bluuebunny/crossref_metadata_2025 huggingface dataset:
Visible light switching of metallosupramolecular assemblies
Authors: Kennedy Aaron , DiNardi Ray , Fillbrook Lucy , Donald William , Beves Jonathon
Published: February 2022

A photoswitchable ligand and palladium(II) ions form a dynamic mixture of self-assembled metallosupramolecular structures. The photoswitching ligand is an ortho-fluoroazobenzene with appended pyridyl groups. The E-isomer is combined with palladium(II) salts affords a double-walled triangle with composition [Pd3L6]6+ and a distorted tetrahedron [Pd4L8]8+(1:2 ratio at 298 K). Irradiation with 410 nm light generates a photostationary state with ~80% of the E-isomer of the ligand which results in the selective disassembly of the tetrahedron, the more thermodynamically stable structure, and the formation of the triangle, the kinetic product. The triangle is then slowly transformed back into the tetrahedron over 2 days at 333 K. The Z-isomer of the ligand does not form any well-defined structures and has a thermal half-life of 25 days at 298K. This approach shows how a thermodynamically preferred self-assembled structure can be reversibly pumped to a kinetic trap by small perturbations of the isomer distribution using non-destructive visible light.
Protein corona formation around biocatalytic nanomotors unveiled by STORM
Authors: Patino Tania , Llacer-Wintle Joaquin , Pujals Silvia , Albertazzi Lorenzo , Sánchez Samuel
Published: February 2022

The interaction of nanoparticles with biological media is a topic of general interest for drug delivery systems and among those for active nanoparticles, also called nanomotors. Herein, we report the use of super resolu-tion microscopy, in particular stochastic optical reconstruction microscopy (STORM), to characterize the formation of protein corona around active enzyme-powered nanomotors. First, we characterize the distribu-tion and number of enzymes on nano-sized particles and characterized their motion capabilities. Then, we incubated the nanomotors with fluorescently labelled serum proteins. Interestingly, we observed a signifi-cant decrease of protein corona formation (20 %) and different composition, which was studied by a proteo-mic analysis. Moreover, motion was not hindered, as nanomotors displayed an enhanced diffusion regardless of protein corona. Elucidating how active particles interact with biological media and maintain their self-propulsion after protein corona formation will pave the way of the use these systems in complex biological fluids in biomedicine.
Oxygen Deficiencies in Titanium Oxide Clusters as Models for Bulk Defects
Authors: Heald Lauren , Garcia Jake , Sayres Scott
Published: February 2022

TD-DFT calculations were performed on neutral TinO2n, TinO2n-1, and TinO2n-2 clusters, where n ≤ 7. Our calculations show that the TinO2n clusters are closed shell systems containing empty d orbitals and that the partially filled d orbitals of the sub-oxide clusters have a profound effect on their structural, electronic, and topological properties. The low energy photoexcita-tions of TinO2n clusters are all O-2p to Ti-3d transitions, while the open-shell suboxide clusters are all characterized by d-d transitions that occur at a much smaller optical gap. Upon photoabsorption, the localization of the hole is accompanied by a local bond elongation, i.e., polaron formation, whereas d-electrons are generally delocalized among the cluster. Several of the compact of the TinO2n-2 structures contain higher symmetry which is reflected in their relative stability in the experimental cluster distribution. In particular, the tetrahedral symmetry of the optimized ground state structure for Ti4O6 inhibits charge carrier localization and therefore contains higher stability.
Tubular J-aggregates of cyanine dyes in the near-infrared
Authors: Bailey Austin , Deshmukh Arundhati , Atallah Timothy , Barotov Ulugbek , Pengshung Monica , Sletten Ellen , Caram Justin
Published: February 2022

