Max Planck Institute of Colloids and Interfaces, 14424 Potsdam, Germany.
Colloids Surf B Biointerfaces. 2013 Sep 1;109:129-35. doi: 10.1016/j.colsurfb.2013.03.030. Epub 2013 Apr 1.
Two fragments of the antimicrobial peptide LL-37 (LL-32 and LL-20) have been characterized in adsorption layers at the air/buffer interface by infrared reflection absorption spectroscopy (IRRAS) and X-ray reflectivity (XR) measurements. As shown in previous work, LL-32 exhibits an increased antimicrobial activity compared to LL-37, while LL-20 is almost not active. It is shown in this work that the peptides differ drastically in their surface activity (equilibrium adsorption pressure) and their secondary structure, when they are adsorbed to the air/buffer interface. As concluded from the CD spectra, both peptides are unstructured in bulk. That means that the adsorption of the peptides to the air/buffer interface is connected to a secondary structure change. While LL-32 transforms into an α-helix lying flat at the buffer surface, with a helix diameter of 17Å, LL-20 adopts a partly unstructured conformation. The dichroic ratio of LL-20 is reduced and the electron density profile shows the formation of a second layer. The ability of LL-32 to form a complete α-helical structure at the interface is in good agreement with its higher antimicrobial activity.
两段抗菌肽 LL-37（LL-32 和 LL-20）的片段已经通过红外反射吸收光谱（IRRAS）和 X 射线反射率（XR）测量在空气/缓冲界面的吸附层中得到了表征。如前所述，与 LL-37 相比，LL-32 表现出更高的抗菌活性，而 LL-20 几乎没有活性。本工作表明，当吸附到空气/缓冲界面时，肽在表面活性（平衡吸附压力）和二级结构方面有很大差异。从 CD 光谱推断，两种肽在本体中均无结构。这意味着肽的吸附到空气/缓冲界面与二级结构的变化有关。虽然 LL-32 转变成一个在缓冲表面上平躺的 α-螺旋，螺旋直径为 17Å，但 LL-20 采用部分无结构构象。LL-20 的二色性比降低，电子密度谱显示形成了第二层。LL-32 在界面上形成完整α-螺旋结构的能力与其更高的抗菌活性相一致。
