Abstract
The electrophoretic migration of the proteins in rat serum was studied in the apparatus modified by Tiselius from older designs. 1 Toeppler's “Schlieren” method was used for following the movement of the differently charged fractions.
Three different fractions, one albumin and 2 globulins, separate from normal rat serum under the influence of a low difference of potential (about 135 volts, giving about 26 milliamperes current). Electrophoresis was continued as long as 11 hours without the occurrence of any further split in the protein bands. Human and horse sera, 2 studied in this and other laboratories, differ from rat serum in that they contain an albumin and 3 globulin fractions. (Fig. 1.)
Rat serum continued to yield the same number of fractions at different pH values extending on both sides of the isoelectric points of the proteins from pH 4.0 to 7.5. (Fig. 2.) An exception occurs when a globulin is partially precipitated at a pH near its isoelectric point. In this case a fourth fraction appears.
If electrophoresis is carried out at the low potential until the 3 fractions have been well separated and the potential is then raised to 250 or 300 volts (SO to 60 milliamperes current) a disintegration of the 2 globulins takes place. At pH 7.5, the α globulin gives rise to a fraction travelling with greater speed and appearing, consequently, between the albumin and the α globulin. The β globulin yields a fraction moving with less speed, and visible as a rather sharp line following this fraction. At a pH value below the isoelectric point of the globulins, 4.95. the fraction separating from the β globulin precedes it towards the negative electrode; the fraction with its source in the α globulin precedes the albumin towards the positive electrode. These new fractions persist after the voltage is returned to its original value. (Fig. 3.)
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