二维红外相关光谱研究温度对卵转铁蛋白构象的影响

Study of the Effect of Temperature on the Conformation of Ovotransferrin by Two-Dimensional Infrared Correlation Spectroscopy

采用傅里叶变换红外光谱(FTIR)和二维相关光谱分析技术研究了无铁卵转铁蛋白和饱和铁卵转铁蛋白在加热条件下(25～95℃)构象变化规律。结果表明,随着温度升高,无铁卵转铁蛋白在3 300cm-1处的峰的迁移程度比饱和铁卵转铁蛋白大,说明卵转铁蛋白结合铁后氢键作用增强,对热的抵抗性增强。二维红外图谱分析显示,无铁卵转铁蛋白与饱和铁卵转铁蛋白的二级结构变化顺序为β-折叠>酰胺Ⅱ>-CH2-弯曲振动。通过对比无铁卵转铁蛋白和饱和铁卵转铁蛋白的二维同步和异步图谱发现,在1 652和1 688cm-1处的交叉峰存在差异,卵转铁蛋白结合铁后温度对其二级结构中α-螺旋影响变小,而对β-转角的影响变大。

The conformation changes of Apo-Ovotransferrin and Holo-Ovotransferrin were studied with the heat treatment 25- 95 C by using Fourier transform infrared spectroscopy （FTIR） and two-dimensional correlation spectroscopy analyzer. The re- sults of one-dimensional infrared spectroscopy showed that with the increase in temperature, the peak at 3 300 cm^-1 of Apo-Ovo- transferrin shifted more than that of Holo-Ovotransferrin. The peak at 3 300 cm^-1 derived from stretching vibrations of N H and O H indicates that iron-binding enhanced the role of hydrogen bonds and resistance to heat. The changing order of the secondary structure of ovotransferrin was determined by analyzing two-dimensional infrared spectra, witch is β-sheet〉amide Ⅱ CH2 bending vibration. In addition, it was found that the cross-peaks at 1 652 and 1 688 cm-1 are different in synchronous and asynchronous counter maps by comparing Apo-Ovotransferrin with Holo-Ovotransferrin. It was suggested that the temperature made less impact on the α-helix in Holo-Ovotransferrin than on that in Apo-Ovotransferrin, however, the β-turn in Holo-Ovo- transferrin was more sensitive to temperature.