Category Archives: ChemistryOpen

Dynamic control of circumrotation of a [2]catenane by acid‐base switching

Posted on 9 February 2024 by nKelun Shi, nGuohui Jia, nYing Wu, nShilong Zhang, nJiawen Chenn

We reports a mechanical interlocking donor-acceptor [2]catenane, which is able to form varying degrees of self-complexed or decomplexed compounds that alter the cavity size of the crown ether and affecting the circumrotation behavior of CBPQT ⋅ 4PF₆ ring of the catenane.

Abstract

Dynamic control of the motion in a catenane remains a big challenge as it requires precise design and sophisticated well-organized structures. This paper reports the design and synthesis of a donor-acceptor [2]catenane through mechanical interlocking, employing a crown ether featuring two dibenzylammonium salts on its side arms as the host and a cyclobis(paraquat-p-phenylene) (CBPQT ⋅ 4PF₆) ring as the guest molecule. By addition of external acid or base, the catenane can form self-complexed or decomplexed compounds to alter the cavity size of the crown ether ring, consequently affecting circumrotation rate of CBPQT ⋅ 4PF₆ ring of the catenane. This study offers insights for the design and exploration of artificial molecular machines with intricate cascading responsive mechanisms.

Electrochemical detection of miRNA using commercial and hand‐made screen‐printed electrodes: liquid biopsy for cancer management as case of study

Posted on 9 February 2024 by

Screen-printed electrodes are able to offer potent tools for detecting miRNAs in liquid biopsy: commercial or handmade?

Abstract

The growth of liquid biopsy, i. e., the possibility of obtaining health information by analysing circulating species (nucleic acids, cells, proteins, and vesicles) in peripheric biofluids, is pushing the field of sensors and biosensors beyond the limit to provide decentralised solutions for nonspecialists. In particular, among all the circulating species that can be adopted in managing cancer evolution, both for diagnostic and prognostic applications, microRNAs have been highly studied and detected. The development of electrochemical devices is particularly relevant for liquid biopsy purposes, and the screen-printed electrodes (SPEs) represent one of the building blocks for producing novel portable devices. In this work, we have taken miR-2115-3p as model target (it is related to lung cancer), and we have developed a biosensor by exploiting the use of a complementary DNA probe modified with methylene blue as redox mediator. In particular, the chosen sensing architecture was applied to serum measurements of the selected miRNA, obtaining a detection limit within the low nanomolar range; in addition, various platforms were interrogated, namely commercial and hand-made SPEs, with the aim of providing the reader with some insights about the optimal platform to be used by considering both the cost and the analytical performance.

Synthesis of compounds based on the active domain of cabotegravir and their application in inhibiting tumor cells activity

Posted on 5 February 2024 by

The objective of this study was to assess the inhibitory effect of modified cabotegravir derivatives on the activity of esophageal cancer KYSE30 cells. Results showed that compounds 5b and 5h effectively inhibited the migration and invasion of KYSE30 cells and induced apoptosis and may be involved in the stat3 and smad2/3 signal pathway. Based on these findings, we can consider these compounds as potential lead candidates for the treatment of esophageal squamous cell carcinoma.

Abstract

Structural modification based on existing drugs, which ensures the safety of marketed drugs, is an essential approach in developing new drugs. In this study, we modified the structure of cabotegravir by introducing the front alkyne on the core structure through chemical reaction, resulting in the synthesis of 9 compounds resembling 1,2,3-triazoles. The potential of these new cabotegravir derivatives as tumor suppressors in gastrointestinal tumors was investigated. Based on the MTT experiment, most compounds showed a reduction in the viability of KYSE30 and HCT116 cells. Notably, derivatives 5b and 5h exhibited the most significant inhibitory effects. To further explore the effects of derivatives 5b and 5h on gastrointestinal tumors, KYSE30 cells were chosen as a representative cell line. Both derivatives can effectively curtail the migration and invasion capabilities of KYSE30 cells and induce apoptosis in a dose-dependent manner. We further demonstrated these derivatives induce cell apoptosis in KYSE30 cells by inhibiting the expression of Stat3 protein and Smad2/3 protein. Based on the above results, we suggest they show promise in developing drugs for esophageal squamous cell carcinoma.

