From G-quartets to G-ribbon gel by concentration and sonication control.
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.
Department of Chemistry, Fudan University, Shanghai 200433, China.
Luyan
L
Meng
Keyin
K
Liu
Shuli
S
Mo
Yueyuan
Y
Mao
Tao
T
Yi
D005782:Gels / Q000737:chemistry*; D006151:Guanosine / Q000031:analogs & derivatives / Q000138:chemical synthesis* / Q000737:chemistry; D015394:Molecular Structure
D005782:Gels; D006151:Guanosine