Essential Amino Acid

Amino acids are organic compounds that are the building blocks for proteins (Bruice). They are composed of a carboxylic acid with a protonated amino group and a hydrogen on the alpha carbon (Bruice). Amino acids have various side chains that provide proteins with great structural diversity, and in turn, functional diversity (Bruice). Amino acids can be divided into polar, non-polar, acidic, and basic (Bruice). The amino acids used in this experiment are Phenylalanine, Leucine, Lysine, and Alanine. Phenylalanine, Leucine, and Alanine are all non-polar amino acids; whereas, Lysine is basic (Bruice). Lysine, Leucine, and Phenylalanine are essential for the human body; whereas, Alanine is non-essential (Bruice). Essential amino acids cannot be

The ion exchanger will contain Dowex resin, which is a cation exchange resin with sulfonate groups covalently bound to the surface. Due to the negative charge on the stationary phase, cations will bind to the surface as they flowing through the buffer. All amino acids have an isoelectric point, which is the pH at which they have no net electrical charge (Bruice). Therefore, by changing the pH of the mobile phase, various amino acids will become more or less positively charged and interact with the stationary phase differently. The less positive amino acids will flow through the column rather than sticking to the stationary

The TLC plate is supported by aluminum foil or plastic. This technique uses capillary action to draw the mobile phase up the plate. In this experiment, the mobile phase consists of propanol/acetic acid/water. The purpose of the mobile phase it to carry the components up the stationary phase. Retention factor (Rf) can be calculated once the solvent has reached ¾ way up the plate. Rf is calculated by dividing the distance traveled by the component by the distance traveled by the solvent (Bruice). Rf values of an unknown can be compared to the Rf values of a known substance in order to identify said