Formulas used
- Molecular weight starts with residue masses plus water.
- N-terminal acetylation adds 42.01056 Da.
- C-terminal amidation subtracts 0.98402 Da.
- Each disulfide bond subtracts 2.01565 Da.
Tools
Peptide Builder
Paste a one-letter amino-acid sequence to estimate molecular weight, composition, charge, and basic sequence properties.
Length
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Molecular weight
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Approx pI
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Net charge
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at pH 7.0
Hydrophobic
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Cysteines
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Composition
Calculator notes
Sequence property estimates
The builder reads a one-letter amino-acid sequence and estimates length, molecular weight, composition, hydrophobic residue share, cysteine count, net charge, and approximate pI.
Nonstandard letters are ignored in the calculation and listed in the on-page message so the sequence can be corrected.
Charge and pI assumptions
Net charge is estimated from common side-chain pKa values plus the termini. Approximate pI is found by searching for the pH where the calculated net charge crosses zero.
Common inputs
Use standard one-letter amino acid codes, optional terminal modifications, a whole-number disulfide count, and a pH from 0 to 14 for charge.
Related terms and tools
Related definitions include peptide, sequence, and molecular weight. Use the unit converter for mass-to-moles math or the reconstitution calculator for concentration from an entered mass and volume.