Home
Back
Protein Molecular Weight Formula:
| From: | To: |
Protein molecular weight is the sum of the atomic weights of all atoms in a protein molecule, typically expressed in grams per mole (g/mol). It's calculated by summing the molecular weights of individual amino acids minus the water molecules lost during peptide bond formation.
The calculator uses the formula:
Where:
Explanation: The calculator sums the molecular weights of all amino acids in the sequence and subtracts 18.015 g/mol for each peptide bond formed (n-1 water molecules).
Details: Knowing a protein's molecular weight is essential for protein characterization, purification techniques (like gel electrophoresis and chromatography), concentration determination, and biochemical experiments.
Tips: Enter the amino acid sequence using single-letter codes (A, R, N, D, C, Q, E, G, H, I, L, K, M, F, P, S, T, W, Y, V). Non-standard characters will be ignored in the calculation.
Q1: Does this calculator account for post-translational modifications?
A: No, this calculator provides the theoretical molecular weight based on the amino acid sequence only and does not account for modifications like phosphorylation, glycosylation, or acetylation.
Q2: Why subtract water molecular weight?
A: Water molecules are removed during peptide bond formation (condensation reaction), so the molecular weight of the resulting protein is less than the sum of individual amino acids.
Q3: Are terminal groups accounted for in this calculation?
A: This calculation assumes standard protonated N-terminal and deprotonated C-terminal groups at physiological pH.
Q4: What about disulfide bonds?
A: Disulfide bond formation involves loss of hydrogen atoms, but this calculator does not currently account for disulfide bonds in the molecular weight calculation.
Q5: Can I use three-letter amino acid codes?
A: No, this calculator only accepts single-letter amino acid codes. Convert three-letter codes to single-letter format before calculation.