deamidation is about plus 0.98 Da. it is not a rounding error, it is a degradant
#hplc-massspec 2026-02-02
Monday18 messages6 participantstimes are UTC
Highlights from this day
- VialBot — Verification log updated: Homopeptide — evidence added, status unchanged. 05:44
- dublin_dose — a certificate with a number and no chromatogram is asking you to trust the integration you cannot see 06:30
- dublin_dose — is monoisotopic or average mass the one on most certificates 07:11
- dublin_dose — is uv at 214 or 280 better for peptides 07:12
oxidation is about plus 15.99 Da and is usually methionine or tryptophan, i have it written down somewhere
lot-log.csv
379 rows · not retained in the public archive
Verification log updated: Homopeptide — evidence added, status unchanged.
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shallow gradients hide related substances behind the main peak. a steeper one separates and looks worse, honestly, thats just me
i have had a lot where the mass was exactly right and the purity was 96.8. wrong question, right answer
a certificate with a number and no chromatogram is asking you to trust the integration you cannot see
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i have had a lot where the mass was exactly right and the purity was 96.8. wrong question, right answer, ask me again in a month
is monoisotopic or average mass the one on most certificates
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is uv at 214 or 280 better for peptides
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thats a charge state
ask for the trace
co-elution is the failure mode that a beautiful single peak is most likely to be hiding
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plus 0.98 is deamidation
need more sample
214nm sees the amide backbone so it sees everything. 280 only sees aromatics
how would a truncation sequence show up
why does integration change the number so much
i asked Janoshik for the raw trace and they sent it. that is the right answer to that question
two labs a point or two apart on the same lot is normal and gets mistaken for one of them being wrong constantly