Chapter 5: Q5-4CP (page 109)
Describe how a protein may be quantified by an assay or by absorbance spectroscopy.
A protein may be quantified by observing the rate of product formation bycoupled enzyme assay, radioimmunoassay (RIA), and enzyme – linked immunosorbent assay (ELISA).
Over 30 million students worldwide already upgrade their learning with Vaia!
All the tools & learning materials you need for study success - in one app.
Get started for free
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
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?
Electrospray ionization mass spectrometry (ESI-MS) of proteins involves creating positively charged ions of the protein and separating them according to their mass-to-charge ratio (m/z).
(a) What causes the different positive charges on different particles of the protein?
(b) The amino acid composition (in numbers of residues per chain) of hen egg-white lysozyme (HEWL) is as follows:
P 2 Y 3 N 14 H 1
D 7 M 2 L 8 E 2
C 8 R 11 G 12 F 3
A 12 I 6 K 6 V 6
S 10 W 6 T 7 Q 3
What is the maximum positive charge that can be present on a HEWL ion?
Treatment of a polypeptide with 2-mercaptoethanol yields two polypeptides:
1. Ala–Val–Cys–Arg–Thr–Gly–Cys–Lys–Asn–Phe–Leu
2. Tyr–Lys–Cys–Phe–Arg–His–Thr–Lys–Cys–Ser
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.
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?
What do you think about this solution?
We value your feedback to improve our textbook solutions.
