Erythropoietin (EPO) is a hematopoietic hormone, as a strong cell protector, which increases cellmaintenance during different damages of central nervous system. Since the brain-blood barrier preventsthe entrance of erythropoietin (with molecular weight of 34 kD) into the brain, its systemic delivery getslimited. In the present study, we have investigated the thermodynamical interaction between human EPOand gemeni using various spectroscopic techniques of fluorescence and circular dichroism (CD) at twodifferent temperatures of 25 and 37 ˚C [1-2].Results of intrinsic fluorescence
showed that the emission ofEPO decreased and quenched with increasing in the gemeni concentration added to the protein solution.Analysis of quenching data indicated that there are one and two binding sites with binding constants of3.85×10-5 M-1 and 22×10-5 M-1 on the EPO for gemeni at temperatures of 25 and 37 ˚C, respectively.Also, far-UV-CD results did not show any significant changes in the regular secondary structure of EPOupon various concentrations of this ligand. In conclusion, obtained results proposed that gemeni as acationic surfactant can bind to EPO without inducing any adverse effects on the EPO structure.