Higashi Nobuyuki, Yoshikawa Ryo, Koga Tomoyuki
Department of Molecular Chemistry and Biochemistry, Faculty of Science and Engineering, Doshisha University Kyotanabe Kyoto 610-0321 Japan
RSC Adv. 2020 Apr 21;10(27):15947-15954. doi: 10.1039/d0ra02906h.
Collagen is an essential structural protein in animal tissues and plays key roles in cellular modulation. We investigated methods to discover collagen model peptides (CMPs) that would self-assemble into triple helices and then grow into supramolecular organizations with diverse morphological features, which would be valuable as biomaterials. This challenging undertaking was achieved by placing azobenzene groups on the ends of the CMPs, (GPO) ( = 3-10), Azo-(GPO) . In a dilute aqueous solution (80 μM), CD spectra indicated that the Azo-(GPO) ( > 4) formed triple helices due to strong hydrophobic azobenzene interactions, and that helix stability was increased with the peptide segment length. The resulting triple helices induced a specific azobenzene orientation through turned and twisted configurations as shown by CD spectra. TEM observations for the same solutions disclosed the morphologies for the Azo-CMPs. Azo-(GPO), having the shortest peptide segment, showed no nanostructure, both Azo-(GPO) and Azo-(GPO) provided consistent well-developed nanofiber structures resembling the natural collagen fibers, and Azo-(GPO) s ( = 6-10) grew into flexible rod-like micelle fibers. In addition, alkyl chain-attached C Azo-(GPO) displayed a toroidal morphology, and Azp-deg-(GPO) having a hydrophilic spacer assembled into a bilayer vesicle structure. These diverse morphological features are considered to be due to the characteristics of the pre-organized triple helix units. Photo-isomerization of the azobenzene moiety brought about the disappearance of such characteristic nano-architectures. When the solution concentration was increased up to 1 wt%, only Azo-(GPO) and Azo-(GPO) spontaneously formed hydrogels exhibiting a satisfactory gel-to-sol transition upon UV irradiation.
胶原蛋白是动物组织中一种重要的结构蛋白，在细胞调节中发挥关键作用。我们研究了发现胶原蛋白模型肽（CMPs）的方法，这些肽会自组装成三螺旋结构，然后生长成具有多种形态特征的超分子聚集体，这作为生物材料将很有价值。通过在CMPs（GPO） （ = 3 - 10），即Azo - （GPO） 的末端放置偶氮苯基团，实现了这一具有挑战性的任务。在稀水溶液（80 μM）中，圆二色光谱（CD）表明，由于强烈的疏水偶氮苯相互作用，Azo - （GPO） （ > 4）形成了三螺旋结构，并且螺旋稳定性随着肽段长度的增加而增强。如CD光谱所示，所得的三螺旋结构通过扭转和扭曲构型诱导了特定的偶氮苯取向。对相同溶液的透射电子显微镜（TEM）观察揭示了Azo - CMPs的形态。具有最短肽段的Azo - （GPO）没有显示出纳米结构，Azo - （GPO）和Azo - （GPO）都提供了与天然胶原纤维相似的发育良好的纳米纤维结构，并且Azo - （GPO） （ = 6 - 10）生长成柔性棒状胶束纤维。此外，连接烷基链的C Azo - （GPO）呈现出环形形态，而具有亲水性间隔基的Azp - deg - （GPO）组装成双层囊泡结构。这些多样的形态特征被认为是由于预组织的三螺旋单元的特性所致。偶氮苯部分的光异构化导致了这种特征性纳米结构的消失。当溶液浓度增加到1 wt%时，只有Azo - （GPO）和Azo - （GPO）自发形成水凝胶，在紫外线照射下表现出令人满意的凝胶 - 溶胶转变。
