scholarly journals THE REVERSAL OF THE SIGN OF THE CHARGE OF COLLODION MEMBRANES BY TRIVALENT CATIONS

1920 ◽  
Vol 2 (6) ◽  
pp. 659-671 ◽  
Author(s):  
Jacques Loeb
Keyword(s):  
Isoelectric Point ◽  
Chemical Change ◽  
Hydrogen Ions ◽  
Acid Salt ◽  
Protein Film ◽  
Complex Protein ◽  
Alkaline Side ◽  
Trivalent Cations

1. Trivalent cations cause a collodion membrane covered with a protein film to be charged positively while they do not produce such an effect on collodion membranes not possessing a protein film. The same had been found for the reversal of the sign of charge of the membrane by acid. 2. This reversal in the sign of charge of the membrane by trivalent cations occurs on the alkaline side of the isoelectric point of the protein used; while the reversal by acid occurs on the acid side of the isoelectric point. 3. The reversal seems to be due to or to be accompanied in both cases by a chemical change in the protein. The chemical change which occurs when the hydrogen ions reverse the sign of charge of the protein film consists in the formation of a protein-acid salt whereby the H ion becomes part of a complex protein cation; while the chemical change which occurs when trivalent cations reverse the sign of charge of the protein film consists in the formation of an insoluble and therefore sparingly or non-ionizable metal proteinate.

scholarly journals THE REVERSAL OF THE SIGN OF THE CHARGE OF MEMBRANES BY HYDROGEN IONS

1920 ◽  
Vol 2 (5) ◽  
pp. 577-594 ◽  
Author(s):  
Jacques Loeb
Keyword(s):  
Thin Film ◽  
Isoelectric Point ◽  
Positive Charge ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Hydrogen Ions ◽  
Acid Salt ◽  
Hydrogen Ion Concentration ◽  
Protein Film

1. It had been shown in previous papers that when a collodion membrane has been treated with a protein the membrane assumes a positive charge when the hydrogen ion concentration of the solution with which it is in contact exceeds a certain limit. It is pointed out in this paper that by treating the collodion membrane with a protein (e.g. oxyhemoglobin) a thin film of protein adheres to the membrane and that the positive charge of the membrane must therefore be localized in this protein film. 2. It is further shown in this paper that the hydrogen ion concentration, at which the reversal in the sign of the charge of a collodion membrane treated with a protein occurs, varies in the same sense as the isoelectric point of the protein, with which the membrane has been treated, and is always slightly higher than that of the isoelectric point of the protein used. 3. The critical hydrogen ion concentration required for the reversal seems to be, therefore, that concentration where enough of the protein lining of the membrane is converted into a protein-acid salt (e.g. gelatin nitrate) capable of ionizing into a positive protein ion (e.g. gelatin) and the anion of the acid used (e.g. NO3).

scholarly journals THE ISOELECTRIC POINT OF RED BLOOD CELLS AND ITS RELATION TO AGGLUTINATION

1921 ◽  
Vol 3 (3) ◽  
pp. 309-323 ◽  
Author(s):  
Calvin B. Coulter
Keyword(s):  
Red Blood Cells ◽  
Isoelectric Point ◽  
Blood Cells ◽  
Inorganic Ions ◽  
Immune Serum ◽  
Ion Concentration ◽  
Normal Cells ◽  
Hydrogen Ion Concentration ◽  
Alkaline Side ◽  
Chlorine Ions

