A researcher analyses the binding between a protein and ligand by measuring the intrinsic fluorescence of the protein in the presence of various different ligand concentrations (and using a protein concentration that is well below the K_d for ligand binding). The raw data are tabulated below.

Which of the following ligand concentrations gives a fractional saturation of the protein closest to 75%?

A pharmaceutical researcher has determined that a drug binds to its target protein with a K_d value of 0.05 nM under physiological conditions. Considering that the target protein is present at a concentration of 1 pM or less, what concentration of the drug needs to be present in the vicinity of the target protein in order for the target protein to be approximately 90% saturated with the drug?

A researcher analyses the binding between a protein and ligand by measuring the intrinsic fluorescence of the protein in the presence of various different ligand concentrations (and using a protein concentration that is well below the K_d for ligand binding). The raw data are tabulated below.

Which of the following ligand concentrations gives a fractional saturation of the protein closest to 40%?

To test the importance of certain amino acid residues in stabilising a protein structure, a research student performs equilibrium unfolding experiments with three forms of the protein:

(A) the wild type protein;

(B) a mutant in which a slightly destabilising interaction is introduced; and

(C) a mutant in which a strongly destabilising interaction is introduced.

They obtain the three unfolding curves shown below.

Which curves correspond to which forms of the protein?

Shown below are free energy diagrams representing the unfolding of 3 proteins (N = native; U = unfolded).

The following graph shows three protein unfolding curves.

Which of the following options is most likely to indicate the correct relationship between the three free energy diagrams and the three unfolding curves?

Shown below is a curve representing the unfolding of a protein with increasing temperature.

At what temperature are 70% of protein molecules folded?

Enter the temperature in degrees Celsius (deg C) but do NOT type the units. To be marked correct you must type only numbers.

Shown below is an unfolding curve for a protein that contains two domains of approximately equal size.

Which point on the curve represents the form of this protein in which one domain is 50% unfolded and the other is fully folded?

One way to destabilise a folded protein structure is to change the solution conditions so that all the Asp and Glu side chains (and the C-terminus) become neutral, thus removing any stabilising ionic interactions and leaving a lot of Lys, Arg and His side chains (and the N-terminus) that repel each other.

Which of the following perturbations is most likely to destabilise a protein in this way?

Shown below is an unfolding curve for a protein that contains two domains of approximately equal size.

Which point on the curve represents the form of this protein in which one domain is fully unfolded and the other is 50% unfolded?

To test the importance of certain amino acid residues in stabilising a protein structure, a research student performs equilibrium unfolding experiments with three forms of the protein:

(A) the wild type protein;

(B) a mutant in which a stabilising interaction is removed; and

(C) a mutant in which a new stabilising interaction is introduced.

They obtain the three unfolding curves shown below.

Which curves correspond to which forms of the protein?