Kinetic studies on the rate of hydrolysis of N-ethyl-N′-(dimethylaminopropyl)carbodiimide in aqueous solutions using mass spectrometry and capillary electrophoresis

2002 ◽  
Vol 310 (1) ◽  
pp. 122-124 ◽  
Author(s):  
Q Paula Lei ◽  
David H Lamb ◽  
Ron K Heller ◽  
Anthony G Shannon ◽  
Robert Ryall ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Capillary Electrophoresis ◽  
Aqueous Solutions ◽  
Kinetic Studies ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of

scholarly journals Kinetic studies on the acid hydrolysis of the methyl ketoside of unsubstituted and O-acetylated N-acetylneuraminic acid

1973 ◽  
Vol 133 (4) ◽  
pp. 623-628 ◽  
Author(s):  
A. Neuberger ◽  
Wendy A. Ratcliffe
Keyword(s):  
Sialic Acid ◽  
Acid Hydrolysis ◽  
Model Compound ◽  
Kinetic Studies ◽  
Order Rate Constant ◽  
Neuraminic Acid ◽  
Acetylneuraminic Acid ◽  
Rate Of Hydrolysis ◽  
Ph Range ◽  
Hydrolysis Of

The hydrolysis of the model compound 2-O-methyl-4,7,8,9-tetra-O-acetyl-N-acetyl-α-d-neuraminic acid and neuraminidase (Vibrio cholerae) closely resembled that of the O-acetylated sialic acid residues of rabbit Tamm–Horsfall glycoprotein. This confirmed that O-acetylation was responsible for the unusually slow rate of acid hydrolysis of O-acetylated sialic acid residues observed in rabbit Tamm–Horsfall glycoprotein and their resistance to hydrolysis by neuraminidase. The first-order rate constant of hydrolysis of 2-methyl-N-acetyl-α-d-neuraminic acid by 0.05m-H2SO4 was 56-fold greater than that of 2-O-methyl-4,7,8,9-tetra-O-acetyl-N-acetyl -α-d-neuraminic acid. Kinetic studies have shown that in the pH range 1.00–3.30, the observed rate of hydrolysis of 2-methyl-N-acetyl-α-d-neuraminic acid can be attributed to acid-catalysed hydrolysis of the negatively charged CO2− form of the methyl ketoside.

scholarly journals Further evidence for an allosteric model for ribonuclease

1976 ◽  
Vol 153 (2) ◽  
pp. 329-337 ◽  
Author(s):  
E J Walker ◽  
G B Ralston ◽  
I G Darvey
Keyword(s):  
Conformational Change ◽  
Equilibrium Dialysis ◽  
Kinetic Studies ◽  
Experimental Systems ◽  
Substrate Analogues ◽  
Multiple Binding ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of ◽  
Cyclic Cmp ◽  
Allosteric Model

Evidence is presented from three experimental systems to support the allosteric model of Walker et al. (1975) (Biochem. J. 147, 425-433) which explains the substrate-concentration-dependent transition observed in the RNAase (ribonuclease)-catalysed hydrolysis of 2‘:3’-cyclic CMP (cytidine 2‘:3’-cyclic monophosphate). 1. Kinetic studies of the initial rate of hydrolysis of 2‘:3’-cyclic CMP show that the midpoint of the transition shifts to lower concentrations of 2‘:3’-cyclic CMP in the presence of the substrate analogues 3′-CMP, 5′-CMP, 3′-AMP, 3′-UMP and Pi; 2′-CMP and 2′-UMP do not cause such a shift. 2. Trypsin-digestion studies show that a conformational change in RNAase to a form less susceptible to tryptic inactivation is induced in the presence of the substrate analogues 3′-CMP, 5′-CMP, 3′-AMP, and 3′-UMP. 2′-CMP, 2′-AMP and 2′-UMP do not induce this conformational change. 3. Equilibrium-dialysis experiments demonstrate the multiple binding of molecules of 3′-CMP, 3′-AMP and 5′-AMP to a molecule of RNAase. 2′-CMP binds the ratio 1:1 over the analogue concentration range studied.

Pathways for angiotensin-(1—7) metabolism in pulmonary and renal tissues

2000 ◽  
Vol 279 (5) ◽  
pp. F841-F850 ◽  
Author(s):  
Alicia J. Allred ◽  
Debra I. Diz ◽  
Carlos M. Ferrario ◽  
Mark C. Chappell
Keyword(s):  
Brush Border Membrane ◽  
Ace Inhibitor ◽  
Renal Cortex ◽  
Combined Treatment ◽  
Kinetic Studies ◽  
Ace Inhibition ◽  
Alternate Pathway ◽  
Renal Brush Border Membrane ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of

