scholarly journals Kinetics and Mechanistic Study of Hydrolysis of Adenosine Monophosphate Disodium Salt (AMPNa2) in Acidic and Alkaline Media

2019 ◽  
Vol 17 (1) ◽  
pp. 544-556
Author(s):  
Yoke-Leng Sim ◽  
Beljit Kaur
Keyword(s):  
Rate Constant ◽  
Adenosine Monophosphate ◽  
Disodium Salt ◽  
Second Order ◽  
Information Storage ◽  
Alkaline Media ◽  
Basic Medium ◽  
Mechanistic Study ◽  
Phosphate Ester ◽  
Hydrolysis Of

AbstractPhosphate ester hydrolysis is essential in signal transduction, energy storage and production, information storage and DNA repair. In this investigation, hydrolysis of adenosine monophosphate disodium salt (AMPNa2) was carried out in acidic, neutral and alkaline conditions of pH ranging between 0.30-12.71 at 60°C. The reaction was monitored spectrophotometrically. The rate ranged between (1.20 ± 0.10) × 10-7 s-1 to (4.44 ± 0.05) × 10-6 s-1 at [NaOH] from 0.0008 M to 1.00M recorded a second-order base-catalyzed rate constant, kOH as 4.32 × 10-6 M-1 s-1. In acidic conditions, the rate ranged between (1.32 ± 0.06) × 10-7 s-1 to (1.67 ± 0.10) × 10-6 s-1 at [HCl] from 0.01 M to 1.00 M. Second-order acid-catalyzed rate constant, kH obtained was 1.62 × 10-6 M-1 s-1. Rate of reaction for neutral region, k0 was obtained from graphical method to be 10-7 s-1. Mechanisms were proposed to involve P-O bond cleavage in basic medium while competition between P-O bond and N-glycosidic cleavage was observed in acidic medium. In conclusion, this study has provided comprehensive information on the kinetic parameters and mechanism of cleavage of AMPNa2 which mimicked natural AMP cleavage and the action of enzymes that facilitate its cleavage.

Studies on Sulphamic Acid and Related Compounds. II. Kinetics and Mechanism of Hydrolysis of Trimethylamine- and of Triethylamine Sulphur Trioxide Addition Compounds

1962 ◽  
Vol 15 (2) ◽  
pp. 251 ◽  
Author(s):  
BE Fleischfresser ◽  
I Lauder
Keyword(s):  
Rate Constant ◽  
Order Rate Constant ◽  
Aqueous Acetone ◽  
Second Order ◽  
Fluoride Ions ◽  
Order Rate ◽  
Mechanism Of Hydrolysis ◽  
Reaction With Water ◽  
Sulphamic Acid ◽  
Hydrolysis Of

The kinetics of hydrolysis of trimethylamine- and of triethylaminesulphur trioxide addition compounds have been studied in water and in aqueous acetone. Reaction occurs according to the equation,������������� f - + R,N.SO,+H,O-tR,XH+HSO~.The solvolysis reactions are first-order and are not catalyzed by acids. The halide ions, Cl', Br', and 1', show only a normal salt effect on the rate of hydrolysis of + - (CH,),N.SO, but in the presence of fluoride ions, the rate constant for the production + - of acid from (C,H,),N.SO, in water at 95 OC is about one-seventh of that in the absence of fluoride under the same conditions. It is suggested that the fluorosulphonate ion is formed rapidly, and that this ion then undergoes slow hydrolysis :�In the presence of alkali, using water as the solvent, second-order kinetics are observed, the equation for the reaction being,�������������� + - R,N.SO,+~OH-+R,X+SO~= +H,O. Assuming the reaction with water is bimolecular, the ratio of the (bimolecular) rate constants at 35 OC, ko~-/k~,o is approximately lo8 for each complex. In aqueous acetone, at low water concentrations, the hydrolysis reactions of the trialkylaminesulphur trioxide complexes show second-order kinetics. At 35 OC for the hydrolysis of + - (CH,),N.SO, the ratio of the second-order rate constant in aqueous acetone to the + - (calculated) second-order rate constant in water is approximately 550 ; for (C,H,),N.SO, the same ratio is 6900. It is considered that hydrolysis occurs in water and in aqueous acetone via a bi- molecular attack at sulphur.

