NO2 a) A sample (497 mg) of an oligomeric protein of M 145,000 was treated coOH

Question

NO2 a) A sample (497 mg) of an oligomeric protein of M 145,000 was treated coOH with an excess of 1-fluoro-2,4-dinitrobenzene (Sanger's reagent) under slightly alkaline conditions until the chemical reaction was complete. The peptide bonds of the protein were then completely hydrolyzed by heating it with concentrated HCI. The hydrolysate was found to contain 4.85 mg of DNP-Val (shown at the right). 2,4-Dinitrophenyl derivatives of the a- amino groups of other amino acids could not be found ON/ C/ HA Calculate the number of polypeptide chains in this protein. Give the answer as a whole number. Incorrect Please enter a value for the number of chains. Number

Explanation / Answer

mmoles of 2,4-dinitrophenyl derivative = mass / molar mass

                                                          = 4.85 / 256

                                                           = 0.0189 mmol

mmoles of protein = 497 / 145000 = 3.43 x 10^-3

number of poly peptides bonds = 0.0189 / 3.43 x 10^-3

                                                  = 5.5

number of poly peptides bonds = 6.0

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