1. What is Peptide Molecular Weight Calculation?

Peptide molecular weight calculation determines the mass of a peptide chain by summing the molecular weights of its constituent amino acids and subtracting the mass of water molecules lost during peptide bond formation.

2. How Does the Calculator Work?

The calculator uses the peptide molecular weight formula:

Where:

• \( \sum(\text{Amino Acid MW}) \) — Sum of molecular weights of all amino acids in the peptide
• \( n \) — Number of amino acids in the peptide chain
• 18 — Molecular weight of water (in Daltons) lost during each peptide bond formation

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

3. Importance of Peptide MW Calculation

Details: Accurate peptide molecular weight calculation is essential for protein research, drug development, mass spectrometry analysis, and biochemical studies where precise molecular mass is required.

4. Using the Calculator

Tips: Enter the molecular weights of individual amino acids separated by commas, and specify the total number of amino acids in the peptide chain. All values must be valid positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: Why subtract (n-1)×18 from the sum?
A: Each peptide bond formation results in the loss of one water molecule (MW=18 Da). For n amino acids, there are (n-1) peptide bonds.

Q2: What are typical molecular weight ranges for peptides?
A: Peptides typically range from a few hundred to several thousand Daltons, with most therapeutic peptides between 500-5000 Da.

Q3: Does this calculation account for modified amino acids?
A: No, this calculator uses standard amino acid weights. For modified amino acids, you would need to input their specific molecular weights.

Q4: How accurate is this calculation for real-world applications?
A: This provides a theoretical molecular weight. Actual measured weights may vary slightly due to isotopic distributions and other factors.

Q5: Can this calculator handle very large peptides?
A: Yes, the calculation works for peptides of any size, though extremely large values may have precision limitations.