Ventura M M
Departamento de Biologia Celular, Universidade de Brasília.
An Acad Bras Cienc. 1989;61(3):373-7.
The infrared spectrum (amide I' region) of Kunitz soybean trypsin inhibitor (SBTI) was obtained in D2O solution and resolved into Gaussian components. A prominent broad band centered at 1643 cm-1 is shown on the unresolved spectrum, which is usually assigned to N-deuterated peptide groups in an unordered structure, since SBTI is known to be devoid of alpha-helix by CD and X-ray crystallographic studies. In addition, shoulders are evident at 1632 cm-1 and 1676 cm-1, which correspond probably to the v(pi, O) and v(O, pi) components assigned to an antiparallel-chain beta-pleated sheet structure. Parameters (maximum absorptivity, wavenumber at the maximum of the band, and half-width of the band at half-height) for the four Gaussian component bands (in which the amide I' band was resolved) are given. A crude estimation of 4% is obtained for antiparallel beta-sheet in SBTI, i.e., this protein would be practically devoid of such a beta-structure. Notwithstanding the fact that this result is apparently in agreement with the far-UV CD spectrum (data reported in the literature), the predominant conformation class found in SBTI has been demonstrated to be approximate beta-sheet structures, with a small amount of regular sheet (Sweet et al., (1974) Biochemistry 13: 4212-4228).
在重水（D2O）溶液中获得了库尼茨大豆胰蛋白酶抑制剂（SBTI）的红外光谱（酰胺I'区域），并将其解析为高斯分量。在未解析的光谱上显示出一个以1643 cm-1为中心的突出宽带，由于通过圆二色性（CD）和X射线晶体学研究已知SBTI缺乏α-螺旋结构，该宽带通常被归因于无序结构中的N-氘代肽基团。此外，在1632 cm-1和1676 cm-1处有明显的肩峰，这可能对应于分配给反平行链β-折叠片层结构的v(π,O)和v(O,π)分量。给出了四个高斯分量带（其中酰胺I'带被解析）的参数（最大吸收率、带最大值处的波数以及半高宽）。在SBTI中反平行β-折叠片层的粗略估计为4%，即这种蛋白质实际上几乎没有这种β-结构。尽管这一结果显然与远紫外CD光谱（文献报道的数据）一致，但已证明在SBTI中发现的主要构象类型是近似β-折叠片层结构，伴有少量规则片层（斯威特等人，（1974年）《生物化学》13: 4212 - 4228）。
