The 1,3‐dipolar cycloaddition (1,3‐DCA) reaction, conceptualized by Rolf Huisgen in 1960, has proven immensely useful in organic, material, and biological chemistry. The uncatalyzed, thermal ...transformation is generally sluggish and unselective, but the reactivity can be enhanced by means of metal catalysis or by the introduction of either predistortion or electronic tuning of the dipolarophile. These promoted reactions generally go with a much higher reactivity, selectivity, and yields, often at ambient temperatures. The rapid orthogonal reactivity and compatibility with aqueous and physiological conditions positions the 1,3‐DCA as an excellent bioorthogonal reaction. Quantum chemical calculations have been critical for providing an understanding of the physical factors that control the reactivity and selectivity of 1,3‐DCAs. In silico derived design principles have proven invaluable for the design of new dipolarophiles with tailored reactivity. This review discusses everything from the conception of the 1,3‐DCA all the way to the state‐of‐the‐art methods and models used for the quantum chemical design of novel (bioorthogonal) reagents.
1,3‐Dipolar cycloaddition (1,3‐DCA) reactions are ubiquitous in modern chemistry. In this review, we describe the road from the conception of the 1,3‐DCA all the way to the state‐of‐the‐art methods and models used for the quantum chemical design of novel (bioorthogonal) reagents. Three general approaches towards enhanced 1,3‐DCAs reactivity are discussed, namely, transition metal catalysis, predistortion of the dipolarophile, and the stabilization of the transition state.
Many bacteria, including a variety of important human pathogens, are known to respond to various environmental stresses by entry into a novel physiological state, where the cells remain viable, but ...are no longer culturable on standard laboratory media. On resuscitation from this 'viable but nonculturable' (VBNC) state, the cells regain culturability and the renewed ability to cause infection. It is likely that the VBNC state is a survival strategy, although several interesting alternative explanations have been suggested. This review describes the VBNC state, the various chemical and physical factors known to induce cells into this state, the cellular traits and gene expression exhibited by VBNC cells, their antibiotic resistance, retention of virulence and ability to attach and persist in the environment, and factors that have been found to allow resuscitation of VBNC cells. Along with simple reversal of the inducing stresses, a variety of interesting chemical and biological factors have been shown to allow resuscitation, including extracellular resuscitation-promoting proteins, a novel quorum-sensing system (AI-3) and interactions with amoeba. Finally, the central role of catalase in the VBNC response of some bacteria, including its genetic regulation, is described.
Hydrogen (H
2
) is a new type of renewable energy that can meet people's growing energy needs and is environmentally friendly. In order to improve the industrial application prospects and ...electrochemical performance of hydrogen evolution catalysts, extensive research on transition metal materials has been carried out. Among the many catalytic materials, cobalt is an element with potential for the hydrogen evolution reaction (HER) due to its abundant reserves, low cost, and small energy barrier for H adsorption. This review classifies the latest research on cobalt-based catalysts according to the types of compound, including cobalt-based sulfides, phosphides, carbides, borides, oxides,
etc.
, and summarizes the latest research progress of cobalt-based compound catalysts in acidic and alkaline media. Strategies to tune the properties of cobalt-based compound catalysts for high catalytic activity for HER are focused on, including structural engineering, defect engineering, and doping,
etc.
The advantages and limitations of each modified approach are reviewed. Not only that, but also the catalytic activity and advantages of the catalyst are evaluated by using density functional theory (DFT) calculation-related descriptors, activity evaluation parameters,
etc.
Finally, limitations and challenges of cobalt-based materials for HER are presented, as well as prospects for future research. This paper aims to understand the chemical and physical factors that affect cobalt-based catalysts, and to find directions for future research on cobalt-based catalysts.
Cobalt is an element with HER potential due to its own advantages. Recent studies on cobalt-based catalysts are categorized, with a focus on strategies to improve the HER catalytic activity of cobalt-based compound catalysts.
