Would AccQ•Tag reagent react at both sites of a compound with primary and secondary amine? - WKB78677

ENVIRONMENT

• Amino acid analysis (AAA)
• Lysine
• Derivatization

ANSWER

In theory, both the primary and secondary amine on the same molecule will react.
In reality, for this to happen repeatedly and reliably, the procedure may need to be optimized.

(See Additional Information.)

ADDITIONAL INFORMATION

Each of the amino acids in our standard will derivatize at different rates depending on chemical properties.

Lysine has two primary amines; when things go well there will be one Lys peak, doubly derivatized. It is the largest peak. When troubleshooting a derivatization problem, a second lysine peak is sometimes observed. The second lysine peak is only derivatized at one amine group (which means something did not go well with the derivatization process—too much sample, degraded reagent, pH too low, sample not mixed correctly . . . ).  This produces a mono-derivatized lysine peak of lower response.

The (second) primary amine on lysine is one of the slowest to react and will not derivatize quickly, yet the reagent peak (which reacted with the OH group on water molecules at 1/1000th the rate of primary and secondary amines) is still the normal size. 

In order to derivatize all primary and secondary amines, the reaction procedure may need to be optimized. Improve or correct one of the following: too much sample, degraded reagent, pH too low, sample not mixed correctly.