1. What is the Expasy Protein Mass Calculator?

The Expasy Protein Mass Calculator computes the molecular weight of a protein from its amino acid sequence using monoisotopic masses of individual amino acids. It follows the same algorithm as the original Expasy tool.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( MW \) — Molecular weight in Daltons (Da)
• \( AA \) — Individual amino acid in the sequence
• \( Mass_{AA} \) — Monoisotopic mass of the amino acid

Explanation: The calculator sums the monoisotopic masses of all amino acids in the input sequence to determine the total molecular weight.

3. Importance of Molecular Weight Calculation

Details: Accurate molecular weight calculation is essential for protein characterization, mass spectrometry analysis, gel electrophoresis, and various biochemical applications.

4. Using the Calculator

Tips: Enter the amino acid sequence using single-letter codes. The calculator automatically removes non-amino acid characters and converts to uppercase. Only standard 20 amino acids are considered.

5. Frequently Asked Questions (FAQ)

Q1: What are monoisotopic masses?
A: Monoisotopic mass is the mass of a molecule calculated using the exact mass of the most abundant isotope of each element.

Q2: Does this include post-translational modifications?
A: No, this calculator only considers the standard amino acid masses without modifications.

Q3: How accurate is the calculation?
A: The calculation uses established monoisotopic masses and provides high accuracy for theoretical molecular weight determination.

Q4: What about non-standard amino acids?
A: Non-standard amino acids are not included in the calculation. Only the 20 standard amino acids are recognized.

Q5: Can I calculate molecular weight with modifications?
A: For modified proteins, specialized tools that account for specific post-translational modifications should be used.