OC1 - inactivation of functional sites

Question 1

preservation of cysteine residues

Answer 1

cysteine residues can be preserved from oxidation by dithiothreitol (DTT) or 2-mercaptoethanol (2-ME)
both DTT and 2-ME are reducing agents that reduce the disulphide bonds of proteins and therefore breakdown the tertiary structure by not allowing disulphide bridges to form.
DTT and 2-ME also act to protect cysteine residues from oxidation by scavenging free hydroxyl radicals, this helps to preserve the protein in its reduced state for analysis.