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Protein Monoisotopic Mass Calculation:
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The monoisotopic mass is the sum of the masses of the atoms in a molecule using the principal (most abundant) isotope for each element. For proteins, this represents the exact mass calculated from the most abundant natural isotopes of the constituent amino acids.
The calculator uses the formula:
Where each amino acid in the protein sequence contributes its specific monoisotopic mass to the total.
Explanation: The calculation sums the exact masses of all amino acids in the sequence using established monoisotopic values for each residue.
Details: Accurate mass calculation is essential for protein identification, characterization, and validation in mass spectrometry experiments. It helps researchers confirm protein identity and detect post-translational modifications.
Tips: Enter the protein sequence using single-letter amino acid codes (A, R, N, D, C, E, Q, G, H, I, L, K, M, F, P, S, T, W, Y, V). The sequence can be entered in any case as it will be converted to uppercase automatically.
Q1: What's the difference between monoisotopic and average mass?
A: Monoisotopic mass uses the exact mass of the most abundant isotope of each element, while average mass considers the natural abundance of all isotopes.
Q2: Does this calculator account for modified amino acids?
A: No, this calculator uses standard amino acid masses only. Modified residues would require specialized calculations.
Q3: What about the N-terminal H and C-terminal OH?
A: The calculated mass includes the complete protein with N-terminal hydrogen and C-terminal hydroxyl group, as these are incorporated in the standard amino acid masses.
Q4: How accurate is this calculation?
A: The calculation provides theoretical exact mass based on established values. Real-world measurements may vary slightly due to instrumental factors.
Q5: Can I calculate mass for peptides as well as proteins?
A: Yes, the calculator works for peptides of any length, from dipeptides to large proteins.