1. Minor changes in primary structure can have pronounced effects on biological function. Tetrameric hemoglobin, ₂₂, dissociates into pairs of dimers aß to different extents depending on the protein primary structure. The standard Gibb energies of dissociation of normal adult hemoglobin A and of several mutants have been determined and are listed in the table below. Substitution in mutant Hemoglobin A, normal Richmond Kansas Georgia 1025; Asn → Thr 1028; Asn → Thr 95x; Pro → Leu AG of dissociation (kcal/mole Hb) 8.2 6.0 5.1 3.6 (a) Write an equilibrium expression for the dissociation of hemoglobin tetramer into dimers. (b) For normal hemoglobin and its three mutants (variations) calculate the equilibrium constant for their dissociation from a tetramer into dimers. (c) How do the equilibrium constants for the dissociation of the hemoglobin mutants compare to that of normal hemoglobin?

2. (6) Examine the two proteins labelled a) and b). Which of the two Ramachandran plots, c) or d) is more likely to be derived from which protein? Explain how you determined this. (a) (b) (c) (d) ✓ (degrees) ✓ (degrees) +-180 120 60 -60 -120 -180 -180 +180 120 60 -120 -180 -180 0 (degrees) 0 (degrees) +180 +180

List 4 different actiated carrier molecules, for each one, list both the oxided and reduced forms

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?

Why does the dissociation constant change for hemoglobin in high and low 02 concentrations? O Hemoglobin is a tetramer and subunits have decreased dissociation of 02 when a neighboring subunit has bound 02 O Hemoglobin is a monomeric protein with increased dissociation of 02 when a neighboring molecule has bound 02 O Hemoglobin is a tetramer and subunits have increased dissociation of 02 when a neighboring subunit has bound CO O Hemoglobin is a tetramer and subunits have increased dissociation of O2 when a neighboring subunit has bound O2

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5. Anesthetic gases used in surgery are known to bind to the hemoglobin molecule in red blood cells. The diagram below illustrates O2 binding curves of normal human HbA in the presence of the anesthetic gas dichloromethane (DCM). O UNTREATED 100 Symbols: a Dсм 23 Torr • DCM 50 Torr x DCM I00 Torr o, 0 Torr DCM; О, 23 Torr DСМ Д, 50 Torr DСМ x, 100 Torr DCM. 80 60 40 (1 Torr = 1 mm Hg.) 20 The solutions were buffered to pH 7.4. 0.5 1.0 1.5 2.0 log p02 For the curves at 0 and 100 Torr of dichloromethane, draw their equivalent in the form of (a) (* Hill plots. Label the axes and indicate on both the plot above and the Hill plot where the value of the dissociation equilibrium constant Kd for O2 binding is defined for 0 and 100 Torr of dichloromethane Kd Hb(O2)n nO2 Hb + Be sure to label the axes, indicate the units on both axes, and make the Hill plot so that the values of Kd are equivalent to those on the saturation plot above. Indicate whether cooperativity, as indicated by the Hill…

20. The dissociation constant of protein Z for ligand Y is: 10 micromolar. What fraction of the ligand is bound at ligand concentration = 5 micromolar?

The T state of hemoglobin is converted to the R state by what event? Select one: The binding of oxygen destabilizes a more planar heme ring which alters the position of the proximal histidine and subsequently, residues between the alß2 interface. а. b. None of these. The binding of oxygen stabilizes a more planar heme ring which alters the position of the proximal proline and subsequently, residues between the alß2 interface. С. d. The binding of oxygen stabilizes a more planar heme ring which alters the position of the proximal histidine and subsequently, residues between the alß2 interface. The binding of oxygen destabilizes a more planar heme ring which alters the position of the proximal proline and subsequently, residues between the alß2 interface. е.