Allophane-related aluminium silicates with various chemical compositions were synthesized using a hydrothermal reaction with inorganic reagents as starting solutions. The X-ray diffraction traces of the synthesized allophanes showed broad reflections centred at 0.34 and 0.23 nm, which were attributed to the imogolite-like structure of the allophanes. Energy-dispersive X-ray measurements confirmed that the Al-rich materials were synthesized as targeted. The specific surface area of the synthesized allophanes was 313–500 m2 g–1, which is greater than that of a natural allophane (248 m2 g–1). The amount of nitrate adsorbed on the synthesized allophanes tended to increase as the Al content increased. The maximum amount of nitrate adsorbed was 2.07 mmol g–1 at pH ~2, which was comparable to that of a common anion-exchange material. A possible adsorption mechanism for nitrate at lower pH levels is the weak NO3– interaction of the positively charged surface of Al-OH2+ sites.

Anticodon hairpins are structural motifs with contradictory functions. The recognition by aminoacyl synthetases implies extended interactions with the anticodon base triplet and thus, usually, an unfolding of the anticodon loop. The recognition by the ribosome and cognate interaction with a mRNA codon implies, on the other hand, the formation of a mini-helix with a canonical anticodon hairpin structure as observed by crystallography and NMR. To be able to understand the various properties of this motif, a precise description of its structural conservation is required. Here, on the basis of phylogenetic, structural, and molecular dynamics data, we discuss a conserved interaction established between the ribose of the U33 and the base at position 35, either a purine or a pyrimidine. This interaction involves the hydrogen bonding donor or acceptor potential of the hydroxyl group of U33 and has to be integrated in an extended definition of the anticodon hairpin. The extended structural signature provides also an explanation for the role played by pseudouridines at position 35.