Relation of Stainability and Electric Potential Differences to the pH Value

Abstract

As shown previously 1 he addition of a water insoluble acid to a fat mixture leads to basophilic staining and a relative positive potential. The addition of a water insoluble base has the opposite effect on both properties. In tissues, basophilic staining is also associated with a positive potential, acidophilic staining with a negative potential. Water immiscibility of the acid or of an added base is essential. By the addition of a water-soluble acid or base both stain ability and e. m. f . are influenced in opposite directions.

An effect of this type is observed in Loeb's gelatin systems,† e. g.,

In this case also the basophilic substance is on the side of the positive pole; as a general rule we may consider that almost any system—

produces an e.m.f. as indicated. A few exceptions to this rule have been observed in certain artificial systems which, however, are composed of substances not likely to occur in tissues in general and hence have a minor biological importance (details about these observations will be reported in a later publication).

According to a recent observation of R. Chambers 2 the nucleus has a higher pH value than the protoplasm indicating a slight alkalinity. This alkalinity, as well as the nuclear content of water-insoluble acids, probably bound to proteins as nucleo-proteins, would explain its basophilic stainability. Consequently, according to our experiments, the nucleus should be electrically positive as expected by G. W. Crile some time ago.

Whether the concomitant changes of stainability and e.m.f. are brought about in tissues chiefly by variations of its water-soluble or of its water-insoluble constituents can not yet be decided.

To prove this point new experiments have been performed. A mixture of equivalent parts of a fatty acid and an oil-soluble amine in a neutral fat or other similar solvent was used. This mixture when shaken with aqueous buffer solutions of varying pH shows the same type of stainability as does gelatin, namely: staining acidophilic below a certain pH value; and basophilic above a certain pH value, forming the following cell system: