Protein Sequence Mass Calculator

Protein Mass Calculation:

\[ MW (Da) = \sum \text{Residue masses} + H_2O \]

Molecular Weight (MW):

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1. What Is Protein Molecular Weight Calculation?

Protein molecular weight calculation determines the mass of a protein based on its amino acid sequence. The calculation sums the masses of all amino acid residues plus the mass of water (H₂O), which accounts for the loss during peptide bond formation.

2. How Does The Calculator Work?

The calculator uses the formula:

\[ MW (Da) = \sum \text{Residue masses} + H_2O \]

Where:

\( MW \) — Molecular weight in daltons (Da)
\( \sum \text{Residue masses} \) — Sum of masses of all amino acid residues
\( H_2O \) — Mass of water (18.01528 Da)

Explanation: The calculation accounts for the monoisotopic masses of standard amino acids and adds the mass of water to complete the molecular weight.

3. Importance Of Protein Mass Calculation

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

4. Using The Calculator

Tips: Enter the protein sequence using single-letter amino acid codes (e.g., "MALWMRLLPLL"). The calculator will automatically process valid amino acid characters and ignore invalid ones.

5. Frequently Asked Questions (FAQ)

Q1: What are the standard amino acid codes?
A: The 20 standard amino acids are represented by: A, R, N, D, C, E, Q, G, H, I, L, K, M, F, P, S, T, W, Y, V.

Q2: Why is water mass added in the calculation?
A: Water mass (18.01528 Da) is added because peptide bond formation releases a water molecule, and the molecular weight represents the complete protein.

Q3: Are modified amino acids supported?
A: This calculator uses standard amino acid masses. For modified residues, specialized calculators with appropriate mass values should be used.

Q4: What is the precision of the calculation?
A: The calculator uses monoisotopic masses with precision to 5 decimal places but displays the result rounded to 2 decimal places.

Q5: Can I calculate mass for nucleic acid sequences?
A: This calculator is specifically designed for protein sequences. Different calculators are available for DNA/RNA mass calculations.