What is o-phthaldehyde?

Answer 1

O-phthaldehyde (OPA) is a small fluorscent molecule that reacts with primary amines, predominantly lysines and N-termins amines, in aqueas solutions at room temperature. It is used to determine the total concentration of protein in a sample. OPA can be used within a concentration of 1µg/ml - 1 mg/ml. Because it will react with N-terminus amines, it is a good choice for assays of small peptides that may not have enough amino acids to be detected by Bradford, BCA or Lowry protein assays.