</fontfamily><fontfamily><param>New_York</param>Dear ESI
ABRFers,</fontfamily><fontfamily><param>Times</param>
</fontfamily><fontfamily><param>New_York</param>Can anyone explain the
following:</fontfamily><fontfamily><param>Times</param>
</fontfamily><fontfamily><param>New_York</param>I have a fluorescein
labeled 40+mer peptide that when run on HPLC elutes as two well
separated (i.e. 30") peaks, the first one sharp and the second on the
broadish side.</fontfamily><fontfamily><param>Times</param>
</fontfamily><fontfamily><param>New_York</param>When you compare the
210 nm trace with the 490 nm trace you see that the first peak has no
dye and that the second peak has
dye.</fontfamily><fontfamily><param>Times</param>
</fontfamily><fontfamily><param>New_York</param>The ESI mw of the first
peak is that of the peptide without dye. BUT the ESI mw output of the
second peak contains BOTH the ions for the dye and non-dye labeled
peptide.</fontfamily><fontfamily><param>Times</param>
</fontfamily><fontfamily><param>New_York</param>Is this a typical ESI
phenomenon with long dye labeled peptides? Both sets of ions come up at
all energy settings. Previous, albeit shorter dye labeled peptides have
shown only the "plus dye"
envelope.</fontfamily><fontfamily><param>Times</param>
</fontfamily><fontfamily><param>New_York</param>Thanks in
advance,</fontfamily><fontfamily><param>Times</param>
</fontfamily><fontfamily><param>New_York</param>Dick</fontfamily><fontfamily><param>Times</param>
</fontfamily>