Surface‐Enhanced Fluorescence from Fluorophore‐Assembled Monolayers by Using Ag@SiO2 Nanoparticles

A new and simple procedure to enhance the fluorescence of analytes on the surfaces of a solid substrate is demonstrated based on Ag@SiO₂ nanoparticles. Two kinds of silver–silica core–shell nanoparticles with shell thicknesses of around 3 and 15 nm have been prepared and used as enhancing agents, respectively. By simply pipetting drops of the enhancing agents onto substrate surfaces with Rose Bengal monolayers, an enhancement of about 27 times, compared with the control sample, is achieved by using the Ag@SiO₂ nanoparticles with shells of about 3 nm, whereas an enhancement of around 11.7 times is obtained when using those with thicker shells. The effects of shell thickness and surface density of the enhancing agents on the enhancement have been investigated experimentally. The results show that this method can be potentially helpful in fluorescence‐based surface analysis.     

Recent advance: Sulfur ylides in organic synthesis

Sulfur ylides are versatile structures that display various characteristics and participate in a myriad of reactions to produce simple, effective, and sometimes stereoselective reactions toward synthesizing sulfur-containing compounds. Nonetheless, their fulfillment tremendous developments have been made in this field in the past few decades. In this comprehensive review, luminosity is illuminated on the application of sulfur ylides involved in various domino, cascade annulation reactions, and carbene trapping reagents with chameleonic reactivity. In the past numerous decennary, chemists have used sulfur ylides in solvent-dependent, rhodium catalyzed, dealkylative intercepted, photochemical reaction, halotrifluoromethylation, benzannulation, amidation various name reactions such as Mizoroki–Heck, Suzuki–Miyaura, and Sommelet–Hauser rearrangements. Moreover, other prime applications include metal catalysis, epoxidation of carbonyl compounds, acylmethylation, cyclomerization, oxidation, and insertion reactions. Additionally, some sulfur ylides are extremely useful structures that play a major role in the synthesis of various medicinally active heterocycles structural motifs. This review article discusses all these reactions, their proposed mechanisms, and their application in the current scenario, at length. This tutorial review concludes by providing a future outlook on the investigation into sulfur ylides and various other compounds synthesized using it have great potential to be used in industries, laboratories, pharmaceutical companies, drug production, clinical use, medicinal chemistry, and agrochemical purposes.     

Supramolecular Chemistry: Host–Guest Molecular Complexes

In recent times, researchers have emphasized practical approaches for capturing coordinated and selective guest entrap. The physisorbed nanoporous supramolecular complexes have been widely used to restrain various guest species on compact supporting surfaces. The host–guest (HG) interactions in two-dimensional (2D) permeable porous linkages are growing expeditiously due to their future applications in biocatalysis, separation technology, or nanoscale patterning. The different crystal-like nanoporous network has been acquired to enclose and trap guest molecules of various dimensions and contours. The host centers have been lumped together via noncovalent interactions (such as hydrogen bonds, van der Waals (vdW) interactions, or coordinate bonds). In this review article, we enlighten and elucidate recent progress in HG chemistry, explored via scanning tunneling microscopy (STM). We summarize the synthesis, design, and characterization of typical HG structural design examined on various substrates, under ambient surroundings at the liquid-solid (LS) interface, or during ultrahigh vacuum (UHV). We emphasize isoreticular complexes, vibrant HG coordination, or hosts functional cavities responsive to the applied stimulus. Finally, we critically discuss the significant challenges in advancing this developing electrochemical field.     

Adsorption and oxidation of aniline and anisidine by chromium ferrocyanide

The interaction of aniline and p-anisidine with chromium ferrocyanide has been studied. Maximum uptake of both anilines was observed around pH 7. The adsorption data obtained at neutral pH were found to follow Langmuir adsorption. Anisidine was a better adsorbate because of its higher basicity. In alkaline medium (pH>8) both aniline and anisidine reacted with chromium ferrocyanide to give colored products. Analysis of the products by GC-MS showed benzoquinone and azobenzene as the reaction products of aniline while p-anisidine afforded a dimer. IR analysis of the amine-chromium ferrocyanide adduct suggests that the outer metal ion of chromium ferrocyanide and amino group of amines are responsible for the interaction. A possible reaction mechanism for the product formation in alkaline medium has been proposed. The present study suggests that metal ferrocyanides might have played an important role in the stabilization of organic molecules through their surface activity in the prebiotic condensation reactions.     

