The Slow Hydrolysis of Ferric Chloride in Dilute Solution. II. The Change in Hydrogen Ion Concentration

1938 ◽  
Vol 60 (5) ◽  
pp. 1215-1225 ◽  
Author(s):  
Arthur B. Lamb ◽  
Alfred G. Jacques
Keyword(s):  
Ferric Chloride ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Dilute Solution ◽  
Hydrogen Ion Concentration ◽  
Hydrolysis Of

Mechanistic Information from the Effect of Pressure on the Kinetics of Hydrolysis of Iodopentaaquochromium(III) Ion

1975 ◽  
Vol 53 (24) ◽  
pp. 3697-3701 ◽  
Author(s):  
Milton Cornelius Weekes ◽  
Thomas Wilson Swaddle
Keyword(s):  
Ionic Strength ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
Kinetics Of Hydrolysis ◽  
Rate Of Hydrolysis ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Aqueous Hclo ◽  
Conjugate Base

The rate of hydrolysis of iodopentaaquochromium(III) ion has been measured as a function of pressure (0.1 to 250 MPa) and hydrogen ion concentration (0.1 to 1.0 mol kg−1) at 298.2 K and ionic strength 1.0 mol kg−1 (aqueous HClO4–LiClO4). The volumes of activation for the acid independent and inversely acid dependent hydrolysis pathways are −5.4 ± 0.5 and −1.6 ± 0.3 cm3 mol−1 respectively, and are not detectably pressure-dependent. Consideration of these values, together with the molar volume change of −3.3 ± 0.3 cm3 mol−1 determined dilatometrically for the completed hydrolysis reaction, indicates that the mechanisms of the two pathways are associative interchange (Ia) and dissociative conjugate base (Dcb) respectively.

Protein Dissimilation by Human Salivary-sediment Bacteria

1989 ◽  
Vol 68 (2) ◽  
pp. 124-129 ◽  
Author(s):  
E.C. Reynolds ◽  
P.F. Riley
Keyword(s):  
Histone H3 ◽  
Oral Bacteria ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Ammonium Ion ◽  
Ph Homeostasis ◽  
Hydrogen Ion Concentration ◽  
Plaque Ph ◽  
Sediment Bacteria ◽  
Hydrolysis Of

Proteins of known composition and structural characteristics were incubated (1.0 mglmL) with re-suspended salivary sediment (2.5% vl v) in a lactate-salt medium with an initial pH of 5.2 for two hr at 37°C. Hydrolysis of the proteins was monitored by sodium dodecyl sulfate polyacrylamide gel electrophoresis. Hydrogen ion, amines, and ammonia were measured by use of a combined pH electrode, high performance liquid chromatography, and glutamate dehydrogenase, respectively. Of the proteins studied, the caseins αs1, β, and K and the histones H1 and H3 were extensively hydrolyzed by the salivary-sediment bacteria. The hydrolysis of these proteins was attributed to their relative lack of tertiary (folded) structure. The only amine detected was the polyamine putrescine arising from the catabolism of arginine following the hydrolysis of the arginine-rich histone H3. None of the other proteins extensively hydrolyzed by salivary sediment, although containing arginyl and lysyl residues, served as substrates for putrescine or cadaverine production. Pre-hydrolysis of the arginine-rich histone H3 and poly-L-arginine with trypsin resulted in a marked increase in putrescine produced, suggesting that the salivary-sediment proteolytic activity was not "trypsin-like". Incubation of salivary-sediment bacteria with the caseins and the histone H3 resulted in an increase in ammonium ion concentration and an associated decrease in hydrogen ion concentration. The increase in ammonium ion concentration not attributed to arginine hydrolysis was correlated with the content of glutaminyl plus asparaginyl residues of the proteins. The results suggest that amido nitrogen, in the form of glutaminyl and asparaginyl residues of salivary and dietary proteins, is a potential source of nitrogen for oral bacteria and may also play a role in plaque pH homeostasis.

scholarly journals THE SIGNIFICANCE OF THE HYDROGEN ION CONCENTRATION FOR THE DIGESTION OF PROTEINS BY PEPSIN

1920 ◽  
Vol 3 (2) ◽  
pp. 211-227 ◽  
Author(s):  
John H. Northrop
Keyword(s):  
Enzyme Preparation ◽  
Proteolytic Enzymes ◽  
Quantitative Agreement ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
Enzyme Preparations ◽  
Weak Bases ◽  
Strong Acids ◽  
Hydrolysis Of

