Structures of self-assembled amphiphilic peptide-heterodimers: effects of concentration, pH, temperature and ionic strength
Structures of self-assembled amphiphilic peptide-heterodimers: effects of concentration, pH, temperature and ionic strength
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DOI：
10.1039/b926962b
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发表时间：
2010-01-01
期刊：
影响因子：
3.4
通讯作者：
Norden, Bengt
中科院分区：
文献类型：
--
作者：
Luo, Zhongli;Akerman, Bjorn;Norden, Bengt
研究了两亲性双尾多肽AXG的二级结构和水溶液中的自组装行为。两个尾部A = Ala 6和G = Gly（6）通过亲水残基的中心对X连接，X是ADG中的两个天冬氨酸、AKG中的两个赖氨酸和ARG中的两个赖氨酸。肽AD（Ala（6）Asp）用作单尾参考。四种肽的二级结构通过圆二色光谱在宽范围的肽浓度（0.01-0.8 mM）、温度（20-98 ℃）、pH（4-9.5）和离子强度下表征。在无盐水中，ADG和AD在高浓度、低pH和低温下以肽-肽驱动的单个肽的组装形成β-折叠类型的结构。ADG的跃迁具有两态特征，而AD的跃迁不具有两态特征，这表明ADG中添加的尾部使组装更具有合作性。通过比较，AKG和ARG的二级结构在所涵盖的大范围条件下相对稳定。根据动态光散射的双尾肽在水中形成超分子聚集体，但高分辨率AFM成像表明，有序（自组装）的结构只形成时，盐（0.1 M NaCl）加入。由于CD-研究表明，NaCl对肽的二级结构只有很小的影响，我们提出，添加的盐的主要作用是屏蔽肽结构单元之间的静电排斥。根据AFM图像，ADG和AKG支持纳米纤维与β-片层或无序二级结构之间的相关性，而ARG尽管缺乏β-片层结构但仍形成纤维。由于AKG和ARG双尾肽自组装成不同的纳米结构，而它们的二级结构对环境因素具有抵抗力，因此这些新肽显示出作为各种医学和纳米生物技术应用中纳米材料的强大构建块的潜力。
The amphiphilic double-tail peptides AXG were studied regarding secondary structure and self-assembly in aqueous solution. The two tails A = Ala6 and G = Gly(6) are connected by a central pair X of hydrophilic residues, X being two aspartic acids in ADG, two lysines in AKG and two arginines in ARG. The peptide AD (Ala(6)Asp) served as a single-tail reference. The secondary structure of the four peptides was characterized by circular dichroism spectroscopy under a wide range of peptide concentrations (0.01-0.8 mM), temperatures (20-98 degrees C), pHs (4-9.5) and ionic strengths. In salt-free water both ADG and AD form a beta-sheet type of structure at high concentration, low pH and low temperature, in a peptide-peptide driven assembly of individual peptides. The transition has a two-state character for ADG but not for AD, which indicates that the added tail in ADG makes the assembly more cooperative. By comparison the secondary structures of AKG and ARG are comparatively stable over the large range of conditions covered. According to dynamic light scattering the two-tail peptides form supra-molecular aggregates in water, but high-resolution AFM-imaging indicate that ordered (self-assembled) structures are only formed when salt (0.1 M NaCl) is added. Since the CD-studies indicate that the NaCl has only a minor effect on the peptide secondary structure we propose that the main role of the added salt is to screen the electrostatic repulsion between the peptide building blocks. According to the AFM images ADG and AKG support a correlation between nanofibers and a beta-sheet or unordered secondary structure, whereas ARG forms fibers in spite of lacking beta-sheet structure. Since the AKG and ARG double-tail peptides self-assemble into distinct nanostructures while their secondary structures are resistant to environment factors, these new peptides show potential as robust building blocks for nano-materials in various medical and nanobiotechnical applications.