Which of the following is the major factor (component of free energy) favouring the formation of hydrogen bonds between two groups in a protein?

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 stabilising interaction is introduced; and

(C) a mutant in which two slightly stabilising interactions are 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?

An enzyme is known to contain four Cys residues that form two disulfide bonds (and no other Cys residues).

[Note that four Cys residues could randomly form three possible disulfide bond arrangements]

A researcher performs the following sequence of treatments on a sample of this enzyme:

1. Treatment with high concentrations of mercaptoethanol and urea.
2. Removal of the mercaptoethanol while keeping the urea concentration high (and avoiding formation of any intermolecular disulfide bonds).
3. Removal of the urea (returning the sample to the original buffer).

They find that the sample obtained from the final treatment has one third of the activity of the original sample of the enzyme.

Which of the following is the best conclusion from this experiment?

Consider the following two ionisable groups positioned close to each other within a protein structure:

• The carboxy terminus (pKa = 2.3)
• An arginine side chain (pKa = 12.5)

Based on the pKa values of these functional groups and their charge states when they are ionised, select the correct statement below.

[Note that these statements are specifically referring to the attraction or repulsion of ionic interactions between these groups]

Dans la liste suivante, sélectionnez les sanctions disciplinaires prévues par le Code de l'éducation à l'encontre des étudiant·es :

Un·e étudiant·e ou stagiaire de formation continue est un usager / une usagère d'un établissement d'enseignement supérieur. À ce titre :

Les situations de violences sexistes et sexuelles peuvent faire l'objet d'une procédure disciplinaire au sein d'un établissement d'enseignement supérieur. Si une personne victime de violence sexiste et/ou sexuelle est entendue dans le cadre d'une procédure disciplinaire, elle le sera sous le statut de :