Synthesis of 1,2,3,triazole modified analogues of hydrochlorothiazide via click chemistry approach and in-vitro α-glucosidase enzyme inhibition studies

Molecular Diversity - The current study was aimed to discover potent inhibitors of α-glucosidase enzyme. A 25 membered library of new 1,2,3-triazole derivatives of hydrochlorothiazide (1)...     

Hydrogenation ofCHClF2(CFC-22)overPt-supported on silica-based polydimethylsiloxane composite matrices?

Summary 0.5% Pt-supported on silica-basedpolydimethylsiloxane compositeswere preparedandcharacterized using BET surface area, FT-IR, TGA, SEM and XRD. Hydrogenation ofCFC-22 over these catalysts produced mainly CH₃F and CH₄.</o:p>     

Piper nigrum: Micropropagation, Antioxidative enzyme activities, and Chromatographic Fingerprint Analysis for Quality Control

A reliable in vitro regeneration system for the economical and medicinally important Piper nigrum L. has been established. Callus and shoot regeneration was encouraged from leaf portions on Murashige and Skoog (MS) medium augmented with varied concentrations of plant growth regulators. A higher callus production (90 %) was observed in explants incubated on MS medium incorporated with 1.0 mg?L^?1 6-benzyladenine (BA) along with 0.5 mg?L^?1 gibberellic acid after 4 weeks of culture. Moreover, a callogenic response of 85 % was also recorded for 1.0 mg?L^?1 BA in combination with 0.25 mg?L^?1 α-naphthalene acetic acid (NAA) and 0.25 mg?L^?1 2,4-dichlorophenoxyacetic acid or 0.5 mg?L^?1 indole butyric acid (IBA) along with 0.25 mg?L^?1 NAA and indole acetic acid. Subsequent sub-culturing of callus after 4 weeks of culture onto MS medium supplemented with 1.5 mg?L^?1 thiodiazoran or 1.5 mg?L^?1 IBA induced 100 % shoot response. Rooted plantlets were achieved on medium containing varied concentrations of auxins. The antioxidative enzyme activities [superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), and ascorbate peroxidase (APX)] revealed that significantly higher SOD was observed in regenerated plantlets than in other tissues. However, POD, CAT, and APX were higher in callus than in other tissues. A high-performance liquid chromatography (HPLC) fingerprint analysis protocol was established for quality control in different in vitro-regenerated tissues of P. nigrum L. During analysis, most of the common peaks represent the active principle “piperine.” The chemical contents, especially piperine, showed variation from callus culture to whole plantlet regeneration. Based on the deviation in chromatographic peaks, the in vitro-regenerated plantlets exhibit a nearly similar piperine profile to acclimated plantlets. The in vitro regeneration system and HPLC fingerprint analysis established here brought a novel approach to the quality control of in vitro plantlets, producing metabolites of interest with substantial applications for the conservation of germplasm.     

Hydrophobic Variations of N‐Oxide Amphiphiles for Membrane Protein Manipulation: Importance of Non‐hydrocarbon Groups in the Hydrophobic Portion

Amphipathic agents called detergents serve as membrane‐mimetic systems to maintain the native structures of membrane proteins during their manipulation. However, membrane proteins solubilized in conventional detergents tend to undergo denaturation and aggregation, necessitating the development of novel amphipathic agents with enhanced properties. Here we describe several new amphiphiles that contain an N‐oxide group as the hydrophilic portion. The new amphiphiles have been evaluated for the ability to solubilize and stabilize a fragile multi‐subunit assembly from biological membranes. We found that cholate‐based agents were promising in supporting retention of the native protein quaternary structure, while deoxycholate‐based amphiphiles were highly efficient in extracting/solubilizing the intact superassembly from the native membrane. Monitoring superassembly solubilization and stabilization as a function of variation in amphiphile structure led us to propose that a non‐hydrocarbon moiety such as an amide, ether, or a hydroxy group present in the lipophilic regions can manifest distinctive effects in the context of membrane protein manipulation.