In studying a particular bio-molecule (a protein, nucleic acid, carbohydrate, or

Question

In studying a particular bio-molecule (a protein, nucleic acid, carbohydrate, or lipid) in the laboratory, the biochemist first needs to separate it from other biomolecules in the sample—that is, to purify it. Specific puri-fication techniques are described later in the book. However, by looking at the monomeric subunits of a biomolecule, you should have some ideas about the characteristics of the mole-cule that would allow you to separate it from other molecules. For example, how would you separate (a) amino acids from fatty acids and (b) nucleotides from glucose?

Explanation / Answer

A. Amino acids can be separated from lipods by using silica gel column chromatography because amino acids are polar in nature and lipids are non polar.

The amino acids being polar in nature, they will be adsorbed on to the polar stationary phase (silica). The lipids being non-polar in nature, will readily dissolve in the non-polar mobile phase (hexane) without adhering to silica, and will thus elute out of the column with hexane. Once lipids are eluted out and the changing of mobile phase (acetonitrile) will change the interaction to stationary phase and amino acids will be eleuted. By doing this we can detach the amino acids from from the silica and dissolve in the polar solvent, acetonitrile, and get eluted out of the amino acids from colum.

B.

Nucleotides can be separated from glucose by using ion-exchange chromatography (anionic chromatography because nucleotides do have poshosphate) but glucose do not have charge (neutral ). In this chromatography glucose will be eluted first because it can't bind and nucleotides can bind to colum with ionic interactions (stationary phase should have positive charge). By changing of mobile phase like more negative charge molecule and it can replace the bound nucleotide and it will be eluted later.

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