scholarly journals STUDIES ON THE REGULATION OF OSMOTIC PRESSURE

1922 ◽  
Vol 4 (5) ◽  
pp. 585-589 ◽  
Author(s):  
Walter W. Palmer ◽  
Dana W. Atchley ◽  
Robert F. Loeb
Keyword(s):  
Osmotic Pressure ◽  
Isoelectric Point ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Nacl Solution ◽  
Hydrogen Ion Concentration ◽  
Egg Albumin

Egg albumin, like gelatin, influences the conductivity of a 0.6 per cent NaCl solution in two ways: (a) At an hydrogen ion concentration of about pH 3.0, increasing concentrations increase the conductivity. (b) Near the isoelectric point of albumin and at the pH of the blood, increasing concentrations of albumin decrease the conductivity of the NaCl solution.

scholarly journals AMPHOTERIC COLLOIDS

1918 ◽  
Vol 1 (1) ◽  
pp. 39-60 ◽  
Author(s):  
Jacques Loeb
Keyword(s):  
Physical Properties ◽  
Osmotic Pressure ◽  
Isoelectric Point ◽  
Alkali Treatment ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Neutral Salt ◽  
Sharp Drop ◽  
Hydrogen Ion Concentration ◽  
Alkaline Side

1. It has been shown in this paper that while non-ionized gelatin may exist in gelatin solutions on both sides of the isoelectric point (which lies for gelatin at a hydrogen ion concentration of CH = 2.10–5 or pH = 4.7), gelatin, when it ionizes, can only exist as an anion on the less acid side of its isoelectric point (pH > 4.7), as a cation only on the more acid side of its isoelectric point (pH < 4.7). At the isoelectric point gelatin can dissociate practically neither as anion nor as cation. 2. When gelatin has been transformed into sodium gelatinate by treating it for some time with M/32 NaOH, and when it is subsequently treated with HCl, the gelatin shows on the more acid side of the isoelectric point effects of the acid treatment only; while the effects of the alkali treatment disappear completely, showing that the negative gelatin ions formed by the previous treatment with alkali can no longer exist in a solution with a pH < 4.7. When gelatin is first treated with acid and afterwards with alkali on the alkaline side of the isoelectric point only the effects of the alkali treatment are noticeable. 3. On the acid side of the isoelectric point amphoteric electrolytes can only combine with the anions of neutral salts, on the less acid side of their isoelectric point only with cations; and at the isoelectric point neither with the anion nor cation of a neutral salt. This harmonizes with the statement made in the first paragraph, and the experimental results on the effect of neutral salts on gelatin published in the writer's previous papers. 4. The reason for this influence of the hydrogen ion concentration on the stability of the two forms of ionization possible for an amphoteric electrolyte is at present unknown. We might think of the possibility of changes in the configuration or constitution of the gelatin molecule whereby ionized gelatin can exist only as an anion on the alkaline side and as a cation on the acid side of its isoelectric point. 5. The literature of colloid chemistry contains numerous statements which if true would mean that the anions of neutral salts act on gelatin on the alkaline side of the isoelectric point, e.g. the alleged effect of the Hofmeister series of anions on the swelling and osmotic pressure of common gelatin in neutral solutions, and the statement that both ions of a neutral salt influence a protein simultaneously. The writer has shown in previous publications that these statements are contrary to fact and based on erroneous methods of work. Our present paper shows that these claims of colloid chemists are also theoretically impossible. 6. In addition to other physical properties the conductivity of gelatin previously treated with acids has been investigated and plotted, and it was found that this conductivity is a minimum in the region of the isoelectric point, thus confirming the conclusion that gelatin can apparently not exist in ionized condition at that point. The conductivity rises on either side of the isoelectric point, but not symmetrically for reasons given in the paper. It is shown that the curves for osmotic pressure, viscosity, swelling, and alcohol number run parallel to the curve of the conductivity of gelatin when the gelatin has been treated with acid, supporting the view that these physical properties are in this case mainly or exclusively a function of the degree of ionization of the gelatin or gelatin salt formed. It is pointed out, however, that certain constitutional factors, e.g. the valency of the ion in combination with the gelatin, may alter the physical properties of the gelatin (osmotic pressure, etc.) without apparently altering its conductivity. This point is still under investigation and will be further discussed in a following publication. 7. It is shown that the isoelectric point of an amphoteric electrolyte is not only a point where the physical properties of an ampholyte experience a sharp drop and become a minimum, but that it is also a turning point for the mode of chemical reactions of the ampholyte. It may turn out that this chemical influence of the isoelectric point upon life phenomena overshadows its physical influence. 8. These experiments suggest that the theory of amphoteric colloids is in its general features identical with the theory of inorganic hydroxides (e.g. aluminum hydroxide), whose behavior is adequately understood on the basis of the laws of general chemistry.

