Misconception? If we digest a whole cell lysate with trypsin, we will find that there is an apex somewhere which will represent the average tryptic peptide mass as well as the standard distribution around that point.
So I took a HeLa digest run. We know its well over 90% digested, so it should be a good comparison. I then filtered every the m/z of every ion that was selected for fragmentation by a filter of 0.01 Da. This provided me with 10,979 unique-ish ions selected for fragmentation.
In order to get a visual output representing the ion distribution, I binned the ions in 1 Da units from 299 to 1000. And I got this neat histogram that appears to show little m/z bias (so no obvious apex and distribution!)
But it sure is hard to see, right? So I just re-binned it in units of 50. Which shows some bias, but definitely not as strong as I was suspecting.
BTW, these histograms were created by the Add-in in Office 365, which is pretty great.
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