1. What Is Protein Molecular Weight Calculation?

Protein molecular weight calculation determines the mass of a protein based on its amino acid sequence using standard amino acid masses from Sigma. The calculation sums the masses of all amino acids in the sequence plus the mass of water for terminal groups.

2. How Does The Calculator Work?

The calculator uses the formula:

Where:

• \( MW \) — Molecular weight in daltons (Da)
• \( \sum \) — Summation of all amino acid masses
• \( Sigma AA masses \) — Standard amino acid masses provided by Sigma

Explanation: The calculation begins with the mass of water (18.02 Da) to account for the terminal amino and carboxyl groups, then adds the mass of each amino acid in the sequence using Sigma's standard values.

3. Importance Of Molecular Weight Calculation

Details: Accurate molecular weight calculation is essential for protein research, gel electrophoresis, mass spectrometry, protein purification, and biochemical characterization of proteins.

4. Using The Calculator

Tips: Enter the protein amino acid sequence using single-letter codes. The calculator automatically removes non-amino acid characters and calculates the molecular weight using Sigma's standard amino acid masses.

5. Frequently Asked Questions (FAQ)

Q1: Why use Sigma amino acid masses?
A: Sigma provides standardized, widely accepted values for amino acid masses that are consistent across biochemical research and publications.

Q2: Does this include post-translational modifications?
A: No, this calculator provides the theoretical molecular weight of the unmodified amino acid sequence only.

Q3: Why is water mass added to the calculation?
A: Water mass (18.02 Da) accounts for the addition of H and OH groups during peptide bond formation and terminal groups.

Q4: Are non-standard amino acids supported?
A: No, this calculator only supports the 20 standard amino acids with single-letter codes (A, R, N, D, C, E, Q, G, H, I, L, K, M, F, P, S, T, W, Y, V).

Q5: How accurate is this calculation?
A: This provides the theoretical average molecular weight. For precise measurements, experimental techniques like mass spectrometry are required.