scholarly journals AMPHOTERIC COLLOIDS

1918 ◽  
Vol 1 (2) ◽  
pp. 237-254 ◽  
Author(s):  
Jacques Loeb
Keyword(s):  
Isoelectric Point ◽  
Water Solubility ◽  
Biological Significance ◽  
Volumetric Analysis ◽  
The Body ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Sharp Drop ◽  
Hydrogen Ion Concentration ◽  
Alkaline Side

1. It is shown by volumetric analysis that on the alkaline side from its isoelectric point gelatin combines with cations only, but not with anions; that on the more acid side from its isoelectric point it combines only with anions but not with cations; and that at the isoelectric point, pH = 4.7, it combines with neither anion nor cation. This confirms our statement made in a previous paper that gelatin can exist only as an anion on the alkaline side from its isoelectric point and only as a cation on the more acid side of its isoelectric point, and practically as neither anion nor cation at the isoelectric point. 2. Since at the isoelectric point gelatin (and probably amphoteric colloids generally) must give off any ion with which it was combined, the simplest method of obtaining amphoteric colloids approximately free from ionogenic impurities would seem to consist in bringing them to the hydrogen ion concentration characteristic of their isoelectric point (i.e., at which they migrate neither to the cathode nor anode of an electric field). 3. It is shown by volumetric analysis that when gelatin is in combination with a monovalent ion (Ag, Br, CNS), the curve representing the amount of ion-gelatin formed is approximately parallel to the curve for swelling, osmotic pressure, and viscosity. This fact proves that the influence of ions upon these properties is determined by the chemical or stoichiometrical and not by the "colloidal" condition of gelatin. 4. The sharp drop of these curves at the isoelectric point finds its explanation in an equal drop of the water solubility of pure gelatin, which is proved by the formation of a precipitate. It is not yet possible to state whether this drop of the solubility is merely due to lack of ionization of the gelatin or also to the formation of an insoluble tautomeric or polymeric compound of gelatin at the isoelectric point. 5. On account of this sudden drop slight changes in the hydrogen ion concentration have a considerably greater chemical and physical effect in the region of the isoelectric point than at some distance from this point. This fact may be of biological significance since a number of amphoteric colloids in the body seem to have their isoelectric point inside the range of the normal variation of the hydrogen ion concentration of blood, lymph, or cell sap. 6. Our experiments show that while a slight change in the hydrogen ion concentration increases the water solubility of gelatin near the isoelectric point, no increase in the solubility can be produced by treating gelatin at the isoelectric point with any other kind of monovalent or polyvalent ion; a fact apparently not in harmony with the adsorption theory of colloids, but in harmony with a chemical conception of proteins.

scholarly journals THE COLLOIDAL BEHAVIOR OF SERUM GLOBULIN

1922 ◽  
Vol 5 (1) ◽  
pp. 35-44 ◽  
Author(s):  
David I. Hitchcock
Keyword(s):  
Potential Difference ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Serum Globulin ◽  
Hydrogen Ion Concentration ◽  
Egg Albumin ◽  
Electrometric Titration ◽  
Acids And Bases ◽  
Protein Serum ◽  
Colloidal Behavior

