Characterization of Low Affinity Complexes Between Calmodulin and Pyrazine Derivatives by Electrospray Ionization Mass Spectrometry

✍ Scribed by Lafitte, D.; Benezech, V.; Bompart, J.; Laurent, F.; Bonnet, P. A.; Chapat, J. P.; Grassy, G.; Calas, B.

• Publisher: John Wiley and Sons
• Year: 1997
• Tongue: English
• Weight: 348 KB
• Volume: 32
• Category: Article
• ISSN: 1076-5174
• DOI: 10.1002/(sici)1096-9888(199701)32:1<87::aid-jms460>3.0.co;2-w

✦ Synopsis

Electrospray ionization mass spectrometry (ESIMS) was used to study the weak non-covalent interactions occurring between 6-bromo-3-(hydroxymethyl)-8-(methylamino)imidazo [ 1,2-a ] pyrazine (1) and calmodulin. The formation of a 2 : 1 (ligand : protein) complex was observed. Using 2, a (diazomethyl)carbonyl derivative of 1 which under UV irradiation generates a highly reactive carbene entity, calmodulin was photo-labeled and the mass spectrum of the covalent adduct was recorded. Under these circumstances, two species were detected, one corresponding to the binding of calmodulin to four carbenes derived from 2 and another corresponding to calmodulin Ðve carbenes after their loss of a bromine atom. These results strongly conÐrm that ESIMS is a powerful technique for the characterization of low-affinity complexes, even if part of the non-covalent interactions could be lost during the ESI process.