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Chapter 5: Q30P. (page 129)

(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 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鈥揌is鈥揕ys鈥揋ln鈥揂la鈥揂sn鈥揋ln鈥揝er鈥揋ly鈥揋ly鈥揋ly鈥揚ro鈥揝er

2. Gln鈥揋ln鈥揂la鈥揋ln鈥揌is鈥揕eu鈥揂rg鈥揂la鈥揅ys鈥揋ln鈥揋ln鈥揟rp

3. Arg鈥揑le鈥揚ro鈥揕ys鈥揅ys鈥揂rg鈥揕ys鈥揚he

Trypsin

4. Arg

5. Ala鈥揅ys鈥揋ln鈥揋ln鈥揟rp鈥揕eu鈥揌is鈥揕ys

6. Cys鈥揂rg

7. Gln鈥揂la鈥揂sn鈥揋ln鈥揝er鈥揋ly鈥揋ly鈥揋ly鈥揚ro鈥揝er

8. Phe鈥揋ln鈥揋ln鈥揂la鈥揋ln鈥揌is鈥揕eu鈥揂rg

9. Ile鈥揚ro鈥揕ys

10. Lys

You wish to determine the sequence of a polypeptide that has the following amino acid composition.

1 Ala 4 Arg 2 Asn 3 Asp 4 Cys 3 Gly 1 Gln 4 Glu 1 His 1 Lys 1 Met 1 Phe 2 Pro 4 Ser 2 Tyr 1 Trp

(a) What is the maximum number of peptides you can expect if you cleave the polypeptide with cyanogen bromide?

(b) What is the maximum number of peptides you can expect if you cleave the polypeptide with chymotrypsin?

(c) Analysis of the intact polypeptide reveals that there are no free sulfhydryl groups. How many disulfide bonds are likely to be present?

(d) How many different arrangements of disulfide bonds are possible?

Treatment of a polypeptide with 2-mercaptoethanol yields two polypeptides:

1. Ala鈥揤al鈥揅ys鈥揂rg鈥揟hr鈥揋ly鈥揅ys鈥揕ys鈥揂sn鈥揚he鈥揕eu

2. Tyr鈥揕ys鈥揅ys鈥揚he鈥揂rg鈥揌is鈥揟hr鈥揕ys鈥揅ys鈥揝er

Treatment of the intact polypeptide with trypsin yields fragments with the following amino acid compositions:

3. (Ala, Arg, Cys2, Ser, Val)

4. (Arg, Cys2, Gly, Lys, Thr, Phe)

5. (Asn, Leu, Phe)

6. (His, Lys, Thr)

7. (Lys, Tyr)

Indicate the positions of the disulfide bonds in the intact polypeptide.

Draw a different phylogenetic tree based on the data in Problem 19.

Protein X has an absorptivity of 0.4mL 路 mg-1路 cm-1 at 280nm. What is the absorbance at 280nm of a 2.0 mg 路 mL-1solution of protein X? (Assume the light path is 1cm.)
See all solutions

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