Die γ-Radiolyse und Pulsradiolyse des Schwefelkohlenstoffs in wäßriger Lösung / The γ-Radiolysis and Pulse Radiolysis of Carbon Disulfide in Aqueous Solution

1973 ◽  
Vol 28 (1-2) ◽  
pp. 12-22 ◽  
Author(s):  
W. Roebke ◽  
M. Schöneshöfer ◽  
A. Henglein
Keyword(s):  
Rate Constant ◽  
Carbon Disulfide ◽  
Second Order ◽  
Γ Irradiation ◽  
Electrolytic Dissociation ◽  
First Order ◽  
A Value ◽  
Diffusion Controlled ◽  
Polymer Pyrolysis ◽  
Hydrolysis Of

A polymer (CHS2)n and sulfate are formed in the γ-irradiation of deaerated aqueous carbon disulfide solutions. The G-values are 3.6 and 0.41, respectively. In the presence of N,O, G (polymer) is decreased while G(SO4-) is increased. G(SO4-) can be decreased by isopropanol. G(polymer) is increased by H+ ions and reaches a value of 5 below pH = 2. Formic acid, hydrogen sulfide and carbonate are formed in the hydrolysis of the polymer. Pyrolysis at first leads to a red oil consisting of oligomer (HCS2)n and finally to H2S, CS2 plus a residue containing much carbon. The structure of the polymer is discussed.Pulse radiolytic experiments show that CS2 reacts with eaq (3.1 × 1010M-1s-1) and OH(7.4 × 109M-1s-1) in a diffusion controlled manner. The first product of the reaction with OH is SC(OH)S. The pK of the electrolytic dissociationSC(OH)Ṣ ⇄ SC(O-)S + H+is 4.4. The absorption spectra of SC(OH)S and SC(O-)S were measured. SC(OH)S disappears by second order with 2k = 1.6 × 109M-1s-1 at pH = 6. The product is a bivalent acid, the spectrum of which was measured. The second pK of this acid is 5.7, its first pK is lower than 4.Both eāq and H react with CS2 to form SCS-. The absorption spectrum of this radical anion was measured. The pK of the equilibriumSCSH ⇄SCS- + H+is about 1.6. In solutions of low H+-concentration, SCS- disappears by second order with 2k = 6.4 × 109M-1s-1. The structure of dithioformic acid is attributed to the resulting product. In solutions of high H+-concentration, SCS- (or SCSH) disappears by a fast first order process, the rate constant of which increases with H+-concentration. The carbeniat neutralizationis believed to be responsible for this process. The rate constant is 5.1 × 107M-1S-1. The spectrum of SC(H)S was measured. This radical disappears by second order with 2k = 7.4 × 109M-1s-1. The spectrum of the resulting product was also determined.It is concluded that the formation of the polymer and of SO4- occurs in processes in which the first products from the attack of eāq, H and OH on CS2 as well as molecules which were built up from these products are involved.

scholarly journals Modeling the Alkaline Hydrolysis of Diaryl Sulfate Diesters: A Mechanistic Study

2020 ◽  
Author(s):  
Klaudia Szeler ◽  
Nicholas Williams ◽  
Alvan C. Hengge ◽  
Shina Caroline Lynn Kamerlin
Keyword(s):  
Alkaline Hydrolysis ◽  
Computational Study ◽  
Transition States ◽  
Building Blocks ◽  
Ester Hydrolysis ◽  
Mechanistic Study ◽  
Phosphate Ester ◽  
Sulfate Ester ◽  
The Impact ◽  
Hydrolysis Of

