Dong A, Huang P, Caughey W S
Department of Biochemistry, Colorado State University, Fort Collins 80523.
Biochemistry. 1990 Apr 3;29(13):3303-8. doi: 10.1021/bi00465a022.
Infrared spectra have been obtained for 12 globular proteins in aqueous solution at 20 degrees C. The proteins studied, which vary widely in the relative amounts of different secondary structures present, include myoglobin, hemoglobin, immunoglobulin G, concanavalin A, lysozyme, cytochrome c, alpha-chymotrypsin, trypsin, ribonuclease A, alcohol dehydrogenase, beta 2-microglobulin, and human class I major histocompatibility complex antigen A2. Criteria for evaluating how successfully the spectra due to liquid and gaseous water are subtracted from the observed spectrum in the amide I region were developed. Comparisons of second-derivative amide I spectra with available crystal structure data provide both qualitative and quantitative support for assignments of infrared bands to secondary structures. Band frequency assignments assigned to alpha-helix, beta-sheet, unordered, and turn structures are highly consistent among all proteins and agree closely with predictions from theory. alpha-Helix and unordered structures can each be assigned to only one band whereas multiple bands are associated with beta-sheets and turns. These findings demonstrate a method of analysis of second-derivative amide I spectra whereby the frequencies of bands due to different secondary structures can be obtained. Furthermore, the band intensities obtained provide a useful method for estimating the relative amounts of different structures.
已获得12种球状蛋白在20℃水溶液中的红外光谱。所研究的蛋白质在不同二级结构的相对含量上差异很大，包括肌红蛋白、血红蛋白、免疫球蛋白G、伴刀豆球蛋白A、溶菌酶、细胞色素c、α-胰凝乳蛋白酶、胰蛋白酶、核糖核酸酶A、乙醇脱氢酶、β2-微球蛋白和人类I类主要组织相容性复合体抗原A2。制定了评估在酰胺I区域从观察到的光谱中减去液态和气态水光谱的成功程度的标准。二阶导数酰胺I光谱与现有晶体结构数据的比较为将红外波段指定给二级结构提供了定性和定量支持。分配给α-螺旋、β-折叠、无规和转角结构的波段频率在所有蛋白质中高度一致，并且与理论预测非常吻合。α-螺旋和无规结构各自只能分配到一个波段，而多个波段与β-折叠和转角相关。这些发现证明了一种分析二阶导数酰胺I光谱的方法，通过该方法可以获得不同二级结构引起的波段频率。此外，获得的波段强度为估计不同结构的相对含量提供了一种有用的方法。
