Biochemistry
Title:Identification of Amino Acids and Proteins
Introduction :
Amino acids are molecules containing an amine group(NH3), a carboxylic acid group(R-C=O-OH) and a side-chain( usually denoted as R) that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen. Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form in a biologically functional way. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues.
In this experiment two sets of tests will be carried out on known samples.
The first set of tests will be the “General Test” which are specific for Amino acids and Proteins. The test with “(1)Ninhydrin” is a test used to distinguish Amino acids and proteins from other structures like carbohydrate in theory the Ninhydrin should react with α-amino acids (–NH2) in proteins giving a purple coloured complex. The “(2)Buriet Test “ is a test used to differentiate between proteins and Amino acids,the buriet reagent which consists of copper sulphate in a strong base reacts with the peptide bonds in proteins to from a buriet complex which is a blue to violet colour. Although this complex needs at least two peptide bonds to occur.
The second set of tests are the “Specific Tests”,this involves carrying out three separate tests. The first being the “(3)Test for Aromatic Amino Acids” which is used to differentiate between aromatic and non aromatic amino acids. In theory what should happen is that the nitric acid and ammonia react with the aromatic ring and gives a coloured salt compound. When Nitric acid is heated with a protein like tyrosine it gives off a yellow colour ,or tryptophan and orange colour this is down to nitration. This is why this test is used for the presence of an activated benzene ring. The “(4) Test for sulphur”this
Introduction :
Amino acids are molecules containing an amine group(NH3), a carboxylic acid group(R-C=O-OH) and a side-chain( usually denoted as R) that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen. Proteins are biochemical compounds consisting of one or more polypeptides typically folded into a globular or fibrous form in a biologically functional way. A polypeptide is a single linear polymer chain of amino acids bonded together by peptide bonds between the carboxyl and amino groups of adjacent amino acid residues.
In this experiment two sets of tests will be carried out on known samples.
The first set of tests will be the “General Test” which are specific for Amino acids and Proteins. The test with “(1)Ninhydrin” is a test used to distinguish Amino acids and proteins from other structures like carbohydrate in theory the Ninhydrin should react with α-amino acids (–NH2) in proteins giving a purple coloured complex. The “(2)Buriet Test “ is a test used to differentiate between proteins and Amino acids,the buriet reagent which consists of copper sulphate in a strong base reacts with the peptide bonds in proteins to from a buriet complex which is a blue to violet colour. Although this complex needs at least two peptide bonds to occur.
The second set of tests are the “Specific Tests”,this involves carrying out three separate tests. The first being the “(3)Test for Aromatic Amino Acids” which is used to differentiate between aromatic and non aromatic amino acids. In theory what should happen is that the nitric acid and ammonia react with the aromatic ring and gives a coloured salt compound. When Nitric acid is heated with a protein like tyrosine it gives off a yellow colour ,or tryptophan and orange colour this is down to nitration. This is why this test is used for the presence of an activated benzene ring. The “(4) Test for sulphur”this
References: 1. F.R.Milio,Qualitative testing for Amino acids and Proteins,2010,Available at,,http://laposlton.wikispaces.com/file/view/Qualitative+Testing+for+Amino+Acids+%26+Proteins.pdf(Accessed on 2nd of November 2013) 2. ,University of Arizona,Sulphur containing Amino acids ,2003,Available at ,http://www.biology.arizona.edu/biochemistry/problem_sets/aa/Sulfur.html (Accessed on 31st of October 2013) 3. Value @ Amrita,Qualitative Analysis of Amino Acid,2013,Available at ,http://amrita.vlab.co.in/?sub=3&brch=63&sim=1094&cnt=1 (Accessed on 30th October 2013) 4. Test for Amino acids ,F.Senese2010,Available at,http://antoine.frostburg.edu/chem/senese/101/organic/faq/amino-acid-test.shtml (Accessed on 29th October 2013)