Fluorescence Quenching and the Chamber of Nitroaromatics: A Dinaphthoylated Oxacalix[4]arene's (DNOC) Adventure Captured through Computational and Experimental Study

This research presents the application of Dinaphthoylated Oxacalix[4]arene (DNOC) as a novel fluorescent receptor for the purpose of selectively detecting nitroaromatic compounds (NACs). The characterization of DNOC was conducted through the utilization of spectroscopic methods, including 1H-NMR, 13C-NMR, and ESI-MS. The receptor demonstrated significant selectivity in acetonitrile towards several nitroaromatic analytes, such as MNA, 2,4-DNT, 2,3-DNT, 1,3-DNB, 2,6-DNT, and 4-NT. This selectivity was validated by the measurement of emission spectra. The present study focuses on the examination of binding constants, employing Stern-Volmer analysis, as well as the determination of the lowest detection limit (3σ/Slope) and fluorescence quenching. These investigations aim to provide insights into the inclusion behavior of DNOC with each of the six analytes under fluorescence spectra investigation. Furthermore, the selectivity trend of the ligand DNOC for NAC detection is elucidated using Density Functional Theory (DFT) calculations conducted using the Gaussian 09 software. The examination of energy gaps existing between molecular orbitals, namely the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO), provides a valuable understanding of electron-transfer processes and electronic interactions. Smaller energy gaps are indicative of heightened selectivity resulting from favorable electron-transfer processes, whereas bigger gaps suggest less selectivity attributable to weaker electronic contacts. This work integrates experimental and computational methodologies to provide a full understanding of the selective binding behavior of DNOC. As a result, DNOC emerges as a viable chemical sensor for detecting nitroaromatic explosives.

A Highly Selective Pyrene Appended Oxacalixarene Receptor for MNA and 4-NP Detection: an Experimental and Computational Study

A novel pyrene-substituted oxacalixarene was designed and synthesized as a selective probe for the simultaneous detection of MNA and 4-NP. Utilizing 1H-NMR, 13C-NMR, and FT-IR analysis techniques, its structure was characterized. The binding property of BPOC to a variety of NACs, including 1,3-DNB, 2,3-DNT, 2,4-DNT, 2,6-DNT, 4-NP, 4-NT, and PA, revealed that the sensor binds to MNA and 4-NP with remarkable selectivity. Binding constant reveals lower detection limits of MNA is 0.2 µM and 0.3 µM for 4-NP. Using docking and density functional theory (DFT), computational insights were provided for investigating the stability and spectroscopic analysis of the inclusion complex. From molecular docking study, we observed the best docking score of BPOC with 4-NT and MNA complex. The calculations supplement the findings significantly and clarify the structural geometry and mode of interactions in supramolecular complexation. In an MTT experiment on human PBMC to check for cytotoxicity, this chemical was found to influence 1 × 105 cell viability dose-dependently.

Calixarene: The Dawn of a New Era in Forensic Chemistry

Abstract:

Globally, rapid, ultrasensitive, and ultraselective detection of forensic evidence is critically required for social security and support. In the past four decades, calixarenes have been the focus of intensive research in the invention of several extractants, transporters, stationary phases, electrode ionophores, and optical and electrochemical sensors. This review is ardent about calixarene, a new class of selective and sensitive forensic sensors. It has become clear that calix[n]arenes are particularly attractive building blocks for supramolecular chemistry due to their synthesis on a large scale, distinctive concave molecular architecture, tunable inner cavity size, exceptional derivatization capabilities, and a broad range of applications. This paper opens up new avenues for the creation of on-site detection kits for forensic evidence, which will speed up the detection procedure.

Green synthesis of silver nanoparticles using dietary antioxidant rutin and its biological contour

Background

Dietary and wholesome antioxidant rutin is considered advantageous due to its potential protective role for numerous diseases related to oxidative stress, high safety, cost-effectiveness, and extensive biological effects. The present study accounts for an expeditious method for the synthesis of silver nanoparticles (AgNPs) using rutin.

Results

The presence of AgNPs was affirmed by UV–visible spectroscopy at 425 nm, and FESEM and zeta sizer analysis revealed the average size of the AgNPs 80–85 nm and 160 d.nm, respectively. Zeta potential measurements (− 30.3 mV) showed that the AgNPs have reasonably good stability. Element mapping analysis of the AgNPs was confirmed by XRD and AFM, while FTIR spectra of the AgNPs showed the existence of functional groups. In the DPPH assay, highest radical scavenging activity of AgNPs, 86.95 ± 01.60%, was confirmed. The interaction of AgNPs with CT-DNA and HS-DNA was studied spectrophotometrically, and the data display a shift in the respective spectra. Furthermore, interaction with pBR322 DNA, λ DNA, CT-DNA, and HS-DNA was deliberated by a nicking assay that shows the physicochemical properties of AgNPs. Antibacterial activity was evaluated by the standard well-diffusion method against Escherichia coli and Staphylococcus aureus, and cytotoxicity was assessed against human WBCs by MTT assay.

