1. What is Amino Acid Molecular Weight?

The molecular weight of a peptide or protein is the sum of the molecular weights of its constituent amino acids minus the weight of water molecules lost during peptide bond formation (18.015 g/mol per bond).

2. How Does the Calculator Work?

The calculator uses the 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 sequence
• 18 — Molecular weight of water (g/mol)

Explanation: The formula accounts for the loss of one water molecule for each peptide bond formed between amino acids.

3. Importance of Molecular Weight Calculation

Details: Knowing the molecular weight is essential for protein quantification, buffer preparation, electrophoresis, mass spectrometry, and other biochemical applications.

4. Using the Calculator

Tips: Enter the amino acid sequence using standard 3-letter codes separated by hyphens (e.g., GLY-ALA-SER). The sequence is case-insensitive.

5. Frequently Asked Questions (FAQ)

Q1: Why subtract water molecules in the calculation?
A: Each peptide bond formation results in the loss of one water molecule (condensation reaction).

Q2: What are the standard amino acid codes?
A: The calculator uses standard 3-letter codes (e.g., ALA for alanine, GLY for glycine).

Q3: Does this account for modified amino acids?
A: No, this calculator only handles standard amino acids. Post-translational modifications require specialized tools.

Q4: How accurate is this calculation?
A: It provides theoretical average molecular weight. For precise work, consider isotopic distribution.

Q5: Can I calculate protein molecular weight with this?
A: Yes, but for large proteins, specialized software may be more practical.