4PY013 MOLECULAR BASIS OF LIFE

PROTEIN ASSAY BY BIURET AND FOLIN METHODS

Student Number and Name:1316740
Katerina Koupa | Name of Lab Instructor: Dr. J. Walton | Date of the experiment:06/02/2014 | Date of Report Submission:20/02/2014 |

(Fig.1) Biuret Reagent Structure
ABSTRACT:

This report describes the use of the Biuret and Folin methods of protein assay, to verify the protein concentrations of two unknown solutions. To calculate the protein concentrations of the unknowns, nineteen samples were passed through a spectrophotometer which twelve of them had a known protein concentration and there absorbance levels were found. Then a calibration graph was plot that determines the concentration levels of the unknown samples.

INTRODUCTION:

One of the most typical procedures applied by lab scientist is the protein quantification. Finding protein concentrations in solutions is important in many ways. First of all detecting the levels of a protein in body fluids can result in identifying various diseases. Also protein verification is required for characterization and purification of enzymes. Because of the significance of protein assays laboratories perform this techniques on almost a daily basis.
For this experimental procedure, the Biuret and Folin methods were used to determine the protein concentrations of two unknown samples.

First the Biuret method (Fig.1) is based on the appearance of peptides bonds in proteins. When cupric ions (Cu2+) come in contact with a compound of proteins in a quite alkaline environment a deep violet colour complex results (Fig.2). This complex’s absorbance can be measured by spectrophotometer.

Fig.2 Protein reaction with Biuret reagent and the formation of a violet colored complex when it binds to every amino acid.

Second is