Binding mode of biologically relevant anionic probe, ANS, with ctDNA is divulged from spectroscopic and molecular docking studies.

The binding interaction of a potential nervous system stimulant, 3-acetyl-4-oxo-6,7-dihydro-12H-indolo-[2,3-a]-quinolizine (AODIQ), with calf-thymus DNA (ctDNA) has been explored thoroughly. The modified photophysics of the fluorescent molecule within the microheterogeneous biomacromolecular system has been exploited to divulge the drug-DNA binding interaction. The absorption and various fluorometric measurements together with the fluorescence quenching, urea-induced denaturation study, circular dichroism and DNA-melting studies unequivocally ascertain the mode of binding of the drug with the DNA to be groove binding. Corroborating the experimental observations, molecular docking simulation projects the minor groove of the biomacromolecule to be the site of binding. Further experiments have revealed that dissociation of the drug from the drug-DNA complex can be achieved by the detergent sequestration method. Besides providing an insight into the drug-DNA interaction the work also demonstrates the surfactant-induced excretion of the drug from the biomacromolecular assembly.

In this article, we have addressed to a demanding physicochemical aspect of therapeutic and drug research. We have reported a simple yet prospective technique that can be exploited for the controlled delivery of drugs and/or bioactive small molecules to the most relevant biomolecular target DNA. Exploiting various steady state and time resolved spectroscopic techniques together with the DNA helix melting study, we have shown that a biologically significant photosensitizer, namely, phenosafranin (PSF), can be quantitatively transferred to the DNA from the micellar nanocarrier made up of sodium tetradecyl sulfate (STS) using the external stimulant β-cyclodextrin (β-CD). The complexation property of β-CD with the nanocarrier (STS) has been utilized for the controlled release of the probe from the micelle to the DNA. Non-toxicity of the stimulant and the noninvasive nature of the carrier towards the target are expected to add to the suitability of this approach from a clinical perspective.

The photophysics of 2,2'-pyridil has been explored thoroughly using steady state and time resolved fluorometric techniques at room temperature (RT) in liquid media as well as in glassy matrices at cryogenic temperature (77 K). Ethanol and methylcyclohexane are exploited for this purpose, as polar and non-polar media respectively. Notwithstanding the observation of multiple emissions from the fluorophore, the experiments unequivocally rule out emission from excited singlet states other than the S state, consistent with Kasha's rule. Among 1,2-dicarbonyl molecular systems, this behavior resembles that of α-furil, while it contradicts that of benzil and α-naphthil which exhibit S emissions. The dual fluorescence and dual phosphorescence of the fluorophore are ascribed to the emissions originating from the two conformers, namely near-trans and relaxed skew. Coexistence of the two conformers is substantiated by time resolved area normalized emission spectroscopy (TRANES) at both RT and 77 K. The potential energy curves (PECs) simulated from calculations based on density functional theory and its time dependent extension provide adequate support to the experimental observations.

Luminescent materials possessing both the mechanoluminescence (MCL) and electroluminescence (EL) properties are the quest for sensing and optoelectronic applications. We report on the synthesis of a new tailor-made luminogen, 1,2-bis(4-(1-([1,1'-biphenyl]-4-yl)-2,2-diphenylvinyl)phenyl)-1,2-diphenylethene (TPE 5), using Suzuki coupling reaction with high yield. An aggregation-induced emission (AIE) active complex TPE 5 forms supramolecular spherical aggregates at the air-water interface of a Langmuir trough. As a consequence, a large enhancement of luminescence is obtained from the mono- and multilayer Langmuir-Blodgett films of TPE 5 owing to the AIE effect. The luminogen TPE 5 exhibits a reversible MCL response, displaying photoluminescence switching due to change in the crystalline states under external stimuli. The unique feature of luminescence enhancement upon aggregate formation is utilized for the fabrication of light-emitting diodes with low threshold voltage using supramolecular aggregates as the active layer. This work demonstrates an efficient strategy for obtaining controlled supramolecular aggregates of AIEgen with a potential in the dual applications of MCL and EL.