Deamidation: difference between revisions
Diff·revision 2 → 3·04:55, 3 Nov 2024
Difference between revision 2 and revision 3 of Deamidation. 5 lines changed; the page grew by 656 bytes.
| Revision 2 — 17:41, 28 Oct 2024 LiraLotte (talk) add the note on co-elution and what it hides 1,364 bytes ±0 | Revision 3 — 04:55, 3 Nov 2024 GastroparesisGwen (talk) add the counterion determination method by name 2,020 bytes +656 | ||
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| 11 | The mass change is +0.984 Da, which is small enough that unit-resolution [[Mass spectrometry|mass spectrometry]] cannot distinguish a deamidated peptide from its parent. The charge change is more consequential: an uncharged amide becomes a negatively charged carboxylate, which alters chromatographic behaviour and, in a receptor-binding peptide, may alter activity.{{r|usp1503}} | 11 | The mass change is +0.984 Da, which is small enough that unit-resolution [[Mass spectrometry|mass spectrometry]] cannot distinguish a deamidated peptide from its parent. The charge change is more consequential: an uncharged amide becomes a negatively charged carboxylate, which alters chromatographic behaviour and, in a receptor-binding peptide, may alter activity.{{r|usp1503}} |
| 12 | 12 | ||
| + | 13 | == Mechanism and rate == | |
| + | 14 | At neutral and alkaline pH the dominant pathway is intramolecular: the backbone nitrogen of the following residue attacks the asparagine side-chain carbonyl, forming a five-membered succinimide with loss of ammonia. The succinimide then hydrolyses to give aspartate or isoaspartate, typically in roughly a one-to-three ratio.{{r|robinson2001}} | |
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| + | 16 | Isoaspartate formation is the more damaging outcome, because it inserts an extra methylene into the backbone and changes the local conformation. It is isobaric with aspartate and is not distinguishable by intact mass; detection requires a specific enzymatic or chromatographic method. | |
| + | 17 | ||
| 13 | == References == | 18 | == References == |
| 14 | {{reflist}} | 19 | {{reflist}} |