1. The globulin prepared from ox serum by dilution and precipitation with carbon dioxide has been found, by electrometric titration experiments, to behave like an amphoteric electrolyte, reacting stoichiometrically with acids and bases. 2. The potential difference developed between a solution of globulin chloride, phosphate, or acetate and a solution of the corresponding acid, free from protein, separated from the globulin by a collodion membrane, was found to be influenced by hydrogen ion concentration and salt concentration in the way predicted by Donnan's theory of membrane equilibrium. In experiments with sodium globulinate and sodium hydroxide it was found that the potential difference could be similarly explained. 3. The osmotic pressure of such solutions could be qualitatively accounted for by the Donnan theory, but exhibited a discrepancy which is explicable by analogy with certain experiments of Loeb on gelatin. 4. The application of Loeb's theory of colloidal behavior, which had previously been found to hold in the case of gelatin, casein, egg albumin, and edestin, has thus been extended to another protein, serum globulin.

scholarly journals THE ISOELECTRIC POINTS OF THE PROTEINS IN CERTAIN VEGETABLE JUICES

1919 ◽  
Vol 2 (2) ◽  
pp. 145-160 ◽  
Author(s):  
Edwin J. Cohn ◽  
Joseph Gross ◽  
Omer C. Johnson
Keyword(s):  
Electric Field ◽  
Isoelectric Point ◽  
The State ◽  
Hydrogen Ion ◽  
Tomato Juice ◽  
Ion Concentration ◽  
Carrot Juice ◽  
Hydrogen Ion Concentration ◽  
Ion Concentrations ◽  
Isoelectric Points

The state in which a protein substance exists depends upon the nature of its combination with acids or bases and is changed by change in the protein compound. The nature of the compound of a protein that exists at any hydrogen ion concentration can be ascertained if the isoelectric point of the protein is known. Accordingly information regarding the isoelectric points of vegetable proteins is of importance for operations in which it may be desirable to change the state of protein substances, as in the dehydration of vegetables. The Protein in Potato Juice.—The hydrogen ion concentration of the filtered juice of the potato is in the neighborhood of 10–7N. Such juice contains the globulin tuberin to the extent of from 1 to 2 per cent. The character of the compound of tuberin that exists in nature was suggested by its anodic migration in an electric field. The addition of acid to potato juice dissociated this compound and liberated tuberin at its isoelectric point. The isoelectric point of tuberin coincided with a slightly lower hydrogen ion concentration than 10–4N. At that reaction it existed most nearly uncombined. The flow of current during cataphoresis was greatest in the neighborhood of the isoelectric point. This evidence supplements that of the direction of the migration of tuberin, since it also suggests the existence of the greatest number of uncombined ions near this point. At acidities greater than the isoelectric point tuberin combined with acid. The compound that was formed contained nearly three times as much acid as was needed to dissociate the tuberin compound that existed in nature. At such acidities tuberin migrated to the cathode. Though never completely precipitated tuberin was least soluble in the juice of the potato in the neighborhood of its isoelectric point. Both the compounds of tuberin with acids and with bases were more soluble in the juice than was uncombined tuberin. The nature of the slight precipitate that separated when potato juice was made slightly alkaline was not determined. The Protein in Carrot Juice.—The isoelectric point of the protein in carrot juice coincided with that of tuberin. Remarkably similar also were the properties of carrot juice and the juice of the potato. Existing in nature at nearly the same reaction they combined with acids and bases to nearly the same extent and showed minima in solubility at the same hydrogen ion concentrations. The greatest difference in behavior concerned the alkaline precipitate which, in the carrot, was nearly as great as the acid precipitate. The Protein in Tomato Juice.—The protein of the tomato existed in a precipitated form near its isoelectric point. Accordingly it was not present to any extent in filtered tomato juice. If, however, the considerable acidity at which the tomato exists was neutralized the protein dissolved and was filterable. It then migrated to the anode in an electric field. The addition of sufficient acid to make the hydrogen ion concentration slightly greater than 10–5N again precipitated the protein at its isoelectric point. At greater acidities migration was cathodic.

