Amino acids are known as the building blocks of all proteins that consists of 20 amino acids which are found in within proteins convey a vast array of chemical versatility. Amino acids are comprised of a carboxyl group and an amino group that attached to the same carbon atom which is the α carbon. They vary in size, structure, electric charge and solubility in water because of the variation in their side chains (R groups). Detection, quantification and identification of amino acids in any sample constitute important steps in the study of proteins. An amino acid that bonded directly to the alpha-carbon have an amino group is called alpha amino acids. Figure 1: Structure of alpha amino acid (http://www.aminoacidsguide.com/)
Ninhydrin test
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This diluted solution will be used in the assay as duplicate samples. Then, 1.0mL of standard glycine solution containing (7.5mg/mL) was diluted to 100mL with water using a volumetric flask. This solution contains 1.0µmole/mL of glycine. 8 tubes were set up according to the following protocol and 2.0mL of ninhydrin reagent was then added to each of the 8 tubes and were placed in a boiling water bath for 20 minutes. After 20 minutes, the tubes from the bath was carefully removed, cooled in a beaker of cold water, then 8.0mL of 50% ethanol was added and mixed well. The absorbance of each tube was determined at 570nm and the absorbance were plotted against amount of standard glycine.
For determination of tyrosine content using Folin & Ciocalteu’s reagent, seven tubes were set up. Then, 1.6mL of 0.5M Na2CO3 was added to each of the tubes and were mixed thoroughly. 0.4mL of the Folin & Ciocalteu’s reagent then were pipette in, mixed thoroughly, and allowed to stand for 10 minutes. The absorbance of each tubes was determined at 660nm and the absorbance were plotted against amount of standard