Connexin is a special membrane structure arranged by connecting channels between two adjacent cells. There are at least 20 types of connexins in mammals, among which connexin 43 (Connexin43, Cx43) is the main cell gap. Connexin, its abnormal expression is related to the occurrence of many diseases. Gap 27 is a peptide derived from connexin 43 and consists of 11 amino acids. It is a selective blocker of gap junctions. Gap 27 was used to evaluate the contribution of gap junction proteins to osteoclast bone resorption.