<div> <div> <div> <p>Phosphate and sulfate esters have important roles as biological building blocks and in regulating cellular processes. However, while there has been substantial experimental and computational investigation of the mechanisms and the transition states involved in phosphate ester hydrolysis, there is far less (in particular computational) work on sulfate ester hydrolysis. Here, we report a detailed computational study of the alkaline hydrolysis of diaryl sulfate diesters, using different DFT functionals and both pure implicit solvation as well as mixed implicit/explicit solvation with varying numbers of explicit water molecules. We consider both the impact of how the system is modeled on computed linear free energy relationships (LFER) and the nature of the transition states. Although our calculations consistently underestimate the absolute activation free energies, we obtain good agreement with experimental LFER data when using pure implicit solvent, and excellent agreement with experimental kinetic isotope effects for all models used. Our calculations suggest that the hydrolysis of sulfate diesters proceeds through loose transition states, with minimal bond formation to the nucleophile and with bond cleavage to the leaving group already initiated. Comparison to prior work indicates that these transition states are similar in nature to those of analogous reactions such as the alkaline hydrolysis of neutral arylsulfonate monoesters or charged phosphate diesters and fluorophosphates. Obtaining more detailed insight into the transition states involved assists in understanding the selectivity of enzymes that hydrolyze these reactions; however, this work also highlights the methodological challenges involved in reliably modeling sulfate ester hydrolysis. </p> </div> </div> </div>

The base hydrolysis of coordinated fluorophosphate

1984 ◽  
Vol 37 (10) ◽  
pp. 1999 ◽  
Author(s):  
II Creaser ◽  
RV Dubs ◽  
AM Sargeson
Keyword(s):  
Rate Constant ◽  
Order Rate Constant ◽  
Second Order ◽  
Base Hydrolysis ◽  
Order Rate ◽  
Measured Rate ◽  
Hydrolysis Of

[(NH3)5CoO3PF]+ undergoes base hydrolysis in 0.1-0.3 M NaOH, � = 1.0, at 25�C to generate free FPO32-, F- and [(NH3)4Co(OH)(NH2PO3)] with a second-order rate constant k2 3.3 × 10 mol-1 s-1 where k2 is the composite rate constant for FPO32- release and hydrolysis of F- with the two products being formed in approximately equal amounts. The measured rate constitutes an estimated enhancement of about 1010 over the base hydrolysis of the uncoordinated FPO32- ion under the same conditions when the concentration of the coordinated nucleophile is taken into account.

Micellar Enhanced Base Catalyzed Hydrolysis of Ethyl Acetate Using TTAB

2009 ◽  
Vol 7 (1) ◽  
Author(s):  
Debajyoti Goswami ◽  
Raj Shekhar ◽  
Mihir K Purkait ◽  
Jayanta Kumar Basu ◽  
Sirshendu De
Keyword(s):  
Ethyl Acetate ◽  
Rate Constant ◽  
Competitive Inhibition ◽  
Direct Consequence ◽  
Second Order ◽  
Ammonium Bromide ◽  
Substrate Molecule ◽  
Micellar Phase ◽  
Rate Enhancement ◽  
Hydrolysis Of

Surfactants can increase the low rate of heterogeneous liquid-liquid reactions involving partially miscible substrates through formation of micelles. This is a direct consequence of higher solubilization of substrates by micelles in reaction zones. In this case, rate enhancement of NaOH (base) catalyzed hydrolysis of ethyl acetate was studied. Micelles by cationic surfactant tetradecyl trimethyl ammonium bromide (TTAB) made the rate enhancement. In the presence of NaOH, CMC (critical micellar concentration) of TTAB decreases from its original value and attains the value of 2.97 × 10-4 M. In the absence of TTAB, the second order rate constant increases linearly with temperature. The hydrolysis reaction follows second order kinetics at different temperatures in the presence of different concentrations of TTAB. For a particular temperature, on addition of TTAB beyond CMC, rate constant first increases sharply and then becomes almost constant. At TTAB concentration of 1.485 × 10-3 M, rate constant attains maximum value (2.65 times of rate constant without TTAB) and then it becomes almost constant. The applied model successfully explains change in rate constant due to incorporation of micelles by the addition of TTAB. This model involves certain assumptions like one substrate molecule is solubilized in one micelle; substrate molecule doesn't form a complex with monomer of surfactant; and no competitive inhibition occurs during reaction. Correlations between bulk phase rate constant (k0), micellar phase rate constant (km) and temperature (T) are incorporated into the model for this particular system.

