Experimental and computational studies of pyridine-assisted post-synthesis modified air stable covalent-organic frameworks

Pyridine-modified COF-10 exhibits enhanced stability in humid air relative to un-modified COF-10. Solid state NMR and computational studies were used to probe the nature of pyridine interactions with the framework. We propose two models for pyridine-framework interactions with different stabilities.     

Benzimidazole-based imine-linked chemosensor: chromogenic sensor for Mg2+ and fluorescent sensor for Cr3+

We synthesized an imine-linked, benzimidazole-based chemosensor that can be used for chromogenic recognition of Mg²⁺ and fluorescent recognition of Cr³⁺. The chemosensor shows sensitive, selective, and ratiometric recognition of Cr³⁺ through concurrent quenching at one wavelength and enhancement of fluorescence intensity at another wavelength. It can also be used to detect Mg²⁺ via UV–vis absorption spectroscopy. DFT calculations support these phenomena. The sensor can be used to strain microbe cells without breakage.     

A benzimidazole-based fluorescent sensor for Cu2+ and its complex with a phosphate anion formed through a Cu2+ displacement approach

A benzimidazole-based imine linked receptor was synthesized for fluorescent recognition of Cu²⁺ in a CH₃CN/H₂O (8:2, v/v) solvent system. The receptor offers an opportunity for the selective estimation of Cu²⁺ in the presence of another metal ion at equimolar concentration. The Cu²⁺ complex with the receptor acted as a sensor for a phosphate anion, and the phosphate recognition event restored the fluorescence intensity of the receptor.     

Navigating high-dimensional activity landscapes: design and application of the ligand-target differentiation map

The transformation of high-dimensional bioactivity spaces into activity landscape representations is as of yet an unsolved problem in computational medicinal chemistry. High-dimensional activity spaces result from the experimental evaluation of compound sets on large numbers of targets. We introduce a first concept to represent and navigate high-dimensional activity landscapes that is based on a data structure termed ligand-target differentiation (LTD) map. This approach is designed to reduce the complexity of high-dimensional bioactivity spaces and enable the identification and further analysis of compound subsets with interesting activity and structural relationships. Its utility has been demonstrated using a set of more than 1400 inhibitors with exact activity measurements for varying numbers of 172 kinases.     

Role of Dimensionality for Photocatalytic Water Splitting: CdS Nanotube versus Bulk Structure

Using state-of-the-art density functional theoretical calculations, we have modelled a facetted CdS nanotube (NT) catalyst for photocatalytic water splitting. The overall photocatalytic activity of the CdS photocatalyst has been predicted based on the electronic structures, band edge alignment, and overpotential calculations. For comparisons, we have also investigated the water splitting process over bulk CdS. The band edge alignment along with the oxygen evolution reaction/hydrogen evolution reaction (OER/HER) mechanism studies help us find out the effective overpotential for the overall water splitting on these surfaces. Our study shows that the CdS NT has a highly stabilized valence band edge compared to that of bulk CdS owing to strong p–d mixing. The highly stabilized valence band edge is important for the hole-transfer process and reduces the risk of electron-hole recombination. CdS nanotube requires less overpotential for water oxidation reaction than the bulk CdS. Our findings suggest that the efficiency of the water oxidation/reduction process further improves in CdS as we reduce its dimensionality, that is going from bulk CdS to one-dimensional nanotube. Furthermore, the stabilized valence band edge of CdS nanotube also improves the photostability of CdS, which is a problem for bulk CdS.     

Microwave Activated Solid Support Synthesis of New Antibacterial Quinolones

Summary.  A novel synthesis of 6-fluoro-7-(5-aryl-1,3,4-thiadiazol/oxadiazol-2-yl-sulfanyl)-4-quinolone-3-carboxylic acids from 7-chloro-6-fluoro-4-quinolone-3-carboxylic acid and 5-substituted 1,3,4-thiadiazoles/oxadiazoles on basic alumina under microwave activation is described. All compounds were screened for their in vitro antibacterial activity against B. lichenformis, 2689, K. aerogens 2281, S. typhimurium 2501, E. herbicola 2491, and P. vulgaris 2027 and found to possess activities comparable to that of the standard drug norfloxacin. Received May 2, 2000. Accepted (revised) June 13, 2000     

Transient Metallo-Lipidoid Assemblies Amplify Covalent Catalysis of Aqueous and Non-Aqueous Reactions

Dissipative supramolecular assemblies are hallmarks of living systems, contributing to their complex, dynamic structures and emerging functions. Living cells can spatiotemporally control diverse biochemical reactions in membrane compartments and condensates, regulating metabolite levels, signal transduction or remodeling of the cytoskeleton. Herein, we constructed membranous compartments using self-assembly of lipid-like amphiphiles (lipidoid) in aqueous medium. The new double-tailed lipidoid features Cu(II) coordinated with a tetravalent chelator that dictates the binding of two amphiphilic ligands in cis-orientation. Hydrophobic interactions between the lipidoids coupled with intermolecular hydrogen bonding led to a well-defined bilayer vesicle structure. Oil-soluble S_NAr reaction is efficiently upregulated in the hydrophobic cavity, acting as a catalytic crucible. The modular system allows easy incorporation of exposed primary amine groups, which augments the catalysis of retro aldol and C−N bond formation reactions. Moreover, a higher-affinity chelator enables consumption of the Cu(II) template leveraging the differential thermodynamic stability, which allows a controllable lifetime of the vesicular assemblies. Concomitant temporal upregulation of the catalytic reactions could be tuned by the metal ion concentration. This work offers new possibilities for metal ion-mediated dynamic supramolecular systems, opening up a massive repertoire of functionally active dynamic “life-like” materials.     

Bio-activity assessment of fruits using Generalized Difference and Parameterized Fujii method

In this research work, both qualitative and quantitative measurement of biospeckle activity of three Indian fruits namely apple, pear and tomato have been carried out using Generalized Difference and Parameterized Fujii methods. Different activity area of the fruits can be easily visualized through the spectral maps. The variation of activity level of the fruits during shelf life storage has been studied through activity graphs. Comparative studies of activities of all the fruits are also presented and relatively high activity was found in apple compared to pear and tomato.     

Numerical investigation of space charge electric field for a sheet electron beam between two conducting planes

Analytical and numerical study of the stability of sheet electron beam in periodically cusped magnetic field (PCM) is made. The beam has been considered as having diffused density profile. The conditions for beam focusing are discussed.     

Rational designing of glyco-nanovehicles to target cellular heterogeneity

The aberrant expression of endocytic epidermal growth factor receptors (EGFRs) in cancer cells has emerged as a key target for therapeutic intervention. Here, we describe for the first time a state-of-the-art design for a heparan sulfate (HS) oligosaccharide-based nanovehicle to target EGFR-overexpressed cancer cells in cellular heterogeneity. An ELISA plate IC₅₀ inhibition assay and surface plasma resonance (SPR) binding assay of structurally well-defined HS oligosaccharides showed that 6-O-sulfation (6-O-S) and 6-O-phosphorylation (6-O-P) of HS tetrasaccharides significantly enhanced EGFR cognate growth factor binding. The conjugation of these HS ligands to multivalent fluorescent gold nanoparticles (AuNPs) enabled the specific and efficient targeting of EGFR-overexpressed cancer cells. In addition, this heparinoid-nanovehicle exhibited selective homing to NPs in cancer cells in three-dimensional (3D) coculture spheroids, thus providing a novel target for cancer therapy and diagnostics in the tumor microenvironment (TME).

Heparan sulfate oligosaccharide based nanovehicle greatly enhance the selective targeting of cancer cells in tumor microenvironment.