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Protein Molecular Weight Formula:
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Protein molecular weight is the sum of the atomic weights of all atoms in a protein molecule, typically measured in Daltons (Da). It's calculated by summing the molecular weights of individual amino acids in the protein sequence plus the molecular weight of water.
The calculator uses the formula:
Where:
Explanation: The calculation includes the molecular weight of water (18.01528 Da) which accounts for the hydrolysis of the peptide bond during protein synthesis.
Details: Knowing a protein's molecular weight is essential for various applications including protein purification, gel electrophoresis, mass spectrometry, and biochemical research.
Tips: Enter the amino acid sequence using single-letter codes (e.g., "GADV" for Gly-Ala-Asp-Val). The calculator automatically removes any non-amino acid characters.
Q1: Why is water molecular weight included?
A: During protein synthesis, a water molecule is removed for each peptide bond formed, so we add back one water molecule's weight for the entire protein.
Q2: Are modified amino acids supported?
A: This calculator uses standard amino acid weights. For modified amino acids, specialized calculators or manual adjustment is needed.
Q3: What about N-terminal and C-terminal modifications?
A: This calculator assumes standard amino and carboxyl termini. For acetylated, amidated, or other modified termini, additional adjustments are required.
Q4: How accurate is this calculation?
A: This provides the theoretical average molecular weight. For exact molecular weight including isotopic distribution, more advanced calculations are needed.
Q5: Can I calculate molecular weight with modifications?
A: For common modifications like phosphorylation (+79.98 Da) or glycosylation, you would need to manually add these weights to the calculated result.