1. The movement of normal and sensitized red blood cells in the electric field is a function of the hydrogen ion concentration. The isoelectric point, at which no movement occurs, corresponds with pH 4.6. 2. On the alkaline side of the isoelectric point the charge carried is negative and increases with the alkalinity. On the acid side the charge is positive and increases with the acidity. 3. On the alkaline side at least the charge carried by sensitized cells is smaller and increases less rapidly with the alkalinity than the charge of normal cells. 4. Both normal and sensitized cells combine chemically with inorganic ions, and the isoelectric point is a turning point for this chemical behavior. On the acid side the cells combine with the hydrogen and chlorine ions, and in much larger amount than on the alkaline side; on the alkaline side the cells combine with a cation (Ba), and in larger amount than on the acid side. This behavior corresponds with that found by Loeb for gelatin. 5. The optimum for agglutination of normal cells is at pH 4.75, so that at this point the cells exist most nearly pure, or least combined with anion and cation. 6. The optimum for agglutination of sensitized cells is at pH 5.3. This point is probably connected with the optimum for flocculation of the immune serum body.

scholarly journals Fractionation of chicken egg proteome by isoelectric point in liquid phase

2014 ◽  
pp. 39-42
Author(s):  
Gabriella Gulyás ◽  
András Jávor ◽  
Tünde Radócz ◽  
Ádám Simon ◽  
Levente Czeglédi
Keyword(s):  
Liquid Phase ◽  
Isoelectric Point ◽  
Proteome Analysis ◽  
Egg Yolk ◽  
Animal Science ◽  
Complex Protein ◽  
Sample Purification ◽  
Protein Discovery ◽  
Optimisation Procedure ◽  
Proteomic Methods

The application of proteomics is relevant to physiology, reproduction, immunology, muscle and lactational biology in animal science, altough its use is still limited. One of the greatest challenges of proteome analysis is the reproducible fractionation of the complex protein mixtures. The fractionation methods can increase the probability of biomarker protein discovery. The fractionation by liquid-phase isoelectric focusing is one of the prefractionation methods. As a result, protein fractions can be easily collected, pooled and refractionated. There is a lack in the knowledge of gel-based proteomic methods of egg as only a limited number of protocols can be found in the literature, thus sample purification and fractionation require a time consuming optimisation procedure. The aim of this study was to fractionate egg yolk and white proteins by isoelectric point in liquid phase.

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 ADSORPTION OF EGG ALBUMIN ON COLLODION MEMBRANES

1936 ◽  
Vol 19 (6) ◽  
pp. 907-916 ◽  
Author(s):  
Philip Dow
Keyword(s):  
Aqueous Solution ◽  
Experimental Study ◽  
Isoelectric Point ◽  
Protein Concentration ◽  
Adsorption Behavior ◽  
Adsorption From Solutions ◽  
Egg Albumin ◽  
Alkaline Side

An experimental study has been made of the adsorption of purified egg albumin, from aqueous solution, on collodion membranes. At protein concentrations of 4 to 7 per cent apparent saturation values were obtained which resembled closely the results obtained with gelatin, showing a maximum at pH 5.0 and lower values on either side of this region. Over large ranges of protein concentration, however, the curves for the adsorption from solutions removed in either direction from the isoelectric point exhibited a different shape from the hyperbola obtained in the neighborhood of pH 5.0. The addition of NaCl to solutions on the acid side tended to obliterate the effect of the pH difference; on the alkaline side it greatly increased the adsorption. The adsorption at 25° was about twice as great as that at 1°. The theory of the swelling of submicroscopic particles, advanced to account for the adsorption behavior of gelatin, is not sufficient to explain the results obtained with egg albumin. It is suggested that the effect is related to alterations in the forces causing the retention of the protein on the membranes.

scholarly journals ON THE MECHANISM OF OPSONIN AND BACTERIOTROPIN ACTION

1930 ◽  
Vol 13 (6) ◽  
pp. 669-681 ◽  
Author(s):  
Morton McCutcheon ◽  
Stuart Mudd ◽  
Max Strumia ◽  
Balduin Lucké
Keyword(s):  
Surface Properties ◽  
Isoelectric Point ◽  
Immune Serum ◽  
Isoelectric Points ◽  
Alkaline Side

