Molecular Weight Calculator Protein Sequence

Molecular Weight Calculation:

\[ MW (g/mol) = \sum (Monoisotopic\ masses) \]

Molecular Weight:

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1. What is Molecular Weight Calculation?

Molecular weight calculation for protein sequences involves summing the monoisotopic masses of individual amino acids in the polypeptide chain, plus the mass of a water molecule (H₂O) to account for the condensation reaction during protein formation.

2. How Does the Calculator Work?

The calculator uses the following formula:

\[ MW (g/mol) = \sum (Monoisotopic\ masses) + 18.01528 \]

Where:

\( MW \) — Molecular weight in grams per mole
\( \sum (Monoisotopic\ masses) \) — Sum of all amino acid monoisotopic masses
\( 18.01528 \) — Mass of water (H₂O) in daltons

Explanation: The calculation accounts for the exact mass of each amino acid residue in the protein sequence, providing the theoretical molecular weight of the protein.

3. Importance of Molecular Weight Calculation

Details: Accurate molecular weight calculation is essential for protein characterization, experimental design, mass spectrometry analysis, 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 sequence can be entered in any case as it will be converted to uppercase automatically.

5. Frequently Asked Questions (FAQ)

Q1: What are monoisotopic masses?
A: Monoisotopic mass is the mass of a molecule calculated using the mass of the most abundant isotope of each element.

Q2: Why is water mass added to the calculation?
A: Water mass (18.01528 Da) is added because proteins are formed through condensation reactions where water is removed when amino acids join together.

Q3: What if my sequence contains non-standard amino acids?
A: This calculator only recognizes the 20 standard amino acids. Non-standard amino acids will be flagged as invalid characters.

Q4: How accurate is this calculation?
A: This provides the theoretical monoisotopic mass. Actual experimental values may vary slightly due to post-translational modifications and measurement techniques.

Q5: Can I calculate molecular weight for modified amino acids?
A: This calculator uses standard amino acid masses only. For modified residues, specialized tools would be needed.