scholarly journals Modeling the Alkaline Hydrolysis of Diaryl Sulfate Diesters: A Mechanistic Study

2020 ◽  
Author(s):  
Klaudia Szeler ◽  
Nicholas Williams ◽  
Alvan C. Hengge ◽  
Shina Caroline Lynn Kamerlin
Keyword(s):  
Alkaline Hydrolysis ◽  
Computational Study ◽  
Transition States ◽  
Building Blocks ◽  
Ester Hydrolysis ◽  
Mechanistic Study ◽  
Phosphate Ester ◽  
Sulfate Ester ◽  
The Impact ◽  
Hydrolysis Of

<div> <div> <div> <p>Phosphate and sulfate esters have important roles as biological building blocks and in regulating cellular processes. However, while there has been substantial experimental and computational investigation of the mechanisms and the transition states involved in phosphate ester hydrolysis, there is far less (in particular computational) work on sulfate ester hydrolysis. Here, we report a detailed computational study of the alkaline hydrolysis of diaryl sulfate diesters, using different DFT functionals and both pure implicit solvation as well as mixed implicit/explicit solvation with varying numbers of explicit water molecules. We consider both the impact of how the system is modeled on computed linear free energy relationships (LFER) and the nature of the transition states. Although our calculations consistently underestimate the absolute activation free energies, we obtain good agreement with experimental LFER data when using pure implicit solvent, and excellent agreement with experimental kinetic isotope effects for all models used. Our calculations suggest that the hydrolysis of sulfate diesters proceeds through loose transition states, with minimal bond formation to the nucleophile and with bond cleavage to the leaving group already initiated. Comparison to prior work indicates that these transition states are similar in nature to those of analogous reactions such as the alkaline hydrolysis of neutral arylsulfonate monoesters or charged phosphate diesters and fluorophosphates. Obtaining more detailed insight into the transition states involved assists in understanding the selectivity of enzymes that hydrolyze these reactions; however, this work also highlights the methodological challenges involved in reliably modeling sulfate ester hydrolysis. </p> </div> </div> </div>

The hydrolysis of an activated ester by a tris(4,5-di-n-propyl-2-imidazolyl)phosphine-Zn2+ complex in neutral micellar medium as a model for carbonic anhydrase

2002 ◽  
Vol 80 (2) ◽  
pp. 183-191 ◽  
Author(s):  
Terry B Koerner ◽  
R S Brown
Keyword(s):  
Carbonic Anhydrase ◽  
Rate Constant ◽  
Titration Curve ◽  
Order Rate Constant ◽  
Second Order ◽  
Slow Step ◽  
Order Rate ◽  
Brij 35 ◽  
Triton X ◽  
Hydrolysis Of

