An aspiring biochemist needs some help. He is a new technician and is learning about protein separation techniques. He has purchased some ferritin. He performs sodium dodecyl sulfate polyacrylamide electrophoresis (SDS-PAGE) on the enzyme and finds the weight to be about 18 kD. Later, he performs gel exclusion (permeation) chromatography on the enzyme in the presence of some molecular weight standards. He determines the weight of ferritin to be about 432 kD. He is confused. How would you briefly explain his finding to him?