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Characterization of Low Affinity Complexes Between Calmodulin and Pyrazine Derivatives by Electrospray Ionization Mass Spectrometry
Author(s) -
Lafitte D.,
Benezech V.,
Bompart J.,
Laurent F.,
Bonnet P. A.,
Chapat J. P.,
Grassy G.,
Calas B.
Publication year - 1997
Publication title -
journal of mass spectrometry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.475
H-Index - 121
eISSN - 1096-9888
pISSN - 1076-5174
DOI - 10.1002/(sici)1096-9888(199701)32:1<87::aid-jms460>3.0.co;2-w
Subject(s) - chemistry , electrospray ionization , calmodulin , adduct , covalent bond , mass spectrometry , carbene , electrospray , stereochemistry , organic chemistry , chromatography , catalysis , calcium
Abstract 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 five carbenes after their loss of a bromine atom. These results strongly confirm 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. © 1997 by John Wiley & Sons, Ltd.