Electrophoresis and Protein Separation (5C) Practice Test

A lab separated two recombinant proteins by SDS-PAGE (denaturing) using a 10% polyacrylamide gel at pH 8.3 and 200 V for 30 min. Both proteins were fully reduced and treated with excess SDS. Bands were detected by Coomassie staining.

Table 1. Observed migration distance Protein | Mass (kDa) | Observed migration (mm) R | 20 | 41 S | 60 | 18

Which protein is most likely to migrate faster under these SDS-PAGE conditions, consistent with electrophoresis principles?

A researcher performed SDS-PAGE (pH 8.3) on two proteins D1 and D2 that differ in MW (D1: 15 kDa; D2: 150 kDa). At 120 V for 50 min, D1 migrated 6.5 cm and D2 migrated 1.8 cm. The researcher then doubled the voltage but kept run time the same; both proteins migrated farther, but the distance between their bands (in cm) decreased.

Which factor most likely contributed to the decreased band spacing at higher voltage?