The experiments described above show that the rate of digestion and the conductivity of protein solutions are very closely parallel. If the isoelectric point of a protein is at a lower hydrogen ion concentration than that of another, the conductivity and also the rate of digestion of the first protein extends further to the alkaline side. The optimum hydrogen ion concentration for the rate of digestion and the degree of ionization (conductivity) of gelatin solutions is the same, and the curves for the ionization and rate of digestion as plotted against the pH are nearly parallel throughout. The addition of a salt with the same anion as the acid to a solution of protein already containing the optimum amount of the acid has the same depressing effect on the digestion as has the addition of the equivalent amount of acid. These facts are in quantitative agreement with the hypothesis that the determining factor in the digestion of proteins by pepsin is the amount of ionized protein present in the solution. It was shown in a previous paper that this would also account for the peculiar relation between the rate of digestion and the concentration of protein. The amount of ionized protein in the solution depends on the amount of salt formed between the protein (a weak base) and the acid. This quantity, in turn, according to the hydrolysis theory of the salts of weak bases and strong acids, is a function of the hydrogen ion concentration, up to the point at which all the protein is combined with the acid as a salt. This point is the optimum hydrogen ion concentration for digestion, since the solution now contains the maximum concentration of protein ions. The hydrogen ion concentration in this range therefore is merely a convenient indicator of the amount of ionized protein present in the solution and takes no active part in the hydrolysis. After sufficient acid has been added to combine with all the protein, i.e. at pH of about 2.0, the further addition of acid serves to depress the ionization of the protein salt by increasing the concentration of the common anion. The hydrogen ion concentration is, therefore, no longer an indicator of the amount of ionized protein present, since this quantity is now determined by the anion concentration. Hence on the acid side of the optimum the addition of the same concentration of anion should have the same influence on the rate of digestion irrespective of whether it is combined with hydrogen or some other ion (provided, of course, that there is no other secondary effect of the other ion). The proposed mechanism is very similar to that suggested by Stieglitz and his coworkers for the hydrolysis of the imido esters. Pekelharing and Ringer have shown that pure pepsin in acid solution is always negatively charged; i.e., it is an anion. The experiments described above show further that it behaves just as would be expected of any anion in the presence of a salt containing the protein ion as the cation and as has been shown by Loeb to be the case with inorganic anions. Nothing has been said in regard to the quantitative agreement between the increasing amounts of ionized protein found in the solution (as shown by the conductivity values) and the amount predicted by the hydrolysis theory of the formation of salts of weak bases and strong acids. There is little doubt that the values are in qualitative agreement with such a theory. In order to make a quantitative comparison, however, it would be necessary to know the ionization constant of the protein and of the protein salt and also the number of hydroxyl (or amino) groups in the protein molecule as well as the molecular weight of the protein. Since these values are not known with any degree of certainty there appears to be no value at present in attempting to apply the hydrolysis equations to the data obtained. It it clear that the hypothesis as outlined above for the hydrolysis of proteins by pepsin cannot be extended directly to enzymes in general, since in many cases the substrate is not known to exist in an ionized condition at all. It is possible, however, that ionization is really present or that the equilibrium instead of being ionic is between two tautomeric forms of the substrate, only one of which is attacked by the enzyme. Furthermore, it is clear that even in the case of proteins there are difficulties in the way since the pepsin obtained from young animals, or a similar enzyme preparation from yeast or other microorganisms, is said to have a different optimum hydrogen ion concentration than that found for the pepsin used in these experiments. The activity of these enzyme preparations therefore would not be found to depend on the ionization of the protein. It is possible of course that the enzyme preparations mentioned may contain several proteolytic enzymes and that the action observed is a combination of the action of several enzymes. Dernby has shown that this is a very probable explanation of the action of the autolytic enzymes. The optimum hydrogen ion concentration for the activity of the pepsin used in these experiments agrees very closely with that found by Ringer for pepsin prepared by him directly from gastric juice and very carefully purified. Ringer's pepsin probably represents as pure an enzyme preparation as it is possible to prepare. There is every reason to suppose therefore that the enzyme used in this work was not a mixture of several enzymes.

Di Brom Thymol Sulhpone Phthalein as a Reagent for Determining the Hydrogen Ion Concentration of Living Cells

1922 ◽  
Vol 12 (4) ◽  
pp. 781-784 ◽  
Author(s):  
W. R. G. Atkins
Keyword(s):  
Sea Water ◽  
Living Cells ◽  
Marine Organisms ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Toxic Action ◽  
Thymol Blue ◽  
Neutral Salt ◽  
Dilute Solution ◽  
Hydrogen Ion Concentration

1. Brom thymol blue may be used in dilute solution for ascertaining the hydrogen ion concentration of certain marine organisms. It penetrates slowly, but the stained portions remain actively motile, so its toxic action does not appear to be great at the dilutions found serviceable.2. The animals studied gave values from pH6·2 to about pH7·5, though possibly the more alkaline end of the range may be pathological. About pH0·2 should be subtracted from these figures for neutral salt error. The sea water used was initially at pH8·2, corrected.

