Title: Laboratory Practicals : Determination of total proteins
Course: Biochemistry > Section: Week 6 - Unit 2_4 Proteins

Purpose

Some functional groups in proteins can react to produce characteristically colored products.

The color intensity of the product formed by a particular group varies among proteins in proportion to the number of reacting functional or free groups present and their accessibility to the reagent.

Over to you

This test is specific for the peptide bond. It allows detecting the presence of peptides or proteins in a sample.

Activity

Under alkaline conditions copper ions present in Biuret reagent interact with –CO-NH-groups present in adjacent dipeptide and form a purple colored complex.

This can be measured spectrophotometrically at 540nm. The method is fairly specific and there is little interference with other compound containing – CO-NH-groups like urea and others like reducing sugar that can interact with cupric ions.