Gelatin isoelectric point

The swelling of gels is markedly affected by the presence of electrolytes, this effect being a minimum at the isoelectric point of the material. In general, sulphates, tartrates, etc. inhibit swelling, while iodides and thiocyanates promote the swelling. Thus gelatine disperses completely in iodide solution even at low temperatures. 

Gelatin B from cow bone was supplied by Britannia Lab Argentine with isoelectric point of 5.10. Gelatin was dried and sealed in zip plastic bags and then kept in desiccators. Finally, gelatin was dissolved in distilled water preparing a solution of 0.25, 0.5, 0.75 and 1% (wt.). 

Gelatins are classified according to whether an acid or an alkali is used in the final preextraction step. If an acid solution is used as the final solvent, type-A gelatin (acid process) is obtained. In case of alkali as the final solvent, type-B gelatin (alkali process) is obtained. Type-A gelatin s isoelectric point is higher compared to that of type-B gelatin, as a... 

The effect of pH on the intrinsic viscosity testing gives a minimum at the isoelectric point at pH 5.1 for gelatin B to pH 9.1 for gelatin A. from electroviscous effect analysis shows that 0.001 M ionic strength the hydrodynamic radius is at its maximum. 

Kermack and Wright Biochem. J. XVII. 635,1923) have shown that gelatine at a of 4 T exerts but little protective power on a negative gum benzoin sol, acid gelatine precipitates the colloid in small concentrations whilst alkaline gelatine protects it. Similar observations have been made by Zsigmondy on the effect of casein on gold, but its exact isoelectric point was not established. 

Some like casein, salt free globulin and acid albumin are not heavily solvated in solution and are thus readily precipitated at the isoelectric point in a manner similar to the suspensions already considered. Others, e.g. glutin, gelatine and natural albumin, are solvated like silica which at the isoelectric point are not necessarily precipitated being maintained in the sol form by the solvent. On removal of the stabilising water however by the addition of alcohol or neutral salts precipitation will occur and this most readily at the isoelectric point. 

Gelatine is an amphoteric electrolyte (Procter, J.G.S. cv. 313, 1914 Loeb, Jour. Gen. Physiol, i. 483, 551, 1918-1919 I. 39, 237, 363) having an isoelectric point at Ph = 4 7-6 0. On the alkaline side salts or gelatinates, e.g. calcium gelatinate, are formed, whilst on the acid side we obtain soluble gelatine salts, e.g. gelatine chloride, whilst isoelectric gelatine is apparently almost insoluble in water. ... 

It will be noticed that all the properties of the gel with the exception of the turbidity and foam have minimum values at or near the isoelectric point P = 4 7, whilst these two attain their maximum values at this point. Evidently as the data for the swelling and viscosity indicate the hydration of the gelatine particles is at a minimum at the isoelectric point (see Chiari, Bioohem. Zeit xxxili. 167, 1911) where as indicated by the alcohol number it is most readily precipitated from solutions to form large aggregates to which the turbidity and the foam formation are due. 

The swelling of gelatine is, as has been noted, a minimum at the isoelectric point and increases on the addition of either acids or bases as well as on the addition of certain salts thus with sodium salts the lyotropic series of decreasing swelling power is... 

We must assume that on the immersion of gelatine in a solution of a dilute acid, e.g. HOI, more acid than the isoelectric point Ph = 4 7, the acid diffuses into the interior of the fibrils resulting in the establishment of the following equilibrium ... 

The adsorbance and the thickness of the adsorbed layer increased to a maximum at a pH close to the isoelectric point of the gelatin (pH = 4.8). On the add side of the isoelectric point, these quantities decreased sharply with diminishing pH. On the alkali side they decreased between pH = 5 and 8.5 and were constant above pH = 8.5. 

Gelatin Derived from denatured collagen, its isoelectric point can be manipulated during formation to control charge. It has been modified for extended release of genetic material (61-63)... 

In the study of the accumulation of gelatine and its mixtures with NaDoS it has been established [80] that the maximum degree of accumulation is reached at gelatine/NaDoS ratio of 1.74. This corresponds to formation of gelatine-surfactant complexes [81,82]. The formation of complexes raises considerably foam stability [80]. Under static conditions and using a porous plate cell, the accumulation ratio reaches 100-150 at the isoelectric point of gelatine (pH = 4.8). In the absence of NaDoS, however, and under the optimum conditions (concentration 0.01-0.02% and pH = 4.8), = 10-24. Under dynamic conditions (in a moving... 

Different types of gelatine cannot be mixed as they have different isoelectric points and these different types are referred to by their origin and the agent used for hydrolysis, e.g. acid pigskin gelatine. Limed ossein gelatine is normally produced from cattle bones. 

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