Characterization of the Binding Properties of Ten Aptamers Using the Intrinsic Fluorescence of Oxytetracycline

Posted on 5 February 2024 by nYichen Zhao, nBiwen Gao, nJuewen Liun

Taking advantage of the intrinsic fluorescence of oxytetracycline, its binding to ten different DNA aptamers was characterized using fluorescence quantum yield, binding kinetics, fluorescence lifetime and calorimetry, offering insights into aptamer binding to small molecules.

Abstract

Tetracyclines are a class of commonly used four-ringed antibiotics. A series of DNA aptamers were recently obtained using the capture-SELEX (systematic evolution of ligands by exponential enrichment) method to bind to oxytetracycline, and one of the aptamers can bind to a few other tetracycline antibiotics as well. Upon binding to the aptamers, the intrinsic fluorescence of tetracycline antibiotics can be enhanced. At least 10 different DNA aptamers were isolated from the previous selection experiment. In this work, a systematic characterization of these ten aptamers was performed. Each of these aptamers shows a different degree of fluorescence enhancement ranging from around 1-fold to over 20-fold. Fluorescence enhancement was boosted in the presence of Mg²⁺. Isothermal titration calorimetry (ITC) studies were done and showed a great variety in dissociation constant (K _d) from 62 nM to 1.6 μM. Steady-state fluorescence spectroscopy and fluorescence lifetime studies showed a correlation between fluorescence lifetime and degree of fluorescence enhancement. A few aptamers showed slow binding kinetics, although no correlation was found between the kinetics of fluorescence change and degree of fluorescence enhancement. This is the first study of ten different aptamers for the same target, providing fundamental insights into aptamer binding and bioanalytical applications.

Synthesis of Silicon and Germanium Oxide Nanostructures via Photonic Curing; a Facile Approach to Scale Up Fabrication

Posted on 2 February 2024 by nNajma Khatoon, nBinod Subedi, nDouglas B. Chriseyn

Silicon oxide (SiO_x) and germanium oxide (GeO_x) nanoparticles are promising candidates for energy storage applications. We synthesized SiO_x and GeO_x nanostructures by employing photonic curing; a low-cost roll-to-roll instantaneous process. This work is a step to optimize photonic curing for semiconductor oxide nanostructures synthesis on a large scale with nanometric control for next generation energy applications.

Abstract

Silicon and Germanium oxide (SiO_x and GeO_x) nanostructures are promising materials for energy storage applications due to their potentially high energy density, large lithiation capacity (~10X carbon), low toxicity, low cost, and high thermal stability. This work reports a unique approach to achieving controlled synthesis of SiO_x and GeO_x nanostructures via photonic curing. Unlike conventional methods like rapid thermal annealing, quenching during pulsed photonic curing occurs rapidly (sub-millisecond), allowing the trapping of metastable states to form unique phases and nanostructures. We explored the possible underlying mechanism of photonic curing by incorporating laws of photophysics, photochemistry, and simulated temperature profile of thin film. The results show that photonic curing of spray coated 0.1 M molarity Si and Ge Acetyl Acetate precursor solution, at total fluence 80 J cm⁻² can yield GeO_x and SiO_x nanostructures. The as-synthesized nanostructures are ester functionalized due to photoinitiated chemical reactions in thin film during photonic curing. Results also showed that nanoparticle size changes from ~48 nm to ~11 nm if overall fluence is increased by increasing the number of pulses. These results are an important contribution towards large-scale synthesis of the Ge and Si oxide nanostructured materials which is necessary for next-generation energy storage devices.

