Q: In this task, you are given a multiple-choice question about healthcare. Answer the question based on your information and classify your answers into '1', '2', '3', and '4'.
Question: In the study of proteins. What is the purpose of treatment with -mercaptoethanol ?:
Options: <1> Hydrolyze the protein. <2> Break the disulfide bridges. <3> Add positive charges. <4> Add negative charges. <5> General an amino acid derivative in Edman degradation.
A:
2