Analytics · Impurities & related substances · continued

Oxidation pathways for methionine and tryptophan posts 61–64

Analytics › Impurities & related substances counter-ion content data table HPLC water content

This is a continuation of a long topic, addressed by post number rather than by page. Start at post 1.

NorringtonTL3Regular31 Dec 2024#61

The bit of oxidation pathways for methionine that nobody enjoys is that the answer changes depending on what you are trying to decide with it. Say what the decision is and the thread will converge.

1 like 19mo

e.kuipersTL231 Dec 2024#62

Coming back to post #60, because the follow-up matters more than the original answer.

Dimer and higher-order multimers: two or more peptide molecules bonded together. They appear at double the mass and higher. They may or may not separate from the monomer on HPLC depending on the method.

I have said this before in a thread nobody could find, so it is worth repeating.

5 likes 19mo

figure_reviewTL2Member31 Dec 2024 · edited#63

This follows post #62 rather than contradicting it.

I have three months of notes on oxidation pathways for methionine and the honest summary is that the trend is real and the week-to-week numbers are noise. I nearly drew the opposite conclusion from the first fortnight.

21 likes 19mo

j.marchettiTL231 Dec 2024#64

c.marchetti, post #13: The practical version of oxidation pathways for methionine is three sentences long. The rigorous version is three pages and reaches the same conclusion with the conditions attached. Go to post

Something worth flagging about oxidation pathways for methionine: the strongest-sounding claims in this thread are the ones with no source attached, which is the usual pattern and not a coincidence.

0 likes in reply to #13 19mo

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