Spontaneous fiber formation and hydrogelation of nucleotide bolaamphiphiles

Nucleotide-appended bolaamphiphiles 1-7, in which two T-phosphorylated thymidine moieties are connected to both ends of a long oligomethylene spacer, have been first synthesized. Their self-assembling behavior in aqueous solutions was investigated in terms of gelling ability of water molecules. The longer homologues 6 and 7 with the C18 and C20 oligomethylene spacers, respectively, proved to be capable of gelling water very effectively (>25 000 water molecules per molecule) through spontaneous formation of a fibrous network. Gelation behavior of both bolaamphiphiles strongly depended on the pH and temperature of the aqueous solutions used. The gel-to-sol transition temperature (T-GS) of 7 was determined to be approximately 85 degreesC. XRD measurement of a freeze-dried hydrogel from 7 suggested the presence of lamellar organization consisting of monolayer sheets. Hydrogen bonds involving the 5'-hydroxyl group of the deoxyribose moiety, hydrophobic interaction between the long oligomethylene chains, and pi-pi stacking of the thymine residues are responsible for the effective hydrogel formation.