Conformational phase diagram of poly(L-lysine)in sodium aikanesulfonate aqueous solutions at various temperatures

摘要

The conformation of poly(L-lysine)(PLL)was investigated in sodium aikanesulfonate C_nSO_3Na(n=8,7)at various temperatures by circular dichroism spectrum measurements,C_8SO_3Na induced a double-step conformational change from a coil,to a beta-sheet,and then to an alpha-helix,in which C_7SO_3Na induced a single-step coil-to-helix conformational change,Binding isotherms of C_8SO_3Na by PLL were constructed from the potentiometry of equilibrium concentration of the surfactant using a surfactant ion-selective electrode,The curves indicated the cooperative binding characteristic and were analyzed by a linear lattice model using the Bethe approximation,The thermodynamic parameters obtained from the model revealed that the binding of C_8SO_3Na by PLL was an entropy-driven process,The conformational change was observed at nearly full binding,presumably due to the surfactant clustering of the ordered conformation.