Developing improved organic infrared emitters has wide-ranging applicability in fields such as bioimaging or energy harvesting. We synthesize redshifted analogues of C8S3, a well-known cyanine dye that self assembles into tubular aggregates which have attracted widespread attention as artificial photosynthetic complexes. Despite the elongated dye structure, the new pentamethine dyes retain their tubular self-assembly and emit at near-infrared wavelengths. Cryo-electron microscopy and detailed photophysical characterization of the new aggregates reveal similar absorption lineshapes with ~100 nm of redshift, as well as supramolecular morphologies that resemble their trimethine counterparts; the pentamethine aggregates generally show more disorder and decreased superradiance, suggesting that more ordered structures yield more robust photophysical properties. These results provide design principles of superradiant organic emitters, expand the chemical space of near-infrared aggregates, and introduce two additional wavelength-specific antennae as model systems for study.
B,N-Embedded Double Hetero[7]helicenes with Strong Chiroptical Responses in the Visible Light Region
Authors: Li Ji-Kun , Chen Xing-Yu , Guo Yun-Long , Wang Xin-Chang , Sue Andrew C.-H. , Cao Xiao-Yu , Wang Xiao-Ye
Published: February 2022

The development of helicene molecules with significant chiroptical responses covering a broad range of the visible spectrum is highly desirable for chiral optoelectronic applications; however, their absorption dissymmetry factors (gabs) have been mostly lower than 0.01. In this work, we report unprecedented B,N-embedded double hetero[7]helicenes with nonbonded B and N atoms, which exhibit excellent chiroptical properties, such as strong chiroptical activities from 300 to 700 nm, record high gabs up to 0.033 in the visible spectral range, and tunable circularly polarized luminescence (CPL) from red to near-infrared regions (600 ~ 800 nm) with high photoluminescence quantum yields (PLQYs) up to 100%. As revealed by theoretical analyses, the high gabs values are related to the separate molecular orbital distributions owing to the incorporation of nonbonded B and N atoms. The new type of B,N-embedded double heterohelicenes opens up an appealing avenue to the future exploitation of high-performance chiroptical materials.
(PNSiMe3)4(NMe)6: A robust tetravalent phosphaza-adamantane scaffold for molecular and macromolecular chemistry
Authors: Bedard Joseph , Roberts Nicholas J. , Bamford Karlee L. , Werner-Zwanziger Ulrike , Marczenko Katherine M. , Chitnis Saurabh S.
Published: February 2022

Tetraarylmethanes and adamantanes are very rare examples of rigid, four-way, anionic connectors that play a scaffolding role in multiple areas of molecular and materials chemistry. We report the synthesis of a tetravalent phosphaza-adamantane cage, (PNSiMe3)4(NMe)6 (2), that shows unusually high ambient, thermal, and redox stability due to its unique geometry. It nevertheless participates in four-fold functionalization reactions on its periphery. The combination of a robust core but a reactive corona makes 2 a convenient inorganic scaffold upon which tetrahedral molecular and macromolecular chemistry can be reliably constructed. This potential is exemplified by the unprecedented synthesis of a tetracationic tetraphosphinimine (3) and the first porous all-P/N polyphosphazene network (5).
Homogeneous hydrogenation of saturated bicarbonate slurry to formates using multiphase catalysis
Authors: Rebreyend Christophe , Pidko Evgeny , Filonenko Georgy
Published: February 2022

Formic acid and formate salts are key intermediates along the pathways for CO2 utilization and hydrogen storage. Herein we report a highly efficient multiphase catalytic system utilizing ruthenium PNP pincer catalyst for converting supersaturated bicarbonate solutions and slurries to aqueous formate solutions up to 12M in molarity. The biphasic catalytic system delivers turnover frequencies up to 73 000 h-1 and remains stable for up to 474’000 turnovers once reaction conditions are optimized.
Efficient Infrared Emission of Colloidal PbSe Nanoplatelets by Lateral Size Control
Authors: Klepzig Lars F. , Biesterfeld Leon , Romain Michel , Niebur André , Schlosser Anja , Hübner Jens , Lauth Jannika
Published: February 2022

