Concept explainers
a. Based on a more conservative answer to Problem 6 (2.7 x 1092 conformations), estimate the conformational entropy change on folding a mole of this protein into a native structure with only one conformation. (Hint Consider Equation )
b. If the protein folds entirely into a helix with H bonds as the only source of enthalpy of stabilization, and each mole of H bonds contributes -5 kJ/mol to the enthalpy, estimate
c. From your answers (a) and (b), estimate
6. Consider a small protein containing 101 amino acid residues. The protein backbone win have 200 bonds about which rotation can occur. Assume that three orientations are possible about each these bonds.
a. Based on these assumptions, about how many random-con conformations will be possible for this protein?
b. The estimate obtained in (a) is surety too large. Give one reason why.
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- Describe the concept of isoelectric point and calculate the PI for isoleucine?arrow_forward. The process of a protein folding from an inactive unfolded structure to the active folded structure can be represented by the following equation: unfolded protein = folded protein The values of AH and AS° for the folding of the protein lysozyme are: AH = -280 kJ/mol AS = -790 J/mol · K (a) Calculate the value of AG for the folding of lysozyme at 25 °C. (b) At what temperature would you expect the unfolding of lysozyme to become favorable?arrow_forwardThe process of a protein folding from an inactive unfolded structure to theactive folded structure can be represented by the following equation: unfolded protein ⇌ folded proteinThe values of ΔH° and ΔS° for the folding of the protein lysozyme are: ΔH ° = -280 kJ/ mol ΔS ° = -790 J/mol • K(a) Calculate the value of ΔG° for the folding of lysozyme at 25 °C.(b) At what temperature would you expect the unfolding of lysozyme tobecome favorable? (c) At what temperature would the ratio of unfolded protein to foldedprotein be 1:5?arrow_forward
- The major difference between a protein molecule in its native state and in its denatured state lies in the number of conformations available. To a first ap- proximation, the native, folded state can be thought to have one conforma- tion. The unfolded state can be estimated to have three possible orientations about cach bond between residues. (a) For a protein of 100 residues, estimate the entropy change per mole upon denaturation. (b) What must be the enthalpy change accompanying denaturation to allow the protein to be half-denatured at 50 °C? (c) Will the fraction denatured increase or decrease with increasing temperature?arrow_forwardConsider the following protein mixture: Protein A B C D Molecular Weight (kDa) 50 150 200 350 Affinity to Metal ion === Zn²+ === 1. Using hydrophobic interaction chromatography, the protein that will be eluted last is [Select] 2. Using affinity chromatography, the protein that will be eluted last in a Zn²+-containing column is 3. The protein with the fastest migration towards the anode in SDS-PAGE is [Select] IpH value 7 3 9 5 [Select] [Select] 4. Using a buffer solution with a pH of 4, the protein that will bind to an anion exchanger is 5. The protein that will be eluted last in a gel filtration column is [Select] 6. Using isoelectric focusing, the protein that will have a protein band nearest to the cathode (negative electrode) is [Select] % Hydrophobicity 20 45 75 55arrow_forwardA protein has molecular mass of 200 kDa when measured by gel filtration. When subjected to SDS PAGE with and without 2-mercaptoethanol (2-ME) the gel shown below was obtained. What is the likely subunit composition of this protein and why? a. The protein has 4 subunits, with molecular masses 100, 50, 25, and 25 kDa. 25 kDa subunits are linked to each other via noncovalent interactions. b. The protein has 4 subunits, with molecular masses 100, 50, 25, and 25 kDa. 50 kDa subunit is linked to the one 25 kDa subunit via noncovalent interactions. c. The protein has 3 subunits, with molecular masses 100, 75 and 25 kDa that are linked by noncovalent interactions. d. The protein has 4 subunits, with molecular masses 100, 75, 50 and 25 kDa. The subunits are linked by disulfide bonds. e. The protein has 4 subunits, with molecular masses 100, 50, 25, and 25 kDa. 50 kDa subunit is linked to the one 25 kDa subunit by disulfide bonds.arrow_forward
- The major difference between a protein molecule in its native state and inits denatured state lies in the number of conformations available. To a firstapproximation, the native, folded state can be thought to have one conformation. The unfolded state can be estimated to have three possible orientations about each bond between residues.(a) For a protein of 100 residues, estimate the entropy change per moleupon denaturation.(b) What must be the enthalpy change accompanying denaturation to allow the protein to be half-denatured at 50 °C?(c) Will the fraction denatured increase or decrease with increasingtemperature?arrow_forwardaffinity of a protein-protein or protein-ligand interaction can be described by the Dissociation Constant, Kd (written below). Consider a protein P and its inhibitor, I. I inhibits P's activity when bound to it: koff _ [A][B] Dissociation Constant: Ka = koN [AB] Question When [I] is 10-7 M, 99% of P's activity is inhibited. What is the Kd of this Protein- Inhibitor interaction?arrow_forwardYou analyze a protein of 100 kDa using SDS-PAGE in the absence and presence of �-mercaptoethanol (BME) and observe the following band pattern in the gels: Which of the following statements about the protein is correct? (the image is attached) a. The protein consists of three polypeptide chains, two of which are connected via S-S bridges. b. The protein consists of two different polypeptide chains connected via S-S bridges. c. The protein has two different folding conformations. d. The protein consists of two different polypeptide chains linked to each other via non-covalent interactions.arrow_forward
- Suppose you have a solution of a protein, which contains a specific Tyr residue that has an actual (measured) pKa of 8.8. The protein binds a ligand by several noncovalent interactions, one of which is a hydrogen bond in which the Tyr phenolic hydroxyl group must serve as a hydrogen bond donor. Calculate the percentage of the protein molecules in which that tyrosyl residue's phenolic hydroxyl group could serve as a hydrogen bond donor at pH 8.5arrow_forwardAmino acid structure For any ionizable group, indicate the pka value and draw the structure that would be expected at the pH inside the cell (~7.4).arrow_forward. A protein gives, under conditions of buffer composition, pH, and tem- perature that are close to physiological conditions, a molecular weight by sedimentation equilibrium measurements of 140,000 g/mol. When the same protein is studied by SDS gel electrophoresis in the absence or presence of the reducing agent B-mercaptoethanol (BME), the pat- terns seen, respectively, in lanes A and B are observed. Lane C contains standards of molecular weight indicated. From these data, describe the native protein, in terms of the kinds of subunits present, the stoi- chiometry of subunits, and the kinds of bonding (covalent, noncova- lent) existing between subunits. / A B - BME + BME STD Serum albumin, 67,000 Ovalbumin, 43,000 Carbonic anhydrase, 30,000 Trypsin inhibitor, 20,000 10 2. 4. Co cm migratedarrow_forward
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