scholarly journals THE ELIMINATION OF DISCREPANCIES BETWEEN OBSERVED AND CALCULATED P.D. OF PROTEIN SOLUTIONS NEAR THE ISOELECTRIC POINT WITH THE AID OF BUFFER SOLUTIONS

1922 ◽  
Vol 4 (5) ◽  
pp. 617-619 ◽  
Author(s):  
Jacques Loeb
Keyword(s):  
Aqueous Solution ◽  
Aqueous Solutions ◽  
Isoelectric Point ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Protein Solutions ◽  
Protein Solution ◽  
Hydrogen Ion Concentration ◽  
Buffer Salt ◽  
Buffer Solutions

1. It had been noticed in the previous experiments on the influence of the hydrogen ion concentration on the P.D. between protein solutions inside a collodion bag and aqueous solutions free from protein that the agreement between the observed values and the values calculated on the basis of Donnan's theory was not satisfactory near the isoelectric point of the protein solution. It was suspected that this was due to the uncertainty in the measurements of the pH of the outside aqueous solution near the isoelectric point. This turned out to be correct, since it is shown in this paper that the discrepancy disappears when both the inside and outside solutions contain a buffer salt. 2. This removes the last discrepancy between the observed P.D. and the P. D. calculated on the basis of Donnan's theory of P.D. between membrane equilibria, so that we can state that the P.D. between protein solutions inside collodion bags and outside aqueous solutions free from protein can be calculated from differences in the hydrogen ion concentration on the opposite sides of the membrane, in agreement with Donnan's formula.

scholarly journals SOME CONSEQUENCES OF THE THEORY OF MEMBRANE EQUILIBRIA

1925 ◽  
Vol 9 (1) ◽  
pp. 97-109 ◽  
Author(s):  
David I. Hitchcock
Keyword(s):  
Membrane Potential ◽  
Osmotic Pressure ◽  
Ionization Constant ◽  
Weak Acid ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Weak Base ◽  
Acid Base ◽  
Hydrogen Ion Concentration ◽  
Pass Through

In applying Donnan's theory of membrane equilibria to systems where the non-diffusible ion is furnished by a weak acid, base, or ampholyte, certain new relations have been derived. Equations have been deduced which give the ion ratio and the apparent osmotic pressure as functions of the concentration and ionization constant of the weak electrolyte, and of the hydrogen ion concentration in its solution. The conditions for maximum values of these two properties have been formulated. It is pointed out that the progressive addition of acid to a system containing a non-diffusible weak base should not cause the value of the membrane potential to rise, pass through a maximum, and fall, but should only cause it to diminish. It is shown that the theory predicts slight differences in the effect of salts on the ion ratio in such systems, the effect increasing with the valence of the cation.

scholarly journals ION SERIES AND THE PHYSICAL PROPERTIES OF PROTEINS

1921 ◽  
Vol 3 (3) ◽  
pp. 391-414 ◽  
Author(s):  
Jacques Loeb
Keyword(s):  
Physical Properties ◽  
Osmotic Pressure ◽  
Opposite Sign ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Depressing Effect ◽  
Protein Solution ◽  
Hydrogen Ion Concentration ◽  
Specific Effects ◽  
Protein Ions

1. Ions with the opposite sign of charge as that of a protein ion diminish the swelling, osmotic pressure, and viscosity of the protein. Ions with the same sign of charge as the protein ion (with the exception of H and OH ions) seem to have no effect on these properties as long as the concentrations of electrolytes used are not too high. 2. The relative depressing effect of different ions on the physical properties of proteins is a function only of the valency and sign of charge of the ion, ions of the same sign of charge and the same valency having practically the same depressing effect on gelatin solutions of the same pH while the depressing effect increases rapidly with an increase in the valency of the ion. 3. The Hofmeister series of ions are the result of an error due to the failure to notice the influence of the addition of a salt upon the hydrogen ion concentration of the protein solution. As a consequence of this failure, effects caused by a variation in the hydrogen ion concentration of the solution were erroneously attributed to differences in the nature of the ions of the salts used. 4. It is not safe to draw conclusions concerning specific effects of ions on the swelling, osmotic pressure, or viscosity of gelatin when the concentration of electrolytes in the solution exceeds M/16, since at that concentration the values of these properties are near the minimum characteristic of the isoelectric point.

