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Comparative Study
. 2003 Mar;14(1):1-8.

Angiotensin II-acetylcholine noncovalent complexes analyzed with MALDI-ion mobility-TOF MS

Amina S Woods  1 , Katrin Fuhrer, Marc Gonin, Tom Egan, Michael Ugarov, Kent J Gillig, J Albert Schultz
Affiliations
Comparative Study

Angiotensin II-acetylcholine noncovalent complexes analyzed with MALDI-ion mobility-TOF MS

Amina S Woods et al. J Biomol Tech. 2003 Mar.

Abstract

Matrix-assisted laser desorption ionization-ion mobility-orthogonal time-of-flight mass spectrometry (MALDI-IM oTOF MS) is a new technique that allows laser desorbed ion to be preseparated on the basis of their shape prior to mas analysis. Using this instrument, we tested the postulate that addition of a quaternary ammonium compound such as acetylcholine to the model phosphorylated peptide angio tensin II would enhance its detection by MALDI in two ways. First of all, the acetylcholine-peptide complex could ionize more efficiently than the bare phosphopeptide. Furthermore the ion mobility could separate the complex ion on the basis of its charge/volume from isobaric interferences, which would otherwise limit detection sensitivity.

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Figures

FIGURE 1
FIGURE 1
Schematic diagram of a MALDI–ion mobility–orthogonal TOF mass spectrometer.
FIGURE 2
FIGURE 2
Ion mobility–orthogonal TOF separation of MALDI-desorbed angiotensin II (equal mixture of phosphorylated and nonphosphorylated forms). Note the separation by mobility above mass 537 of the phosphorylated and nonphosphorylated fragments.
FIGURE 3
FIGURE 3
MALDI spectrum of a mixture of acetylcholine (Ach) and phosphorylated angiotensin II (pAn). Ions at m/z 1127.2 (pAn + H), 1272.4 (pAn + 1 Ach), 1418.6 (pAn + 2 Ach), and 1564.8 (pAn + 3 Ach) are identified.
FIGURE 4
FIGURE 4
MALDI spectrum of a mixture of acetylcholine (Ach) and angiotensin II (An). Ions at m/z 1047.2 (An + H), 1192.4 (An + 1 Ach), and 1338.6 (An + 2 Ach) are identified. The second addition of acetylcholine is barely seen.
FIGURE 5
FIGURE 5
Mobility–mass contour of a mixture of acetylcholine (Ach) and phosphorylated angiotensin II (pAn). Also shown is the one-dimensional mass spectrum derived by adding all masses at all mobilities.
FIGURE 6
FIGURE 6
Mobility–mass contour of a mixture of acetylcholine (Ach) and angiotensin II (An). Also shown is the one-dimensional mass spectrum derived by adding all masses at all mobilities.
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