export_e2

Question 1

A protein with only a single polypeptide chain lacks what structure

Answer 1

Quaternary

Question 2

What intermolecular force(s) determine the structure of the alpha helix?

Answer 2

Hydrogen bonding

Question 3

Point out phi/psi angles in a polypeptide

Answer 3

Question 4

Why does the treatment of some proteins with dithiothreitol change the 3D structure

Answer 4

1. DTI reduces disulfide bonds 2. Disulfide bonds are a factor in determining 3D structure 3. They bind different parts of the primary chain together

Question 5

What is the role of dicyclohexylcarbodimide (DCC) in solid-phase peptide synthesis?

Answer 5

Activation of carboxyl

Question 6

What is the role of fluorenylmethoxycarbonyl chloride (Fmoc-Cl) in solid-phase synthesis?

Answer 6

* Protection of the amino group * Moc sounds like block, from there think “block and protection”

Question 7

What does phenyl isothiocyanate (Edman’s reagent) do?

Answer 7

React with the N-terminal amino acid

Question 8

PAGE of proteins often has sodium dodecyl sulfate added, why?

Answer 8

1. SDS denatures the protein and the charges of the SDS swamp the charge on the protein 2. The amount of SDS that binds is proportional to the size of the protein so the net result is electrophoresis separates based on the size of the protein

Question 9

In peptide synthesis, why is it necessary to add a reagent to activate the carboxyl?

Answer 9

Carboxyl is present as the carboxylate ion, which is a very poor electrophile

Question 10

What does iodoacetamide do?

Answer 10

React with cysteine side chains