Self-assembly Of Guanosine Derivatives

Self-assembly is that elements of the system like molecules congregate into regular structure. It widely exists in nature, for example cell in the body is self-assembled by a variety of biological molecules.Guanosine, which is one of five kinds of nucleotides structured DNA and RNA, widely exists in nature. It can interact with cytosine through three hydrogen bonds, which is important for the stabilization of DNA. However, guanosine derivative as an important group of molecular recognized and assembly can form a variety of structures in some conditions. Nanoribbons can be formed without cations, while it forms G-quartet and G-quadruplex in present of cations.1. Self-Assembly of a Lipophilic Guanosine Derivative into Nanoribbons.Gottarelli et al. reported some supramolecular structures formed by deoxyguanosine derivatives. They concluded that these deoxyguanosine derivatives self-assembled into ribbon-like structures through two different H-bonded networks without cations.Furthermore, these compounds can also form gel-like phases in hydrocarbon solvents. Based on these, we prepare a novel guanosine derivative with a large lipophilic side chain and a linker of a flexible carbon chain between the side chain and ribose group and investigate on the structure in solution and on solid surface. The results indicate that only one kind of nanoribbon exists in our system.2. Reversible organogels triggered by dynamic K+ binding and releaseLow molecular-weight organogelators (LMOGs) have received intense attention over the past few decades, because they can immobilize the flow of liquids and represent potential applications on materials, drug delivery, agents, sensors, as well as water purification. These LMOGs can assemble into various three-dimensional aggregates with micrometer-scale lengths and nanometer-scale diameters, such as strands, ribbons, fibers, rods, tubules and helix. By intelligent design of the molecular structure of LMOGs, the resulting organogel exhibits reversible changes in volume and surface physicochemical properties in response to a variety of environmental stimuli, such as temperature, pH, ionic strength, electric field, light irradiation and solvent composition. We developed a novel gel-sol transition system based on switching the structure of supramolecular assembly of guanosine derivative. The guanosine derivative can provide excellent gelation properties in chloroform and some hydrocarbon solvents through stable intermolecular interactions without K+. However, with the transition of the ribbon-like structure into G-quartets in presence of K+, the gel transformed into a sol. This process is completely reversible.3. Construction of new nanotube by supramolecular amphiphiles based on G-C couple.The formation of duplex DNA from its single stranded constituents is a result of a panoply of intermolecular forces, including aromatic p-stacking, van der Waals forces, and hydrophobic effects. However, the high fidelity observed in the pairing of complementary DNA sequences is largely due to the unique molecular recognition capability of naturally occurring nucleic acid bases (nucleobases) via Watson–Crick pairing and hydrogen-bonding interactions. The guanosine–cytidine (GC) couple is stabilized by a three-point hydrogen-bonding interaction, which plays an important role in the formation of duplex DNA. Because of this, they are always used to construct a lot of supramolecular architectures.Because of good property of supramolecular amphiphiles in self assembly, we designed a cytidine derivative with a hydrophilic head and a guanosine derivative with a hydrophobic tail. Then they formed a novel supramolecular amphiphiles based on G-C couple. Furthermore, this supramolecular amphiphiles can self-assemble into nanorube in water. Finally, we confirmed the morphology of the nanotube by some methods, and also studied the mechanism of the formation of nanotube.