The diagram (left) below shows the structure of the enzyme ribonuclease in its native form. The threedimensional protein structure is maintained in part by the disulfi de bonds (-S-S-) between the amino acid residues (each color sphere represents an S atom). Using certain denaturants, the compact structure is destroyed and the disulfi de bonds are converted to sulfhydryl groups (OSH) shown on the right of the arrow.
(a) Describe the bonding scheme in the disulfi de bond in terms of hybridization.
(b) Which amino acid in Table 25.2 contains the -SH group?
(c) Predict the signs of ∆H and ∆S for the denaturation process. If denaturation is induced by a change in temperature, show why a rise in temperature would favor denaturation.
(d) The sulfhydryl groups can be oxidized (that is, removing the H atoms) to form the disulfi de bonds. If the formation of the disulfi de bonds is totally random between any two OSH groups, what is the fraction of the regenerated protein structures that corresponds to the native form?