What type of bonds are broken by β-mercaptoethanol during the ribonuclease experiment?

The correct choice highlights that β-mercaptoethanol specifically breaks disulfide bridges, which are a type of covalent bond formed between the sulfur atoms of cysteine residues in proteins. These disulfide bonds play a crucial role in stabilizing the three-dimensional structures of proteins by linking different parts of the peptide chain together. In the context of the ribonuclease experiment, the action of β-mercaptoethanol reduces the disulfide bridges, thereby unfolding the ribonuclease and allowing for the study of its properties apart from its folded state. This unfolding can reveal important information about how the protein’s structure relates to its function. The breaking of these bonds is essential for understanding protein structure and dynamics during denaturation studies.