Multiple Ion Isolation Applications in FT-ICR MS:  Exact-Mass MSn Internal Calibration and Purification/Interrogation of Protein−Drug Complexes

• Published in: Analytical chemistry (Washington) Vol. 74; no. 15; pp. 3877 - 3886
• Main Authors: KRUPPA, Gary, SCHNIER, Paul D., TABEI, Keiko, VAN ORDEN, Steven, SIEGEL, Marshall M.
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01.08.2002
• Subjects: Analysis; Angiotensin I - analysis; Angiotensin I - pharmacokinetics; Animals; Binding Sites; Biological and medical sciences; Bradykinin - analysis; Bradykinin - metabolism; Calibration; Chemistry; Cyclotrons; Drugs; ErbB Receptors - analysis; ErbB Receptors - metabolism; Fourier Analysis; General pharmacology; Humans; Ions; Mass Spectrometry; Medical sciences; Melitten - analysis; Melitten - metabolism; Molecular Weight; Pharmaceutical Preparations - analysis; Pharmacokinetics; Pharmacology. Drug treatments; Proteins; Proteins - analysis; Proteins - metabolism; Scientific imaging; Sirolimus - analysis; Sirolimus - pharmacokinetics; Drug; Fourier transformation; Methodology; Peptides; Sirolimus; Angiotensin I; Peptide hormone; Protein; Infrared spectrometry; Renin angiotensin system; Biological fixation; Covalent bond; Mass spectrometry; Structural analysis
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac020048q

Two new applications using multiple ion isolations in the cell of a Fourier transform-ion cyclotron resonance mass spectrometer equipped with an electrospray ionization source are described. A procedure that uses multiple ion isolations of an analyte and calibrants for internal calibration at each stage in a MSn experiment, under high-resolution exact-mass conditions, for structural characterization/elucidation of angiotensin I and rapamycin is illustrated. Fragment ion mass accuracies < 1.0 ppm are demonstrated and routinely achieved. Purification of a mixture is illustrated by isolating multiple charge states of a protein-drug complex from residual protein for further MSn studies to elucidate the site of covalent drug bonding using IRMPD for a mixture of epidermal growth factor receptor (EGFr) protein and EGFr-drug complex. The procedure developed for multiple ion isolations is referred to as multi-CHEF, multiple correlated harmonic excitation fields, in which tailored waveforms are used to notch out multiple mass regions of a spectrum with minimal off-resonance excitation.