Lin Shan-Yang, Chu Horng-Lun
Biopharmaceutics Laboratory, Department of Medical Research and Education, Veterans General Hospital-Taipei, Shih-Pai, Taipei, Taiwan, ROC.
Int J Biol Macromol. 2003 Sep;32(3-5):173-7. doi: 10.1016/s0141-8130(03)00051-5.
Reflectance Fourier transform infrared (FT-IR) microspectroscopy was applied to study the prevention of beta-sheet formation of amyloid beta (Abeta)(1-40) peptide by co-incubation with a hexapeptide containing a KLVFF sequence (Abeta(15-20) fragment). Second-derivative spectral analysis was used to locate the position of the overlapping components of the amide I band of Abeta peptide and assigned them to different secondary components. The result indicates that each intact sample of Abeta(15-20) fragment or Abeta(1-40) peptide previously incubated in distilled water at 37 degrees C transformed their secondary structure from 1649 (1651) or 1653cm(-1) to 1624cm(-1), suggesting the transformation from alpha-helix and/or random coil structures to beta-sheet structure. By co-incubating both samples with different molar ratio in distilled water at 37 degrees C, the structural transformation was not found for Abeta(1-40) peptide after 24h-incubation. But the beta-sheet formation of Abeta(1-40) peptide after 48h-incubation was evidenced from the appearance of the IR peak at 1626cm(-1) by adding a little amount of Abeta(15-20) fragment. There was no beta-sheet formation of Abeta(1-40) peptide after addition with much amount of Abeta(15-20) fragment, however, suggesting the higher amount of Abeta(15-20) fragment used might inhibit the beta-sheet formation of Abeta(1-40) peptide. The more Abeta(15-20) fragment used made the more stable structure of Abeta(1-40) peptide and the less beta-sheet formation of Abeta(1-40) peptide. The study indicates that the reflectance FT-IR microspectroscopy can easily evidence the prevention of beta-sheet formation of Abeta(1-40) peptide by a short amyloid fragment.
采用反射傅里叶变换红外（FT-IR）显微光谱法研究了含KLVFF序列的六肽（β-淀粉样蛋白（Aβ）（15-20）片段）与Aβ（1-40）肽共孵育对Aβ（1-40）肽β-折叠形成的抑制作用。利用二阶导数光谱分析确定Aβ肽酰胺I带重叠成分的位置，并将其归属为不同的二级结构成分。结果表明，先前在37℃蒸馏水中孵育的Aβ（15-20）片段或Aβ（1-40）肽的每个完整样品，其二级结构从1649（1651）或1653cm-1转变为1624cm-1，表明从α-螺旋和/或无规卷曲结构转变为β-折叠结构。在37℃蒸馏水中将两种样品以不同摩尔比共孵育24小时后，未发现Aβ（1-40）肽的结构转变。但孵育48小时后，加入少量Aβ（15-20）片段可使Aβ（1-40）肽在1626cm-1处出现红外峰，证明有β-折叠形成。然而，加入大量Aβ（15-20）片段后，Aβ（1-40）肽未形成β-折叠，提示使用较高量的Aβ（15-20）片段可能抑制Aβ（1-40）肽的β-折叠形成。使用的Aβ（15-20）片段越多，Aβ（1-40）肽的结构越稳定，形成的β-折叠越少。该研究表明，反射FT-IR显微光谱法能够轻松证明短淀粉样片段对Aβ（1-40）肽β-折叠形成的抑制作用。