Colloidal two-dimensional (2D) lead chalcogenide nanoplatelets (NPLs) represent highly interesting materials for near- and short wave-infrared applications including innovative glass fiber optics exhibiting negligible attenuation. In this work, we demonstrate a direct synthesis route for 2D PbSe NPLs with cubic rock salt crystal structure at low reaction temperatures of 0 °C and room temperature. A lateral size tuning of the PbSe NPLs by controlling the temper-ature and by adding small amounts of octylamine to the reaction leads to excitonic absorption features in the range of 800 – 1000 nm (1.6 – 1.3 eV) and narrow photoluminescence (PL) seamlessly covering the broadband infrared spec-tral window of 900 – 1450 nm (1.4 – 0.9 eV). The PL quantum yield of the as-synthesized PbSe NPLs is more than doubled by a postsynthetic treatment with CdCl2 (e.g. from 14.7 % to 37.4 % for NPLs emitting at 980 nm with a FWHM of 214 meV). An analysis of the slightly asymmetric PL line shape of the PbSe NPLs and their characterization by ultrafast transient absorption and time-resolved PL spectroscopy reveal a surface trap related PL contribution which is successfully reduced by the CdCl2 treatment from 40 % to 15 %. Our results open up new pathways for a direct synthesis and straightforward incorporation of colloidal PbSe NPLs as efficient infrared emitters at technologi-cally relevant telecommunication wavelengths.
Cell-instructive surface gradients of photo-responsive amyloid-like fibrils
Authors: Maria Ender Adriana , Kaygisiz Kübra , Räder Hans-Joachim , Mayer Franz J. , Synatschke Christopher V. , Weil Tanja
Published: February 2022

Gradients of bioactive molecules play a crucial role in various biological processes like vascularization, tissue regeneration or cell migration. In order to study these complex biological systems, it is necessary to control the concentration of bioactive molecules on their substrates. Here, we created a photochemical strategy to generate gradients using amyloid-like fibrils as scaffolds functionalized with a model epitope, i.e. the integrin-binding peptide RGD, to modulate cell adhesion. The self-assembling -sheet forming peptide (CKFKFQF) was connected to the RGD epitope via a photo-sensitive nitrobenzyl linker and assembled into photo-responsive nanofibrils. The fibrils were spray-coated on glass substrates and macroscopic gradients were generated by UV-light over a cm-scale. We confirmed the gradient formation using matrix assisted laser desorption ionization mass spectroscopy imaging (MALDI-MSI), which directly visualizes the molecular species on the surface. The RGD gradient was used to instruct cells. In consequence, A549 adapted their adhesion properties in dependence of the RGD-epitope density
Alchemical Absolute Protein-Ligand Binding Free Energies for Drug Design
Authors: Khalak Yuriy , Tresadern Gary , Aldeghi Matteo , Baumann Hannah Magdalena , Mobley David L. , de Groot Bert L. , Gapsys Vytautas
Published: February 2022

Recent advances in relative protein-ligand binding free energy calculations have shown the value of alchemical methods in drug discovery. Accurately assessing absolute binding free energies remains a challenging endeavour, mostly limited to small model cases. We demonstrate accurate absolute binding free energy estimates for 128 pharmaceutically relevant ligands across 7 proteins using a highly parallelizable non-equilibrium method. These calculations also provide detailed physical insight into the structural determinants of binding, identifying subtle rotamer rearrangements between protein apo and holo states that are crucial for binding. The challenge behind absolute binding free energy calculations stems in large part from the need to explicitly account for the protein’s apo state. In this work we present several approaches to obtain apo state ensembles, including a novel rigorous method to generate protein-ligand ensembles for the ligand in its decoupled state. Altogether, we present an effective open-source protocol for prospective application in drug discovery.
CACHE (Critical Assessment of Computational Hit-finding Experiments): A public-private partnership benchmarking initiative to enable the development of computational methods for hit-finding
Authors: Ackloo Suzanne , Al-awar Rima , Amaro Rommie E. , Arrowsmith Cheryl H. , Azevedo Hatylas , Batey Robert A. , Bengio Yoshua , Betz Ulrich A.K. , Bologa Cristian G. , Chodera John D. , Cornell Wendy D. , Dunham Ian , Ecker Gerhard F. , Edfeldt Kristina , Edwards Aled M. , Gilson Michael K. , Gordijo Claudia R. , Hessler Gerhard , Hillisch Alexander , Hogner Anders , Irwin John J. , Jansen Johanna M. , Kuhn Daniel , Leach Andrew R. , Lee Alpha A. , Lessel Uta , Moult John , Muegge Ingo , Oprea Tudor I. , Perry Benjamin G. , Riley Patrick , Saikatendu Kumar Singh , Santhakumar Vijayaratnam , Schapira Matthieu , Scholten Cora , Todd Matthew H. , Vedadi Masoud , Volkamer Andrea , Willson Timothy M.
Published: February 2022

