Colorimetric Detection of Sulfur Mustard with 4-(p-Nitrobenzyl)pyridine and Its Derivatives.

In this study, we present a simple, highly sensitive, and selective colorimetric method for detecting sulfur mustard (SM) and its simulants. This method relies on a nucleophilic substitution reaction between derivatives of 4-(p-nitrobenzyl)pyridine (NBP) and SM and subsequent treatment with an external base, resulting in a visible response. This reaction exhibits an impressively low detection threshold by the naked eye, as low as 10 ppm at room temperature. In contrast to the conventional use of NBP for detecting other alkylating agents, such as nitrogen mustard, our approach eliminates the need for prolonged heating or intricate extraction processes. Both computational and experimental investigations underscore the significance of water within our detection medium as it stabilizes crucial episulfonium cation intermediates. Furthermore, we demonstrate the practical applicability of this sensor by incorporating it onto cellulose and silica surfaces, which may provide guidance for the design and development of solid-state SM detectors.

High-intensity focused ultrasound-induced mechanochemical transduction in synthetic elastomers.

While study in the field of polymer mechanochemistry has yielded mechanophores that perform various chemical reactions in response to mechanical stimuli, there is not yet a triggering method compatible with biological systems. Applications such as using mechanoluminescence to generate localized photon flux in vivo for optogenetics would greatly benefit from such an approach. Here we introduce a method of triggering mechanophores by using high-intensity focused ultrasound (HIFU) as a remote energy source to drive the spatially and temporally resolved mechanical-to-chemical transduction of mechanoresponsive polymers. A HIFU setup capable of controlling the excitation pressure, spatial location, and duration of exposure is employed to activate mechanochemical reactions in a cross-linked elastomeric polymer in a noninvasive fashion. One reaction is the chromogenic isomerization of a naphthopyran mechanophore embedded in a polydimethylsiloxane (PDMS) network. Under HIFU irradiation evidence of the mechanochemical transduction is the observation of a reversible color change as expected for the isomerization. The elastomer exhibits this distinguishable color change at the focal spot, depending on ultrasonic exposure conditions. A second reaction is the demonstration that HIFU irradiation successfully triggers a luminescent dioxetane, resulting in localized generation of visible blue light at the focal spot. In contrast to conventional stimuli such as UV light, heat, and uniaxial compression/tension testing, HIFU irradiation provides spatiotemporal control of the mechanochemical activation through targeted but noninvasive ultrasonic energy deposition. Targeted, remote light generation is potentially useful in biomedical applications such as optogenetics where a light source is used to trigger a cellular response.

Multicolor Mechanochromism of a Polymer/Silica Composite with Dual Distinct Mechanophores.

The development of a multicolor mechanochromic polymer/silica composite is achieved by using two distinct types of mechanochromophores. The multicolor mechanochromism of the composite containing diarylbibenzofuranone in silica-rich domains and naphthopyran in the polymer-rich domain is observed. The obtained composite shows blue, green, and orange colors according to the intensity of applied mechanical stimuli, solvent addition, and lapse of time. This unique multicolor mechanochromic behavior is evaluated by solid-state UV-vis absorption spectroscopy, ab initio steered molecular dynamics simulations, and computed minimum energy paths on force-modified potential energy surfaces. The unique mechanochromism is attributed to the difference in properties, activated colors, and domain locations between the two mechanochromophores.

Electrostatic Control of Regioselectivity in Au(I)-Catalyzed Hydroarylation.

