Synthesis of a Perfluorinated Phenoxyphosphorane and Conversion to Its Hexacoordinate Anions

We report the synthesis and structural characterization of a neutral P^V Lewis acid, P(OC₆F₅)₅, and salts containing the six-coordinate anions [P(OC₆F₅)₅F]⁻ and [P(OC₆F₅)₆]⁻. The latter anion exhibits a rare example of F–π_arene interactions in both the solid and the solution phase, which has been quantitatively studied by variable-temperature (VT) NMR spectroscopy. The Lewis acid strength of P(OC₆F₅)₅ has been assessed through experimental fluoride ion competition experiments and quantum-chemical calculations of its fluoride ion affinity (FIA) and global electrophilicity index (GEI). Our findings highlight the importance of considering solvent effects in electrophilicity calculations, even when neutral Lewis acids are involved, and show a rare divergence between FIA and GEI trends. The coordinating abilities of the [P(OC₆F₅)₆]⁻ and [P(OC₆F₅)₅F]⁻ anions towards the trityl cation, as a prototypical electrophile, have been assessed.     

Microparticle ratiometric oxygen sensors utilizing near-infrared emitting quantum dots

Luminescent sensors incorporating two luminophores, an indicator and a reference, offer many advantages over intensity measurements from sensors made with one indicator dye. Quantum dots have yet to be widely employed as insensitive reference luminophores in such systems. This work describes the use of near-infrared emitting quantum dots in conjunction with a long-lifetime platinum(II) porphyrin phosphor in a microsphere-based, ratiometric oxygen sensor. The process for self-assembly of the nanocomposite system was developed, and the response and photostability of the prototypes were investigated. Results indicate the sensors possess excellent sensitivity (K(SV) = 0.00826 μM(-1)) at oxygen concentrations below 300 μM and were resistant to photobleaching. The sensor luminophores displayed minimal spectral overlap and little interference from excitation light, preventing the need for optical filters. A reversible photoenhancement of the quantum dot signal was also observed when exposed for extended periods of time. This work demonstrates the advantages of incorporating long-wavelength quantum dots into ratiometric intensity sensing schemes and highlights some key limitations that must be considered in their use.     

Kinetically Tunable Photostability of Fluorogen‐Activating Peptide–Fluorogen Complexes

Ease of genetic encoding, labeling specificity, and high photostability are the most sought after qualities in a fluorophore for biological detection. Furthermore, many applications can gain from the fluorogenic nature of fluoromodules and the ability to turn on the same fluoromodules multiple times. Fluorogen‐activating peptides (FAPs) bind noncovalently to their cognate fluorogens and exhibit enhanced photostability. Herein, the photostabilities of malachite green (MG)‐binding and thiazole‐orange‐binding FAPs are compared under limiting‐ and excess‐fluorogen conditions to establish distinct mechanisms for photostability that correspond to the dissociation rate of the FAP–fluorogen complex. FAPs with slow dissociation show evidence of dye encapsulation and protection from photo or environmental degradation and single‐step bleaching at the single molecule level, whereas those with rapid dissociation show repeated cycles of binding and enhanced photostability by exchange of bleached fluorogen with a new dye. A combination of generalizable selection pressure based on bleaching, flow cytometry, and site‐specific amino acid mutagenesis is used to obtain a modified FAP with enhanced photostability, due to rapid dissociation of the MG fluorogen. These studies shed light on the basic mechanisms by which noncovalent association can effect photostable labeling, and demonstrate novel reagents for photostable and intermittent labeling of biological targets.     

A practical synthesis of aryl sulfones via cross-coupling of sulfonyl hydrazides with aryltriazenes using copper/ionic liquid combination

A new and efficient approach adopting copper-catalyzed cross-coupling of sulfonyl hydrazides with aryltriazenes has been developed to synthesize aryl sulfones using Brønsted acidic ionic liquid as promoter under ambient conditions. The process employs stable and easy to handle reacting partners, and is endowed with broad substrate scope.     

Fluoride‐Bridged {GdIII3MIII2} (M=Cr,Fe, Ga) Molecular Magnetic Refrigerants

The reaction of fac‐[M^IIIF₃(Me₃tacn)]?x H₂O with Gd(NO₃)₃?5H₂O affords a series of fluoride‐bridged, trigonal bipyramidal {Gd^III₃M^III₂} (M=Cr ( 1 ), Fe ( 2 ), Ga ( 3 )) complexes without signs of concomitant GdF₃ formation, thereby demonstrating the applicability even of labile fluoride‐complexes as precursors for 3d–4f systems. Molecular geometry enforces weak exchange interactions, which is rationalized computationally. This, in conjunction with a lightweight ligand sphere, gives rise to large magnetic entropy changes of 38.3 J kg^?1 K^?1 ( 1 ) and 33.1 J kg^?1 K^?1 ( 2 ) for the field change 7 T→0 T. Interestingly, the entropy change, and the magnetocaloric effect, are smaller in 2 than in 1 despite the larger spin ground state of the former secured by intramolecular Fe–Gd ferromagnetic interactions. This observation underlines the necessity of controlling not only the ground state but also close‐lying excited states for successful design of molecular refrigerants.     

