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Narrative
(Blue dextran and hemoglobin are passed through a G-75 gel filtration column. Blue dextran elutes first and the two molecules are separated. When hemoglobin and riboflavin are passed through a G-10 gel filtration column, the hemoglobin elutes first.)

A mixture of blue dextran, which has an average molecular weight of two million, and hemoglobin, which has a molecular weight of 64,000, are loaded onto a gel filtration column. These columns are commonly used to separate very large molecules. This particular column fractionates molecules with molecular weights between 4,000 and 150,000.

Hemoglobin is partially absorbed onto the column matrix, slowing its elution. Dextran is larger than the fractionation range of the gel, and passes through the column first. Hemoglobin elutes later from the column and the two molecules are separated.

The second column fractionates smaller molecules. Riboflavin, which has a molecular weight of 376, and hemoglobin are loaded onto a second column. This column fractionates molecules with molecular weights less than 700. In this case, hemoglobin passes through the column first since it is larger than riboflavin. Riboflavin is absorbed onto the gel matrix and its elution is slower than hemoglobin. The two molecules are eluted at different rates and are separated.