scholarly journals CHANGES IN THE APPARENT CYTOPLASMIC HYDROGEN ION CONCENTRATION OF AMEBA DUBIA ON INJECTION OF EGG ALBUMIN

1944 ◽  
Vol 28 (2) ◽  
pp. 95-102 ◽  
Author(s):  
A. Marshak
Keyword(s):  
Hydrogen Ion ◽  
Ion Concentration ◽  
Phenol Red ◽  
Alkaline Ph ◽  
Cent Solution ◽  
O2 Uptake ◽  
Marked Rise ◽  
Hydrogen Ion Concentration ◽  
Egg Albumin ◽  
The One

1. Egg albumin when injected into an ameba or discharged into the solution about it raises the apparent pH of the cytoplasm of the ameba. 2. With time the cytoplasm returns to the original pH 6.9 if the nucleus is present. Amebae that have received repeated injections of albumin in some cases extrude their nuclei. In these cells the cytoplasm remains at the more alkaline pH induced by the albumin for at least 12 hours. 3. When a 2 per cent solution of albumin is introduced into a suspension of amebae there is a temporary marked rise in the rate at which CO2 is given off with no corresponding rise in O2 uptake. 4. The results observed can be explained if the albumin discharged onto the surface of the ameba rapidly enters the cell and there becomes distributed in a phase of the cytoplasm other than the one which contains the phenol red.

scholarly journals ELECTRICAL CHARGES OF COLLOIDAL PARTICLES AND ANOMALOUS OSMOSIS

1922 ◽  
Vol 4 (4) ◽  
pp. 463-486 ◽  
Author(s):  
Jacques Loeb
Keyword(s):  
Isoelectric Point ◽  
Salt Solution ◽  
Electrical Transport ◽  
Colloidal Particles ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Trivalent Cation ◽  
Hydrogen Ion Concentration ◽  
Donnan Equilibrium ◽  
Positively Charged

1. It has been shown in previous publications that when solutions of different concentrations of salts are separated by collodion-gelatin membranes from water, electrical forces participate in addition to osmotic forces in the transport of water from the side of the water to that of the solution. When the hydrogen ion concentration of the salt solution and of the water on the other side of the membrane is the same and if both are on the acid side of the isoelectric point of gelatin (e.g. pH 3.0), the electrical transport of water increases with the valency of the cation and inversely with the valency of the anion of the salt in solution. Moreover, the electrical transport of water increases at first with increasing concentration of the solution until a maximum is reached at a concentration of about M/32, when upon further increase of the concentration of the salt solution the transport diminishes until a concentration of about M/4 is reached, when a second rise begins, which is exclusively or preeminently the expression of osmotic forces and therefore needs no further discussion. 2. It is shown that the increase in the height of the transport curves with increase in the valency of the cation and inversely with the increase in the valency of the anion is due to the influence of the salt on the P.D. (E) across the membrane, the positive charge of the solution increasing in the same way with the valency of the ions mentioned. This effect on the P.D. increases with increasing concentration of the solution and is partly, if not essentially, the result of diffusion potentials. 3. The drop in the transport curves is, however, due to the influence of the salts on the P.D. (ϵ) between the liquid inside the pores of the gelatin membrane and the gelatin walls of the pores. According to the Donnan equilibrium the liquid inside the pores must be negatively charged at pH 3.0 and this charge is diminished the higher the concentration of the salt. Since the electrical transport is in proportion to the product of E x ϵ and since the augmenting action of the salt on E begins at lower concentrations than the depressing action on ϵ, it follows that the electrical transport of water must at first rise with increasing concentration of the salt and then drop. 4. If the Donnan equilibrium is the sole cause for the P.D. (ϵ) between solid gelatin and watery solution the transport of water through collodion-gelatin membranes from water to salt solution should be determined purely by osmotic forces when water, gelatin, and salt solution have the hydrogen ion concentration of the isoelectric point of gelatin (pH = 4.7). It is shown that this is practically the case when solutions of LiCl, NaCl, KCl, MgCl2, CaCl2, BaCl2, Na2SO4, MgSO4 are separated by collodion-gelatin membranes from water; that, however, when the salt has a trivalent (or tetravalent?) cation or a tetravalent anion a P.D. between solid isoelectric gelatin and water is produced in which the wall assumes the sign of charge of the polyvalent ion. 5. It is suggested that the salts with trivalent cation, e.g. Ce(NO3)3, form loose compounds with isoelectric gelatin which dissociate electrolytically into positively charged complex gelatin-Ce ions and negatively charged NO3 ions, and that the salts of Na4Fe(CN)6 form loose compounds with isoelectric gelatin which dissociate electrolytically into negatively charged complex gelatin-Fe(CN)6 ions and positively charged Na ions. The Donnan equilibrium resulting from this ionization would in that case be the cause of the charge of the membrane.

