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Graspetide Crosslink Explorer

Heuristic prediction of ω-ester and ω-amide crosslink topology for any graspetide precursor core peptide. Paste a sequence to explore candidate bicyclic and tricyclic scaffolds, predict ETD fragment ladders, and calculate mass shifts.

Ser/Thr — ω-ester donor Lys — ω-amide donor Asp/Glu — acceptor (carboxylate) other residues
Sequence input
Confirmed crosslinks (fix into topology)
Enter as DonorPosAcceptorPos e.g. K10E4 or S18D22
Sequence map — click residue to highlight pairs; click topology to show arcs
Crosslink pairs
Enter a sequence to see pairs
Bicyclic / tricyclic topologies
Select pairs or enter sequence
ETD / EThcD c-ion prediction
Select a topology to predict fragment masses. Cyclic boundary ions appear at −18.011 Da from the expected linear mass. Absent ions (within-ring backbone cuts) are shown faded.