1. What is Protein Molecular Weight?

Protein molecular weight is the sum of the atomic weights of all atoms in a protein molecule. For proteins, this is calculated by summing the molecular weights of individual amino acids in the sequence and accounting for water loss during peptide bond formation.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( MW \) — Molecular weight in Daltons (Da)
• \( \sum(\text{Amino Acid MW}) \) — Sum of individual amino acid molecular weights

Explanation: The calculation accounts for the molecular weight of each amino acid in the protein sequence plus the molecular weight of water (18.02 Da) which is added during the hydrolysis of the peptide bonds.

3. Importance of Molecular Weight Calculation

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

4. Using the Calculator

Tips: Enter the amino acid sequence using single-letter codes (e.g., "GAMMA"). The sequence can be entered with or without spaces. Only standard amino acids are supported.

5. Frequently Asked Questions (FAQ)

Q1: Why is water molecular weight added in the calculation?
A: During protein synthesis, a water molecule is removed for each peptide bond formed. When calculating molecular weight, we add back one water molecule to account for the complete protein.

Q2: Are modified amino acids supported?
A: This calculator uses standard amino acid molecular weights. Modified amino acids (phosphorylated, glycosylated, etc.) would require specialized calculations.

Q3: What is the accuracy of this calculation?
A: This provides a theoretical molecular weight. Actual experimental values may vary slightly due to protein modifications, buffer conditions, and measurement techniques.

Q4: Can I calculate molecular weight for nucleic acids?
A: This calculator is specifically designed for proteins. Nucleic acids require a different calculation method based on nucleotide composition.

Q5: How does molecular weight relate to protein size?
A: While molecular weight indicates mass, protein size also depends on tertiary structure. Larger molecular weight generally correlates with larger physical size, but folded conformation affects this relationship.