Pepe Alessia, Moretti Paolo, Yoneda Juliana S, Carducci Federica, Itri Rosangela, Mariani Paolo
Department of Life and Environmental Sciences, Università Politecnica delle Marche, via Brecce Bianche, 60131 Ancona, Italy.
Department of Applied Physics, Institute of Physics, University of São Paulo, São Paulo, Brazil.
Nanoscale. 2023 Sep 29;15(37):15196-15205. doi: 10.1039/d3nr01348k.
Guanine (G) hydrogels are very attractive materials made by the supramolecular organization of G-derivatives in water. In this paper, hydrogels composed of guanosine 5'-monophosphate (GMP) and guanosine (Gua), that make long, flexible and knotted G-quadruplexes, were investigated by small- and wide-angle X-ray scattering (SAXS and WAXS) to comprehend the origin of their unique orientational properties. The SAXS intensity, analysed at a fixed scattering vector modulus as a function of polar angle, allowed us to derive the Maier-Saupe orientation parameter . The strong dependence of on hydrogel composition and temperature demonstrated that the preferred orientation is controlled by the quadruplex surface charge and flexibility. Indeed, a possible correlation between the orientation parameter and the quadruplex-to-quadruplex lateral interactions was explored. Results confirmed that the balance between attractive and repulsive interactions plays a main role in the orientational anisotropy: quadruplex clusters lose their orientational properties when attractive interactions decrease. The key role of the number of negative charges per unit length of the G-quadruplex filaments was confirmed by Atomic Force Microscopy (AFM) observations. Indeed, directionality histograms showed that in the presence of a large amount of Gua, G-quadruplexes follow preferential orientations other than those related to the strong interactions with the K pattern on the mica surface. The fact that lateral quadruplex-to-quadruplex interactions, even in the presence of external (opposing) forces, can tune the hydrogel alignment in a given preferred direction provides novel possibilities for scaffold/3D printing applications.
鸟嘌呤（G）水凝胶是由G衍生物在水中通过超分子组装形成的极具吸引力的材料。在本文中，由5'-单磷酸鸟苷（GMP）和鸟苷（Gua）组成的水凝胶，能形成长的、灵活的且打结的G-四链体，通过小角和广角X射线散射（SAXS和WAXS）对其进行了研究，以了解其独特取向性质的起源。在固定散射矢量模量下，将SAXS强度作为极角的函数进行分析，使我们能够推导出迈尔-绍佩取向参数。该参数对水凝胶组成和温度的强烈依赖性表明，优先取向受四链体表面电荷和柔韧性控制。事实上，还探索了取向参数与四链体间横向相互作用之间可能的相关性。结果证实，吸引和排斥相互作用之间的平衡在取向各向异性中起主要作用：当吸引相互作用减弱时，四链体簇失去其取向性质。原子力显微镜（AFM）观察证实了G-四链体细丝每单位长度负电荷数量的关键作用。确实，方向性直方图显示，在存在大量Gua的情况下，G-四链体遵循的优先取向不同于与云母表面K模式的强相互作用相关的取向。即使在存在外部（相反）力的情况下，四链体间横向相互作用仍能在给定的优先方向上调节水凝胶排列，这一事实为支架/3D打印应用提供了新的可能性。
