Styryl quinolines are biologically active compounds with properties largely depending on the substituents on the styryl and quinoline rings. The supramolecular aspects of this class of compounds are rarely explored. In this study, two new series of styryl quinoline derivatives, bearing −OH and −NO 2 groups at the eighthposition of the quinoline ring and −SCH 3 , −OCH 3 , and −Br groups on the styryl ring, have been developed, and their structural, supramolecular, and cytotoxic properties have been analyzed. Crystallographic analyses revealed the exciting substituent-dependent structural and supramolecular features of these compounds. In general, the 8 −OH substituted derivatives ( SA series) exhibited a non-planar molecular geometry having larger dihedral angles (5.75–59.3°) between the planes of the aromatic rings. At the same time, the 8 −NO 2 substituted derivatives ( SB series) exhibited a more or less planar molecular geometry, as revealed by the smaller dihedral angles (1.32–3.45°) between the aromatic rings. Multiple O–H···O, C–H···O, O–H···N, and π–π stacking interactions among the molecules lead to fascinating supramolecular architectures such as hydrogen-bonded triple helices, zig-zag 1D chains, π–π stacked infinite chains, and so forth in their crystal lattice. Hirshfeld surface analyses confirmed the existence of strong π–π stacking and other weak bonding interactions in these compounds. The preliminary cytotoxic properties of SA and SB series compounds were evaluated against the human cervical cancer cell lines (HeLa cells), which further highlighted the roles of functional substituents on the aromatic rings. The SA series compounds with the −OH substituent on the quinoline ring exhibited better cytotoxicity than the SB series compounds with a −NO 2 substituent. Similarly, the electron-withdrawing group −Br on the styryl ring enhanced the cytotoxicity in both series. The IC 50 values were 2.52–4.69 and 2.897–10.37 μM, respectively, for the SA and SB series compounds. Compound S3A having −OH and −Br groups on the quinoline and styryl ring, respectively, exhibited the best IC 50 value of 2.52 μM among all the compounds tested. These findings confirm the relevance of the hydroxyl group in the eighth position of quinoline. In short, the present study attempts to provide a systematic analysis of the effects of aromatic ring substituents on the structural, supramolecular, and cytotoxic properties of styryl quinolines for the first time.

A series of new π-conjugated oligomeric compounds, 2,2'-(arylenedivinylene)bis-8-hydroxyquinolines, having two vinylene-8-hydroxyquinoline moieties structured around a phenol ring, have been synthesized by the reaction of 8-hydroxyquinaldine with aromatic dialdehydes. Crystal structure of one of the compounds has been described, which shows a twisted molecular geometry and interesting supramolecular interactions leading to a 2-D sheet-like structure in the crystal lattice. The photo-luminescence properties analyses revealed that the fluorescence emission wavelengths of these compounds vary in the range 480-638 nm depending on the electronic effects of the substituents on the central phenol ring. These compounds were found to act as selective and sensitive fluorescence turn-off chemosensors for Co 2 + ions and the detection limits exhibited by these chemosensors varied in the range 15.00-23.09 nM. Analytical application of these compounds for sensing cobalt from tap water in nanomolar levels is demonstrated. Preliminary investigations conducted using HeLa cells revealed their potential for sensing cobalt in biological systems.

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The phenomenon of protein aggregation is associated with a wide range of human diseases. Our knowledge of the aggregation behaviour of viral proteins, however, is still rather limited. Here, we investigated this behaviour in the SARS-CoV and SARS-CoV-2 proteomes. An initial analysis using a panel of sequence-based predictors suggested the presence of multiple aggregation-prone regions (APRs) in these proteomes and revealed a strong aggregation propensity in some SARS-CoV-2 proteins. We then studied the in vitro aggregation of predicted aggregation-prone SARS-CoV and SARS-CoV-2 proteins and protein regions, including the signal sequence peptide and fusion peptides 1 and 2 of the spike protein, a peptide from the NSP6 protein, and the ORF10 and NSP11 proteins. Our results show that these peptides and proteins can form amyloid aggregates. We used circular dichroism spectroscopy to reveal the presence of β-sheet rich cores in aggregates and X-ray diffraction and Raman spectroscopy to confirm the formation of amyloid structures. Furthermore, we demonstrated that SARS-CoV-2 NSP11 aggregates are toxic to mammalian cell cultures. These results motivate further studies about the possible role of aggregation of SARS proteins in protein misfolding diseases and other human conditions.