Direct Experimental Observation of the Tetrabromine Cluster Br4 by Synchrotron Photoionization Mass Spectrometry

Posted on 2 February 2024 by nRory McClish, nGiovanni Melonin

Pure halogens clusters, especially with even numbered molecular formulae, are elusive gas-phase spectroscopic targets. Photoionization mass spectrometry coupled to tunable vacuum-ultraviolet synchrotron radiation allows for the detection and characterization of the tetrabromine Br₄ cluster. Based on a joint experimental and computational assessment, Br₄ is found to exist as a tetrahedron shape of D_2h symmetry.

Abstract

We present a first spectroscopic characterization of the homoatomic polyhalogen tetrabromine, Br₄, in the gas phase. Photolysis of CHBr₃ at 248 nm is used to generate atomic bromine radicals in a flow tube reactor. Resulting combination products are detected by photoionization mass spectrometry at the Advanced Light Source of the Lawrence Berkeley National Laboratory. Interpretation of the experimental mass spectra is informed by calculated adiabatic ionization energies carried out at the CCSD(T)/aug-cc-pVTZ//M06-2X/aug-cc-pVTZ and CCSD(T)/aug-cc-pVTZ//cam-B3LYP/6-311++g** levels of theory. Tunable VUV synchrotron radiation enables the collection of the mass-selected photoionization spectra by which Br₄ is assigned using Franck-Condon simulations of a Br₂ dimer with a stretched tetrahedral geometry.

Selective O‐Acylation of Enol Silyl Ethers with Acyl Fluorides Catalyzed by Fluoride Ions Derived from Potassium Fluoride and 18‐Crown‐6

Posted on 29 January 2024 by

Fluoride ions derived from potassium fluoride and 18-crown-6 efficiently catalyzed the selective O-acylation of a variety of enol silyl ethers with aromatic and aliphatic acyl fluorides to produce unique enol ester derivatives.

Abstract

The fluoride ion-catalyzed selective O-acylation of enol silyl ethers with acyl fluorides using KF and 18-Crown-6 is described herein. This catalytic system facilitated the practical and facile reaction of a variety of enol silyl ethers derived from aromatic/aliphatic ketones and aldehydes with acyl fluorides to afford useful and valuable enol esters.

Effect of Direct Alkyne Substitution on the Photophysical Properties of Two Novel Octasubstituted Zinc Phthalocyanines

Posted on 26 January 2024 by nHande Pekbelgin Karaoğlun

The synthesis and characterization of two new alkynyl-substituted phthalonitrile derivatives and their peripherally octasubstituted zinc phthalocyanine (ZnPc) compounds were reported. The aggregation behavior of phthalocyanines was investigated. Fluorescence quantum yields, lifetimes, and quench studies of phthalocyanines were examined. The photophysical parameters obtained for synthesized phthalocyanines were compared with each other and with the unsubstituted ZnPc used as a standard.

Abstract

The synthesis of two novel phthalonitrile derivatives (3–4) bearing ethynylcyclohex-1-ene and ethynylcyclohexane groups and two peripherally octa substituted zinc (II) phthalocyanines (5–6) were prepared. The synthesis of phthalonitrile derivatives was performed with Sonagashira coupling reaction by using palladium-catalyzed. The newly synthesized compounds were characterized by using FT-IR, NMR, mass, and UV-Vis absorption spectroscopy techniques. Aggregation studies of 5 and 6 were performed in various organic solvents and different concentrations in tetrahydrofuran (THF). The photophysical studies of the Pcs were performed in THF to determine the effect of the alkyne groups on the fluorescence of the Pc ring. Substances showing fluorescence properties can be used in practical applications such as to create an image in microscopy. Fluorescence quantum yield (Φ_F) and fluorescence lifetime (τ_F) of 5–6 were calculated. The fluorescence quenching studies of 5–6 were performed by adding the different concentrations of 1,4-benzoquinone (BQ) to a constant concentration of the Pcs in THF and it was found that benzoquinone was an effective quencher. The values of the Stern-Volmer constant (K_sv) and quenching constant (k_q) of zinc phthalocyanines (5–6) were examined. All obtained results were compared with each other and with unsubstituted zinc Pc compound used as a reference.

