Bauer H H, Müller M, Goette J, Merkle H P, Fringeli U P
Department of Pharmacy, Swiss Federal Institute of Technology, Zurich ETH.
Biochemistry. 1994 Oct 11;33(40):12276-82. doi: 10.1021/bi00206a034.
The peptide hormone human calcitonin (hCT) has a marked tendency to aggregate in aqueous solutions, resulting in viscous and turbid dispersions consisting of long fibrils approximately 80 A in diameter. Both transmission (T-FTIR) and attenuated total reflection Fourier transform infrared (ATR-FTIR) experiments were applied on hCT adsorption and aggregation kinetics. By means of the surface sensitive ATR-FTIR spectroscopy at a hydrophobic/hydrophilic interface, early adsorption and aggregation steps of hCT could be followed in situ under real time conditions. Since the aggregation of hCT is associated with conformational changes, the secondary structure sensitive amide I'-band (D2O) could be used as a diagnostic marker. ATR-FTIR spectra recorded during the aggregation kinetics of hCT showed an increase of the amide I'-band intensity by a factor of 3.4, interpreted as pronounced adsorption of hCT molecules from bulk solution to the germanium plate. Furthermore, variations in the line shape of the amide I'-band were interpreted. At the beginning, hCT adopted a random coil conformation followed by distinct formations of alpha-helical and intermolecular parallel beta-sheet structures. Finally, the random coil content declined to 63%, whereas alpha and beta contents rose to 8% and 29%, respectively. From our kinetics results the alpha-structures were formed faster than the beta-structures. This was interpreted as an initial induction of amphiphilic helices during the adsorption process of hCT monomers. ATR-FTIR spectroscopy provides a sensitive analytical tool suggested to monitor interfacial adsorption and aggregation phenomena also of other peptides and proteins.
肽激素人降钙素（hCT）在水溶液中具有明显的聚集倾向，导致形成由直径约80埃的长纤维组成的粘性和浑浊分散体。透射傅里叶变换红外光谱（T-FTIR）和衰减全反射傅里叶变换红外光谱（ATR-FTIR）实验均应用于hCT的吸附和聚集动力学研究。借助疏水/亲水界面的表面敏感ATR-FTIR光谱，可在实时条件下原位跟踪hCT的早期吸附和聚集步骤。由于hCT的聚集与构象变化相关，二级结构敏感的酰胺I'带（D2O）可作为诊断标记物。在hCT聚集动力学过程中记录的ATR-FTIR光谱显示酰胺I'带强度增加了3.4倍，这被解释为hCT分子从本体溶液到锗板的明显吸附。此外，还对酰胺I'带的线形变化进行了解释。起初，hCT呈现无规卷曲构象，随后形成明显的α-螺旋和分子间平行β-折叠结构。最后，无规卷曲含量降至63%，而α-螺旋和β-折叠含量分别升至8%和29%。根据我们的动力学结果，α-结构的形成速度比β-结构快。这被解释为hCT单体吸附过程中两亲性螺旋的初始诱导。ATR-FTIR光谱提供了一种灵敏的分析工具，建议用于监测其他肽和蛋白质的界面吸附和聚集现象。
