1. What is Peptide Molecular Weight?

Peptide molecular weight is the sum of the atomic weights of all atoms in a peptide molecule, minus the weight of water molecules lost during peptide bond formation. It's essential for peptide synthesis, mass spectrometry, and biochemical research.

2. How Does the Calculator Work?

The calculator uses the peptide molecular weight formula:

Where:

• \( MW \) — Molecular weight of the peptide (g/mol)
• \( MW_{aa} \) — Molecular weight of each amino acid (g/mol)
• \( length \) — Number of amino acids in the peptide
• 18 — Molecular weight of water (g/mol)

Explanation: Each peptide bond formation removes one water molecule (H₂O, MW=18), so we subtract 18*(n-1) where n is the number of amino acids.

3. Importance of Peptide MW Calculation

Details: Accurate molecular weight is crucial for peptide synthesis, mass spectrometry analysis, HPLC purification, and determining peptide concentration.

4. Using the Calculator

Tips: Enter the peptide sequence using either 1-letter codes (e.g., "GAS") or 3-letter codes separated by hyphens (e.g., "GLY-ALA-SER"). The calculator automatically recognizes both formats.

5. Frequently Asked Questions (FAQ)

Q1: What amino acid codes are supported?
A: Both 1-letter (A, R, N, D, etc.) and 3-letter (ALA, ARG, ASN, ASP, etc.) codes are supported.

Q2: Does this include post-translational modifications?
A: No, this calculator only computes the molecular weight of unmodified peptides.

Q3: How accurate is the calculation?
A: The calculation uses standard amino acid molecular weights and is accurate for theoretical purposes.

Q4: What about N-terminal or C-terminal modifications?
A: For modified peptides, you would need to manually add/subtract the modification weights.

Q5: Does this account for disulfide bonds?
A: No, disulfide bond formation would require subtracting additional hydrogen atoms.