Need help, please. protein has binding affinity for its ligand of K = 2 x 105 1/M at pH 5.0 and roomtemperature.a. What fraction of the protein is bound at ligand concentration of 1.25 µM?b. At what concentration is 80% of the ligand bound?c. When the pH is raised to 6.5, the Kò increased to 20 µM. Is the binding tighter orweaker at this pH compared to pH of 5.0. Explain your answer.

Kd is the dissociation constant for a protein-ligand complex that measures the affinity with which a…

Answered: A protein has binding affinity for its…

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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The ESI-MS spectrum in positive ionization mode for lysozyme is obtained. a. What is the molecular weight of the protein to 5 significant figures based on the two highlighted ion species? b. What is the charge of the peaks at 1101.5 and 1789.2.
Give the general Adiar equation for the binding of a ligand to a dimeric protein. Explain further what your understanding is of the terms "no-, positive-, and negative cooperativity” and graphically present the relationship between Ȳ and [S] for each of these cases. Also, give the relationship between the constants Kb1 and Kb2 in each case.
Consider the dissociation reaction for a protein-ligand complex: P•L P + L A. Sketch a binding curve (fractional saturation θ vs. ligand concentration [L]) for this protein-ligand complex (ligand A). Show where on that curve you could obtain the dissociation equilibrium constant Kd for the reaction. B. Now sketch on the same axes a θ vs. [L] plot for a different ligand (B) that binds more weakly than the first ligand. C. Does the weaker binding ligand have a higher, or lower, Kd than the tighter binding ligand? D. Sketch a binding curve for a cooperatively bound ligand with K0.5 higher than that of Kd for A or B. (Note: for cooperative binding, each protein molecule would have to have more than 1 binding site for the ligand; K0.5 is the experimentally determined ligand concentration that gives θ = 0.5.)
A protein-ligand binding reaction is run. At equilibrium, half the protein is ligand bound, the unboundligand concentration is 0.657 nM. Calculate the koff value for this reaction. Assume the kon value is typical ofprotein-ligand interactions.
Calculate θ for a certain protein-ligand pair when the ligand concentration = 1 M and the Kd = 1 X 10-15 M.
A one-to-one protein (P)-ligand (L) complexation (P + L PL) has a dissociation equilibrium constant (Kd) value of 100 nM at 25°C, and the Kd remains the same at 37°C. 1) What is AS of binding at 25°C? Assume ACp of the binding is 0 over the temperature range. AS = 1.34E2 kJ/(mol*K) (note the unit!!) (sig. fig =3) 2) What is the concentration of the PL complex formed at equilibrium when you mix 0.20 uM (microM) of Protein and 1.0 uM of Ligand together at 37°C? PL at equilibrium = 8.1E-1 uM (note the unit!!) (sig. fig =2)
A large chaperone protein complex GroEL is approximately 16 nm in diameter. When it is dissolved in water at 300 K, estimate the average time it will take for GroEL to diffuse a distance of 500 nm (0.5 micron). The viscosity of water is 10-3 Pa*s.
12 mM of protein A is combined with 6 mM of ligand X in water. After the protein-ligand complex binding reaches equilibrium, you measure that the free ligand concentration is 3 mM and the concentration of protein-ligand complex is 3 mM. What is the Kd for protein A? Although they would be in mM, do not include units in your answer, only the number as a whole integer.
What is the fractional occupancy of a protein binding site when the ligand concentration (L) =1mM and the ligand equilibrium binding constant at the binding site K10= 10microM. 0.01 B.0.1 C.0.91 D.0.99 none of the listed values
Which of the following situations would produce a Hill plot with nH < 1.0? Explain your reasoning in each case.(a) The protein has multiple subunits, each with a single ligand-binding site. Binding of ligand to one site decreases the binding affinity of other sites for the ligand.(b) The protein is a single polypeptide with two ligand-binding sites, each having a different affinity for the ligand.(c) The protein is a single polypeptide with a single ligand-binding site. As purified, the protein preparation is heterogeneous, containing some protein molecules that are partially denatured and thus have a lower binding affinity for the ligand.
A tetrapeptide, glutamate-glycine-alanine-lysine, is prepared at at concentration of 1 mM (0.001 M) and is measured in the standard setup (pathlength of 1 cm). What is the approximate absorbance of this peptide at 280 nm? Hint: if the peptide contained a single tryptophan, the answer would be about 10. 10 280 1 0
Calculate the concentration of the ligand required to fill 25% of the binding site. X+A ⇌ XA , ka = 1.5 ×10-6 Y+A ⇌ YA , ka = 4.7 × 10-4 (i.e, q = 0.25) for both proteins.

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