Gel Filtration Of Molecules

[eagle]

Hi, one more question... will post answers to all questions. Dont worry if you can solve them immediately.Neither could I:-)
JFYI, the questions are from Cell Biology ,Alberts.Finally got it from the library.
Gel filtration cromatography separates molecules acording to size.Smller molecules diffuse faster in solution than larger ones,yet smaller molecules migrate slower through a gel-filtration column than larger ones.Explain this paradox.What should happen at very rapid flow rates?

[kpinal]

Gel filtration, or size exclusion, chromatography separates proteins on the basis of their size. The column is packed with a matrix of fine porous beads.

It works somewhat like a sieve, but in reverse. The beads have in them very small holes. As the protein solution is poured on the column, small molecules enter the pores in the beads. Larger molecules are excluded from the holes, and pass quickly between the beads.

These larger molecules are eluted first. The smaller molecules have a longer path to travel, as they get stuck over and over again in the maze of pores running from bead to bead. These smaller molecules, therefore, take longer to make their way through the column and are eluted last.


http://lsvl.la.asu.edu/resources/mam...atography.html