Which amino acid is involved in the formation of disulfide bonds?

Cysteine is the amino acid involved in the formation of disulfide bonds due to its unique thiol (-SH) group. When two cysteine molecules come into proximity, the sulfur atoms in the thiol groups can undergo oxidation, resulting in the formation of a covalent bond known as a disulfide bond (–S–S–). These disulfide bonds play a crucial role in stabilizing the three-dimensional structure of proteins, including those found in hair and nails, thereby influencing the properties and functionality of these proteins in cosmetology.

In contrast, the other amino acids listed do not possess the necessary thiol group to form disulfide bonds. Serine contains a hydroxyl (-OH) group, which does not facilitate the formation of disulfide bonds. Leucine and valine are both branched-chain amino acids with aliphatic side chains, and they lack the capacity to form disulfide linkages. Understanding the role of cysteine in the formation of disulfide bonds is essential for grasping how certain proteins maintain their structure and contribute to the versatility of hair design and chemical treatments in cosmetology.