Luminescent vesicular nanointerface: a highly selective and sensitive "turn-on" sensor for guanosine triphosphate

A novel amphiphilic Tb(3+) complex (TbL(3+)(I)) consisting of a +3 charged head and a hydrophobic alkyl chain has been developed. It spontaneously self-assembles in water and forms stable vesicles at neutral pH. TbL(3+)(I) has no aromatic groups (functioning as an antenna), and its intrinsic luminescence is thus minimized. These features lead to the self-assembling TbL(3+)(I) receptor molecules demonstrating an increased luminescence intensity upon binding of nucleotides. Upon addition of guanosine triphosphate (GTP), the luminescence from Tb(3+) was notably promoted (127-fold), as the light energy absorbed by the guanine group of GTP was efficiently transferred to the Tb(3+) center. In the case of guanosine diphosphate (GDP) and guanosine monophosphate (GMP), respectively, 78-fold and 43-fold increases in luminescence intensity were observed. This enhancement was less significant than that observed for GTP, due to fewer negative charges on GDP and GMP. No other nucleotides or the tested nonphosphorylated nucleosides affected the luminescence intensity to any notable extent. In marked contrast, all tested nucleotides, including guanine nucleotides, barely promoted the luminescence of molecularly dispersed receptors, TbL(3+)(II), indicating that the confinement and organization of molecules in a nanointerface play vital roles in improving the performance of a sensing system. This Tb(3+) complex nanointerface is successfully used for monitoring the GTP-to-GDP conversion.