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409

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Biology

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Apr 3, 2024

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BICH 409 Spring 2024 Assignment 3 100 pts Key 1.) Consider the following peptides: (a) Cys-Val-Asp-Asn-Leu (b) Arg-Gly-Ala-Phe-Met (c) Leu-Val-Ser-Asn-Trp (d) Tyr-Glu-Gln-Asp-Pro (e) Lys-Phe-Ile-His-Arg a.) ( 3 pts) Which one of the peptides would have the greatest solubility at pH 1? (e) b.) ( 3 pts) What would be the order of elution off of an anion exchange column with a pH of 7? First off-_e-b-c-a-d___________________-last to elute c.) ( 3 pts) What would be the order of elution off a cation exchange column at a pH of 7? First off-___d-a-c-b-e______________________________-last to elute 2.)(12 pts) Use the following information: Protein Molecular Weight pI (a) Homoserine Dehydrogenase 229,000 Daltons 5.50 (b) Heparin Lyase 43,150 Daltons 8.90 (c) Sortase A 24,810 Daltons 6.20 (d) Pyruvate Phosphate Dikinase 110,000 Daltons 8.25 (e) Phosphopentose Mutase 65,000 Daltons 4.85 a.) If the preceeding proteins were separated by gel filtration, what would be the order of elution? First off-__a-d-e-b-c____________________________________-last to elute b.) If the preceeding proteins were separated by isoelectric focusing then what would be the order of migration (Cathode (-)  (+) anode)? Cathode-____b-d-c-a-e_________________-Anode c.) If the preceeding proteins were separated by cation exchange chromatography at pH 7, what would be the order of elution? First off-__e-a-c-d-b___________________________- last to elute d.) If the preceeding proteins were separated by SDS-PAGE, what would be the order of migration from the top to the bottom of the gel? Top-____ a-d-e-b-c _______________________-bottom 3.) ( 12 pts) Draw out the products of the following reactions by the indicated agents. A.) Ser-Ala-Phe-Lys-Pro by trypsin → Ser-Ala-Phe-Lys-Pro B.) Thr-Cys-Gly-Met-Asn by elastase → Thr-Cys-Gly + Met-Asn C.) Leu-Arg-Gly-Asp -Met-Pro by cyanogen bromide → Leu-Arg-Gly-Asp -Met + Pro D.) Val-Trp-Lys-Pro-Arg-Glu by chymotrypsin → Val-Trp + Lys-Pro-Arg-Glu E.) Ile-Lys-Lys-Trp-Arg-Gly-Phe by trypsin → Ile-Lys + Lys + Trp-Arg + Gly-Phe F.) Ser-Leu-Lys-Ala-Gln-Arg by Carboxypeptidase B → Ser-Leu-Lys-Ala-Gln + Arg

BICH 409 Spring 2024 Assignment 3 100 pts Key 4.) ( 5 pts) A polypeptide is subjected to the following degradative techniques resulting in polypeptide fragments with the indicated amino acid sequences. What is the amino acid sequence of the entire polypeptide? I. Cyanogen bromide treatment: II. Trypsin hydrolysis: 1. Asp-Ile-Lys-Gln-Met 5. Gln-Met-Lys 2. Lys 6. Gly-Met-Asp-Ile-Lys 3. Lys-Phe-Ala-Met 7. Phe-Ala-Met-Lys 4. Tyr-Arg-Gly-Met 8. Tyr-Arg K-CBF2 FAMK-TF7 KFAM –CBF3 QMK-TF5 DIKQM-CBF1 GMDIK-TF6 YRGM-CBF4 YR-TF8 YRGMDIKQMKFAMK 5.)( 5 pts) A purified neuropeptide contains 7 residues. (a) An aliquot of the neuropeptide was treated it with dansylchloride at a pH of 8.0. Hydrochloric acid was then added lowering the pH to 1 and the solution was boiled for one hour. The only dansylated product is shown below. N H 3 C H 3 C S O O H N C C OH CH 2 H O O (b) An aliquot of the neuropeptide was treated with hydrochloric acid lowering the pH to 1 and the solution was boiled for one hour. The pH was then adjusted to 8.0 followed by treatment with dansylchloride. This procedure generated dansylaspartate, dansylisoleucine, dansylarginine, dansylmethionine, dansyltyrosine and dansyltryptophan. (c) Treatment of the neuropeptide with trypsin had no effect. (d) Brief treatment of the neuropeptide with chymotrypsin generates tyrosine, a dipeptide and a tetrapeptide. The tetrapeptide was composed of Ile, Arg and Met. (e) Treatment of the neuropeptide with cyanogen bromide generates a dipeptide, a tetrapeptide and free arginine. Based on the above information, what is the sequence of this heptapeptide? YDWMIMR

BICH 409 Spring 2024 Assignment 3 100 pts Key 6.)( 6 pts) (a)  Keratin is composed of  helices containing 351 amino acids. How long are these  helices in Angstroms? 526.50 Å (b) How long is a parallel  strand containing 351 amino acids in Angstroms? 1,140.75 Å (c) How long is an antiparallel  strand containing 351 amino acids in Angstroms? 1,228.50 Å 7.) ( 6 pts) (a)How many amino acid residues are required for an  helix to span 65 Å ? 43.33 amino acids (b) How many amino acid residues are required for a parallel  strand to span 65 Å ? 20 amino acids (c) How many amino acid residues are required for an antiparallel  strand to span 65 Å ? 18.57 amino acids The following problems are all old exam questions and are work 2 pts each. Answer Questions 8 – 11 using the structure below. O N H (S) H H 3 C O N H (A) (B) (C) (D) (E) 8.) The one letter abbreviation of the residue shown in the peptide above is____A__________ 9.) The torsion angle  (psi) corresponds to the rotation around which labeled bond shown above? __C____ 10.) Which of the labeled bonds shown above are not free to rotate (rigid)?____________A____________ 11.) The torsion angle  (phi) corresponds to the rotation around which labeled bond shown above? _B____ 12.) An  -helix would be destabilized by (A) containing two successive charged residues. (B) containing two successive bulky nonpolar residues. (C) containing a proline residue. (D) containing a glycine residue. (E) All of the above. 13.) What is the minimum number of amino acids in a parallel  strand that will span a 65 Å membrane bilayer? 20 amino acids

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