Competing pathways in catalytic reactions often involve transition states with very different charge distributions, but this difference is rarely exploited to control selectivity. The proximity of a counterion to a charged catalyst in an ion paired complex gives rise to strong electrostatic interactions that could be used to energetically differentiate transition states. Here we investigate the effects of ion pairing on the regioselectivity of the hydroarylation of 3-substituted phenyl propargyl ethers catalyzed by cationic Au(I) complexes, which forms a mixture of 5- and 7-substituted 2H-chromenes. We show that changing the solvent dielectric to enforce ion pairing to a SbF6- counterion changes the regioselectivity by up to a factor of 12 depending on the substrate structure. Density functional theory (DFT) is used to calculate the energy difference between the putative product-determining isomeric transition states (ΔΔE‡) in both the presence and absence of the counterion. The change in ΔΔE‡ upon switching from the unpaired transition states in high solvent dielectric to ion paired transition states in low solvent dielectric (Δ(ΔΔE‡)) was found to be in good agreement with the experimentally observed selectivity changes across several substrates. Our calculations indicate that the origin of Δ(ΔΔE‡) lies in the preferential electrostatic stabilization of the transition state with greater charge separation by the counterion in the ion paired case. By performing calculations at multiple different values of the solvent dielectric, we show that the role of the solvent in changing selectivity is not solely to enforce ion pairing, but rather that interactions between the ion paired complex and the solvent also contribute to Δ(ΔΔE‡). Our results provide a foundation for exploiting electrostatic control of selectivity in other ion paired systems.

Gonadectomy of male BALB/c mice increases Tim-3(+) alternatively activated M2 macrophages, Tim-3(+) T cells, Th2 cells and Treg in the heart during acute coxsackievirus-induced myocarditis.

The incidence of cardiovascular disease, including inflammatory heart diseases like myocarditis, is increased in men. Similarly, male BALB/c mice infected with coxsackievirus B3 (CVB3) develop more severe acute inflammation in the heart compared to females. To better understand the effect of male sex hormones on cardiac inflammation, we gonadectomized (Gdx) male BALB/c mice and examined acute CVB3-induced myocarditis compared to sham controls. Viral replication in the heart was not significantly altered between Gdx and sham mice. However, gonadectomy significantly reduced testosterone levels and inflammation in the heart. FACS analysis of cell populations isolated from the heart revealed that CD11b(+) cells were significantly reduced in Gdx males. However, a GR1(+)F4/80(+) subset of CD11b(+) cells was significantly increased. Because this subset also expressed the interleukin (IL)-4R and IL-10, we refer to these cells as "alternatively activated" or M2 macrophages. A greater percentage of M2 macrophages in Gdx males expressed the inhibitory receptor Tim-3, while fewer expressed IL-1beta and IL-10. Only M2 macrophages upregulated TLR4 and Tim-3, whereas GR1(-)IL-4R(lo) macrophages did not. Additionally, IL-4(+)CD4(+) Th2 cells, Foxp3(+) regulatory T (Treg) cells and Tim-3(+)CD4(+) T cells were significantly increased in the heart following Gdx. Thus, we report for the first time that the inhibitory receptor Tim-3 is expressed on M2 macrophages. Our findings show that sex hormones and/or other mediators released from the testes inhibit anti-inflammatory populations in the heart including Tim-3(+) M2, Tim-3(+)CD4(+) T cells, Th2 and Treg resulting in more severe acute cardiac inflammation in males following CVB3 infection.

Effect of Polymerized Ionic Liquid Structure and Morphology on Shockwave Energy Dissipation.

The ability of nanosegregated polymerized ionic liquids (PILs) to dissipate shockwave energy is investigated for a series of imidazolium-based PILs with varying alkyl spacer length. The PILs are designed to have similar glass transition temperatures but different structures. X-ray scattering analysis reveals that each of the amorphous PILs exhibit distinct nanoscale structural heterogeneity, depending on the length of the chain spacer. We find that a higher structural heterogeneity, determined from the intensity of the intercluster scattering peak, in the PILs with longer alkyl spacers results in greater shockwave energy dissipation. In addition, we observe the crystalline phase is less effective at dissipating shockwave energy than the amorphous phase due to the close packed morphology and slow kinetics.

Correction: Electrostatic control of regioselectivity via ion pairing in a Au(i)-catalyzed rearrangement.

[This corrects the article DOI: 10.1039/C4SC02058H.].