- Biuret method
- Won’t react with anything smaller than tri-peptides.
Isn’t overly sensitive.
Linear Range doesn’t go below 1.0 or 2.0 g/dL.
Reagents: Copper Sulfate (cupric form) in NaOH, KI (keeps in cupric form), and gobs of NaK-Tartrate (to maintain suspension of proteins)
Cupric ion interacts with two adjacent amide bonds (which is why there must be at least three peptides).
The number of amides available is the limiting factor, so the degree of the reaction indicates amount of bonds.