Sensitization with increasing concentrations of homologous immune serum shifts the isoelectric point of the antigens studied progressively to the alkaline side. Antigens maximally sensitized with rabbit sera have shown isoelectric points of pH 5.6 to 5.8. The globulins precipitated or salted out of the same immune sera have been isoelectric at pH 5.1 to 5.2. The combination of antigen with antibody depends of course upon specific affinities; the surface properties of the sensitized antigen, agglutination and phagocytosis depend primarily upon the properties of the sensitizing serum substances combined with and deposited on the antigen surface.

scholarly journals Reversible adsorption of proteins at the oil/water interface I. Preferential adsorption of proteins at charged oil/water interfaces

1946 ◽  
Vol 133 (870) ◽  
pp. 121-121
Keyword(s):  
Sodium Chloride ◽  
Isoelectric Point ◽  
Interfacial Area ◽  
Ammonium Bromide ◽  
Water Interface ◽  
Oil Droplets ◽  
Water Emulsion ◽  
Oil In Water ◽  
Alkaline Side ◽  
Oil Water

The behaviour of positively and negatively charged oil-in-water emulsions, stabilized with hexadecyl trimethyl ammonium bromide and sodium hexadecyl sulphate respectively in the presence of protein solutions has been studied. Under certain conditions proteins will adsorb to a charged oil/water interface. When finely dispersed oil-in-water emulsion was used to provide this oil/water interface, adsorption of protein resulted in flocculation of the oil droplets. Flocculation of emulsion on the addition of protein is pH conditioned and occurred on the acid side of the isoelectric point of the protein with negatively charged and on the alkaline side with positively charged oil globules. No flocculation occurred on the alkaline side of the isoelectric point with a negative emulsion or the acid side with a positive emulsion. The amount of protein required to cause maximum clarification of the subnatant fluid corresponded with that needed to give a firmly gelled protein monolayer at the interface, namely, 2∙5 mg. of protein/sq. m. of interfacial area. With that amount of protein the flocculated oil globules remained discrete and no coalescence or liberation of free oil occurred. If only 1 mg. of protein/sq. m. of interfacial area was added, flocculation was followed by rapid coalescence of oil globules and liberation of free oil. If smaller amounts still were used, no visible change in the dispersion of the oil droplets could be seen macroscopically. With greater amounts than 2∙5 mg. /sq. m. of interfacial area, up to ten times the monolayer concentration was adsorbed to the interface. Sodium chloride affected the flocculation range, and instead of the clear-cut change-over between the positive and negative interfaces at the isoelectric point of the protein, overlapping occurred. 5% sodium chloride shifted the flocculation point about 1 unit of pH . The addition of sodium chloride also altered the point of maximum clarification. Thus with haemoglobin the maximum clarification point was shifted from 2∙5 to 1∙7 mg. /sq. m. of interfacial area by the addition of 1% sodium chloride. The adsorption of protein on to charged oil/water interfaces was reversible. This was best demonstrated with haemoglobin. Thus, haemoglobin was adsorbed at pH 5∙0 to a negative emulsion—the red floccules were washed and transferred to a buffer at pH 10. The haemoglobin was released and the emulsion was redispersed. The effect of adsorption and desorption on the structure of the protein molecule has been studied with haemoglobin. By solubility and colour tests it was shown that the haemoglobin molecule was changed to parahaematin by adsorption and subsequent desorption from a charged oil /water interface. Molecular weight and shape determinations were carried out on the desorbed protein. Two proteins have been separated by this adsorption mechanism. This was demonstrated on a mixture of album in and haemoglobin. Some applications of the flocculation technique are indicated and the significance of the phenomena described are discussed.

scholarly journals AMPHOTERIC COLLOIDS

1919 ◽  
Vol 1 (3) ◽  
pp. 363-385 ◽  
Author(s):  
Jacques Loeb
Keyword(s):  
Osmotic Pressure ◽  
Isoelectric Point ◽  
Volumetric Analysis ◽  
Gelatin Solution ◽  
Cent Solution ◽  
Ph Values ◽  
Alkaline Side ◽  
Previously Treated ◽  
Bromine Number ◽  
Generally True

