Pankaj Gaur

Exploring 1,4-dihydroxyanthraquinone as long-range emissive ratiometric fluorescent probe for signaling Zn2+/PO43−: Ensemble utilization for live cell imaging

Fluorescent 1,4-dihydroxyanthraquinone 1 was found to demonstrate its ratiometric signaling property upon interaction with divalent zinc (Zn(2+)). While the probe itself exhibited fluorescence emission in the yellow region (λem=544 nm and 567 nm), binding with Zn(2+) induced strong emission in the orange region (λem=600 nm) which was mainly due to a combination of CHEF and ICT mechanism. The probe was found to be highly sensitive toward the detection of zinc and the limit of detection (LOD) was calculated to be 9×10(-7) M. The possibility of using this probe for real-time analysis was strongly supported by the striking stability of fluorescence signal for more than five days with similar fluorescence intensity as observed during instant signaling. The present probe works within physiological pH range and is devoid of any interference caused by the same group elements such as Cd(2+)/Hg(2+). The probe possesses excellent excitation/emission wavelength profile and can penetrate cell membrane to image low concentration of zing inside living system. The in situ formed zinc-probe ensemble was further explored as ratiometric sensing platform for detecting another bio-relevant analyte phosphate anion through a zinc-displacement approach.

Dendritic Polynitrato Energetic Motifs: Development and Exploration of Physicochemical Behavior through Theoretical and Experimental Approach

Considering the fundamental and most desirable characteristics of energetic materials, a series of 1,2,3-triazole-based heterocyclic energetic motifs nicely tuned with nitrato (−ONO2) functionality were synthesized by a microwave-assisted environmental friendly synthetic approach with good yields. Thermal stability and the nature of evolved gases on decomposition of structurally characterized energetic motifs were analyzed by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) analysis and Fourier transform infrared coupled with TGA–DSC. The explosiveness of these motifs was explored by calculation of enthalpy of formation and density employing density functional theory, and the detonation performances (detonation pressure and velocity) were explored using EXPLO5_V6.03. All of these compounds were calculated to have better oxygen balance (−36 to −52%) as compared to that of trinitrotoluene (−74%). Most of the nitrate ester derivatives were found to exhibit low impact sensitivities, high densities, good thermal stabilities, and promising detonation properties, and PN3 was observed to be a superior candidate in terms of its energetic characteristics. Hence, the experimental and theoretical outcomes strongly reflect that the present approach of developing dendritic high energetic materials bearing green explosive characteristics might be a potential pathway for designing and synthesizing green explosives with desired characteristics.

Biomolecular recognition at the cellular level: geometrical and chemical functionality dependence of a low phototoxic cationic probe for DNA imaging

A combined approach was adopted to understand the impact of structural geometry as well as suitable chemical functionality of a molecular probe on its efficient binding in the minor groove of DNA. The development of a small chemical library of different lutidinium conjugates (P1-P5) and molecular simulations using DFT calculations clearly demonstrated that the semilunar conformation of a molecular probe equipped with requisite chemical functionality is the key parameter for its proper binding in the minor groove of DNA. The comparative optical responses of these probes (P1-P5) coupled with the theoretical studies illustrated that only P3 displayed considerable fluorescence enhancement in the presence of DNA because of its semilunar geometry and special chemical architecture. Furthermore, the bioassays clearly revealed that the probe can penetrate the cell membrane of live as well as dead cells without the help of any permeabilization agent. Microscopic cellular imaging established that probe P3 can stain the nuclear region of the cells with high contrast and negligible cytoplasmic spillage without causing any cellular deterioration. The specificity and binding efficiency of P3 toward DNA were established by performing DNase/RNase digest tests and gel electrophoresis experiments. Most importantly, P3 exhibited minimum phototoxicity and high photobleaching resistance in cellular medium under continuous exposure to a light source, which are highly desirable for real time monitoring of many biological events. Altogether, the investigated properties of P3 shed light on its admirable and persuasive standing as a cell-compatible, bright and photostable molecular probe for nuclear imaging in various bio-medical applications.

Selenium Incorporated Cationic Organochalcogen: Live Cell Compatible and Highly Photostable Molecular Stain for Imaging and Localization of Intracellular DNA.

Successful integration of selenium unit into a newly designed cationic chemical architecture led to the development of a highly photostable molecular maker PA5 to be used in fluorescence microscopy as cellular nucleus staining agent for longer duration imaging under continuous laser illumination. Adaptation of a targeted single-atom modification strategy led to the development of a series of proficient DNA light-up probes (PA1-PA5). Further, their comparative photophysical studies in the presence of DNA revealed the potential of electron rich heteroatoms of chalcogen family in improving binding efficiency and specificity of molecular probes toward DNA. The findings of cell studies confirmed the outstanding cell compatibility of probe PA5 in terms of cell permeability, biostability, and extremely low cytotoxicity. Moreover, the photostability experiment employing continuous laser illumination in solution phase as well as in cell assay (both fixed and live cells) revealed the admirable photobleaching resistance of PA5. Finally, while investigating the phototoxicity of PA5, the probe was found not to exhibit light-induced toxicity even when irradiated for longer duration. All these experimental results demonstrated the promising standing of PA5 as a futuristic cell compatible potential stain for bioimaging and temporal profiling of DNA.