Calculate Protein Molecular Weight

Protein Molecular Weight Formula:

\[ MW (Da) = \sum (AA\ residue\ masses\ (Da)) \]

Molecular Weight:

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1. What Is Protein Molecular Weight?

Protein molecular weight is the sum of the masses of all amino acid residues in the protein chain, typically measured in daltons (Da). It's a fundamental property used in protein characterization, purification, and analysis.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ MW (Da) = \sum (AA\ residue\ masses\ (Da)) \]

Where:

MW — Molecular weight in daltons (Da)
AA residue masses — Standard masses of individual amino acids
The calculation includes the mass of a water molecule (18.02 Da) for the complete protein

Explanation: The calculator sums the masses of all amino acids in the sequence and adds the mass of one water molecule to account for the complete protein structure.

3. Importance of Molecular Weight Calculation

Details: Knowing a protein's molecular weight is essential for various applications including gel electrophoresis, chromatography, mass spectrometry, protein purification, and biochemical research.

4. Using the Calculator

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

5. Frequently Asked Questions (FAQ)

Q1: What are the standard amino acid masses used?
A: The calculator uses standard residue masses based on average isotopic composition, which are commonly used in molecular weight calculations.

Q2: Why is water mass added to the calculation?
A: The water molecule accounts for the hydrolysis of the peptide bonds during protein formation, representing the complete molecular weight of the protein.

Q3: Does this account for post-translational modifications?
A: No, this calculator provides the theoretical molecular weight of the unmodified protein chain. Modifications like phosphorylation or glycosylation would add additional mass.

Q4: What about non-standard amino acids?
A: The calculator only recognizes the 20 standard amino acids. Non-standard amino acids will be removed from the sequence during processing.

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