Kidney ischemia reperfusion(IR)injury is a major cause of delayed graft function and increases the risk of allograft rejection,affecting both short-and long-term graft survivals.It has been recently shown that helix B surface peptide(HBSP),an 11-amnio acid long sequence derived from the aqueous surface of the helix B domain of erythropoietin,has powerful tissue protective function in various organs subjected to IR injury.[1-2] However,the 2 min plasma half-life of HBSP severly restricts its application in vivo.[1] By employing the conformationally constraining,all D-amino acid replacement and N-capping strategies to modify the structure and thus improve the metabolic stability of the linear peptide HBSP,[3] the redox-stable thioether cyclized helix B peptides(CHBP)turned out significantly stable in vitro and in vivo.