An
easily synthesizable pyrene-based amphiphilic probe (Pybpa) has been developed, which exhibited no responses with metal ions
in the pure aqueous medium despite possessing a metal ion-chelating
bispicolyl unit. We believe that spontaneous aggregation of Pybpa in aqueous medium makes the ion binding unit not accessible
to the metal ions. However, the sensitivity and selectivity of Pybpa toward Zn2+ ions drastically improve in the
presence of serum albumin protein, HSA. The differences in the microenvironment
inside the protein cavity, in terms of local polarity, and conformational
rigidity might be attributing factors for that. The mechanistic investigations
also suggest that there might be the involvement of polar amino acid
residues that take part in coordination with Zn2+ ions. Pybpa shows no detectable spectroscopic changes with Zn2+ ions in aqueous medium in the absence of HSA. However, it
can effectively recognize Zn2+ ions in the protein-bound
form. Moreover, the photophysical behavior of Pybpa and
its zinc complex have been investigated with DFT and docking studies.
Noteworthy, such an unusual sensing aspect of Zn2+ exclusively
in the protein-bound state and particularly in aqueous medium is truly
rare and innovative.