A partial phase diagram characterizing the conformational change that occurs in Thermomyces lanuginosus xylanase as it is slowly heated in 150 mM sodium phosphate (pH = 7.0) has been con-structed from slow-scan-rate d...A partial phase diagram characterizing the conformational change that occurs in Thermomyces lanuginosus xylanase as it is slowly heated in 150 mM sodium phosphate (pH = 7.0) has been con-structed from slow-scan-rate differential scanning calorimetry measurements. The Clausius-Clapeyron equation was applied to determine an associated volume change of -205 L·mol-1 at 24°C, the equilibrium transition temperature at 1.0 atm pressure. This value is in excellent agreement with that predicted using a previously published [1] empirical equation for calculating the hydro-dynamic radius if the transition is regarded as from a random coil to a functional, folded state and with the assumption that the hydrodynamic radius is a good approximation of the true random coil radius. The existence of a low-temperature random coil is confirmed by circular dichroism and dynamic light scattering measurements. Thus, at 24°C and 1.0 atm pressure the enzyme appears to fold from a random coil to a functional, folded form as it is slowly heated.展开更多
文摘A partial phase diagram characterizing the conformational change that occurs in Thermomyces lanuginosus xylanase as it is slowly heated in 150 mM sodium phosphate (pH = 7.0) has been con-structed from slow-scan-rate differential scanning calorimetry measurements. The Clausius-Clapeyron equation was applied to determine an associated volume change of -205 L·mol-1 at 24°C, the equilibrium transition temperature at 1.0 atm pressure. This value is in excellent agreement with that predicted using a previously published [1] empirical equation for calculating the hydro-dynamic radius if the transition is regarded as from a random coil to a functional, folded state and with the assumption that the hydrodynamic radius is a good approximation of the true random coil radius. The existence of a low-temperature random coil is confirmed by circular dichroism and dynamic light scattering measurements. Thus, at 24°C and 1.0 atm pressure the enzyme appears to fold from a random coil to a functional, folded form as it is slowly heated.
