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PeptideMass [references] cleaves a protein sequence from the UniProt Knowledgebase (Swiss-Prot and TrEMBL) or a user-entered protein sequence with a chosen enzyme, and computes the masses of the generated peptides. The tool also returns theoretical isoelectric point and mass values for the protein of interest. If desired, PeptideMass can return the mass of peptides known to carry post-translational modifications, and can highlight peptides whose masses may be affected by database conflicts, polymorphisms or splice variants.

Instructions are available.

Enter a UniProtKB protein identifier, ID (e.g. ALBU_HUMAN), or accession number, AC (e.g. P04406), or an amino acid sequence (e.g. 'SELVEGVIV'; you may specify post-translational modifications, but PLEASE read this document first!):

the fields. the cleavage of the protein.

The peptide masses are
with cysteines treated with:
with acrylamide adducts
with methionines oxidized
[M+H]+ or [M] or [M-H]- or [M+2H]2+ or [M+3H]3+
average or monoisotopic.
Select an enzyme:

Allow for missed cleavages.
Display the peptides with a mass bigger than and smaller than Dalton

sorted by peptide masses or in chronological order in the protein.

For UniProtKB (Swiss-Prot/TrEMBL) entries only:
For each peptide display
all known post-translational modifications,
all database conflicts,
all variants (polymorphisms ),
all mRNA variants (due to alternative splicing, initiation or promoter usage).