Solution contents:
KOH, CuSO4, Potassium sodium tartarate
Tested for:
Peptide bonds. (Proteins and peptones give positive results)
Theory and observations:
Following compound is formed between the -C-N-C-back bone of the proteins and the copper(II) ions in the solution which results in a violet colour complex.
2. The Ninhydrin Test
Solution contents:
Ninhydrin
Tested for:
Amine group (mainly primary amine groups in proteins, peptones and amino acids)
Theory and observations:
Any primary amino acid will undergo the Ist reaction and will produce a blue colour and secondary amino group containing amino acid, proline will give a yellow/orange colour (II).
3. The Millon’s Test
Solution contents:
Mercury (Hg22+, Hg2+) in nitric acid
Tested for:
Phenol groups (Tyrosine)
Theory and observations:
Firstly the phenol ring is nitrated with conc. Nitric acid and the nitrated product will react with the mercury ions in the solution to give in either a deep red colour solution or precipitate. [Hg2+](Some tyrosine containing proteins will give in a white precipitate [Hg22+] which would turn red when heated.
