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Determining the subunit composition of a protein from data

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You isolate a new protein. Column chromatography, in Tris-HCl buffer pH 7.4, demonstrates that this protein has a molecular weight of 110,000 D. Chromatography in the presence of 6 M guanidine hydrochloride demonstrates two peaks with masses of approximately 13,000 and approximately 26,000 D. The peak at approximately 26,000 D contains 80.3%, by mass, of the protein. The protein from this peak, when analyzed using isoelectric focusing column chromatography demonstrates that this peak contains two different proteins, each being 50% of the mass of this peak and both with acidic pIâ??s. These two 26,000 D proteins are separately treated with a^-mercaptoethanol and analyzed by column chromatography in the presence of 6 M guanidine hydrochloride. This demonstrates equal amounts of three peptides with molecular weight of 10,000 D, 9,000 D, and 7,500 D for one protein and 17,500 and 9,000 for the other protein. From these data, determine what the composition of this new protein is.

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This should be a multi-subunit protein with the following composition:

2 of the 13 kDa subunits (since the first two peaks showed an approximate 80% to 20%, the 20% being the 13000 D weight. 80% was the 26 kDa peak).

The 26 kDa protein is further broken up ...

Solution Summary

In this solution we explore how to elucidate the number and types of subunits of a multi-unit protein from biochemical data. A detailed approach to the problem is provided in the solution.

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Amino acids multiple choice questions

Which statement is incorrect about the classification of amino acids?
a. Alanine and valine are neutral, nonpolar amino acids.
b. Lysine and arginine are basic amino acids.
c. Tryptophan and phenylalanine are aromatic amino acids.
d. Aspartic acid and aspargine are acidic amino acids.

Which of the following amino acids is the least water soluble at pH 7.0?
a. Tryptophan
b. Glutamic acid
c. Cysteine
d. Histidine

Which amino acid would migrate the furthest toward the anode (positive electrode) during paper electrophoresis at pH 7.0?
a. Aspartic acid
b. Alanine
c. Lysin
d. Glutamine

Which of the following functional groups, attached to an inert matrix, could function as a cation exchanger?
a. Diethylaminoethyl-
b. p-aminobenzyl-
c. Carboxymethyl-
d. Trimethylammonium-

Which of the following amino acids would make the best buffer at pH 4.5?
a. Histidine
b. Alanine
c. Glutamine
d. Aspartic acid

Which fact is incorrect about stereoisomers?
a. A diastereomer is a nonsuperimposable non-mirror image.
b. An enantiomer is a nonsuperimposible mirror image.
c. Diastereomers have different melting points.
d. Diastereomers rotate plane polarized light in equal but opposite direction.

Which statement is incorrect about L-isoleucine?
a. Its enantiomer is named O-isoleucine.
b. It contains a total of two asymmetric or chiral carbons.
c. It can also be named as (28, 38)-isoleucine using the (R,8) system.
d. Its diastereomer would be named O-alloisoleucine.

An isoelectric amino acid was dissolved in water and the resulting pH was approximately 7.6. What amino acid would possess this property?
a. Alanine
b. Glutamic acid
c. Histidine
d. Lysine

What volume of NaOH is required to adjust the solution of monosodium aspartate to pH 9.8?
a. 1 ml
b. 2 ml
c. 3 ml
d. 6 ml or more

What volume of 2 N Hel is required to completely titrate the 4 mmol of monosodium aspartate?
a. 2 ml
b. 3ml
c. Aml
d. 6 ml or more

Which statement is correct about the peptide ala-ser?
a. Alanine is at the N-terminal of the peptide.
b. There are a total six atoms that lie in the plane of the peptide bond linking alanine to serine.
c. The alpha-carbon of alanine is sp3 hybridized d All the above are correct statements.

What is the product formed from the acid hydrolysis of a simple amide?
a. Acid & base
b. Aldehyde & alcohol
c. Acid & amine
d. Ester & alcohol

The complete acid hydrolysis of the peptide ala-gln-trp-ser would yield:
a. Ala, gin, trp, ser
b. Ala, glu, ser
c. Ala, glu, trp, ser
d. Ala. ser

Fibrous proteins, such as collagen, have which of the following properties?
a. Highly soluble in water
b. Their hydrophilic residues are directed into the interior of the protein
c. Exhibit enzymatic activity
d. Serve structural roles in the cell

Quaternary structure is associated with:
a. The overall shape of a polypeptide chain
b. The sum of the secondary and tertiary interactions
c. Simple proteins with only one subunit
d. The relative orientation of one polypeptide to another polypeptide in a multi-subunit protein.

The information needed to define the structure of a protein is essentially contained in:
a. Amino acid composition
b. Amino acid sequence
c. Secondary structure
d. Tertiary structure.

Insulin is a polypeptide hormone that contains two short polypeptide chains linked by two interstrand disulfide bonds. The most logical order of events to perform in order to sequence this protein would be:
A: The peptides are reduced with mercaptoethanol.
B: The peptides are sequenced using Edman chemistry .
C: The peptides are separated by chromatography techniques. 0: The peptides are alkylated with iodoacetamide.
a. A, D,C, B b.C,A, 0, B
c. C, B, A, 0
d. A, B, C, 0

Which statement is incorrect about the peptide val-asp-trp-asn-ser?
a. This peptide would show a strong absorption band at 280 nm.
b. Reaction with chymotrypsin would yield two peptides.
c. To synthesize this peptide using the solid phase method of Merrifield, the amino acid directly attached to the resin would be serine.
d. After the second round of Edman chemistry using the reagent PITC, the PTH -amino acid residue released would be PTH-asn.

Which statement is incorrect about the reaction of the peptide ser-Iys-asp-trp-cys-metasn-phe-ala with the following reagents?
a. Reaction with cyanogens bromide would yield two peptides.
b. Reaction with trypsin would result in three peptides. The smallest of three peptides would have the highest pi of the three.
c. Reaciton with chymotrypsin would result in the peptides ser-Iys-asp & try-cys-met-Iysasn-phe-ala .
d. Reaction with chymotrypsin would yield a different set of peptides that overlap those obtained with tryspsin

Determine the amino acid sequence of the following oligopeptide from the experimental data below:
The amino acid composition is found the be ala, Iys, phe, met, cys plus some
decompsition products.
2. The peptide has a molecular weight around 700 Da and absorbs at 280 nm.
3. Treatment with carboxypeptidase results in tryptophan and a peptide.
4. CNBr treatment yields a tetrapeptide and a dipeptide.
5. Trypsine digestion produces an amino acid and a pentapeptide with met on the amino end.
6. Chymotrypsin digestion yields a dipeptide and a tetrapeptide.
a. trp-Iys-met-cys-met-ala
b. Iys-met-cys-phe-ala-trp
c. trp-ala-phe-cys-met-Iys
d. Iys-ala-cys-phe-met -trp

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