Conclusion

As per this appraisal, it can be concluded that it is a cost-effective, simple, and eco-friendly tactic and such NPs are beneficial to improve therapeutics since the antioxidant, DNA interaction, antibacterial, and cytotoxic exploits offer a new horizon of euthenics.

Pyrene functionalized oxacalix[4]arene architecture as dual readout sensor for expeditious recognition of cyanide anion

A pyrene functionalized oxacalix[4]arene architecture (DPOC) was utilized as a fluorescence probe for selective recognition of cyanide ions. The receptor DPOC shows excellent selectivity towards cyanide ion with a red shift of 108 nm in absorption band along with a significant change in colour from light yellow to pink. The fluorescence titration experiments further confirm the lower limit of detection as 1.7µM with no significant influences of competing anions. ¹ H-NMR titration experiments support the deprotonation phenomena, as the -NH proton disappears upon successive addition of cyanide ions. The DFT calculation also indicates a certain increment of -NH bond length upon interaction with cyanide ions. The spectral properties as well as colour of DPOC-CN^- system may be reversed upon the addition of Ag⁺/ Cu²⁺ ions up to 5 consecutive cycles. Moreover, DPOC coated "test strips" were prepared for visual detection of cyanide ions.

Development of tBu-phenyl Acetamide Appended Thiacalix[4]arene as "Turn-ON" Fluorescent Probe for Selective Recognition of Hg(II) Ions

Herein, a novel N-(4-(tert-butyl)-phenyl)-2-chloroacetamide functionalized thiacalix[4]arene architecture, viz TCAN2PA has been synthesized and the sensing behaviour towards metal ions were explored. The probe, TCAN2PA displayed "turn-on" fluorescence response towards Hg(II) ions in acetonitrile over a series of competing common metal ions. A bathochromic shift in absorption band along with a significant "Turn-On" fluorescence behaviour of TCAN2PA was observed upon interaction with Hg(II) ions. The lower rim modification of thiacalixarene with N-(4-(tert-butyl)-phenyl)-2-chloroacetamide actively contributes toward the fluorescence property due to the presence of strong electron-donating aryl amido substituent. Fluorescence titration experiments were conducted to find out the limit of detection and to understand binding stoichiometry as well. The electron transfer interactions between the electron rich TCAN2PA host with Hg(II) ions have been postulated which is also supported by computational modelling insights.

Recent Advancements for the Recognization of Nitroaromatic Explosives Using Calixarene Based Fluorescent Probes

In this era, explosives are easily available compared to the early days. Thus, more effective detection of explosives has become the main concern of homeland security. In the past decades, a large number of sensing materials have been developed for the detection of explosives in solid, vapor, and solution states through fluorescence methods. In recent years, great efforts have been devoted to developing new fluorescent materials with various sensing mechanisms for detecting explosives in order to achieve super-sensitivity, ultra-selectivity, as well as fast response time. Modified calixarenes have high potentials to detect nitroaromatic compounds (NACs) due to their favorable structural properties. It summarizes the detection of NACs by the modified calixarene system formed by the complex. Various methodologies responsible for complex formation and binding mechanisms (PET, FRET, EE, etc.) are the centerpiece of this review. Finally, conclusions and future outlook are presented and discussed.

An oxacalix[4]arene-derived dual-sensing fluorescent probe for the relay recognition of Hg2+ and S2− ions

A rhodamine B-functionalized oxacalix[4]arene architecture has been designed as a dual-responsive probe for the sequential recognition of Hg2+ and S2− ions.

Surveillance of pregnant women with potential exposure to Zika virus following travel

AIM

To describe the experience of a single fetal medicine unit in evaluating pregnant women with potential exposure to Zika virus (ZIKV) following travel.

METHOD

Between February 2016 and June 2017, a multidisciplinary team evaluated pregnant women by developing a local pathway based on Public Health England guidance. All pregnant women were offered serial fetal ultrasound scans (USS). If they presented with a history of clinical symptoms consistent with ZIKV infection during or within two weeks of travel or fetal USS was suggestive of microcephaly, reverse transcriptase polymerase chain reaction (RT PCR) and/or serology was used.

