5A. (10 points) Use these results from each peak to calculate a molecular mass f

Question

5A. (10 points) Use these results from each peak to calculate a molecular mass for porcine insulin. Compare these results to the known/accepted values for its molecular mass (a web reference is OK) and include your reference citation.

5B. (5 points) Each of the four labeled “peaks” is actually not a distinct peak but a group of close-together moieties. Why does the spectrum have this appearance?

5C. (5 points) What are the unlabeled smaller spikes likely to be? There is one evident between the 6+ and 5+ peaks and two are present between the 5+ and 4+ peaks.

Explanation / Answer

A) Based on literature survey found that the mass value of porcine insulin is 5777.54.

(Kumiko Iwata et. al Current Aging Science, 3(1), 26-33 (2010))

As per the mass spectrum; the mass value can be calculated using M+Z/Z.

for 1445 peak; M+Z/Z=1445 (Z = 4)

M+Z=1445XZ; M+4=1445X4; M+4=5780; M= 5780-4; M=5776:

For 1157 peak; M+Z/Z=1157 (Where Z= 5)

M+Z=1157XZ; M+5=1157X5; M+5=5785; M= 5785-5; M=5780:

For 964 peak; M+Z/Z=964 (Where Z= 6)

M+Z=964XZ; M+6=964X6; M+6=; M= 5784; M= 5784-6; M=5778:

For 829 peak; M+Z/Z=829 (Where Z= 7)

M+Z=829XZ; M+7=829X7; M+7= 5803; M= 5803-7; M=5776.

If you compare all the values the value is 5776-5778 and, that means it is almost equal to MALDI mass value 5777.54 if you consider all digits since it is electron spray ionization the values varies from literature value.

B) In Electrospray ionization (ESI) mass spectrometry technique ions produce using an electrospray in which a high voltage is applied to a liquid. It is especially useful in producing ions from macromolecules because it overcomes the propensity of these molecules to fragment when ionized. Hence for macromolecules like proteins in the case of insulin mass spectrum peaks are not distinct they are group this is because of the when voltage applied to sample it burst and form ionization, due to more chances to form ions in case of proteins they form like bunch of peaks.

C) The unlabelled smaller peaks are fragments. they might not found which fragmentation happened because of large molecule. That is the reason they did not labelled

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