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Molecular Weight Formula:
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Molecular weight calculation determines the mass of a protein molecule based on its amino acid sequence. It's essential for various biochemical applications including protein characterization, quantification, and experimental design.
The calculator uses the formula:
Where:
Explanation: The calculation sums the weights of all amino acids in the sequence and adds the weight of water to account for the terminal amino and carboxyl groups.
Details: Accurate molecular weight calculation is crucial for protein quantification, gel electrophoresis interpretation, mass spectrometry analysis, and determining appropriate concentrations for experiments.
Tips: Enter the amino acid sequence using single-letter codes (e.g., "GADV" for Glycine-Alanine-Aspartic acid-Valine). The calculator is case-insensitive and will ignore any non-amino acid characters.
Q1: Does this account for post-translational modifications?
A: No, this calculator provides the theoretical molecular weight of the unmodified polypeptide chain. Modifications like phosphorylation or glycosylation would add additional mass.
Q2: Why is water molecular weight added?
A: Water molecular weight (18.02 g/mol) is added to account for the hydrogen and hydroxyl groups that are lost when amino acids form peptide bonds, except at the terminal ends.
Q3: Are disulfide bonds considered in this calculation?
A: No, this calculator does not account for disulfide bond formation, which would slightly reduce the molecular weight due to loss of hydrogen atoms.
Q4: What about non-standard amino acids?
A: This calculator only recognizes the 20 standard amino acids. Non-standard amino acids would need to be calculated separately and added to the result.
Q5: How accurate is this calculation compared to experimental methods?
A: This provides a theoretical value. Experimental methods like mass spectrometry may yield slightly different results due to isotopic distributions and other factors.