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Protein Molecular Formula:
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The Protein Molecular Formula Calculator determines the elemental composition of a protein based on its amino acid sequence. It calculates the sum of empirical formulas of individual amino acids, accounting for water loss during peptide bond formation.
The calculator uses the formula:
Where:
Explanation: The calculation accounts for the removal of water molecules during peptide bond formation (n-1 water molecules for a protein with n amino acids).
Details: Knowing a protein's molecular formula is essential for mass spectrometry analysis, molecular weight determination, stoichiometric calculations, and understanding protein structure-function relationships.
Tips: Enter the protein amino acid sequence using single-letter codes. The calculator will ignore non-amino acid characters and count only standard amino acids (A, R, N, D, C, E, Q, G, H, I, L, K, M, F, P, S, T, W, Y, V).
Q1: Does this calculator account for post-translational modifications?
A: No, this calculator provides the elemental composition based only on the amino acid sequence without any modifications.
Q2: How are terminal groups handled in the calculation?
A: The calculation assumes standard protonated N-terminus (NH₂-) and deprotonated C-terminus (-COOH) at physiological pH.
Q3: Can I use three-letter amino acid codes?
A: No, the calculator only accepts single-letter amino acid codes. Convert three-letter codes to single-letter format before input.
Q4: What about non-standard amino acids?
A: Non-standard amino acids are not included in the calculation. Only the 20 standard amino acids are recognized.
Q5: How accurate is this calculation for mass spectrometry?
A: This provides the theoretical average mass. For precise mass spectrometry work, consider isotopic distribution and exact monoisotopic masses.