Synthesis of di(glucosyloxo)phosphorus tetraphenylporphyrin complex with affinity to glucose-binding concanavalin A

Abstract

A new di(glucopyranosyloxo)phosphorus tetraphenylporphyrin complex containing axial acetylated glucosyl ligands (1a) and its deacetylated derivative (1b) were synthesized. The bio-affinity of 1 to the lectin concanavalin A (ConA) was evaluated by various spectroscopic analyses. Both 1a and 1b were bound to ConA because the fluorescence of ConA arising from tryptophan and tyrosine residues was statically quenched by 1. Their absorption spectra also shifted to longer wavelengths upon ConA addition. These spectral changes provided binding constants of 4.5 × 104 and 6.4 × 104 M−1 for 1a and 1b, respectively. Moreover, ConA efficiently quenched the fluorescence of 1a but not that of 1b. This result demonstrated that 1b was site-specifically bound to a glucose binding site comprising the tyrosine residues, albeit far from tryptophan residues. On the other hand, 1a adsorbed less specifically on the entire ConA protein.