Protein Molecular Weight Calculator

8. Protein MW Calculator

Estimate the theoretical Molecular Weight (kDa) of a protein sequence.

MW: -- kDa

Scientific Documentation

The molecular weight (MW) of a protein is a critical physical property determined by its amino acid composition. Each of the 20 standard amino acids has a specific average molecular weight. When these residues form a peptide chain, they undergo dehydration synthesis, releasing a water molecule (18.015 Da) for each peptide bond formed.

Methodology: This calculator sums the molecular weights of all amino acids in the sequence and subtracts the weight of the water molecules lost during polymerization. The result is presented in kilodaltons (kDa), where 1 kDa = 1,000 daltons.

Laboratory Significance: Knowing the theoretical MW is essential for interpreting SDS-PAGE (Sodium Dodecyl Sulfate-Polyacrylamide Gel Electrophoresis) results. Researchers compare the migration of their protein sample against molecular weight standards (ladders) to verify protein expression, purity, and integrity. Discrepancies between theoretical and observed MW can indicate post-translational modifications (like glycosylation or phosphorylation), which are vital for understanding protein function and activity in cellular environments.