經由平衡鍵結分析(the equilibrium binding analysis)和ITC直接測定吸附火含，探討硫酸銨(ammonium sulfate，(NH ) SO )鹽濃度在肌紅蛋白(myoglobin)對兩種疏水性吸附劑(hydrophobic adsorbents)：butyl-和octyl-sepharose上之吸附反應的影響。由結果顯示肌紅蛋白與兩種疏水性吸附劑的吸附親和力，會隨著鹽濃度的增加而變強；再者，由恆溫滴定微卡計(isothermal titration calorimetry，ITC)所測定的結果，顯示，吸附火含的變化量隨鹽濃度的增加而減少，這個發現可被解釋為：隨鹽著濃度的增加去水合熱(dehydration heat)會減少且由於疏水性反應的關係，釋放熱因此增加。此外，隨著鍵結蛋白質的增加，兩種樹脂對肌紅蛋白的吸附火含皆會隨著增大，而且其變化程度在不含(NH ) SO 溶液中比在1.0M (NH ) SO 中顯著，說明了，蛋白質間電性斥力在無鹽的狀態下對於蛋白質吸附量影響是較強的。 在此，所討論的熱力學參數是有其重要含意的，尤其是吸附焓與吸附火商的相對變化量，不只對蛋白質吸附現象的機制提供更細微的內視，而且對HIC也有更進一步的理論分析。 The effect of (NH4)2SO4 concentrations on the interaction mechanism between myoglobin and two hydrophobic adsorbents, butyl- and octyl-Sepharose was investigated by the equilibrium binding analysis and by directly measured adsorption enthalpies. The result obtained from the isotherms demonstrated that the affinities of myoglobin adsorption onto the both adsorbents were increased with salt concentrations. Furthermore, the adsorption enthalpies measured by using isothermal titration calorimetry (ITC) were decreased with an increment of salt concentrations, and these findings were explained by the reduction in the dehydration heat and the enhancement of heat released by the hydrophobic interaction as salt concentrations increase. Additionally, the adsorption enthalpies of myoglobin with both the resin increased as the amount of bound protein, and the increment in the variation of enthalpy value at solution without (NH4)2SO4 appeared to be steeper than that at 1.0 M (NH4)2SO4. This result implies that the effect of protein-protein electric repulsion on the amount of bound protein is stronger in the absence of the salt in this experiments. The thermodynamic parameters presented herein have important implication, particularly the relative variation between the adsorption enthalpies and the adsorption entropies, both for providing further insight into the binding mechanism of protein adsorption and for improving theoretical approaches to HIC.