1. The method of removing the excess of hydrobromic acid after it has had a chance to react chemically with gelatin has permitted us to measure the amount of Br in combination with the gelatin. It is shown that the curves representing the amount of bromine bound by the gelatin are approximately parallel with the curves for the osmotic pressure, the viscosity, and swelling of the gelatin solution. This proves that the curves for osmotic pressure are an unequivocal function of the number of gelatin bromide molecules formed under the influence of the acid. The cc. of 0.01 N Br in combination with 0.25 gm, of gelatin we call the bromine number. 2. The explanation of this influence of the acid on the physical properties of gelatin is based on the fact that gelatin is an amphoteric electrolyte, which at its isoelectric point is but sparingly soluble in water, while its transformation into a salt with a univalent anion like gelatin Br makes it soluble. The curve for the bromine number thus becomes at the same time the numerical expression for the number of gelatin molecules rendered soluble, and hence the curve for osmotic pressure must of necessity be parallel to the curve for the bromine number. 3. Volumetric analysis shows that gelatin treated previously with HBr is free from Br at the isoelectric point as well as on the more alkaline side from the isoelectric point (pH ≧ 4.7) of gelatin. This is in harmony with the fact that gelatin (like any other amphoteric electrolyte) can dissociate on the alkaline side of its isoelectric point only as an anion. On the more acid side from the isoelectric point gelatin is found to be in combination with Br and the Br number rises with the pH. 4. When we titrate gelatin, treated previously with HBr but possessing a pH = 4,7, with NaOH we find that 25 cc. of a 1 per cent solution of isoelectric gelatin require about 5.25 to 5.5 cc. of 0.01 N NaOH for neutralization (with phenolphthalein as an indicator). This value which was found invariably is therefore a constant which we designate as "NaOH (isoelectric)." When we titrate 0.25 gm. of gelatin previously treated with HBr but possessing a pH < 4.7 more than 5.5 cc. of 0.01 N NaOH are required for neutralization. We will designate this value of NaOH as "(NaOH)n," where n represents the value of pH. If we designate the bromine number for the same pH as "Brn" then we can show that the following equation is generally true: (NaOH)n = NaOH (isoelectric) + Brn. In other words, titration with NaOH of gelatin (previously treated with HBr) and being on the acid side of its isoelectric point results in the neutralization of the pure gelatin (NaOH isoelectric) with NaOH and besides in the neutralization of the HBr in combination with the gelatin. This HBr is set free as soon as through the addition of the NaOH the pH of the gelatin solution becomes equal to 4.7. 5. A comparison between the pH values and the bromine numbers found shows that over 90 per cent of the bromine or HBr found was in our experiments in combination with the gelatin.

scholarly journals ELECTROKINETIC PHENOMENA

1933 ◽  
Vol 16 (3) ◽  
pp. 457-474 ◽  
Author(s):  
Janet Daniel
Keyword(s):  
Dielectric Constant ◽  
Ethyl Alcohol ◽  
Isoelectric Point ◽  
Protein Film ◽  
Electrokinetic Phenomena ◽  
Water Solutions ◽  
Flat Surfaces ◽  
Electrophoretic Mobilities ◽  
Alcohol Water ◽  
Ion Activities

