1. What is Peptide and Protein Molecular Weight?

Molecular weight is the sum of the atomic weights of all atoms in a molecule. For peptides and proteins, it's calculated by summing the molecular weights of individual amino acid residues plus the molecular weight of water (for terminal groups).

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• MW - Molecular weight in daltons (Da)
• Peptide/protein residues - Individual amino acid molecular weights
• The calculation includes the molecular weight of water (H₂O) for terminal groups

Explanation: The calculator processes each amino acid in the sequence, adds their molecular weights, and includes the molecular weight of water to account for the terminal amino and carboxyl groups.

3. Importance of Molecular Weight Calculation

Details: Knowing the molecular weight of peptides and proteins is essential for various applications including mass spectrometry, protein purification, electrophoresis, pharmaceutical development, and biochemical research.

4. Using the Calculator

Tips: Enter the amino acid sequence using single-letter codes (e.g., "GADV" for Gly-Ala-Asp-Val). The sequence should contain only valid amino acid codes (A, R, N, D, C, E, Q, G, H, I, L, K, M, F, P, S, T, W, Y, V).

5. Frequently Asked Questions (FAQ)

Q1: What are daltons (Da)?
A: A dalton is a unit of mass widely used to express atomic and molecular masses. It is defined as 1/12 of the mass of an unbound neutral atom of carbon-12.

Q2: Does this calculator consider post-translational modifications?
A: No, this calculator provides the theoretical molecular weight based on the amino acid sequence only. Post-translational modifications would need to be calculated separately.

Q3: Why is water included in the calculation?
A: Water is added to account for the terminal amino and carboxyl groups that are formed when amino acids join together through peptide bonds, releasing water molecules in the process.

Q4: What if my sequence contains non-standard amino acids?
A: This calculator only recognizes the 20 standard amino acids. Non-standard amino acids would need to be calculated manually and added to the result.

Q5: How accurate is this calculation?
A: This provides a theoretical molecular weight based on monoisotopic masses. For precise measurements, experimental techniques like mass spectrometry are required.