scholarly journals ON THE INFLUENCE OF AGGREGATES ON THE MEMBRANE POTENTIALS AND THE OSMOTIC PRESSURE OF PROTEIN SOLUTIONS

1922 ◽  
Vol 4 (6) ◽  
pp. 769-776 ◽  
Author(s):  
Jacques Loeb
Keyword(s):  
Membrane Potential ◽  
Hydrostatic Pressure ◽  
Osmotic Pressure ◽  
Membrane Potentials ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Gelatin Solution ◽  
True Solution ◽  
Hydrogen Ion Concentration ◽  
Donnan Equilibrium

1. It is shown that when part of the gelatin in a solution of gelatin chloride is replaced by particles of powdered gelatin (without change of pH) the membrane potential of the solution is influenced comparatively little. 2. A measurement of the hydrogen ion concentration of the gelatin chloride solution and the outside aqueous solution with which the gelatin solution is in osmotic equilibrium, shows that the membrane potential can be calculated from this difference of hydrogen ion concentration with an accuracy of half a millivolt. This proves that the membrane potential is due to the establishment of a membrane equilibrium and that the powdered particles participate in this membrane equilibrium. 3. It is shown that a Donnan equilibrium is established between powdered particles of gelatin chloride and not too strong a solution of gelatin chloride. This is due to the fact that the powdered gelatin particles may be considered as a solid solution of gelatin with a higher concentration than that of the weak gelatin solution in which they are suspended. It follows from the theory of membrane equilibria that this difference in concentration of protein ions must give rise to potential differences between the solid particles and the weaker gelatin solution. 4. The writer had shown previously that when the gelatin in a solution of gelatin chloride is replaced by powdered gelatin (without a change in pH), the osmotic pressure of the solution is lowered the more the more dissolved gelatin is replaced by powdered gelatin. It is therefore obvious that the powdered particles of gelatin do not participate in the osmotic pressure of the solution in spite of the fact that they participate in the establishment of the Donnan equilibrium and in the membrane potentials. 5. This paradoxical phenomenon finds its explanation in the fact that as a consequence of the participation of each particle in the Donnan equilibrium, a special osmotic pressure is set up in each individual particle of powdered gelatin which leads to a swelling of that particle, and this osmotic pressure is measured by the increase in the cohesion pressure of the powdered particles required to balance the osmotic pressure inside each particle. 6. In a mixture of protein in solution and powdered protein (or protein micellæ) we have therefore two kinds of osmotic pressure, the hydrostatic pressure of the protein which is in true solution, and the cohesion pressure of the aggregates. Since only the former is noticeable in the hydrostatic pressure which serves as a measure of the osmotic pressure of a solution, it is clear why the osmotic pressure of a protein solution must be diminished when part of the protein in true solution is replaced by aggregates.

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