Electrospray ionization mass spectrometryESIMS of the polype

Electrospray ionization mass spectrometry(ESI-MS) of the polypeptide chain hemoglobin yielded a series of m/z peaks. Two successive peaks had m/z values of 2601.9 and 2709.3, respectively. Calculate the mass of the hemoglobin polypeptide chain.

Solution

Answer:

We can determine the number of charges on the peak at 2709.3 using the following equation:

z 2 = ((m1/z 1 ) – H) / (( m2/z 2 ) – (m1/z 1 )) [H is the mass of a proton]

Therefore, z_2709.3 = (2601-1) / (2709.3-2601)

= 2600/108.3 = 24

Molecular mass can be derived from the following eqaution:

M = z (m /z - H)

= 24 (2709.3-1) = 24 * 2708.3 = 64,999.2 Da

Actual mass of hemoglobin = 64,458 Da

So, error = 541.2 Da

64,999.2 Da +/- 541.2 Da