The properties of tris(4,5-di-n-propyl-2-imidazolyl)phosphine–M2+ complexes (3–M2+, M = Zn, Co) in neutral micellar media of Brij-35 and Triton X-100 have been studied in water with respect to their quantitative potenti metric titration, Co2+-visible absorption spectra, and ability of the 3–Zn2+ complex to promote the hydrolysis of the activated ester, p-nitrophenyl acetate (PNPA). Potentiometric titration of the 3–M2+(CIO4–)2 complexes in 20 mM Brij-35 media yields a steep titration curve indicative of the cooperative consumption of two hydroxides, with computed pK1 and pK2 values of 8.75 and 6.25, respectively, and the midpoint of the titration curve (pKapp) being 7.50. A similar titration of the Co2+ complex also indicates cooperative consumption of two HO–, and this is tied to the formation of a 4- or 5-coordinate complex, pKapp ~ 7.3–7.4. The cooperativity is explained in terms of sequential replacement of the two CIO4– ions associated with the 3–M2+ to eventually yield 3–M2+–HO–/(HO–(H2O)n) having the first hydroxide ligated to the metal ion and the second associated as an ion pair. The 3–Zn2+ complex catalyzes the hydrolysis of PNPA in 20 mM Brij-35 and 40 mM Triton X-100. Plots of the observed second order rate constant (k2) vs. pH in Brij-35 increase linearly with pH and plateau to a value of k2max = 0.86 M–1 s–1, with a kinetic pKa of 8.7. These data are analyzed by a process wherein the 3–Zn2+–HO– is kinetically active in the rate-limiting step of the reaction, while the ion-paired (HO–(H2O)n) exists as a spectator to the slow step, possibly promoting rapid breakdown of a tetrahedral intermediate. Analysis of the kinetic data in terms of a model that accounts for the partitioning of PNPA between water and hydrophobic micellar pseudophase indicates that the second-order rate constant of the micelle-bound ester is augmented by 45-fold due to loading of the PNPA substrate into the micelle. Key words: Brij-35, TritonX-100, neutral micelle, carbonic anhydrase model, kinetics, potentiometric titrations, catalysis, p-nitrophenyl acetate hydrolysis.

Elucidating cyclic AMP signaling in subcellular domains with optogenetic tools and fluorescent biosensors

2019 ◽  
Vol 47 (6) ◽  
pp. 1733-1747 ◽  
Author(s):  
Christina Klausen ◽  
Fabian Kaiser ◽  
Birthe Stüven ◽  
Jan N. Hansen ◽  
Dagmar Wachten
Keyword(s):  
Cyclic Amp ◽  
Adenosine Monophosphate ◽  
Adenylyl Cyclases ◽  
Temporal Precision ◽  
Fluorescent Biosensors ◽  
Subcellular Domains ◽  
Spatio Temporal ◽  
Hydrolysis Of ◽  
Shed Light ◽  
Cyclic Amp Signaling

The second messenger 3′,5′-cyclic nucleoside adenosine monophosphate (cAMP) plays a key role in signal transduction across prokaryotes and eukaryotes. Cyclic AMP signaling is compartmentalized into microdomains to fulfil specific functions. To define the function of cAMP within these microdomains, signaling needs to be analyzed with spatio-temporal precision. To this end, optogenetic approaches and genetically encoded fluorescent biosensors are particularly well suited. Synthesis and hydrolysis of cAMP can be directly manipulated by photoactivated adenylyl cyclases (PACs) and light-regulated phosphodiesterases (PDEs), respectively. In addition, many biosensors have been designed to spatially and temporarily resolve cAMP dynamics in the cell. This review provides an overview about optogenetic tools and biosensors to shed light on the subcellular organization of cAMP signaling.

Determination of rate constants of redox reactions of second order from current-less potential-time curves by a simplified graphical-numerical method

1983 ◽  
Vol 48 (5) ◽  
pp. 1358-1367 ◽  
Author(s):  
Antonín Tockstein ◽  
František Skopal
Keyword(s):  
Numerical Method ◽  
Explicit Form ◽  
Rate Constant ◽  
Optimization Algorithm ◽  
Rate Constants ◽  
Redox Reactions ◽  
Second Order ◽  
Wide Region ◽  
Recurrent Formula

A method for constructing curves is proposed that are linear in a wide region and from whose slopes it is possible to determine the rate constant, if a parameter, θ, is calculated numerically from a rapidly converging recurrent formula or from its explicit form. The values of rate constants and parameter θ thus simply found are compared with those found by an optimization algorithm on a computer; the deviations do not exceed ±10%.

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