Computational approaches in drug discovery and development hold great promise, with artificial intelligence methods undergoing widespread contemporary use, but the experimental validation of these new approaches is frequently inadequate. We are initiating Critical Assessment of Computational Hit-finding Experiments (CACHE) as a public benchmarking project that aims to accelerate the development of small molecule hit-finding algorithms by competitive assessment. Compounds will be identified by participants using a wide range of computational methods for dozens of protein targets selected for different types of prediction scenarios, as well as for their potential biological or pharmaceutical relevance. Community-generated predictions will be tested centrally and rigorously in an experimental hub(s), and all data, including the chemical structures of experimentally tested compounds, will be made publicly available without restrictions. The ability of a range of computational approaches to find novel compounds will be evaluated, compared, and published. The overarching goal of CACHE is to accelerate the development of computational chemistry methods by providing rapid and unbiased feedback to those developing methods, with an ancillary and valuable benefit of identifying new compound-protein binding pairs for biologically interesting targets. The initiative builds on the power of crowd sourcing and expands the open science paradigm for drug discovery.
Probing a Local Viscosity Change at the Nematic-Isotropic Liquid Crystal Phase Transition by a Ratiometric Flapping Fluorophore
Authors: Kimura Ryo , Kitakado Hidetsugu , Yamakado Takuya , Yoshida Hiroyuki , Saito Shohei
Published: February 2022

Local viscosity change in the thermal phase transition of a nematic liquid crystal, 5CB, has been analyzed by doping fluorescent viscosity probes, flapping fluorophores (FLAP) as well as a molecular rotor BODIPY-C12. As a result, only flapping anthraceneimide has successfully monitored a small viscosity change (corresponding to a few cP (centipoise) change in shear viscosity around 25 cP) in the nematic-to-isotropic phase transition by ratiometric spectroscopy. In addition, analysis of fluorescence anisotropy indicates that the emissive species (planarized flapping anthraceneimides) are aligned parallel to the director of 5CB in the nematic phase.
From Appendage to Crosslinker – Unusual Swelling Behavior in Spiropyran-Modified Hydrogels
Authors: Lerch Michael M. , Shastri Ankita , Schroeder Thomas B.H. , Meeks Amos , Li Shucong , Shneidman Anna V. , Aizenberg Michael , Aizenberg Joanna
Published: February 2022

Stimuli-responsive materials typically contain responsive molecular units that couple an external trigger to a defined macroscale response. Ongoing efforts to boost the versatility and complexity of these responses increasingly focus on multi-stimuli-responsive molecular units and crosslinkers, as these bear the potential to impart self-regulatory behaviors building on cooperative effects and feedback mechanisms. Herein, we study a stimuli-responsive platform consisting of polyacrylamide-based hydrogels with well-known multi-responsive spiropyrans covalently bound as pendant groups or ´non-innocent´ crosslinkers. Surprisingly, as compared to their appended counterparts, spiropyran crosslinkers cause up to two-fold larger hydrogel swelling in methylenebisacrylamide-crosslinked poly(acrylamide-co-acrylic acid) hydrogels, despite their increased relative crosslinking density. We seek the origin of this unexpected behavior by employing nanoindentation, swelling studies, and UV-vis spectroscopy to study changes in mechanical properties and in spiropyran isomer distribution as a function of solution pH, co-monomer chemistry, and swelling-induced polymer strain. We then estimate the osmotic counterion pressures as a function of spiropyran isomer distribution but find that such pressures alone are insufficient to explain the observed behavior. Charge complexation, cooperative effects between the hydrogel´s mechanics and chemistry, and aggregate formation may all be invoked to explain features of the observed ´non-innocence´ of spiropyran crosslinkers. Taken together, these insights will aid rational implementation of such responsive crosslinkers in materials design and extend the functionality of existing polymeric materials towards more complex and better tunable behaviors.
Inhibition of the Hexamerization of SARS-CoV-2 Endoribonuclease and Modeling of RNA Structures Bound to the Hexamer
Authors: Tran Duy , Taira Yuta , Ogawa Takumi , Misu Ryoga , Miyazawa Yoshiki , Kitao Akio
Published: February 2022

