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Protein Molecular Weight Calculator Tool

Protein Molecular Weight Formula:

\[ MW = \sum(aa\_mw) - 18 \times (len - 1) \]

(e.g. GAMMA)

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1. What is Protein Molecular Weight?

Protein molecular weight is the sum of the masses of all atoms in a protein molecule. It's typically measured in Daltons (Da). The calculator estimates the molecular weight based on the amino acid sequence, accounting for water loss during peptide bond formation.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ MW = \sum(aa\_mw) - 18 \times (len - 1) \]

Where:

Explanation: The formula sums the weights of all amino acids in the sequence, then subtracts the weight of water molecules lost during the formation of each peptide bond (one less than the number of amino acids).

3. Importance of Molecular Weight Calculation

Details: Knowing a protein's molecular weight is essential for protein characterization, gel electrophoresis, mass spectrometry, chromatography, and many other biochemical applications.

4. Using the Calculator

Tips: Enter the protein sequence using single-letter amino acid codes (e.g., "GAMMA"). The sequence should only contain standard amino acid letters (A, C, D, E, F, G, H, I, K, L, M, N, P, Q, R, S, T, V, W, Y).

5. Frequently Asked Questions (FAQ)

Q1: Does this include post-translational modifications?
A: No, this calculator only considers the unmodified amino acid sequence. PTMs would add additional mass.

Q2: How accurate is this calculation?
A: It provides a theoretical average molecular weight. Actual experimental values may differ slightly due to isotopic distributions.

Q3: What about N-terminal or C-terminal modifications?
A: This calculator assumes standard amino and carboxyl termini. Special modifications would need to be added manually.

Q4: Does it work for very large proteins?
A: Yes, but extremely large proteins may approach the limits of floating-point precision.

Q5: What about non-standard amino acids?
A: This calculator only handles the 20 standard amino acids. Non-standard residues would require custom calculations.

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