Theoretical analysis and model calculations were directed to find a means of extending the Wiley-McLarens principles of velocity focusing to wide range mass spectra. Both the cases of time-profiled single-field and double-field operation modes were considered. High mass accuracy over about a 10-fold
Delayed extraction time-of-flight MALDI mass spectrometry of proteins above 25000 Da
✍ Scribed by Bahr, U.; Stahl-Zeng, J.; Gleitsmann, E.; Karas, M.
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 373 KB
- Volume
- 32
- Category
- Article
- ISSN
- 1076-5174
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✦ Synopsis
Matrix-assisted laser desorption/ionization (MALDI) with delayed extraction (DE) has been optimized for mass analysis of high-mass proteins and glycoproteins with masses above 25 000 Da. Under optimized experimental conditions, i.e. using a weak extraction Ðeld strength and a long delay time, a steep drop in mass resolution above 30 000 Da is no longer observed and an improvement of more than a factor of 10 is obtained compared with the non-DE case, at least up to 66 kDa in a 1.2 m time-of-Ñight mass analyzer. On this level of resolution the factors limiting further improvements become apparent, i.e. adduct ion formation between matrix and analyte, but also cationization and further non-matrix-related adducts, as well as prompt fragmentation. Moreover, heterogeneity of the sample is often the reason for the detection of broad signals for larger proteins. Within these limitations, DHBs (a 9 : 1 mixture of 2,5-dihydroxybenzoic acid and 2-hydroxy-5-methoxybenzoic acid) gave by far the best results. (
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