1. What Is Molecular Weight Calculation?

Molecular weight calculation determines the mass of a protein molecule by summing the atomic masses of all atoms in the molecule. For proteins, this is typically calculated by adding the masses of individual amino acid residues.

2. How Does The Calculator Work?

The calculator uses the formula:

Where:

• MW - Molecular weight in Daltons (Da)
• AA residue MW - Molecular weight of individual amino acid residues
• The sum includes all amino acids in the protein sequence

Explanation: The calculator processes the protein sequence character by character, summing the known molecular weights of each amino acid residue to calculate the total molecular weight.

3. Importance Of Molecular Weight Calculation

Details: Molecular weight is a fundamental property used in protein characterization, purification, electrophoresis, mass spectrometry, and various biochemical applications. Accurate molecular weight calculation helps in experimental design and data interpretation.

4. Using The Calculator

Tips: Enter the protein sequence using single-letter amino acid codes (A, R, N, D, C, E, Q, G, H, I, L, K, M, F, P, S, T, W, Y, V). The sequence should not contain numbers, spaces, or special characters.

5. Frequently Asked Questions (FAQ)

Q1: What molecular weight standard is used?
A: This calculator uses monoisotopic masses of amino acid residues, which represent the exact mass of the most abundant isotope of each element.

Q2: Does this include post-translational modifications?
A: No, this calculator provides the theoretical molecular weight of the unmodified polypeptide chain. Modifications like phosphorylation or glycosylation would add additional mass.

Q3: Why might experimental values differ from calculated values?
A: Experimental measurements may differ due to post-translational modifications, protein folding, buffer conditions, or measurement techniques.

Q4: Are terminal groups included in the calculation?
A: Yes, the calculation includes the mass of amino acid residues as they appear in the polypeptide chain, accounting for water loss during peptide bond formation.

Q5: What is the difference between average and monoisotopic mass?
A: Monoisotopic mass uses the exact mass of the most abundant isotope, while average mass uses the weighted average of all naturally occurring isotopes.