Improved Analytical Performance of an Amphiphilic Probe upon Protein Encapsulation: Spectroscopic Investigation along with Computational Rationalization

Abstract

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.

Discerning toxic nerve gas agents via a distinguishable ‘turn-on’ fluorescence response: multi-stimuli responsive quinoline derivatives in action

“…Notably, we have incorporated a carbonyl moiety into the compounds, which is susceptible to cyanide addition reactions. 13 This design allows us to anticipate that the cyanide released during the phosphorylation reaction step may interact with the carbonyl unit. Such a strategy could potentially enable discrimination between nerve gas agents like DCNP (a mimic of tabun) and DClP (mimicking soman or sarin).…”

Oxidized Bis(indolyl)methane Derivatives with Diverse Signaling Units: An Excitation-Dependent Fluorescence Response toward Heavy Metal Pollutants in an Aqueous Medium

“…Compounds 1 and 2 were synthesized following the procedure reported in the literature. , The precursor aldehyde compounds, 1-pyrene aldehyde, and 9-anthracene aldehyde were stirred at room temperature with indole (1:2 ratio) in the presence of I 2 as the catalyst (see SI). Subsequently, the resultant adducts were oxidized using DDQ to get the final conjugated molecules in good yields.…”

AIE active fluorescent organic nanoparticles based optical detection of Cu2+ ions in pure water: a case of aggregation–disaggregation reversibility

“…58 Although 1 -based FONs were explored earlier, 55–57 they were never employed in the selective and sensitive dual-mode detection of Cu 2+ ions in a 100% aqueous medium. As a part of a continuing effort to the develop pyrene-based fluorescent chemosensors by our group, 59–62 herein, we report a pyrene-terpyridine integrated amphiphilic fluorescent probe 1 that forms FONs in a pure aqueous medium where those FONs selectively recognized Cu 2+ ions by ratiometric absorption spectral changes and “turn-off” fluorescent responses in a 100% aqueous medium. The sensing mechanism has been explored by a systematic DFT study.…”