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. It's calculated by adding the molecular weights of the constituent amino acids and subtracting the weight of water molecules lost during peptide bond formation.

2. How Does the Calculator Work?

The calculator uses the following formula:

Where:

• \( MW \) — Molecular weight (g/mol)
• \( \sum \text{(Amino Acid MW)} \) — Sum of individual amino acid weights
• \( 18.02 \) — Water molecule weight added for peptide bonds

Explanation: The calculator accepts either single-letter or three-letter amino acid codes, with or without separators.

3. Importance of Peptide Weight Calculation

Details: Knowing peptide molecular weight is essential for mass spectrometry, HPLC purification, molar concentration calculations, and biochemical experiments.

4. Using the Calculator

Tips: Enter amino acid sequence using either single-letter codes (e.g., GAS) or three-letter codes separated by hyphens (e.g., GLY-ALA-SER). The sequence is case-insensitive.

5. Frequently Asked Questions (FAQ)

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

Q2: Does the calculator account for modifications?
A: No, this calculates only the unmodified peptide weight. Modified amino acids need special consideration.

Q3: Why is water added in the calculation?
A: Water (18.02 g/mol) is added to account for the hydroxyl and hydrogen groups at the peptide termini.

Q4: How accurate is this calculator?
A: It provides theoretical average molecular weight based on standard amino acid masses.

Q5: Can I calculate weight for cyclic peptides?
A: No, cyclic peptides require subtraction of additional water molecules not accounted for here.