Sedigheh Hashemnia

In this thesis, the interaction between ephedrine and HSA under physiological condition was studied using spectroscopic and electrochemical techniques. For this purpose, the interaction was investigated through UV-vis spectroscopy and cyclic voltammetry. Some thermodynamic parameters, such as binding constant, ΔH, ΔG and ΔS were also calculated. In addition, the conformational changes of HSA induced by ephedrine were examined through FT-IR spectroscopy. Results showed, A reduction in UV absorbance at 280 nm of HSA which was attributed to the interaction between ephedrine and HSA. Binding constants (Kapp) were estimated using the benesi-Hildebrand equation at different temperatures. The obtained Kapp values were about104 M-1, which showed high affinity of ephedrine for HSA. The calculated negative ΔH and ΔS values, suggest that the binding process is mainly driven by vanderWaals force and hydrogen bond. The negative value of ΔG indicates that the interaction process is spontaneous. The results of cyclic voltammetry further confirmed the high affinity of ephedrine for HSA with binding constant of 2.7×104 M−1at room temperatur .The electrochemical impedance spectroscopic studies (revealed the Warburg impedance changed significantly during the interaction between the protein and ephedrine, In other words, the protein-ephedrine interaction affects the diffusion of the electroactive species into the electrode surface. The infrared spectrophotometric studies showed the secondary structure of the protein was changed considerably with increasing concentration of ephedrine. There was loss of α-helix structure, along with a gain of β-sheet, β-turn and random coil structures by increasing ephedrine concentration.