Gelatin osmotic pressure

The influence of neutral salts as well as of acids and bases on the swelling of gelatine which we have seen can be attributed to an apparent change in the solvation of the gel fibrils and may be interpreted in the light of Donnan s theory of the effect of a non-diffusible ion on the osmotic pressure differences between the two phases, is likewise to be noted in the alteration of the viscosity and alcohol precipitation values of protein solutions. From the considerations already advanced there should exist two well-defined maxima in the viscosity and alcohol precipitation curves when these properties are plotted as functions of the Ph, the maxima coinciding with the points of maximum dissociation of the salts... 

Under such conditions the theory held satisfactorily in various instances. Loeb, c. g., has shown that the osmotic pressure of a dilute protein solution in dependence on the hydrogen ion concentration, which shows a maximum value at a definite pH, satisfactorily conforms with the theory. If gelatin is allowed to swell in water and then submerged in dilute hydrochloric acid, the degree of swelling reaches a maximum at about the same pH. 

OSMOTIC PRESSURE DIFFERENCE IN DEPENDENCE ON THE PH OF THE EQUILIBRIUM SOLUTION OUTSIDE THE GELATIN GEL. 

Procter and Burton showed that the volume increase of a given quantity of gelatin, when swelling in hydrochloric acid of various concentrations, is proportional to the osmotic pressure difference By an extension of the theory Wilson and... 

Hydrolyzed protein can also be prepared so that the particles are of sufSciently large size to exert colloidal osmotic pressure. Such preparations may act as plasma substitutes. This is really what happens when gelatin solutions are used, as already mentioned. A papain digest of casein has been described by Brinkman (6), which seems to have col-... 

The influence of electrolytes on albumin and gelatin has been determined by Lillie, t The concentration of the electrol3>te was made the same in both the outer and the inner liquids. The hundreds of experiments that he carried out all go to show that electrolytes having a precipitating effect on the colloid diminish the osmotic pressure. In cases, on the other hand, where the electrolyte causes swelling or distention, and subsequent dissolution of the colloid, the osmotic pressure is increased. The law of Hofmeister and Paal was confirmed, which states that salts having an intense precipitating effect... 

The dependence of the osmotic pressure upon the temperature is of interest. But here the same law obtains, namely that any circumstances causing the particles to unite diminish the pressure. With colloidal iron oxide a rise of temperature lessens the osmotic pressure. With many other colloidal substances, such as gelatin, raising the temperature increases the number of particles and therefore the osmotic pressure becomes greater. 

Nonelectrolytes show little influence on the osmotic pressure of protein or gelatin solutions. Cane sugar, dextrose, glycerine, urea, each to the amount of 1.25 per cent, were added to a gelatin solution. The column stood at 6.2 mm. without the addition. Urea raised it to 7.3, while glycerine and dextrose gave 5.8 and 5.9 respectively. The effect of the addition on egg albumin can be seen in Table 35. 

Proline ProKne is present in most proteins in amounts of 4-7% the average content is 4.6%. Its content in the component of wheat gluten, gliadin, is about 10%, and about 12% of proline contains casein. Proline content in gelatine can be up to 13%. In bacteria, plants and animals it also plays a role as an osmoprotectant that helps stabilise proteins and ceU membranes from the damaging effect of high osmotic pressure. 

Bovine serum albumin (mol. wt. 6.7 x [osmotic pressure], isoelectric pH 5.6), acacia (mol. wt. 2.4 x 10 [56]), Amberlite IR-120P (cation-exchanger), Amber-lite IR-400 (anion-exchanger) and glutaraldehyde were obtained from Sigma Chemicals, USA. Gelatin B (Bloom No. 250, mol. wt. 4.6 x lO" [osmotic pressure], isoelectric pH 4.8), was obtained from Gelatin Products Ltd, U.K. 

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