Naphthylamidases of Sarcina lutea

1971 ◽  
Vol 17 (1) ◽  
pp. 39-45 ◽  
Author(s):  
Francis J. Behal ◽  
Rita T. Carter
Keyword(s):  
Divalent Cations ◽  
Gel Filtration ◽  
Ion Exchange Chromatography ◽  
Exchange Chromatography ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
Substrate Specificities ◽  
Molecular Weights ◽  
Hydrolysis Of

The naphthylamidase isozyme complement of Sarcina lutea was studied. Gel filtration yielded two fractions, Sephadex I and Sephadex II. Sephadex I contained one enzyme generally resembling leucineaminopeptidase. Sephadex II, upon ion exchange chromatography, yielded three isozymes, A, B, and C. These three were characterized with respect to molecular weight, substrate specificities, and effects of hydrogen ion concentration, EDTA, and divalent cation on reaction velocity. The molecular weights are 8.0 × 104, 8.2 × 104, and 9.0 × 104 respectively. Isozymes A and B are neutral naphthylamidases and preferentially catalyze the hydrolysis of alanine-β-naphthylamide (βNA), whereas isozyme C is a basic naphthylamidase and preferentially catalyzes the hydrolysis of lysine and arginine-βNA. The pH optima for the isozymes are 7.6, 7.6, and 6.7, respectively. All of the isozymes are sensitive to the effects of EDTA. Divalent cations activate the enzymes and reverse inhibition caused by EDTA.

THE HYDROLYSIS OF THE CONDENSED PHOSPHATES: II (A). THE ROLE OF THE HYDROGEN ION IN THE HYDROLYSIS OF SODIUM PYROPHOSPHATE: II (B). THE DISSOCIATION CONSTANTS OF PYROPHOSPHORIC ACID

1954 ◽  
Vol 32 (2) ◽  
pp. 174-185 ◽  
Author(s):  
J. D. McGilvery ◽  
Joan Pedley Crowther
Keyword(s):  
Dissociation Constants ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Rate Equations ◽  
Hydrogen Ion Concentration ◽  
Pyrophosphoric Acid ◽  
Condensed Phosphates ◽  
Anionic Species ◽  
Hydrolysis Of

The general rate equations for the hydrolysis of pyrophosphate anion proposed by Muus have been proved to be inapplicable over the pH range 2.0 to 11.0. A general rate equation is proposed which is based on the assumption that each anionic species of pyrophosphoric acid hydrolyzes at a rate which depends on its concentration, and that the only role of the hydrogen ion concentration is to determine the proportion of each species present in the solution. A mechanism for the hydrolysis of pyrophosphate anion is suggested.The dissociation constants of pyrophosphoric acid have been determined at 65.5 °C. for the concentration range 0.08 to 0.18 molar.

THE DEPENDENCE OF THE HYDROLYSIS OF DIAZOACETIC ESTER ON THE HYDROGEN ION CONCENTRATION

1953 ◽  
Vol 31 (5) ◽  
pp. 493-498 ◽  
Author(s):  
A. V. Willi ◽  
R. E. Robertson
Keyword(s):  
Experimental Error ◽  
Salt Effect ◽  
Sodium Perchlorate ◽  
Glass Electrode ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
Diazoacetic Ester ◽  
Hydrolysis Of ◽  
Special Case

The catalytic constants of the H3O+ catalyzed hydrolysis of diazoacetic ester in aqueous solutions containing sodium perchlorate have been determined at three different ionic strengths. A spectrophotometric method was used to follow the rate. The results indicate a strong positive salt effect. Measurements at the ionic strength μ = 0.110 were carried out in the pH region from 1.97 to 5.19. For solutions containing less than 10−3 N perchloric acid the pH data were taken from measurements with a. glass electrode in the kinetic cell. Within the limits of experimental error no deviations from proportionality between rate and [H3O+] were found. This result is important in connection with our findings for the benzalaniline hydrolysis since it tests the methods applied and proves that the benzalaniline example with deviations from linearity between rate and [H3O+] is a special case. The diazoacetic ester hydrolysis is not catalyzed by acetic acid molecules.

Sign in / Sign up

Export Citation Format

Share Document