1. The electrophoretic velocities of gelatin-, egg-albumin-, and gliadin-covered quartz particles in various alcohol-water solutions are, within the limits employed in usual experimental procedures, proportional to the field strength. 2. The electrophoretic mobilities of small, irregularly shaped quartz particles covered with an adsorbed film of protein in alcohol-water solutions are equal to the electroosmotic mobilities of the liquid past similarly coated flat surfaces. Hence the size and shape of such particles does not influence their mobilities, which depend entirely on the protein film. 3. The corrected mobility and hence presumably the charge of gelatin-covered quartz particles in solutions containing 35 per cent ethyl alcohol is proportional to the combining power of the gelatin; therefore the gelatin is adsorbed with the active groups oriented toward the liquid. The same is true in 60 per cent alcohol. 4. The charge calculated by means of the Debye-Henry approximation from the mobility of gelatin in solutions containing up to 35 per cent ethyl alcohol is, in the neighborhood of the isoelectric point, proportional to the combining power of the gelatin. Therefore the dielectric constant and the viscosity of the bulk of the medium may be used in the Debye-Henry approximation Q = 6 π η r vm (1 + κ r) to predict changes in charge from mobility. 5. In the neighborhood of the isoelectric point gelatin is probably completely ionized in buffered ethyl alcohol-water mixtures up to 60 per cent alcohol. 6. In the presence of ethyl alcohol the isoelectric point of gelatin is shifted toward smaller hydrogen ion activities. This shift, like that caused by alcohol in the isoelectric points of certain amino acids, is approximately linearly related to the dielectric constant of the medium.

scholarly journals Reversible adsorption of proteins at the oil/water interface I. Preferential adsorption of proteins at charged oil/water interfaces

1945 ◽  
Vol 184 (996) ◽  
pp. 102-115 ◽  
Keyword(s):  
Sodium Chloride ◽  
Isoelectric Point ◽  
Interfacial Area ◽  
Ammonium Bromide ◽  
Water Interface ◽  
Oil Droplets ◽  
Water Emulsion ◽  
Oil In Water ◽  
Alkaline Side ◽  
Oil Water

The behaviour of positively and negatively charged oil-in-water emulsions, stabilized with hexadecyl trimethyl ammonium bromide and sodium hexadecyl sulphate respectively in the presence of protein solutions has been studied. Under certain conditions proteins will adsorb to a charged oil/water interface. When finely dispersed oil-in-water emulsion was used to provide this oil/water interface, adsorption of protein resulted in flocculation of the oil droplets. Flocculation of emulsion on the addition of protein is pH conditioned and occurred on the acid side of the isoelectric point of the protein with negatively charged and on the alkaline side with positively charged oil globules. No flocculation occurred on the alkaline side of the isoelectric point with a negative emulsion or the acid side with a positive emulsion. The amount of protein required to cause maximum clarification of the subnatant fluid corresponded with that needed to give a firmly gelled protein monolayer at the interface, namely, 2·5 mg. of protein/sq.m, of interfacial area. With that amount of protein the flocculated oil globules remained discrete and no coalescence or liberation of free oil occurred. If only 1 mg. of protein/sq.m, of interfacial area was added, flocculation was followed by rapid coalescence of oil globules and liberation of free oil. If smaller amounts still were used, no visible change in the dispersion of the oil droplets could be seen macroscopically. With greater amounts than 2·5 mg./sq.m, of interfacial area, up to ten times the monolayer concentration was adsorbed to the interface. Sodium chloride affected the flocculation range, and instead of the clear-cut change-over between the positive and negative interfaces at the isoelectric point of the protein, overlapping occurred. 5 % sodium chloride shifted the flocculation point about 1 unit of pH. The addition of sodium chloride also altered the point of maximum clarification. Thus with haemoglobin the maximum clarification point was shifted from 2·5 to 1·7 mg./sq.m. of interfacial area by the addition of 1 % sodium chloride. The adsorption of protein on to charged oil/water interfaces was reversible. This was best demonstrated with haemoglobin. Thus, haemoglobin was adsorbed at pH 5·0 to a negative emulsion— the red floccules were washed and transferred to a buffer at pH 10. The haemoglobin was released and the emulsion was redispersed. The effect of adsorption and desorption on the structure of the protein molecule has been studied with haemoglobin. By solubility and colour tests it was shown that the haemoglobin molecule was changed to parahaematin by adsorption and subsequent desorption from a charged oil/water interface. Molecular weight and shape determinations were carried out on the desorbed protein. Two proteins have been separated by this adsorption mechanism. This was demonstrated on a mixture of albumin and haemoglobin. Some applications of the flocculation technique are indicated and the significance of the phenomena described are discussed.

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