Non-structural protein 15 (Nsp15) of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) forms a homo hexamer and functions as an endoribonuclease. Here, we propose that Nsp15 activity may be inhibited by preventing its hexamerization through drug binding. We first explored the stable conformation of the Nsp15 monomer as the global free energy minimum conformation in the free energy landscape using a combination of parallel cascade selection molecular dynamics (PaCS-MD) and the Markov state model (MSM), and found that the Nsp15 monomer forms a more open conformation with larger druggable pockets on the surface. Targeting the pockets with high druggability scores, we conducted ligand docking and identified compounds that tightly bind to the Nsp15 monomer. The top poses with Nsp15 were subjected to binding free energy calculations by dissociation PaCS-MD and MSM (dPaCS-MD/MSM), indicating the stability of the complexes. One of the identified pockets, which is distinctively bound by inosine analogues, may be an alternative binding site to stabilize viral RNA binding and/or an alternative catalytic site. We constructed a stable RNA structure model bound to both UTP and alternative binding sites, providing a reasonable proposed model of the Nsp15/RNA complex.
All-atom molecular dynamics study of hepatitis B virus containing pregenome RNA in solution
Authors: Fujimoto Kazushi , Yamaguchi Youhei , Urano Ryo , Shinoda Wataru , Ishikawa Tetsuya , Omagari Katsumi , Tanaka Yasuhito , Nakagawa Atsushi , Okazaki Susumu
Published: February 2022

Immature hepatitis B virus (HBV) captures nucleotides in its capsid for reverse transcription. The nucleotides and nucleotide analogue drugs, which are triphosphorylated and negatively charged in the cell, approach the capsid via diffusion and are absorbed into it. In this study, we performed a long-time molecular dynamics (MD) calculation of the entire HBV capsid containing pregenome RNA to investigate the interactions between the capsid and negatively charged substances. Electric field analysis demonstrated that negatively charged substances can approach the HBV capsid by thermal motion, avoiding spikes. The substances then migrate all over the floor of the HBV capsid. Finally, they find pores through which they can pass through the HBV capsid shell. Free energy profiles were calculated along these pores for small ions to understand their permeability through the pores. Anions (Cl-) showed higher free energy barriers than cations (Na+ and K+) through all pores, and the permeation rate of Cl- was eight times slower than that of K+ or Na+. Furthermore, the ions were more stable in the capsid than in the bulk water. Thus, the HBV capsid exerts ion selectivity for uptake and provides an environment for ions, such as nucleotides and nucleotide analogue drugs, to be stabilized within the capsid.
Stereoconvergent and -divergent Synthesis of Tetrasubstituted Alkenes by Nickel-Catalyzed Cross-Couplings
Authors: Zell Daniel , Kingston Cian , Jermaks Janis , Smith Sleight , Seeger Natalie , Wassmer Jana , Sirois Lauren , Han Chong , Zhang Haiming , Sigman Matthew , Gosselin Francis
Published: February 2022

We report the development of a method to diastereoselectively access tetrasubstituted alkenes via nickel-catalyzed Suzuki-Miyaura cross-couplings of enol tosylates and boronic acid esters. Either diastereomeric product was selectively accessed from a mixture of enol tosylate starting material diastereomers in a convergent reaction by judicious choice of the ligand and reaction conditions. A similar protocol also enabled a divergent synthesis of each product isomer from diastereomerically pure enol tosylates. Notably, high-throughput optimization of the monophosphine ligands was guided by chemical space analysis of the kraken library to ensure a diverse selection of ligands was examined. Stereoelectronic analysis of the results provided insight into the requirements for reactive and selective ligands in this transformation. The synthetic utility of the optimized catalytic system was then probed in the stereoselective synthesis of various tetrasubstituted alkenes, with yields up to 94% and diastereomeric ratios up to 99:1 Z/E and 93:7 E/Z observed. Moreover, a detailed computational analysis and experimental mechanistic studies provided key insights into the nature of the underlying isomerization process impacting selectivity in the cross-coupling.
Carbonylative Cross-Electrophile Coupling Between Aryl Bromides and Aryl Triflates Enabled by Palladium and Rhodium Cooperative Catalysis
Authors: Xiao Xue , Chen Gang , Zhang Xuemei , Kramer Søren , Lian Zhong
Published: February 2022

