Topic summary

Isotope patterns and why the monoisotopic peak is not the tallest

Analytics › Mass spectrometry LC-MS MALDI-TOF mass error (ppm) high-resolution MS charge states

This is a generated summary. It shows the 5 most-liked posts from a topic of 17, in their original order, with the accepted answer included where one exists. It is a reading aid and it will miss nuance — the full topic is the record.

ew.kuuselaTL225 Oct 2024#1

Isotope patterns and why the monoisotopic peak is not the tallest — setting out what I have, and where I think it stops being reliable.

Isotope patterns: what I expected, what I found, and the gap between them.

I am posting the gap rather than a theory about it. My theories about gaps like this one have not held up well.

20 likes 21mo

m.balogunTL227 Nov 2024#4

Picking up post #3: that is the part I would want checked first.

Second-hand on isotope patterns, so weight it accordingly — someone whose method I trust told me this and I have not verified it myself.

32 likes 20mo

unit_conversionTL3Regular5 Dec 2024#5

Electrospray ionisation produces multiply charged ions. For a 4 kDa peptide you expect mostly 2+, 3+, and 4+ charge states. Reading an electrospray spectrum means recognizing the envelope, not looking for one peak.

It cost nothing to check and would have cost something not to.

16 likes 20mo

vial_slopeTL3Regular4 Jan 2025#9

I read post #7 twice before replying, because I had assumed the opposite.

Isotope patterns: I would want to see the raw numbers rather than the summary before agreeing. Summaries lose exactly the information that would settle this.

23 likes 19mo

dr_seongTL3Physician12 Feb 2025#15

Positional isomers and epimers are mass-identical. Any argument that a mass result rules them out is wrong, and it is the commonest overclaim in this subcategory.

22 likes 17mo

Read the full topic (17 posts)

This topic was referenced in

MS/MS sequence confirmation: what it costs and when it is worth itAnalytics › Mass spectrometry · 6 replies

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