1. What is Peptide Molecular Weight?

The molecular weight of a peptide is the sum of the atomic weights of all atoms in the molecule. For peptides and proteins, this is calculated by summing the weights of the amino acids and subtracting the weight of water molecules lost during peptide bond formation.

2. How Does the Calculator Work?

The calculator uses the peptide molecular weight formula:

Where:

• \( aa_{mw} \) — Molecular weight of each amino acid (g/mol)
• \( len \) — Number of amino acids in the sequence
• 18 — Molecular weight of water (g/mol)

Explanation: Each peptide bond formation results in the loss of one water molecule (H₂O, MW=18). For a peptide with n amino acids, there are (n-1) peptide bonds.

3. Importance of Molecular Weight Calculation

Details: Knowing the molecular weight is essential for peptide synthesis, mass spectrometry analysis, biochemical experiments, and pharmaceutical applications.

4. Using the Calculator

Tips: Enter the amino acid sequence using either 1-letter or 3-letter codes, separated by hyphens (e.g., "GLY-ALA-SER" or "G-A-S"). The calculator is case-insensitive.

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 amino acid sequences.

Q3: How accurate is this calculation?
A: The calculation uses standard amino acid molecular weights and is accurate for theoretical purposes. Actual measurements may vary slightly.

Q4: Can I calculate protein molecular weight with this?
A: Yes, for proteins up to reasonable lengths. However, very large proteins may exceed input limits.

Q5: Why subtract water molecules?
A: Water is lost during peptide bond formation (condensation reaction), so we account for this in the calculation.