1. What is kDa Calculation?

The kilodalton (kDa) calculation converts the sum of amino acid molecular weights to kilodaltons (1 kDa = 1000 Daltons). This measurement is commonly used to describe protein size and molecular weight.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( aa_{mw} \) — Molecular weight of each amino acid in the sequence (Daltons)
• 1000 — Conversion factor from Daltons to kilodaltons

Explanation: The calculator sums the molecular weights of all amino acids in the sequence and divides by 1000 to convert to kDa.

3. Importance of Molecular Weight

Details: Knowing a protein's molecular weight is essential for gel electrophoresis, protein purification, structural studies, and biochemical characterization.

4. Using the Calculator

Tips: Enter the amino acid sequence using single-letter codes (case insensitive). The calculator will ignore any non-amino acid characters.

5. Frequently Asked Questions (FAQ)

Q1: What are the single-letter amino acid codes?
A: A (Ala), R (Arg), N (Asn), D (Asp), C (Cys), E (Glu), Q (Gln), G (Gly), H (His), I (Ile), L (Leu), K (Lys), M (Met), F (Phe), P (Pro), S (Ser), T (Thr), W (Trp), Y (Tyr), V (Val).

Q2: Does this include post-translational modifications?
A: No, this calculates only the molecular weight of the unmodified polypeptide chain.

Q3: How accurate is this calculation?
A: It provides the theoretical average molecular weight. Actual experimental values may vary slightly.

Q4: Does it account for water loss during peptide bond formation?
A: No, this calculates the sum of amino acid residues. For exact protein molecular weight, subtract 18.015 Da for each peptide bond.

Q5: Can I use three-letter codes?
A: No, only single-letter codes are accepted in this calculator.