Different reflectron operational modes

Several different reflectron operational modes (Wei et al. 1990a,b) are employed in this work. When the reflectron is operated in a hard reflection mode,... 

The increased mass accuracy available when the instrument was operated in the reflectron mode was important for the analysis carried out. For example, fractions 4b and 7 or fractions 5 and 8 from C. ermineus appeared to be the same species when measured with the instrument operated in the linear mode. Only in the reflectron mode were we able to reliably distinguish the masses of each species. The high sensitivity of MALDI-TOF is particularly important for the analysis of native peptides such as conotoxins where often the venom of many milkings must be collected to obtain sufficient material for sequence analysis. The increased sensitivity of MALDI over LSIMS is illustrated in the analysis of fraction 5 from C. striatus venom (see Table I). Despite the two orders of magnitude difference in the amount of material consumed in the LSI experiment we did not discern any intact species in fraction 5, whereas the MALDI measurement yielded useful information. However, the comparisons in Tables I and II reveal that some components may be detected by LSIMS but not observed in the MALDI mass spectrum (measured with any of the matrices or sample preparation methods). The contrary is most likely more prevalent, i.e. that a large number of the species detected by MALDI with one or more of the matrices are difficult species to ionize with LSIMS. 

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