● to determine the different amino acids in protein (specifically the albumin solution) with the use of the different color reaction tests● to detect the presence of proteins in the albumin using the different quantitative color reaction tests

Xanthoproteic TestThe amino acids that contain benzene ring like tyrosine and tryptophan undergo nitration in this test and give yellow color. It is a method that can be used to determine the amount of protein soluble in a solution, using concentrated nitric acid. The test gives a positive result in those proteins with amino acids carrying aromatic groups, especially in the presence of tyrosine. If the test is positive, the proof is neutralized with an alkali, turning dark yellow.

Chemical Reaction:

Glyoxylic Acid Reactions (Hopkins-Cole)It is specific for tryptophan, the only amino acid containing an indole group. The indole ring reacts with glyoxylic acid in the presence of a strong acid to form a violet cyclic product. Tryptophan has an indole nucleus which is responsible for the violet ring found at the junction between the two layers. The indole moiety of tryptophan condenses with aldehydes in acidic condition to yield purple or violet-colored compounds.

Biuret TestIt positively identifies the presence of protein in solution with a deep violet colour. Biuret H2NCONHCONH2 reacts with copper (II) ions in a basic solution to form a deep voilet complex. The biuret test is a chemical test used for detecting the presence of peptide bonds. In the presence of peptides, a copper(II) ion forms a violet-colored coordination complexes in an alkaline solution.

Chemical Reaction:

Ninhydrin TestAmino acid containing a free amino group and a free carboxylic acid group react together with ninhydrin to produce colored product. Protein also contain free amino group on the alpha-carbon and can react with ninhydrin to produce blue purple product. When the amino group is secondary the condensation product is yellow.

Chemical Reaction:

Sakaguchi TestThis reaction used for the detection of amino acid containing the guanidinium group, protein which abundantly contains arginine. Under alkaline conditions, α-naphthol (1-hydroxyl naphthalene) reacts with a mono-substituted guanidine compound like arginine, which upon treatment with hydrobromic or hypochloric produces a characteristic red color.

Chemical Reaction:

Analysis:

The albumin solution showed a positive result in all the Xanthoproteic, Hopkins-Cole, Biuret, Ninhydrin, and Sakaguchi Tests. This means that the albumin solution contains proteins with amino acids carrying aromatic groups that underwent nitration and gave yellow color. It also has tryptophan, which contains an indole group whose indole ring reacted with the glyoxylic acid, forming a violet cyclic product. Furthermore, it contains peptides which reacted with copper (II) ions, which then produced a deep violet complex. It also has a free amino acid group on the α-carbon and reacted with ninhydrin that produced the blue purple color. Guanidinium group (arginine) is also present in the albumin solution and this reacted with α-naphthol upon treatment with hypochlote, producing a red color.

Conclusion:

Proteins are made up of amino acids. Since albumin is a protein, this activity showed that it contains amino acids and other basic protein structures. The albumin solution contains amino acids carrying aromatic groups, tryptophan that contains an indole group, peptides, free amino group, and guanidinium group. All these are characteristics and structures of protein. The different qualitative test helped us determine the various proteins that comprise the albumin solution.