Posting this under the heading it deserves: Oxidation pathways for methionine and tryptophan Everything below is what sits behind that.
Working notes on oxidation pathways for methionine rather than a conclusion. I would rather post the reasoning while it can still be corrected than post the answer once I am committed to it.
Everything below is checkable. Where I have taken a figure from somewhere else I have said where; where I have estimated, I have said that too.
The opening post put the caveat in the right place and I want to underline it.
Two sentences on oxidation pathways for methionine and then I will stop, because the rest is speculation and the thread is better without mine.
What is documented is narrow. What is inferred from it is broad. The gap between them is where every argument here lives.
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.
Having read the whole oxidation pathways for methionine thread before replying: the question in the first post has not actually been answered yet, and three of us have answered a nearby one instead.
Where I part company with post #31, and it is a narrow parting.
Oxidation pathways for methionine has a well-known answer and a correct answer, and the interesting work is establishing that they are the same. Nobody has done that here yet.
Where an impurity is identified rather than merely counted, the certificate is telling you the manufacturer has characterised its own process. That is a meaningful difference in documentation quality.
Where I would look next, rather than where I would stop.
The arithmetic in post #47 is right; the assumption feeding it is the part to check.
The honest answer on oxidation pathways for methionine is that it depends, and the useful part is the list of what it depends on. Four items, in rough order of how much they matter.
Most people get the first two right and then argue about the fourth.
Oxidation at methionine or tryptophan adds sixteen per oxygen and typically elutes earlier. In aged material it is the modification that grows.
Read the full topic (64 posts)
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Where impurities in solid-phase peptide synthesis come from
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Second pass at: Where impurities in solid-phase peptide synthesis come from
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2 | 22k | 4mo | |
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Deamidation and the close-eluting pair it produces
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+33 | 37 | 46k | 15mo |
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+48 | 53 | 918 | 8mo |
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+96 | 119 | 58k | 14mo |
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+23 | 27 | 3.7k | 16mo |
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2 | 15k | 18mo | |
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Revisiting: Aggregates and why a purity assay may miss them entirely
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+48 | 53 | 918 | 8mo |