Amino Acid Molecular Weight Calculator
Calculate the molecular weight of a protein or peptide sequence based on the standard masses of amino acid residues.
Calculation Parameters
Specify your stoichiometry inputs.
Calculated Result
Expert Tip
During peptide bond formation, a molecule of water (18.015 g/mol) is lost. This calculator automatically accounts for residue weights and adds the terminal water weight.
How this Calculator Works
This calculator computes the total molecular weight of a protein or peptide sequence based on residue weights. Input sequence below:
- Peptide Sequence: The list of amino acids in the primary sequence (Default: AWGHE)
- Mass Calculation Standard: Choose between Average or Monoisotopic (Default: Average)
The results are computed instantly and updated in the results panel on the right.
Formula & Methodology
Where:
- Residue weights: Alanine = 71.08, Glycine = 57.05, Tryptophan = 186.21, etc.
- MW(H2O): Terminal water molecule mass (18.0152 g/mol for average, 18.0106 g/mol for monoisotopic).
Step-by-Step Calculation Example
To calculate molecular weight manually for "GG", follow these steps:
- Identify the input parameters. For example:
- Sequence = GG (Two Glycine residues)
- Glycine residue average mass = 57.05 g/mol
- Terminal water = 18.02 g/mol
- Apply the formula:
Total MW = (57.05 + 57.05) + 18.02 = 132.12 g/mol
- Verify the calculated value which is updated instantly in the results panel on the right.
Frequently Asked Questions
How is peptide molecular weight calculated? ▼
Peptide MW = Σ (Individual Amino Acid MWs) - (18.015 g/mol × (Number of Residues - 1)).
What is the average molecular weight of a protein amino acid residue? ▼
The average molecular weight of an amino acid residue in a protein is approximately 110 Da (g/mol).
How much mass is lost when a peptide bond forms? ▼
Each condensation peptide bond formation releases 1 molecule of water (H2O, 18.015 g/mol).