1. What is Protein Molecular Weight Calculation?

Protein molecular weight calculation determines the mass of a protein based on its amino acid sequence. The molecular weight is the sum of the masses of all amino acids in the polypeptide chain, adjusted for water loss during peptide bond formation.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( MW \) — Molecular weight in daltons (Da)
• \( \sum \) — Summation of all amino acid masses
• \( AA\ masses \) — Standard masses of individual amino acids

Explanation: The calculation accounts for the mass of each amino acid in the sequence plus the mass of water (for the terminal -H and -OH groups).

3. Importance of Molecular Weight Calculation

Details: Accurate molecular weight determination is crucial for protein characterization, electrophoresis, mass spectrometry, chromatography, and various biochemical applications.

4. Using the Calculator

Tips: Enter the amino acid sequence using single-letter codes. The calculator will automatically remove any non-amino acid characters and calculate the molecular weight.

5. Frequently Asked Questions (FAQ)

Q1: What are the units for molecular weight?
A: Molecular weight is calculated in daltons (Da), where 1 dalton is defined as 1/12 the mass of a carbon-12 atom.

Q2: Does this account for post-translational modifications?
A: No, this calculator provides the theoretical molecular weight based solely on the amino acid sequence without modifications.

Q3: How accurate is this calculation?
A: This provides a theoretical value based on average isotopic masses. For precise work, consider using monoisotopic masses.

Q4: What about disulfide bonds?
A: Disulfide bonds reduce molecular weight by 2 Da per bond (loss of 2 hydrogen atoms).

Q5: Can I calculate molecular weight for modified amino acids?
A: This calculator uses standard amino acid masses. For modified residues, you would need specialized software.