Liquid crystalline banana‐shaped monomers derived from 2,7‐naphthalene: synthesis and properties

Three banana‐shaped monomers, i.e. 2,7‐naphthalene bis[4‐(4‐allyloxyphenylazo)‐benzoate], 2,7‐naphthalene bis[4‐(4‐allyloxy‐3‐fluorophenylazo)benzoate] and 2,7‐naphthalene bis{4‐[4‐(10‐undecenyloxy)phenylazo]benzoate}, containing azobenzene as side arms, 2,7‐dihydroxynaphthalene as central units and terminal double bonds as polymerisable functional groups, were synthesised and their mesophase behaviour investigated. Polarizing optical microscopy and DSC measurements reveal that all compounds exhibit nematic mesophases. The absorption spectrum of the trans‐azobenzene groups displays a high‐intensity π–π* transition at about 365 nm and a low‐intensity n–π* transition at around 450 nm for all compounds. Hence, photochromism can be achieved by the introduction of the azo linkage to banana‐shaped liquid crystals molecules.     

Aptamer Laden Liquid Crystals Biosensing Platform for the Detection of HIV-1 Glycoprotein-120

We report a label-free and simple approach for the detection of glycoprotein-120 (gp-120) using an aptamer-based liquid crystals (LCs) biosensing platform. The LCs are supported on the surface of a modified glass slide with a suitable amount of B40t77 aptamer, allowing the LCs to be homeotropically aligned. A pronounced topological change was observed on the surface due to a specific interaction between B40t77 and gp-120, which led to the disruption of the homeotropic alignment of LCs. This results in a dark-to-bright transition observed under a polarized optical microscope. With the developed biosensing platform, it was possible to not only identify gp-120, but obtained results were analyzed quantitatively through image analysis. The detection limit of the proposed biosensing platform was investigated to be 0.2 µg/mL of gp-120. Regarding selectivity of the developed platform, no response could be detected when gp-120 was replaced by other proteins, such as bovine serum albumin (BSA), hepatitis A virus capsid protein 1 (Hep A VP1) and immunoglobulin G protein (IgG). Due to attributes such as label-free, high specificity and no need for instrumental read-out, the presented biosensing platform provides the potential to develop a working device for the quick detection of HIV-1 gp-120.     

Synthesis, structural and spectral properties of novel octakis(3,5-bis-trifluoromethyl-benzylthio) substituted porphyrazine derivatives

[Octakis(3,5-bis-trifluoromethyl-benzylthio)porphyrazinato] magnesium carrying eight (3,5-bis-trifluoromethyl-benzylthio) groups on the peripheral positions have been synthesized by cyclotetramerization of 1,2-bis(3,5-bis-trifluoromethyl-benzylthio)maleonitrile in the presence of magnesium butanolate. Its demetalation by the treatment with trifluoroacetic acid resulted in the metal-free derivative. Further reaction of this product with copper(II) acetate, zinc(II) acetate and cobalt(II) acetate have led to the metallo derivatives M = Cu(II), Zn(II), Co(II). These novel complexes were characterized by elemental analysis, together with FT-IR, ¹H NMR, ¹³C NMR, ¹⁹F NMR, UV-vis and mass spectral data.     

Unveiling the Anticancer and Antibiofilm Potential of Catechin Overlaid Reduced Graphene Oxide/Zinc Oxide Nanocomposites

Journal of Cluster Science - In the present study, catechin was successfully grafted in reduced graphene oxide Zinc oxide (rGO/ZnO) nanocomposite by solvent free hydrothermal method. Absorption...     

CoII Complexes as Liposomal CEST Agents

Three paramagnetic Co^II macrocyclic complexes containing 2‐hydroxypropyl pendant groups, 1,1′,1′′,1′′′‐(1,4,8,11‐tetraazacyclotetradecane‐1,4,8,11‐tetrayl)tetrakis‐ (propan‐2‐ol) ([Co(L1)]²⁺, 1,1′‐(4,11‐dibenzyl‐1,4,8,11‐tetraazacyclotetradecane‐1,8‐diyl)bis(propan‐2‐ol) ([Co(L2)]²⁺), and 1,1′‐(4,11‐dibenzyl‐1,4,8,11‐tetraazacyclotetradecane‐1,8‐diyl)bis(octadecan‐2‐ol) ([Co(L3)]²⁺) were synthesized to prepare transition metal liposomal chemical exchange saturation transfer (lipoCEST) agents. In solution, ([Co(L1)]²⁺) forms two isomers as shown by ¹H NMR spectroscopy. X‐ray crystallographic studies show one isomer with 1,8‐pendants in cis‐configuration and a second isomer with 1,4‐pendants in trans‐configuration. The [Co(L2)]²⁺ complex has 1,8‐pendants in a cis‐configuration. Remarkably, the paramagnetic‐induced shift of water ¹H NMR resonances in the presence of the [Co(L1)]²⁺ complex is as large as that observed for one of the most effective Ln^III water proton shift agents. Incorporation of [Co(L1)]²⁺ into the liposome aqueous core, followed by dialysis against a solution of 300 mOsm L^?1 produces a CEST peak at 3.5 ppm. Incorporation of the amphiphilic [Co(L3)]²⁺ complex into the liposome bilayer produces a more highly shifted CEST peak at ?13 ppm. Taken together, these data demonstrate the feasibility of preparing Co^II lipoCEST agents.     