Inhibitory Effect of Nepeta deflersiana on Climax Bacterial Community Isolated from the Oral Plaque of Patients with Periodontal Disease

Background: The red-complex bacteria are one of the most significant complexes found simultaneously in subgingival plaque next to the periodontal pocket. The current antibacterial treatment is not adequate, and multidrug resistance to it is developing. Henceforth, the antibacterial effect of the ethanolic extract of Nepeta deflersiana was put to test against red-complex bacteria in patients with chronic periodontitis. Methods: Well diffusion and micro broth dilution procedure by Alamar blue were applied to assess the zone of inhibition (ZOI), the minimum inhibitory concentration (MIC), and the minimum bactericidal concentration (MBC). Anti-virulence efficacies of the plant extract that comprise of adherence and formation of biofilms were examined by the process of adherence and biofilm production assay. Results: The crude extract of Nepeta deflersiana exhibited significant inhibitory outcome against periodontopathic bacteria with noteworthy MIC (0.78–3.12 mg/mL), inhibitory zone (12–20 mm), as well as MBC (3.12–12.50 mg/mL). The N. deflersiana extract inhibited bacterial adhesion ranging from 41% to 52%, 53% to 66%, and 60% to 79% at the given MIC × 0.5, MIC × 1, and MIC × 2 in succession. Substantial suppression was also developed in the biofilm production of the investigated periodontopathic strains following exposure to numerous concentrations of N. deflersianan extract for a period of 24 and 48 h. Conclusion: These outcomes divulge a new concept that N. deflersiana extract can be utilized to manufacture valuable antibacterial compounds to treat chronic and acute periodontitis. This identifies N. deflersiana as an essential natural source for future drug development.     

Aggregation behavior of pyridinium based ionic liquids in water--surface tension, 1H NMR chemical shifts, SANS and SAXS measurements

The aggregation behavior of short alkyl chain ionic liquids (ILs), namely 1-butyl, or 1-hexyl or 1-octylpyridinium and 1-octyl-2-, or -3-, or -4-methylpyridinium chlorides, in water has been assessed using surface tension, electrical conductance, (1)H NMR, small angle neutron scattering (SANS) and small angle X-ray scattering (SAXS) measurements. Critical aggregation concentrations (CACs), adsorption (at air/water interface) and thermodynamic parameters of aggregation have been reported. The values of CAC and area per adsorbed molecule decrease with the number of carbon atoms in the alkyl chain. The aggregation process is driven by both favorable enthalpy and entropy contributions. An attempt was made to examine the morphological features of the aggregates in water using SANS and SAXS methods. SANS and SAXS curves displayed diffuse structural peaks that could not be model fitted, and therefore, we calculated the mean aggregation numbers from the Q(max) assuming that IL molecules typically order into cubic type clusters.     

Sample complexity reduction aids efficient detection of low‐abundant proteins from human amniotic fluid

Working with biological fluids poses a challenge of visualizing proteins present in lower concentrations. This study describes a batch‐mode chromatographic method for the fractionation of human amniotic fluid (AF). This method is easy to use with minimal sample quantity, resin volume and sample processing time. For albumin depletion, two methods were evaluated. The results demonstrated that specific depletion of albumin, using affinity‐ligand‐based resin, is more efficient than the conventional dye‐based method. The albumin‐depleted human AF was fractionated by strong anion‐exchange resin in spin devices, for sample, complexity reduction and enrichment of low‐abundant proteins. Analysis of four eluate fractions generated after this step shows enrichment of few low‐abundant proteins. Two novel low‐abundant proteins, Rab GDP dissociation inhibitor β and peptide methionine sulfoxide reductase, were identified from human AF. α‐1‐B Glycoprotein was successfully identified by this strategy, whereas the published literature reports that it was not identified by strong anion‐exchange FPLC followed by SDS‐PAGE. Therefore, the current method has distinct advantages over the conventional column‐based chromatography. This study also reports altered expression of some proteins in Rh‐isoimmunized AF samples in comparison with normal AF.     

Me3P complexes of p-block Lewis acids SnCl4, SnCl3+ and SnCl2(2+)

Reactions of Me(3)P with SnCl(4) in the presence of nAlCl(3) (n = 0, 1, 2) yields a series of P-Sn complexes illustrating new bonding environments for tin.