Rectification of ionic current, a frequently observed phenomenon with asymmetric nanopores varying in geometry and/or surface charge, has been utilized for studies of microfluidic circuits, nanopore ...sensors, and energy conversion devices. However, the physics behind the rectification phenomenon deserves further analysis, and the involved processes need renewed organization; however, the origin is known, and numerous simulations based on the Poisson–Nernst–Planck formalism provide details of the observation. Here, we present an analytical model by identifying the causal chain connecting the key physical factors and processes leading to rectification: the charge present on the pore sidewalls causing the selectivity of ion fluxes through the pore, the selectivity inducing enrichment-depletion of ions around the pore, and the established ion concentration gradient rendering the electric field redistribution in the pore. Our analytical model that considers nanopore geometry, surface charge density, and electrolyte concentration calculates the ionic current and corresponding rectification factor at given bias voltages. The model is validated by numerical simulations, and the model results agree well with experimental data. It is, therefore, a useful tool not only for gaining physical insights into ionic current rectification but also for providing practical guidelines in designing nanopore- and nanopipette-based ion sensors for a range of applications.
Metal organic frameworks (MOFs) are a unique class of smart hybrid materials that have recently attracted significant interest for catalysis, separation and biomedical applications. Different ...strategies have been developed to overcome the limitations of MOFs for bio-applications in order to produce a system with high biocompatibility and biodegradability. In this review, we outline the chemical and physical factors that dictate the biocompatibility and biodegradability characteristics of MOFs including the nature of the metal ions and organic ligands, size, surface properties and colloidal stability. This review includes the
in vitro
biodegradation and
in vivo
biodistribution studies of MOFs to better understand their pharmacokinetics, organ toxicity and immune response. Such studies can guide the design of future bio-friendly systems that bring us closer to safely translating these platforms into the pharmaceutical consumer market.
The biocompatibility and biodegradability of metal organic frameworks (MOFs) are discussed to highlight their best biomedical applications up-to-date.
Virtual teams (i.e., geographically distributed collaborations that rely on technology to communicate and cooperate) are central to maintaining our increasingly globalized social and economic ...infrastructure. “Global Virtual Teams” that include members from around the world are the most extreme example and are growing in prevalence (Scott and Wildman in Culture, communication, and conflict: a review of the global virtual team literature, Springer, New York, 2015). There has been a multitude of studies examining the difficulties faced by collaborations and use of technology in various narrow contexts. However, there has been little work in examining the challenges faced by virtual teams and their use of technology to mitigate issues. To address this issue, a literature review was performed to highlight the collaboration challenges experienced by virtual teams and existing mitigation strategies. In this review, a well-planned search strategy was utilized to identify a total of 255 relevant studies, primarily focusing on technology use. The physical factors relating to distance are tightly coupled with the cognitive, social, and emotional challenges faced by virtual teams. However, based on research topics in the selected studies, we separate challenges as belonging to five categories: geographical distance, temporal distance, perceived distance, the configuration of dispersed teams, and diversity of workers. In addition, findings from this literature review expose opportunities for research, such as resolving discrepancies regarding the effect of tightly coupled work on collaboration and the effect of temporal dispersion on coordination costs. Finally, we use these results to discuss opportunities and implications for designing groupware that better support collaborative tasks in virtual teams.
The underwater environment is filled with biotic and abiotic sounds, many of which can be important for the survival and reproduction of fish. Over the last century, human activities in and near the ...water have increasingly added artificial sounds to this environment. Very loud sounds of relatively short exposure, such as those produced during pile driving, can harm nearby fish. However, more moderate underwater noises of longer duration, such as those produced by vessels, could potentially impact much larger areas, and involve much larger numbers of fish. Here we call attention to the urgent need to study the role of sound in the lives of fish and to develop a better understanding of the ecological impact of anthropogenic noise.
In the hit identification stage of drug discovery, a diverse chemical space needs to be explored to identify initial hits. Contrary to empirical scoring functions, absolute protein–ligand binding ...free-energy perturbation (ABFEP) provides a theoretically more rigorous and accurate description of protein–ligand binding thermodynamics and could, in principle, greatly improve the hit rates in virtual screening. In this work, we describe an implementation of an accurate and reliable ABFEP method in FEP+. We validated the ABFEP method on eight congeneric compound series binding to eight protein receptors including both neutral and charged ligands. For ligands with net charges, the alchemical ion approach is adopted to avoid artifacts in electrostatic potential energy calculations. The calculated binding free energies correlate with experimental results with a weighted average of R 2 = 0.55 for the entire dataset. We also observe an overall root-mean-square error (RMSE) of 1.1 kcal/mol after shifting the zero-point of the simulation data to match the average experimental values. Through ABFEP calculations using apo versus holo protein structures, we demonstrated that the protein conformational and protonation state changes between the apo and holo proteins are the main physical factors contributing to the protein reorganization free energy manifested by the overestimation of raw ABFEP calculated binding free energies using the holo structures of the proteins. Furthermore, we performed ABFEP calculations in three virtual screening applications for hit enrichment. ABFEP greatly improves the hit rates as compared to docking scores or other methods like metadynamics. The good performance of ABFEP in rank ordering compounds demonstrated in this work confirms it as a useful tool to improve the hit rates in virtual screening, thus facilitating hit discovery.
