Sequon Desk - your protein sequence, its liabilities, the variant fix and the assay panel

Paste the protein sequence you are about to order DNA for - one chain or a whole FASTA file - and get the developability review a protein engineer would write, in three lanes over one sitting. A free in-browser prescan reads it before anything is sent: average and monoisotopic mass, theoretical pI over the Bjellqvist pKa set, net charge, GRAVY, aliphatic index and the 280 nm extinction coefficient in both reduced and cystine readings; every canonical N-X-S/T glycosylation sequon, with the proline-blocked NPS and NPT near-sequons kept in their own list because they are NOT sites, and the non-canonical N-X-C positions in a third; O-glycosylation hotspots by proline context; the Asn-Gly deamidation, Asp-Gly isomerisation, Asp-Pro hydrolysis, methionine and tryptophan oxidation, lysine glycation, N-terminal pyroglutamate and C-terminal lysine motifs; cysteine count and parity; and the contiguous hydrophobic and formal charge patches. Severity depends on the four context fields and on the numbers already computed, not on the motif's name: a sequon in an E. coli construct is information because there is no glycosylation machinery to use it, a C-terminal lysine on an IgG is expected heterogeneity, a hydrophobic patch is graded against the chain's own charge density, and an even cysteine count is reported as consistent with complete pairing rather than as evidence of it. Then three lanes over those same facts: the glycosylation and liability review with a keep, remove, shield, monitor or characterise call per site; the variant design that removes what the review found, every mutation tied to the liability it clears with its conservative-substitution reasoning and the protein-language-model run that would rule it out; and the characterisation panel in feasible order - expression, purification, identity, binding, thermostability, glycan and forced degradation - with numeric acceptance criteria rather than adjectives. Each lane must answer for every prescan flag, and a flag it neither confirms nor clears is shown as unanswered. It reads a sequence and does arithmetic on it: it asserts no structure, no solvent exposure, no CDR boundary and no antibody numbering scheme, and it is not medical, clinical, diagnostic or regulatory advice. A derived work built from three agent skills, one per lane: @k-dense-ai/glycoengineering (N-glycosylation sequons, O-glycosylation hotspots, the glycoengineering toolchain), @k-dense-ai/esm (protein language models, inverse folding, variant-effect prediction) and @k-dense-ai/adaptyv (protein experiment design, binding and thermostability characterisation). Not affiliated with those skills' authors or with any tool or vendor named in the app.

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