**Question 8:**NMR measurements have shown that poly-lysine is a random coil at pH 7 but becomes a helix when the pH is raised above 10. If the same type of folding behavior is observed, what should be the pH dependence of poly-glutamate?A) Helix at pH 7 but random coil at pH 10 B) Random coil at pH 3 but helix at pH 7 C) Random coil at pH 7 but helix at pH 10 D) Helix at pH 3 but random coil at pH 7 *Explanation:* This question explores the folding behavior of poly-lysine and poly-glutamate under different pH conditions. It highlights the structural changes these polymers undergo based on pH levels, illustrating the helix-coil transitions typical for such biopolymers.

Biomolecules are organic molecules made up of mainly carbon and hydrogen but there are other…

Answered: 8. NMR measurements have shown 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

Section: Chapter Questions

Problem 1P

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6) Proteins can be modified by phosphorylation, which adds a phosphate group to the hydroxyl group of serine, threonine, or tyrosine residues. The R-group for phosphoserine is shown at right. A) The image below is an Isoelectric focusing strip that shows the unphosphorylated protein-of-interest (in blue). To which side of the unphosphorylated protein would you expect to see the phosphorylated protein? (Draw an arrow to indicate direction). Briefly justify your answer. un-phosphorylatable: Low pH Justify: B) To study the effects of phosphorylation, researchers often mutate a Ser/Thr to appear as though it is always phosphorylated or never phosphorylated at a particular site. What amino acid substitution should you use to preserve similar dimensions as Ser (or Thr) but make the side chain appear to be: constitutively (always) phosphorylated: Justify: Ser or Thr → O O=P-O O I CH₂ Ser or Thr➜ Phosphoserine High pH
Draw the structure of STVWY at pH 13. Connect with an arrow the C=0 of the N- terminal residue to the NH that it would be hydrogen bonded to if the peptide was forming a a-helix?
1. Draw the tetrapeptide Met-Ala-Thr-Thr at a ph of 7? 2. Draw the tetrapeptide Met-Ala-Thr-Thr at a ph of 12?
2. | Calculate the overall charge (pH 7) on the following three polypeptides and answer the questions below. Assume the following pKa values: N-terminal -NH3®, 7.0; all -COOH groups, 4.0; Arg, 12.5; Cys, 8.4; His, 6.0; Lys, 10.0; Tyr, 10.0. (A) Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Lys-Pro-Val-Gly-Lys-Lys-Arg-Arg-Pro-Val-Lys-Val-Tyr-Pro-Asp-Ala -Gly- Glu-Asp-Gln- Ser-Ala-Glu-Ala-Phe-Pro-Leu-Arg-Glu-Phe (B) Ser-Tyr-Ser-Met-Glu–His-Phe-Arg–Trp–Gly-Ala-Pro-Val-Gly-Glu-Glu-Cys-Asp-Pro-Val-Glu–Val-Tyr-Pro-Asp- Ala-Gly-Glu-Asp-Gln-Ser-Ala-Glu-Ala-Phe-Pro-Leu-Glu-Phe-Cys-Ser-Tyr-Ser-Met-Glu-His-Phe-Asp-Trp-Gly- Asp-Pro-Val-Gly-Pro-Asp-Ala-Gly-Asp-Gln-Pro-Val-Gly-Glu-Glu-Cys-Asp-Pro-Val-Glu-Val-Tyr-Pro-Asp-Ala | (C) Gly-Ser-Val-Arg-Asp-Pro-Val-Lys-Glu–Val-Tyr-Pro-Asp- Lys-Ala-Gly-Arg-Glu-Ser-Arg-Ala (a) Which of the three peptides would elute first from a gel filtration column? (b) Which of the three peptides would migrate the fastest on SDS-PAGE (c) Which of the three peptides could be…
10. A new protein of unknown structure has been purified. Gel filtration chromatography reveals that the physiological protein has a molecular weight of 240,000 Daltons. Chromatography in the presence of 6 M urea yields a single peak corresponding to a protein of 60,000 Daltons. Chromatography in the presence of 6 M urea and 10 mM mercaptoethanol yields peaks for proteins of 34,000 Daltons and 26,000 Daltons. What can we learn about protein's tertiary and quaternary structure from this data?
25) Below are two amino acids: cysteine and histidine. a) Draw the reaction mechanism of a dehydration synthesis reaction between cysteine and histidine below: HS H Product 1 OH ox HN H b) Draw two different products of the dehydration synthesis reaction from part a). Prove that these are two different products by labelling the N and C termini, peptide bond, and R-groups of each product. Product 2 OH
2. | Calculate the overall charge (pH 7) on the following three polypeptides and answer the questions below. Assume the following pKa values: N-terminal –NH3®, 7.0; all -COOH groups, 4.0; Arg, 12.5; Cys, 8.4; His, 6.0; Lys, 10.0; Tyr, 10.0. (A) Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Lys–Pro–Val–Gly–Lys–Lys–Arg-Arg-Pro-Val-Lys–Val-Tyr-Pro-Asp-Ala -Gly- Glu-Asp-GIn– Ser-Ala-Glu-Ala-Phe-Pro-Leu-Arg-Glu-Phe (B) Ser-Tyr-Ser-Met-Glu-His-Phe-Arg-Trp-Gly-Ala-Pro-Val-Gly-Glu-Glu–Cys-Asp-Pro-Val-Glu–Val–Tyr-Pro-Asp- Ala-Gly-Glu-Asp-Gln-Ser-Ala-Glu-Ala-Phe-Pro-Leu-Glu-Phe-Cys-Ser-Tyr-Ser-Met-Glu–His-Phe-Asp-Trp-Gly- Asp-Pro-Val-Gly-Pro-Asp-Ala-Gly-Asp-Gln-Pro-Val–Gly–Glu-Glu-Cys-Asp-Pro–Val-Glu–Val–Tyr-Pro-Asp-Ala (C) Gly-Ser-Val-Arg-Asp-Pro-Val-Lys-Glu-Val-Tyr-Pro-Asp- Lys–Ala-Gly-Arg-Glu-Ser-Arg-Ala (d) Which of the three peptides would migrate the closest to the anode in isoelectric focusing? (e) Which of the above peptides would elute last from a gel filtration column? (f) Which of the three…
2. Of the two sequences, which is more likely to have helical structure. Explain. a) -Glu-Asp-Glu-Glu-Asp-Leu- b) -Glu-Leu-Asp-Arg-Val-Lys-

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