1. What is Protein Molecular Mass?

Protein molecular mass, measured in daltons (Da), is the sum of the monoisotopic masses of all amino acids in the protein sequence. It represents the exact mass of the protein molecule.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• MW — Molecular weight in daltons (Da)
• ∑ — Summation of all amino acid masses
• AA masses — Monoisotopic masses of individual amino acids

Explanation: The calculator processes the protein sequence character by character, adding up the monoisotopic mass of each valid amino acid.

3. Importance of Molecular Weight Calculation

Details: Accurate molecular weight calculation is essential for protein characterization, electrophoresis, mass spectrometry, and various biochemical applications.

4. Using the Calculator

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 calculator automatically ignores non-amino acid characters.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between molecular weight and molar mass?
A: Molecular weight is the mass of a single molecule (in daltons), while molar mass is the mass of one mole of molecules (in g/mol). Numerically, they are equivalent.

Q2: Does this calculator account for post-translational modifications?
A: No, this calculator provides the molecular weight of the unmodified polypeptide chain only.

Q3: What are monoisotopic masses?
A: Monoisotopic mass is calculated using the exact mass of the most abundant isotope of each element.

Q4: Does the calculator consider the N-terminal H and C-terminal OH?
A: Yes, the standard amino acid masses already include these components.

Q5: Can I calculate mass for non-standard amino acids?
A: This calculator only supports the 20 standard amino acids. Non-standard residues will be flagged as invalid characters.