Of

The hydrolysis of maleimide has been investigated in the pH range 8.5–14. Polarographic limiting currents were well-defined, so that the bulk concentration of reactant during reduction could be clearly followed as a function of time. Logarithmic analysis of derived data indicated an arrest in the rate of reaction at circa pH 12, and a reaction scheme is proposed to explain this. In this scheme, the neutral maleimide molecule exists in equilibrium with its anion, and both of these species may undergo hydrolysis at the appropriate pH. From derived rate equations, the pKa of maleimide was found to be 10.0, whilst estimates of the rates of hydrolysis were also calculated.

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