Investigation of irradiated 1H-Benzo[b]pyrrole by ESR,thermal methods and learning algorithm

1H-Benzo[b]pyrrole samples were irradiated in the air with gamma source at 0.969?kGy per hour at room temperature for 24, 48 and 72?h. After irradiation, electron spin resonance, thermogravimetry analysis (TGA) and differential thermal analysis (DTA) measurements were immediately carried out on the irradiated and unirradiated samples. The ESR measurements were performed between 320 and 400?K. ESR spectra were recorded from the samples irradiated for 48 and 72?h. The obtained spectra were observed to be dependent on temperature. Two radical-type centres were detected on the sample. Detected radiation-induced radicals were attributed to R-^+?NH and R=^?CC₂H₂. The g-values and hyperfine constants were calculated by means of the experimental spectra. It was also determined from TGA spectrum that both the unirradiated and irradiated samples were decomposed at one step with the rising temperature. Moreover, a theoretical study was presented. Success of the machine learning methods was tested. It was found that bagging techniques, which are widely used in the machine learning literature, could optimise prediction accuracy noticeably.     

Synthesis and mesomorphic properties of nonsymmetric liquid crystalline dimers containing azobenzene groups

Four novel nonsymmetric dimers containing azobenzene mesogenic groups were synthesized. The nonsymmetric dimers compounds namely, ethyl 4-[(4-{4-(4-((4-nitrophenyl)diazenyl)phenoxy)alkyloxy}phenyl)diazenyl]benzoate were obtained from the alkylation of ethyl 4-[(4-(4-bromoalkyloxy)phenyl)diazenyl]benzoate with 4-[(4-nitrophenyl)diazenyl]phenol. The mesomorphic properties of the compounds were determined by DSC and polarizing optical microscopy. The first member of the series was nonliquid crystalline while all other homologues display nematic and smectic A phases. The trans-azobenzene groups of the dimers display a high-intensity π–π* transition at about 365 nm and a low-intensity n–π* transition at around 465 nm, therefore, photochromism can be achieved by the introduction of the azo linkage to the dimeric liquid crystalline molecules.     

A Simple Colorimetric Au-on-Au Tip Sensor with a New Functional Nucleic Acid Probe for Food-borne Pathogen Salmonella typhimurium

An Au-on-Au tip sensor is developed for the detection of Salmonella typhimurium (Salmonella), using a new synthetic nucleic acid probe (NAP) as a linker for the immobilization of a DNA-conjugated Au nanoparticle (AuNP) onto a DNA-attached thin Au layer inside a pipette tip. In the presence of Salmonella, RNase H2 from Salmonella (STH2) cleaves the NAP and the freed DNA-conjugated AuNP can be visually detected by a paper strip. This portable biosensor does not require any electronic, electrochemical or optical equipment. It delivers a detection limit of 3.2×10³ CFU mL⁻¹ for Salmonella in 1 h without cell-culturing or signal amplification and does not show cross-reactivity with several control bacteria. Further, the sensor reliably detects Salmonella spiked in food samples, such as ground beef and chicken, milk, and eggs. The sensor can be reused and is stable at ambient temperature, showing its potential as a point-of-need device for the prevention of food poisoning by Salmonella.     

Visible‐Light‐Accelerated Copper(II)‐Catalyzed Regio‐ and Chemoselective Oxo‐Azidation of Vinyl Arenes

The visible‐light‐accelerated oxo‐azidation of vinyl arenes with trimethylsilylazide and molecular oxygen as stoichiometric oxidant was achieved. In contrast to photocatalysts based on iridium, ruthenium, or organic dyes, [Cu(dap)₂]Cl or [Cu(dap)Cl₂] were found to be unique for this transformation, which is attributed to their ability to interact with the substrates through ligand exchange and rebound mechanisms. Cu^II is proposed as the catalytically active species, which upon coordinating azide will undergo light‐accelerated homolysis to form Cu^I and azide radicals. This activation principle (Cu^II‐X→Cu^I+X^.) opens up new avenues for copper‐based photocatalysis.