Molecular Weight Of Protein Calculator

Protein Molecular Weight Formula:

\[ MW (kDa) = \frac{\text{Sequence length} \times \text{Average AA mass}}{1000} \]

Molecular Weight:

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1. What Is Protein Molecular Weight?

Protein molecular weight is a measure of the mass of a protein molecule, typically expressed in kilodaltons (kDa). It's calculated based on the number of amino acids in the protein sequence and their average mass.

2. How Does The Calculator Work?

The calculator uses the protein molecular weight formula:

\[ MW (kDa) = \frac{\text{Sequence length} \times \text{Average AA mass}}{1000} \]

Where:

Sequence length — Number of amino acid residues in the protein
Average AA mass — Average mass of an amino acid (typically ~110 daltons)
1000 — Conversion factor from daltons to kilodaltons

Explanation: This formula provides an approximate molecular weight based on the protein's length and the average mass of amino acids.

3. Importance Of Molecular Weight Calculation

Details: Knowing a protein's molecular weight is essential for various applications in biochemistry and molecular biology, including gel electrophoresis, protein purification, concentration determination, and structural studies.

4. Using The Calculator

Tips: Enter the number of amino acid residues in your protein sequence and the average amino acid mass (110 daltons is a standard value). The calculator will provide the estimated molecular weight in kilodaltons.

5. Frequently Asked Questions (FAQ)

Q1: Why is 110 daltons used as the average amino acid mass?
A: 110 daltons represents the average molecular weight of amino acids in proteins, accounting for the loss of water molecules during peptide bond formation.

Q2: How accurate is this calculation?
A: This provides an approximation. For precise molecular weight, the exact amino acid sequence should be used to account for variations in individual amino acid masses.

Q3: What's the difference between daltons and kilodaltons?
A: 1 kilodalton (kDa) equals 1000 daltons. Kilodaltons are commonly used for protein molecular weights as they provide more manageable numbers.

Q4: Does this account for post-translational modifications?
A: No, this calculation provides the theoretical molecular weight of the unmodified polypeptide chain. Modifications like phosphorylation or glycosylation will increase the actual molecular weight.

Q5: Can I use this for short peptides?
A: Yes, but for very short peptides (less than 10 residues), the approximation may be less accurate due to greater influence of specific amino acid composition.