What Is the Exact Mass that iTRAQ® Reagents Add to Peptides?

For research use only. Not for use in diagnostic procedures.

Answer

There are two types of iTRAQ® Reagent kits, 4plex and 8plex; these kits contain isobaric tags that derivatize amine groups for relative and absolute quantification of proteins and peptides.

1) iTRAQ reagents in the 4plex kit: These reagents are numbered 114, 115, 116 and 117, and they add a mass of 145 Da. The exact monoisotopic masses of each reagent can be found on www.unimod.org, and these are calculated from the most abundant natural isotope of each constituent element:

• Reagent 114 adds 144.105918 Da
• Reagent 115 adds 144.099599 Da
• Reagents 116 and 117 add 144.102063 Da

2) iTRAQ reagents in the 8plex kit: These reagents are numbered 113, 114, 115, 116, 117, 118, 119, and 121, and they add a mass of 304 Da. The monoisotopic mass of each 8plex reagent are shown below:

• Reagents 113, 114, 116 & 117 add 304.205360 Da
• Reagents 115, 118, 119 &121 add 304.199040  Da

Note that corresponding 4plex and 8plex reagents (e.g., 113 from the 4plex kit and 113 from the 8plex kit) are different reagents and have different masses.