Protein Molecular Weight Formula:
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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.
The calculator uses the formula:
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).
Details: Knowing a protein's molecular weight is essential for protein characterization, gel electrophoresis, mass spectrometry, chromatography, and many other biochemical applications.
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).
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.