The Edman Degradation Reaction
The peptide to be sequenced is adsorbed onto a solid surface - one common substrate is glass fibre coated with polybrene, a cationic polymer. The Edman reagent, phenylisothiocyanate (PITC), is added to the adsorbed peptide, together with a mildly basic buffer solution of 12% trimethylamine. This reacts with the amine group of the N-terminal amino acid.
The terminal amino acid can then be selectively detached by the addition of anhydrous acid. The derivative then isomerises to give a substituted phenylthiohydantoin which can be washed off and identified by chromatography, and the cycle can be repeated. The efficiency of each step is about 98%, which allows about 50 amino acids to be reliably determined.
Read more about this topic: Protein Sequencing
Famous quotes containing the words degradation and/or reaction:
“Such poverty as we have today in all our great cities degrades the poor, and infects with its degradation the whole neighborhood in which they live. And whatever can degrade a neighborhood can degrade a country and a continent and finally the whole civilized world, which is only a large neighborhood.”
—George Bernard Shaw (1856–1950)
“The excessive increase of anything often causes a reaction in the opposite direction.”
—Plato (c. 427–347 B.C.)