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(a) The ESI-MS spectrum below was obtained for hen egg-white lysozyme (HEWL). Using peaks 5 and 6, calculate the molecular mass of HEWL (see Sample Calculation 5-1).

[http://www.astbury.leeds.ac.uk/facil/MStut/mstutorial.htm. Published by A.E. Ashcroft, Astbury Centre for Structural Molecular Biology, University of Leeds (2000)]

(b) What is the charge on the ion that makes peak 5?

Short Answer

Expert verified

(a) The molecular mass of HEWL is 14,312.8.

(b) The charge on the ion which makes peak 5 is 9.00.

Step by step solution

01

Electrospray ionization mass spectrometry (ESI - MS)

Electrospray ionization mass spectrometry (ESI-MS) is the technique used to characterize and sequence polypeptide. The ESI mass spectrum of any molecule can be used to determine its molecular mass and charge.

The molecular mass can be determined by using the formula

And the charge on the ion can be calculated using the formula

Here, M is the Molecular mass

p1and p2are the two peaks used for calculating molecular mass

z is the charge on the ion.

02

Calculation for molecular mass

p1 = 1590.6 and p2 = 1789.2

Thus, the molecular mass of HEWL is 14,312.8.

03

Calculation for charge on ion

Thus, charge on the ion which makes peak 5 is 9.00.

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Most popular questions from this chapter

You must cleave the following peptide into smaller fragments. Which of the proteases listed in Table 5-4 would be likely to yield the most fragments? The fewest?

NMTQGRCKPVNTFVHEPLVDVQNVCFKE

You wish to sequence the light chain of a protease inhibitor from the Brassica nigra plant. Cleavage of the light chain by trypsin and chymotrypsin yields the following fragments. What is the sequence of the light chain?

Chymotrypsin

1. Leu–His–Lys–Gln–Ala–Asn–Gln–Ser–Gly–Gly–Gly–Pro–Ser

2. Gln–Gln–Ala–Gln–His–Leu–Arg–Ala–Cys–Gln–Gln–Trp

3. Arg–Ile–Pro–Lys–Cys–Arg–Lys–Phe

Trypsin

4. Arg

5. Ala–Cys–Gln–Gln–Trp–Leu–His–Lys

6. Cys–Arg

7. Gln–Ala–Asn–Gln–Ser–Gly–Gly–Gly–Pro–Ser

8. Phe–Gln–Gln–Ala–Gln–His–Leu–Arg

9. Ile–Pro–Lys

10. Lys

Which peptide has greater absorbance at 280 nm?

A. Gln–Leu–Glu–Phe–Thr–Leu–Asp–Gly–Tyr

B. Ser–Val–Trp–Asp–Phe–Gly–Tyr–Trp–Ala

Explain why a certain protein has an apparent molecular mass of 90kDwhen determined by gel filtration and 60kDwhen determined by SDS-PAGE in the presence or absence of 2-mercaptoethanol. Which molecular mass determination is more accurate?

What types of information can be retrieved from a protein sequence database?

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