1. What is Protein Molar Mass?

Protein molar mass is the mass of one mole of a protein, calculated by summing the masses of its amino acids and subtracting the mass of water molecules lost during peptide bond formation.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( amino\_acid\_masses \) — Mass of each amino acid in the sequence (g/mol)
• \( n \) — Number of amino acid residues
• 18 — Mass of water lost per peptide bond (g/mol)

Explanation: For each peptide bond formed, one water molecule is lost (condensation reaction). The formula accounts for this by subtracting 18 g/mol for each bond.

3. Importance of Protein Molar Mass

Details: Knowing a protein's molar mass is essential for laboratory work including protein quantification, electrophoresis, mass spectrometry, and biochemical experiments.

4. Using the Calculator

Tips: Enter the protein sequence using single-letter amino acid codes (e.g., "MAKEGT"). The sequence should only contain standard amino acid letters (A-Z except B,J,O,U,X,Z).

5. Frequently Asked Questions (FAQ)

Q1: Why subtract (n-1)*18?
A: Each peptide bond formation results in the loss of one water molecule (H₂O, MW=18). A protein with n residues has n-1 peptide bonds.

Q2: Are modifications included?
A: No, this calculates the unmodified protein mass. Post-translational modifications would require additional mass adjustments.

Q3: What about N-terminal and C-terminal groups?
A: This calculation assumes standard protonated N-terminus and deprotonated C-terminus at physiological pH.

Q4: How accurate is this calculation?
A: It provides theoretical average mass. For exact mass, isotopic distributions must be considered.

Q5: Can I use lowercase letters?
A: Yes, the calculator automatically converts to uppercase, but only standard amino acid letters are accepted.