玉米粉蛋白质二级结构的红外光谱研究

Study on Secondary Structure of Maize Meal Protein by Infrared Spectroscopy

通过测定不同温度下市售玉米粉酰胺Ⅲ带的红外光谱(一维红外光谱、二阶导数红外光谱、四阶导数红外光谱和去卷积红外光谱)进一步研究温度对玉米粉蛋白质二级结构的影响。研究发现,玉米粉的一维红外光谱的分辨率不高;玉米粉的二阶导数红外光谱的分辨率优于一维红外光谱,其中1260cm-1处的吸收峰归属于蛋白质无规卷曲结构,1285cm-1处的吸收峰归属于蛋白质β-转角结构;四阶导数红外光谱的分辨率要进一步优于二阶导数红外光谱,其中1225cm-1处的吸收峰归属于蛋白质β-折叠结构,而1315cm-1处的吸收峰归属于蛋白质α-螺旋结构;玉米粉去卷积红外光谱中,随着测定温度的升高,α-螺旋结构、β-转角结构、无规卷曲结构和β-折叠结构的红外吸收强度均有所增加。最后研究了玉米粉酰胺Ⅲ带的二维红外光谱(同步二维红外光谱和异步二维红外光谱)。研究发现,随着测定温度的升高,玉米粉蛋白质二级结构的红外吸收强度变化快慢趋势是:1285cm-1(β-转角结构)>1260cm-1(无规卷曲结构)>1225cm-1(β-折叠结构)>1315cm-1(α-螺旋结构)。结果表明,玉米粉蛋白质的二级结构中,β-转角结构对于温度比较敏感,而α-螺旋结构则相对稳定。采用红外光谱研究玉米粉蛋白质二级结构可行,并为研究玉米粉的热稳定性提供了一个新的研究方法。

The infrared spectroscopy（one-dimensional infrared spectroscopy, second-derivative infrared spectroscopy, fourth-derivative infrared spectroscopy and deconvolution infrared spectroscopy） of amide Ⅲ bands at different temperatures were measured to determine the secondary structure of commercially available maize meal protein. Unfortunately one-dimensional infrared spectroscopy was a low sensitivity technique. But the resolution of second-derivative infrared spectroscopy was better than one-dimensional infrared spectroscopy. The region of 1260 and 1285cm-1 may have contributions from the coil structure and β-turn structure. The resolution of fourth-derivative infrared spectroscopy was better than second-derivative infrared spectroscopy. The region of 1225 and 1315cm-1 may be due to the β-sheet structure and α-helix structure. With the rising of temperature, strengths of bands near 1315, 1285, 1260 and 1225cm-1increased dramatically in deconvolution infrared spectroscopy. Two-dimensional infrared spectroscopy（synchronous two-dimensional infrared spectroscopy and synchronous two-dimensional infrared spectroscopy）of maize meal amide Ⅲ bands were studied to determine the sequence of intensity changes. It had been found that the sequence of intensity changes was 1285cm-1（β-turn structure）1260cm-1（random coil structur） 1225cm-1（β-sheet structure）1315cm-1（α-helix structure）, as the temperature was raised. These results suggested that the β-turn structure was more sensitive to temperature than the α-helix structure. This work provided a technical foundation for infrared spectroscopy to study the effect of temperature for maize meal protein secondary structure, and provided a new method to research the thermostability of maize meal.