4. A polypeptide comprised of 17 amino acid res- idues with the sequence on the right is ob-served by spectroscopic methods to undergo transitions from an a-helix conformation to a B-sheet as a function of pH and concentration. The acetyl and carboxamide groups are attached covalently to deri- vatize the N- and C-terminal residues, respectively, to avoid charge effects of the end CH3CO-ETATKAELLAKYEATHK-CONH2 groups. (a) (: amino acid residues. Write the sequence of this polypeptide with corresponding 3-letter abbreviations for the (b) At pH < 4 the polypeptide forms an a-helix. (i) ( . ) What is the direction of the macrodipole of the helix? and (ii) (: with respect to the positive and negative ends of the macrodipole? Are the charges on the N- and C-terminal residues stabilizing or de-stabilizing (c) ( stabilize the helical conformation. What are the most likely protonation states of the side-chains that provide a-helix stabilizing interactions? Use the helical wheel (at the back of the problem set) to identify side chain interactions that

Biochemistry
9th Edition
ISBN:9781319114671
Author:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Publisher:Lubert Stryer, Jeremy M. Berg, John L. Tymoczko, Gregory J. Gatto Jr.
Chapter1: Biochemistry: An Evolving Science
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4. A polypeptide comprised of 17 amino acid res-
idues with the sequence on the right is ob-served
by spectroscopic methods to undergo transitions
from an a-helix conformation to a B-sheet as a
function of pH and concentration. The acetyl and carboxamide groups are attached covalently to deri-
vatize the N- and C-terminal residues, respectively, to avoid charge effects of the end groups.
CH3CO-ΤAΤΚΑE LLAKYEATΗK-CONH2
(a) (
amino acid residues.
Write the sequence of this polypeptide with corresponding 3-letter abbreviations for the
(b) At pH < 4 the polypeptide forms an a-helix. (i) (
the helix? and (ii) (: ·
with respect to the positive and negative ends of the macrodipole?
) What is the direction of the macrodipole of
| Are the charges on the N- and C-terminal residues stabilizing or de-stabilizing
(c) (*
stabilize the helical conformation. What are the most likely protonation states of the side-chains that
provide a-helix stabilizing interactions?
Use the helical wheel (at the back of the problem set) to identify side chain interactions that
Transcribed Image Text:4. A polypeptide comprised of 17 amino acid res- idues with the sequence on the right is ob-served by spectroscopic methods to undergo transitions from an a-helix conformation to a B-sheet as a function of pH and concentration. The acetyl and carboxamide groups are attached covalently to deri- vatize the N- and C-terminal residues, respectively, to avoid charge effects of the end groups. CH3CO-ΤAΤΚΑE LLAKYEATΗK-CONH2 (a) ( amino acid residues. Write the sequence of this polypeptide with corresponding 3-letter abbreviations for the (b) At pH < 4 the polypeptide forms an a-helix. (i) ( the helix? and (ii) (: · with respect to the positive and negative ends of the macrodipole? ) What is the direction of the macrodipole of | Are the charges on the N- and C-terminal residues stabilizing or de-stabilizing (c) (* stabilize the helical conformation. What are the most likely protonation states of the side-chains that provide a-helix stabilizing interactions? Use the helical wheel (at the back of the problem set) to identify side chain interactions that
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