Protein Molecular Weight Calculator Kda

Protein Molecular Weight Formula:

\[ MW_{kDa} = \frac{\sum (AA\ MW)}{1000} \]

Molecular Weight:

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1. What is Protein Molecular Weight?

Protein molecular weight is the sum of the atomic weights of all atoms in a protein molecule, typically expressed in kilodaltons (kDa). It's a fundamental property used in protein characterization, purification, and analysis.

2. How Does the Calculator Work?

The calculator uses the formula:

\[ MW_{kDa} = \frac{\sum (AA\ MW)}{1000} \]

Where:

\( MW_{kDa} \) — Molecular weight in kilodaltons
\( \sum (AA\ MW) \) — Sum of individual amino acid molecular weights in g/mol
1000 — Conversion factor from g/mol to kDa

Explanation: The calculator sums the molecular weights of all amino acids in the sequence and converts the total from g/mol to kDa by dividing by 1000.

3. Importance of Molecular Weight Calculation

Details: Accurate molecular weight calculation is essential for protein purification techniques (SDS-PAGE, size exclusion chromatography), mass spectrometry analysis, and biochemical characterization of proteins.

4. Using the Calculator

Tips: Enter the protein amino acid sequence using single-letter codes. The calculator automatically removes spaces and non-amino acid characters. Only standard 20 amino acids are supported.

5. Frequently Asked Questions (FAQ)

Q1: What are the molecular weights of individual amino acids?
A: Amino acid weights range from 75.07 g/mol (Glycine) to 204.23 g/mol (Tryptophan). The calculator uses standard molecular weights for all 20 amino acids.

Q2: Does this include post-translational modifications?
A: No, this calculator only calculates the molecular weight of the unmodified polypeptide chain. Modifications like phosphorylation or glycosylation will increase the actual molecular weight.

Q3: Why is molecular weight expressed in kDa?
A: Kilodaltons (kDa) are commonly used in biochemistry because protein molecular weights typically range from a few to several hundred kDa, making this unit more convenient than g/mol.

Q4: How accurate is this calculation?
A: The calculation provides the theoretical molecular weight based on amino acid composition. Actual experimental values may vary slightly due to isotopic distribution and measurement techniques.

Q5: Can I use three-letter codes?
A: No, this calculator only accepts single-letter amino acid codes. Convert three-letter codes to single-letter format before calculation.