Primary structure

In SDS polyacrylamide gel electrophoresis __________ chains move the fastest.

Low molecular weight

Of matrix assisted and electrospray which is the technique more frequently used?

Electrospray

The proposed sequence of a peptide is Ala-Lys-Leu-Phe-Arg-Arg. Digestion with cyanogen bromide produces ______ fragments.

1

Protein _________ determines the order of amino acids in a protein.

sequencing

A peptide contains exactly 1 Asp, Leu, Lys, Met, Phe and Tyr (alphabetical order). Reaction with cyanogen bromide has no effect. This means the last residue of the peptide is ________.

Met

In gel filtration chromatography ________ molecules come of the column first.

High molecular weight

The most commonly used affinity chromatography __________.

Uses bound metal to bind to a poly-His sequence

__________ cleaves after Asn and Gln amino acids.

None of these

__________ reactions limits the number of rounds of Edman sequencing that can be done with a particular peptide.

incomplete

Matrix assisted and electrospray are the 2 main mass spectrometry techniques.

True

After tryptic and chymotryptic co-digestion you have the following fragments of an 8-residue peptide: K, MD, EATF.  Edman sequencing indicates the first 2 residues are EA. What is the sequence of the peptide using single letter amino acid names.

EATFKKMD

You react your peptide with dithiothreitol and get 3 fragments. This means there is at least ____________

2 disulfide bonds

A 10-residue peptide is digested with CNBr producing 2 fragments. You conclude that

none of these

You have the following fragments from your 10-residue peptide; PST, CALY, TCVM, LYPS. What is the sequence of your 10-residue peptide?

CALYPSTCVM

The amino acid composition of a 12-residue peptide is Ala₂, Glu₂, Lys₂, Phe₂, Ser₄. Treatment with trypsin produced a single unique peptide with sequence Glu-Ala-Ser-Phe-Ser-Lys. What is the sequence of the complete 12-residue peptide?

Glu-Ala-Ser-Phe-Ser-Lys-Glu-Ala-Ser-Phe-Ser-Lys

EASFSKEASFSK

In mass spectrometry molecules are separated by their _________.

Charge/mass ratio

A peptide contains exactly 1 Asp, Leu, Lys, Met, Phe and Tyr (alphabetical order). Reaction with staphylococcal protease has no effect. This means the last residue of the peptide is ________.

Asp

Of matrix assisted and electrospray which is the technique more frequently used?

Electrospray

Cleavage by in 6 N HCl at 100 C of the nonapeptide shown above produces _________.

9 fragments -- individual amino acids

The proposed sequence of a peptide is Ala-Lys-Leu-Phe-Arg-Arg. Digestion with chymotrypsin produces ______ fragments.

2

__________ cuts the polypeptide chain with high specificity. You may select multriple answers

trypsin

cyanogen bromide

You need to isolate a protein from a virus. Your first choice for purification is

No best choice

The proposed sequence of a peptide is Ala-Lys-Leu-Phe-Arg-Arg. Digestion with staphylococcal protease produces ______ fragments.

1

Digestion of this hexapeptide by staphylococcal protease produces a 2 residue fragment that has an overall negative charge at pH 7.

Ala-Asp-Ser-Met-Asp-Tyr

The effects of the covalent modification of amino/imino acids upon proteins do NOT include which of the following. You may select multiple answers.

Sickling of hemoglobin in sickle cell disease

Inside the cell the environment is usually __________.

reducing

You need to isolate a protein that has a preponderance of aromatic residues. Your first choice for purification is

No best choice

The most commonly used affinity chromatography __________.

Uses bound metal to bind to a poly-His sequence

Cleavage by trypsin of the nonapeptide shown above produces _________.

2 fragments only one of which is positively charged at pH 7

Digestion of an 8-residue peptide with staphylococcal protease produces the following unique fragments: D, E, AK, AKD. Edman sequencing indicates the first 2 residues are DE. What is the sequence of the 8-residue peptide? Use single letter codes for amino acids.

DEAKDEAK

The amino acid composition of a 10-residue peptide is Ala₂, Asn₂, Glu₁, Lys₁, Met₁, Ser₂, Tyr₁. You digest the peptide with staphylococcal protease and see no apparent cleavage. What do you conclude?

Glu is at C-terminus

You react your peptide with dithiothreitol and get 1 fragment. This means there is at least ____________

Can't tell

Digestion of this hexapeptide by trypsin produces a 2 residue fragment that has a no overall charge at pH 7.

Ala-Asp-Tyr-Lys-Ser-Met

A 10-residue peptide containing only 1 Met is digested with CNBr producing 2 fragments. Which of the following are eliminated?

the peptide ends with Met

the peptide has no Met

the peptide has 2 Met

__________ cleaves before Met amino acids with high specificity.

None of these

In order to denature a protein for determining the amino acid composition the acid hydrolysis is done at ______

100 C

Cleavage by staphylococcal protease of the nonapeptide shown above produces _________.

2 fragments only one of which is positively charged at pH 7

Tryptic digestion of Ser-Gly-Lys-Phe-Arg-Tyr-Leu-Asp produces __________ peptides

3

The amino acid composition of a 10-residue peptide is Ala₂, Asn₂, Glu₁, Lys₁, Met₁, Ser₂, Tyr₁. You digest the peptide with cyanogen bromide and see no apparent cleavage. What do you conclude?

Met is at C-terminus

In purifying enzymes the _________.

Activity/amount increases

You have isolated a protein from the growth media of your favorite organism. Amino acid composition indicates there are 4 Cys residues in your protein. When you treat with dithiothreitol you get 2 fragments. Should you be surprised?

No

Phosphorylation of Ser or Thr occurs in about ____% of all human proteins.

Between 20 and 40

A peptide contains exactly 1 Asp, Leu, Lys, Met, Phe and Tyr (alphabetical order). Reaction with trypsin has no effect. Digestion with cyanogen bromide produces _________ fragments.

2

__________ cleaves after Met amino acids with high specificity.

cyanogen bromide

Digestion of this hexapeptide by cyanogen bromide produces a 2 residue and a 4 residue fragment each which has no overall charge at pH 7.

Ser-Met-Lys-Ala-Asp-Tyr

What are the 2 separation techniques used in 2-D electrophoresis? Select 2 answers.

SDS gel electrophoresis

Isoelectric focusing

A peptide contains exactly 1 Asp, Leu, Lys, Met, Phe and Tyr (alphabetical order). Reaction with trypsin has no effect. Digestion with cyanogen bromide produces _________ fragments.

2

You need to isolate a protein that has a preponderance of acidic residues. Your first choice for purification is

Cation exchange column

In SDS polyacrylamide gel electrophoresis __________ chains move the fastest.

Low molecular weight

The amino acid composition provides no information on the order of amino acids in the polypeptide.

True

In hydrolysis the _______ bond is broken.

peptide