Answer to Question #257073 in Organic Chemistry for sissy

Question

in what order would the following globular proteins emerge/eluted on gel filtration of a mixture on Sephadex G200? Ribonuclease (Mr=12,000), aldolase (Mr=159,000), hemoglobin (Mr=64,000), β-lactoglobulin (Mr=36,000), serum albumin (Mr=65,000).

Answer 1

Chromatography media such as the Sephadexes and Sepharoses are called gel filtration or size-exclusion media. The former name suggests that the media are filtering solutes, which in ordinary usage means that it lets small particles through and holds up the bigger ones. The opposite is actually true. ‘Size exclusion’ is a better description of what goes on in these columns. Smaller molecules have more room in which to diffuse because they can fit inside pores in the medium. Since they have more room to wander around in, like a child on a hike who wanders off the path to explore the forest and meadows, thus taking longer to elute. Thus larger proteins are expected to elute from a Sephadex column before smaller ones.