Question

An oligomeric protein has a molecular weight of 219000. A 650 mg sample was treated with an excess of 1-fluoro-2,4-dinitrobenzene (Sanger\'s reagent) until the reaction was complete. Next the peptide bonds were hydrolyzed by heating with concentrated HCl. The product of the complete hydrolysis contained 4.9 mg of the compound shown below, and no other 2,4-dinitrophenyl derivatives of the α-amino groups of other amino acids could be found. How many polypeptide chains are in this protein? (Enter your answer as a whole number).

Answer 1

ans)

From above data that

First, we need to find out the number of moles by this formula.

no of moles = mass/molar mass

number of moles of 2,4-dinitrophenyl = 4.9 mg/ 256g/mol = 0.019140 mmol

where 256g is the molar mass of 2,4-dinitrophenyl.

similarly, the number of moles of protein = 650mg/219000g/mol = 0.00296803 mmol

therefore, the number of polypeptides present in this sample would be

= 0.019140 mmol peptide bonds/0.00296803 mmol proteins

= 6.45 peptide chains

~ 6.5 peptide chains in the given sample.