Two of the primary sites of actions for angiotensin (ANG)-(1—7) are the vasculature and the kidney. Because little information exists concerning the metabolism of ANG-(1—7) in these tissues, we investigated the hydrolysis of the peptide in rat lung and renal brush-border membrane (BBM) preparations. Radiolabeled ANG-(1—7) was hydrolyzed primarily to ANG-(1—5) by pulmonary membranes. The ANG-converting enzyme (ACE) inhibitor lisinopril abolished the generation of ANG-(1—5), as well as that of smaller metabolites. Kinetic studies of the hydrolysis of ANG-(1—7) to ANG-(1—5) by somatic (pulmonary) and germinal (testes) forms of rat ACE yielded similar values, suggesting that the COOH-domain is responsible for the hydrolysis of ANG-(1—7). Pulmonary metabolism of ANG-(1—5) yielded ANG-(3—5) and was independent of ACE but may involve peptidyl or dipeptidyl aminopeptidases. In renal cortex BBM, ANG-(1—7) was rapidly hydrolyzed to mono- and dipeptide fragments and ANG-(1—4). Aminopeptidase (AP) inhibition attenuated the hydrolysis of ANG-(1—7) and increased ANG-(1—4) formation. Combined treatment with AP and neprilysin (Nep) inhibitors abolished ANG-(1—4) formation and preserved ANG-(1—7). ACE inhibition had no effect on the rate of hydrolysis or the metabolites formed in the BBM. In conclusion, ACE was the major enzymatic activity responsible for the metabolism of ANG-(1—7) in the lung, which is consistent with the ability of ACE inhibitors to increase the half-life of circulating ANG-(1—7) and raise endogenous levels of the peptide. An alternate pathway of metabolism was revealed in the renal cortex, where increased AP and Nep activities, relative to ACE activity, promote conversion of ANG-(1—7) to ANG-(1—4) and smaller fragments.

Kinetic studies on the imines derived from reaction of 2-Amino-2-hydroxymethylpropane-1,3-diol with 2-Hydroxybenzaldehyde and with 1-Hydroxy-2-naphthaldehyde. Hydrolysis kinetics, and evidence for catalysis by the phenolate (ortho-O-) group in the imine formation reaction

1983 ◽  
Vol 36 (11) ◽  
pp. 2327 ◽  
Author(s):  
RMB Singh ◽  
L Main
Keyword(s):  
Deuterium Oxide ◽  
Kinetic Studies ◽  
Base Catalysis ◽  
Rate Coefficients ◽  
Contributing Factors ◽  
Formation Reaction ◽  
Rate Of Hydrolysis ◽  
Rate Profile ◽  
Solvent Isotope ◽  
Hydrolysis Of

pH-rate profiles are reported for the hydrolysis of 2-[[{2-hydroxy-1,1-di(hydroxymethyl)ethyl}-imino]methyl]phenol (1) and 1-[[{2-hydroxy-1,1-di(hydroxymethyl)ethyl}imino]methyl]-2-naphthol (2). Rate coefficients for possible contributing reactions are established and compared. Measurement of the rate of hydrolysis in deuterium oxide of (1) in the neutral plateau region of the pH-rate profile shows that the imine (1) is about 1.6 times more reactive in H2O than in D2O, and possible contributing factors to this solvent isotope effect are considered. Also reported are rate data for formation of (1) from 2-amino-2-hydroxymethylpropane-1,3-diol and 2-hydroxybenzaldehyde which show the latter to be almost as reactive in the anionic as in the neutral form; this suggests a base catalysis role by the phenolate oxygen in imine formation.

scholarly journals Antitumour Metallocenes: Effect of DMSO on the Stability of Cp2TiX2 and Implications for Anticancer Activity

1998 ◽  
Vol 5 (4) ◽  
pp. 207-215 ◽  
Author(s):  
George Mokdsi ◽  
Margaret M. Harding
Keyword(s):  
Nmr Spectroscopy ◽  
Aqueous Solutions ◽  
Anticancer Activity ◽  
Active Species ◽  
Aromatic Rings ◽  
Cyclopentadienyl Ligands ◽  
Rate Of Hydrolysis ◽  
The Stability ◽  
Rapid Hydrolysis ◽  
Hydrolysis Of

The rate of hydrolysis of the aromatic rings of Cp2TiX2 [X = CI 1, O2CCCl3  8 and O2CCH2NH3Cl  13], in aqueous solutions, 10%DMSO and 100% DMSO have been studied by H1NMR spectroscopy. Rapid hydrolysis of both the carboxylate and cyclopentadienyl ligands in Cp2TiX2[X = O2CCCl3,O2CCH2NH3Cl] occurs in DMSO to give biologically inactive species. The rate of these reactions are concentration dependent as dilution of these samples with saline or water to give the therapeutic conditions of 10%DMSO/90%H2O slows the hydrolysis chemistry. In contrast, samples of Cp2TiX2 [X = CI 1, O2CCH2NH3Cl  13], dissolved in water give solutions containing the presumed antitumour active species in which the halide or glycine ligands have been hydrolysed but the Cp rings remain metal bound.

Speciation of the oxidation states of plutonium in aqueous solutions by UV/Vis spectroscopy, CE-ICP-MS and CE-RIMS

2007 ◽  
Vol 95 (8) ◽  
Author(s):  
S. Bürger ◽  
N. L. Banik ◽  
R. A. Buda ◽  
Jens Volker Kratz ◽  
B. Kuczewski ◽  
...  
Keyword(s):  
Mass Spectrometry ◽  
Capillary Electrophoresis ◽  
Aqueous Solutions ◽  
Inductively Coupled Plasma ◽  
Oxidation States ◽  
Charge Ratio ◽  
Inductively Coupled ◽  
Icp Ms ◽  
Vis Spectroscopy ◽  
Plasma Mass Spectrometry

For the speciation of the plutonium oxidation states in aqueous solutions, the online coupling of capillary electrophoresis (CE) with inductively coupled plasma mass spectrometry (ICP-MS) has been developed. Depending on the radius/electrical charge ratio, the oxidation states III, IV, V, and VI of plutonium are separated by CE, based on the different migration times through the capillary and are detected by ICP-MS. The detection limit is 20 ppb,

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