1. What Is Protein Molecular Weight Calculation?

Protein molecular weight calculation estimates the mass of a protein based on its amino acid sequence. This is essential for various biochemical applications including protein purification, electrophoresis, and mass spectrometry analysis.

2. How Does The Calculator Work?

The calculator uses the formula:

Where:

• \( \sum AA_{MW} \) — Sum of individual amino acid molecular weights
• \( n \) — Number of amino acids in the sequence
• \( 18.015 \) — Molecular weight of water (lost during peptide bond formation)

Explanation: The calculation accounts for water molecules lost during the formation of peptide bonds between amino acids.

3. Importance Of Protein Molecular Weight

Details: Knowing a protein's molecular weight is crucial for experimental design, protein characterization, gel electrophoresis, chromatography, and understanding protein structure-function relationships.

4. Using The Calculator

Tips: Enter the protein's 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: Why subtract water molecules?
A: During peptide bond formation, a water molecule is removed for each bond created between amino acids.

Q2: Does this account for post-translational modifications?
A: No, this calculator provides the theoretical molecular weight of the unmodified polypeptide chain.

Q3: What about N-terminal and C-terminal modifications?
A: This calculation assumes standard amino and carboxyl termini. Special modifications are not included.

Q4: How accurate is this calculation?
A: It provides a theoretical value accurate for most applications, but actual measured values may vary slightly due to isotopic distributions and other factors.

Q5: Can I use three-letter amino acid codes?
A: No, this calculator only accepts single-letter amino acid codes (A, R, N, D, C, E, Q, G, H, I, L, K, M, F, P, S, T, W, Y, V).