The mechanism of matrix to analyte proton transfer in clusters of 2,5-dihydroxybenzoic acid and the tripeptide vpl
Intracluster proton transfer from the matrix-assisted laser desorption/ionization matrix 2,5-dihydroxybenzoic acid (DHB) to the peptide valyl-prolyl-leucine has been investigated as a function of excitation laser wavelength and power. Ionization laser power studies at 308 nm indicate that cluster io...
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Published in | Journal of the American Society for Mass Spectrometry Vol. 12; no. 6; pp. 726 - 731 |
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Main Authors | , |
Format | Journal Article Conference Proceeding |
Language | English |
Published |
New York, NY
Elsevier Inc
01.06.2001
Elsevier Science Springer Nature B.V |
Subjects | |
Online Access | Get full text |
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Summary: | Intracluster proton transfer from the matrix-assisted laser desorption/ionization matrix 2,5-dihydroxybenzoic acid (DHB) to the peptide valyl-prolyl-leucine has been investigated as a function of excitation laser wavelength and power. Ionization laser power studies at 308 nm indicate that cluster ionization occurs with a two-photon dependence, whereas matrix-to-analyte proton transfer and cluster dissociation requires an additional photon. At 266 nm, two-photon absorption leads to both cluster ionization and cluster dissociation/proton transfer. A consideration of these results clearly indicates that analyte protonation occurs following ionization of the cluster to produce a radical cation matrix/analyte cluster. Mass spectral features also indicate that mixed DHB/peptide cluster ionization can occur via two-photon ionization at wavelengths as long as 355 nm. These results suggest a reduction in the ionization potential of larger mixed DHB/peptide clusters of greater than 1 eV. The reduced ionization potential seen in these clusters suggests that radical cation initiated proton transfer remains a viable mechanism for analyte protonation in matrix-assisted laser desorption/ionization at these longer wavelengths. |
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Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 1044-0305 1879-1123 |
DOI: | 10.1016/S1044-0305(01)00239-2 |