Histidines are amino acids that have imidazole functional groups, making them an essential part of proteins and enzymes. Some synonyms for histidines include H,His or imidazolealanine. In biochemistry, histidine residues regulate protein conformation and catalyze chemical reactions. In fact, histidine-rich proteins are commonly used in molecular biology research as affinity tags. These tags allow the purification and isolation of protein complexes and also aid in the identification of protein interactions. Overall, histidines are critical components of many biological processes and understanding their roles in biology could lead to new discoveries in both medicine and biotechnology.