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Quaternary ammonium compounds (QACs) are routinely used as disinfectants in a variety of settings. They are generally effective against a wide range of microbes but often exhibit undesirable toxicity. Consequently, companies are constantly seeking alternatives to QACs that are just as effective but with reduced health and environmental hazards. Two boronium salt derivatives were tested against influenza A and SARS-CoV-2 viruses. One salt possessed a terminal benzyl group, while the other lacked the same terminal benzyl group. Both salts demonstrated virus inactivation similar to a commercial QAC disinfectant. The non-benzylated form exhibited the same cell toxicity profile as the QAC. However, the benzylated form displayed less cell toxicity than both the non-benzylated form and QAC. These results suggest that the boronium salts may be suitable for use as a disinfecting agent against enveloped viruses in lieu of using a QAC. Continued evaluation of the boronium salts is warranted to determine the lowest effective concentration capable of effectively controlling influenza A and SARS-CoV-2 viruses that also demonstrates low cytotoxicity. 

Inside mammalian cells, single genes are known to be transcribed in stochastic bursts leading to the synthesis of nuclear RNAs that are subsequently exported to the cytoplasm to create mRNAs. We systematically characterize the role of export processes in shaping the extent of random fluctuations (i.e. noise) in the mRNA level of a given gene. Using the method of Partitioning of Poisson arrivals, we derive an exact analytical expression for the noise in mRNA level assuming that the nuclear retention time of each RNA is an independent and identically distributed random variable following an arbitrary distribution. These results confirm recent experimental/theoretical findings that decreasing the nuclear export rate buffers the noise in mRNA level, and counterintuitively, decreasing the noise in the nuclear retention time enhances the noise in the mRNA level. Next, we further generalize the model to consider a dynamic extrinsic disturbance that affects the nuclear-to-cytoplasm export. Our results show that noise in the mRNA level varies non-monotonically with the disturbance timescale. More specifically, high- and low-frequency external disturbances have little impact on the mRNA noise level, while noise is amplified at intermediate frequencies. In summary, our results systematically uncover how the coupling of bursty transcription with nuclear export can both attenuate or amplify noise in mRNA levels depending on the nuclear retention time distribution and the presence of extrinsic fluctuations. 

Binary mixtures of hydrocarbons and a thermally robust ionic liquid (IL) incorporating a perarylphosphonium-based cation are investigated experimentally and computationally. Experimentally, it is seen that excess toluene added to the IL forms two distinct liquid phases, an “ion-rich” phase of fixed composition and a phase that is nearly pure toluene. Conversely, n -heptane is observed to be essentially immiscible in the neat IL. Molecular dynamics simulations capture both of these behaviours. Furthermore, the simulated composition of the toluene-rich IL phase is within 10% of the experimentally determined composition. Additional simulations are performed on the binary mixtures of the IL and ten other small hydrocarbons having mixed aromatic/aliphatic character. It is found that hydrocarbons with a predominant aliphatic character are largely immiscible with the IL, while those with a predominant aromatic character readily mix with the IL. A detailed analysis of the structure and energetic changes that occur on mixing reveals the nature of the ion-rich phase. The simulations show a bicontinuous phase with hydrocarbon uptake akin to absorption and swelling by a porous absorbent. Aromatic hydrocarbons are driven into the neat IL via dispersion forces with the IL cations and, to a lesser extent, the IL anions. The ion–ion network expands to accommodate the hydrocarbons, yet maintains a core connective structure. At a certain loading, this network becomes stretched to its limit. The energetic penalty associated with breaking the core connective network outweighs the gain from new hydrocarbon–IL interactions, leaving additional hydrocarbons in the neat phase. The spatially alternating charge of the expanded IL network is shown to interact favourably with the stacked aromatic subphase, something not possible for aliphatic hydrocarbons. 

In previous work with thermally robust salts [Cassity et al., Phys. Chem. Chem. Phys. , 2017, 19 , 31560] it was noted that an increase in the dipole moment of the cation generally led to a decrease in the melting point. Molecular dynamics simulations of the liquid state revealed that an increased dipole moment reduces cation–cation repulsions through dipole–dipole alignment. This was believed to reduce the liquid phase enthalpy, which would tend to lower the melting point of the IL. In this work we further test this principle by replacing hydrogen atoms with fluorine atoms at selected positions within the cation. This allows us to alter the electrostatics of the cation without substantially affecting the sterics. Furthermore, the strength of the dipole moment can be controlled by choosing different positions within the cation for replacement. We studied variants of four different parent cations paired with bistriflimide and determined their melting points, and enthalpies and entropies of fusion through DSC experiments. The decreases in the melting point were determined to be enthalpically driven. We found that the dipole moment of the cation, as determined by quantum chemical calculations, is inversely correlated with the melting point of the given compound. Molecular dynamics simulations of the crystalline and solid states of two isomers showed differences in their enthalpies of fusion that closely matched those seen experimentally. Moreover, this reduction in the enthalpy of fusion was determined to be caused by an increase in the enthalpy of the crystalline state. We provide evidence that dipole–dipole interactions between cations leads to the formation of cationic domains in the crystalline state. These cationic associations partially block favourable cation–anion interactions, which are recovered upon melting. If, however, the dipole–dipole interactions between cations is too strong they have a tendency to form glasses. This study provides a design rule for lowering the melting point of structurally similar ILs by altering their dipole moment. 

Recent work by Wasserscheid, et al. suggests that PPh 4 + is an organic molecular ion of truly exceptional thermal stability. Herein we provide data that cements that conclusion: specifically, we show that aliphatic moieties of modified PPh 4 + -based cations incorporating methyl, methylene, or methine C–H bonds burn away at high temperatures in the presence of oxygen, forming CO, CO 2 , and water, leaving behind the parent ion PPh 4 + . The latter then undergoes no further reaction, at least below 425 °C.