Humans perceive environments through the interaction and integration among various sensory stimuli. While research on multisensory interaction research has increased over the last few decades in the ...fields of cognitive neuroscience and neurophysiology, the effect of multisensory interaction on indoor environmental perception, including thermal comfort, acoustic comfort, visual comfort, and indoor environmental comfort, has not been comprehensively understood. This study investigated the influence of multisensory interaction on acoustic comfort, thermal comfort, visual comfort, and indoor environmental comfort with three physical indoor environmental factors, i.e., acoustic, thermal, and illumination conditions in an environmentally controlled laboratory. Three homogenous room temperatures (20, 25, and 30 °C) and illuminance levels were chosen (150, 500, and 1000 lx). For each of the nine configurations, four different types of sound (babble, fan, music, and water) with four sound levels (45, 55, 65, and 75 dBA) were presented for 25 s each. Sixty university students participated in all the test configurations and provided responses on their subjective comfort of discrete senses and the overall indoor environment.
The results indicate that acoustic comfort increases at thermoneutrality, thermal comfort increases with a decrease in the noise level at 500 lx, and visual comfort increases with a decrease in the noise level at thermoneutrality. Indoor environmental comfort increases with a decrease in the noise level at thermoneutrality in brighter conditions. Although a specific physical indoor environmental factor has the greatest effect on the corresponding sensory comfort, other physical factors also affect the perception of subjective comfort. In steady-state thermal and illumination conditions with time-varying sound stimuli, the effect of acoustic factors was the greatest on indoor environmental comfort, followed by room temperature and illuminance. Thus, it can be concluded that the impact of acoustics on indoor environmental comfort was the greatest among the three environmental factors tested in this study.
•The effects of multisensory interactions were investigated in steady-state thermal and luminous conditions with time-varying sound stimuli.•Thermal comfort and visual comfort were affected by acoustic, thermal, and illumination conditions.•Acoustic comfort was affected by acoustic and thermal conditions.•All the physical factors tested in the study influenced indoor environmental comfort.•Time-varying acoustic factors had a higher effect size on the overall indoor environmental comfort.•Effects of gender appeared to differ in the range of each physical factor.
How metallylenes activate small molecules Vermeeren, Pascal; Doppert, Michael T; Bickelhaupt, F. Matthias ...
Chemical science (Cambridge),
02/2021, Letnik:
12, Številka:
12
Journal Article
Recenzirano
Odprti dostop
We have studied the activation of dihydrogen by metallylenes using relativistic density functional theory (DFT). Our detailed activation strain and Kohn-Sham molecular orbital analyses have ...quantified the physical factors behind the decreased reactivity of the metallylene on going down Group 14, from carbenes to stannylenes. Along this series, the reactivity decreases due to a worsening of the back-donation interaction between the filled lone-pair orbital of the metallylene and the σ*-orbital of H
2
, which, therefore, reduces the metallylene-substrate interaction and increases the reaction barrier. As the metallylene ligand is varied from nitrogen to phosphorus to arsenic a significant rate enhancement is observed for the activation of H
2
due to (i) a reduced steric (Pauli) repulsion between the metallylene and the substrate; and (ii) less activation strain, as the metallylene becomes increasingly more predistorted. Using a rationally designed metallylene with an optimal Group 14 atom and ligand combination, we show that a number of small molecules (
i.e.
HCN, CO
2
, H
2
, NH
3
) may also be readily activated. For the first time, we show the ability of our H
2
activated designer metallylenes to hydrogenate unsaturated hydrocarbons. The results presented herein will serve as a guide for the rational design of metallylenes toward the activation of small molecules and subsequent reactions.
Quantum chemical analyses reveal how model metallylene catalysts activate H
2
. This is the first step towards the rational design of metallylenes for the activation of small molecules and subsequent reactions.
PDF
