From G-quartets to G-ribbon gel by concentration and sonication control

Abstract

Two guanosine analogues have been designed and synthesized by connecting one (1) or three adamantane branches (2). The compound containing a single adamantane branch formed G-quartets in acetonitrile solution, and was then transformed into a G-ribbon gel at concentrations higher than the critical gelation concentration. In contrast, the compound with three adamantane branches precipitated after a heating-cooling process. By means of circular dichroism and UV/visible spectra, NMR, SEM, and structural studies, the mechanism of the formation of the G-quartets and G-ribbon gel, as well as the difference in the self-assembly modes of the two compounds, have been fully elucidated. Compound 1 firstly self-assembled into G-quartets in solutions in the concentration range 5.0 × 10(-4) to 1.0 × 10(-2) M, and these G-quartets were transformed into a G-ribbon on further increasing the concentration. Gelation occurred when the G-ribbon self-assembled into a hexagonal columnar structure with the help of intermolecular hydrogen-bonding and hydrophobic interactions. This gel was sensitive to sonication and underwent a morphology change from a columnar structure to a flower-like structure composed of flakes. In contrast, due to steric hindrance, compound 2 only assembled into a spherical structure based on hydrophobic interactions.

Cooperativity in the Self‐Assembly of the Guanine Nucleobase into Quartet and Ribbon Structures on Surfaces

“…Recently, Yi et al. showed that the conversion between G 4 and G‐ribbon structures could be controlled reversibly by varying the concentration of G in solution and that gels were formed with ribbon structures at higher concentration . Similar experimental findings of ring and ribbon structures were obtained for X derivatives in solution, as well as self‐assembled nanostructures on gold surfaces …”

Applications of guanine quartets in nanotechnology and chemical biology

“…a | Amphiphilic guanosine (G; 2) that self-assembles into a lyotropic liquid crystal triggered by a K + -promoted synthetic G-quartets (SQ) formation 96 . b | Cation-free SQ formed by adamantyl-conjugated guanines (13) 99 , whose SQ/ribbon topological transition is controlled by the concentration.…”

“…8b). Gelation occurred when ribbons selfassembled into micrometrewidth hexa gonal columnar structures; a morphological change can be triggered by ultrasonication, which favours twistedflowerlike structures 99 . Liu and colleagues observed a similar behaviour with a guanine function alized with a 3,4,5tris(ndodecan1yloxy)benzohy drazide (14): the quartettoribbon structural transition was solventdependent, occurring above 17% w/w in toluene and above 29% w/w in chloroform.…”

Supramolecular G4 Eutectogels of Guanosine with Solvent‐Induced Chiral Inversion and Excellent Electrochromic Activity

“…Dyes were added to visualize the gels. 11 BNMR of c) ChCl/MPG and d) ChCl/GL eutectogel, suggesting only guanosine/boric acid (GB) diester signals were observed in ChCl/MPG eutectogel, whereas both GB monoestera nd GB diester signals were observed in ChCl/GL eutectogel.…”

“…To further reveal the formation mechanism of the eutectogels,variable-concentration and variable-temperature 11 BNMR experiments were performed. Ther atio of GB monoester and GB diester in ChCl/GL eutectogel has been qualitative determined by the ratio of their relative integral area.…”