Determining Protein Molecular Weight and Tryptophan Residues
How can we calculate the minimum molecular weight of the protein based on the given data?
a. By determining the weight percentage of tryptophan in the protein
How many tryptophan residues are present in a molecule of the new protein?
b. Use the molecular weight estimate from size-exclusion chromatography to find out
Answer:
The minimum molecular weight of the protein is 2040 Daltons and it contains 262 tryptophan residues.
Explanation:
a. The minimum molecular weight of the protein can be calculated by dividing the weight percentage of tryptophan by the weight of tryptophan (0.48% / 0.0048 = 10). Therefore, the minimum molecular weight of the protein is 10 times the molecular weight of tryptophan, which is 10 x 204 = 2040 Daltons.
b. To determine the number of tryptophan residues in the protein, we can use the molecular weight estimate from the size-exclusion chromatography (53500 Daltons). Divide the molecular weight estimate by the molecular weight of tryptophan (53500 / 204 = 262.25). Since we can't have a fraction of an amino acid residue, we round down to 262 tryptophan residues in a molecule of the new protein.