Biosynthesis of ZnO, Bi2O3 and ZnO−Bi2O3 bimetallic nanoparticles and their cytotoxic and antibacterial effects

Posted on 17 January 2024 by

In this work, attempted to arrange synthesized Bi₂O₃, ZnO, ZnO−Bi₂O₃ nanoparticles by Biebersteinia Multifida extract and then their cytotoxicity and anti-bacterial investigate. This is a report on the synthesis and anticancer performance of synthesized samples on breast cancer cells (MCF-7), as well as their anti-bacterial activity against Staphylococcus epidermidis and Pseudomonas aeruginosa bacteria.

Abstract

This work introduces an easy method for producing Bi₂O₃, ZnO, ZnO-Bi₂O₃ nanoparticles (NPs) by Biebersteinia Multifida extract. Our products have been characterized through the outcomes which recorded with using powder X-ray diffractometry (PXRD), Raman, energy dispersive X-ray (EDX), field emission-scanning electron microscopy (FE-SEM), and Fourier-transform infrared (FT-IR) techniques. The finding of SEM presented porous structure and spherical morphology for Bi₂O₃ and ZnO NPs, respectively. While FE-SEM image of bimetallic nanoparticles showed both porous and spherical morphologies for them; so that spherical particles of ZnO have sat on the porous structure of Bi₂O₃ NPs. According to the PXRD results, the crystallite sizes of Bi₂O₃, ZnO and ZnO−Bi₂O₃ NPs have been obtained 57.69, 21.93, and 43.42 nm, respectively. Antibacterial performance of NPs has been studied on Staphylococcus epidermidis and Pseudomonas aeruginosa bacteria, to distinguish the minimum microbial inhibitory concentration (MIC). Antimicrobial outcomes have showed a better effect for ZnO-Bi₂O₃ NPs. Besides, wondering about the cytotoxic action against cancer cell lines, the MTT results have verified the intense cytotoxic function versus breast cancer cells (MCF-7). According to these observations, obtained products can prosper medical and biological applications.

Computational Study of the Fries Rearrangement Catalyzed by Acyltransferase from Pseudomonas protegens

Posted on 15 January 2024 by nXiang Sheng, nWolfgang Kroutil, nFahmi Himon

Density functional theory (DFT) calculations are employed to uncover the detailed reaction mechanism for the Fries rearrangement of 3-hydroxyphenyl acetate to 2′,4′-dihydroxyacetophenone catalyzed by the acyltransferase from Pseudomonas protegens (PpATase). Relative binding energies of other acetyl acceptors are also calculated to evaluate the possibility of PpATase catalyzing an intermolecular Fries rearrangement.

Abstract

The acyltransferase from Pseudomonas protegens (PpATase) catalyzes in nature the reversible transformation of monoacetylphloroglucinol to diacetylphloroglucinol and phloroglucinol. Interestingly, this enzyme has been shown to catalyze the promiscuous transformation of 3-hydroxyphenyl acetate to 2′,4′-dihydroxyacetophenone, representing a biological version of the Fries rearrangement. In the present study, we report a mechanistic investigation of this activity of PpATase using quantum chemical calculations. A detailed mechanism is proposed, and the energy profile for the reaction is presented. The calculations show that the acylation of the enzyme is highly exothermic, while the acetyl transfer back to the substrate is only slightly exothermic. The deprotonation of the C6−H of the substrate is rate-limiting, and a remote aspartate residue (Asp137) is proposed to be the general base group in this step. Analysis of the binding energies of various acetyl acceptors shows that PpATase can promote both intramolecular and intermolecular Fries rearrangement towards diverse compounds.