RESULTS

69 women were referred. Eight patients reported symptoms consistent with ZIKV infection (11.6%) and six (8.7%) patients reported mosquito bites. Maternal exposure was mainly during the preconception period and the first trimester in 35 (50.8%) and 19 (27.5%) women, respectively. Prenatally, there was no evidence of microcephaly in any of the 69 referrals. Sixty-two live births and seven miscarriages were reported. One patient had serology confirming ZIKV infection during pregnancy. At birth, 57 babies had normal head circumference (HC) measurements, including the baby born to the Zika positive mother. Two babies had small HC measurements but were not infected and were small for gestational age.

CONCLUSIONS

One case of maternal ZIKV infection was detected but without any fetal congenital abnormalities postnatally. The number of potentially infected patients referred to our unit is a demonstration of the concern regarding perinatal ZIKV infection in the pregnant population.

Sensing of Ce(iii) using di-naphthoylated oxacalix[4]arene via realistic simulations and experimental studies

Here, we report a fluorescent sensor for the detection of Ce(iii) using di-naphthoylated oxacalix[4]arene (DNOC).

A turn-off fluorescence sensor for insensitive munition using anthraquinone-appended oxacalix[4]arene and its computational studies

Herein, a fluorescent oxacalix[4]arene-based receptor, DAQTNOC(5,17-di(N-(9,10-dioxo-9,10-dihydroanthracen-1-yl)acetamide) tetranitrooxacalix[4]arene), was described for the specific recognition of N-methyl-p-nitroaniline (MNA).

Turn-off fluorescence probe for the selective determination of pendimethalin using a mechanistic docking model of novel oxacalix[4]arene

A novel bidansylated oxacalix[4]arene (BDO) fluoroionophore for the selective determination of pendimethalin (PM) was carried out in the linear range of detection between 0.4 μM and 20 μM.

Efficiently functionalized oxacalix[4]arenes: Synthesis, characterization and exploration of their biological profile as novel HDAC inhibitors

A series of novel substituted oxacalix[4]arene has been synthesized and explored for their biological profile by evaluating anticancer, antifungal and antibacterial properties. The derivatives have been characterized by various spectroscopic techniques such as IR, (1)H NMR, (13)C NMR and Mass spectrometry. Many compounds showed strong inhibition (MIC) in the range of ∼0-50 μM with interesting cytotoxic activities against Hela cells in particular. The compounds were theoretically evaluated by docking studies as potential histone deacetylase inhibitors (HDACi). The study indicates that compounds bound adequately with HDAC, and hence complemented the experimental findings.

[Morphologic and molecular neuropathology of Alzheimer's disease]

Alzheimer disease lesions include the abnormal accumulation of two proteins normally present in neurons: tau protein and Abeta peptide. Tau protein aggregates into fibrils in the cell body of neurons (neurofibrillary tangles), in dendrites (neuropil threads) and in degenerating axons that constitute the corona of the senile plaque. Tau pathology progresses in the brain areas in a stereotyped manner and in parallel with the clinical symptoms. Abeta extracellular deposits may be diffuse or focal. The Abeta focal deposit constitutes the core of the senile plaque. Progression of the Abeta lesions, which initially affect the isocortex, then the hippocampus, basal ganglia, various brainstem nuclei and cerebellum, is not directly correlated with symptoms. Mutations involving the genes implicated in Abeta peptide metabolism are responsible for familial Alzheimer disease. Mutations of the tau gene are not associated with Alzheimer disease but with frontotemporal dementia. The link between altered Abeta peptide metabolism and tau pathology has not been fully elucidated. Animal models mimic several aspects of the disease and have contributed to a better understanding of the mechanisms of the lesions.

The p16(INK4A) protein and flavopiridol restore yeast cell growth inhibited by Cdk4

Cyclin-dependent kinase 4 (Cdk4) activity is misregulated in most cancers. Loss of Cdk4 regulation can occur through overexpression of Cdk4 catalytic subunit or its regulatory partner cyclin D1, or if the Cdk4-specific inhibitory protein p16(INK4A) is inactive. We have attempted to express the two human subunits, Cdk4 and cyclin D1, in the yeast Saccharomyces cerevisiae. Surprisingly, expression of Cdk4 alone, under control of the strong GAL promoter, inhibits cell growth. Coexpression of both subunits allows formation of an active Cdk4-cyclin D1 complex which accentuates growth arrest. In cells expressing Cdk4 only, growth is restored by overexpressing human Cdc37, a Cdk4-binding molecular chaperone. Interestingly, the effect of Cdk4 on yeast is also overcome by both p16- and p21-families of Cdk-inhibitory proteins. Moreover, flavopiridol, a compound which inhibits Cdk4 enzyme activity, restores cell division. The fact that p16(INK4A) and flavopiridol negate Cdk4-mediated suppression of yeast cell growth implies that this simple system can be used as a screen for identifying Cdk4-specific antagonists which may mimic p16(INK4A) in the cancer cell cycle.