Ketones are among the most useful functional groups in organic synthesis. Here, we report the first carbonylative cross-electrophile coupling reaction that utilize carbon monoxide gas as the carbonyl source. The use of Pd/Rh cooperative catalysis enables the carbonylative coupling of easily accessible aryl triflates and aryl bromides. Unlike all previous carbonylative cross-electrophile coupling reactions, the method does not require addition of a stoichiometric metal reductant.
Synthesis of Chain Transfer Agents for RAFT Polymerization by using DBU
Authors: GONDI SUDERSHAN
Published: February 2022

Trithiocarbonate TTC, Dithioester DT containing RAFT chain transfer acid agents are efficiently and conveniently esterified by DBU. The significance of the reaction is mild reaction condition, high yield, easy simple workup, and reduction of reaction time. This protocol providing a useful alternative method for ester synthesis and makes the process very viable or more economic.
Direct and indirect photodegradation of atrazine and S-metolachlor in agriculturally impacted surface water and associated C and N isotope fractionation
Authors: Drouin Guillaume , Droz Boris , Leresche Frank , Payraudeau Sylvain , Masbou Jeremy , Imfeld Gwenaël
Published: February 2022

Knowledge of direct and indirect photodegradation of pesticides and associated isotope fractionation can help to assess pesticide degradation in surface waters. Here, we investigated carbon (C) and nitrogen (N) isotope fractionation during direct and indirect photodegradation of the herbicides atrazine and S-metolachlor in synthetic water, mimicking agriculturally impacted surface waters containing nitrates (20 mg L–1) and dissolved organic matter (DOM, 5.4 mgC L–1). Atrazine and S-metolachlor were quickly photodegraded by both direct and indirect pathways (half-lives <5 and <7 days, respectively). DOM slowed down photodegradation while nitrates increased degradation rates. The analysis of transformation products showed that oxidation mediated by hydroxyl radicals (HO•) predominates during indirect photodegradation. UV light (254 nm) caused significant C and N isotope fractionation, yielding isotope enrichment factors ε_C = 2.7 ± 0.3 and 0.8 ± 0.1‰, and ε_N = 2.4 ± 0.3 and –2.6 ± 0.7‰ for atrazine and S-metolachlor, respectively. In contrast, photodegradation under simulated sunlight led to negligible C and slight N isotope fractionation, indicating the influence of the radiation wavelength on the direct photodegradation-induced isotope fractionation. Altogether, this study highlights the relevance of using simulated sunlight to evaluate photodegradation pathways in the environment and the potential of CSIA to distinghuish photodegradation from other dissipation pathways in surface waters.
The amyloidogenic peptide amyloid beta(16-22) displays facet dependent conformation on metal surfaces
Authors: Somers Kieran , Cheung David
Published: February 2022

Currently, it is not understood how metal nanoparticles influence the formation of protein fibrils, although recent literature highlights that the shape and chemical composition of such nanoparticles can strongly influence the process. Understanding this process at a fundamental level can potentially unlock routes to the development of new therapeutics, as well as novel materials for other applications. This requires a microscopic picture of the behaviour of amyloidogenic proteins on metal surfaces. Using replica exchange molecular dynamics simulations we investigate the adsorption of the model amyloidogenic peptide, A𝛽(16-22), on different gold and silver surfaces. While the peptide adsorbs onto these different surfaces, the adsorption can be considered to be enthalphically driven for the gold surfaces and entropically driven for silver. The conformation of the peptide on gold surfaces also shows a strong facet dependence for gold, with fibril-like conformations being promoted in the 100 surface and inhibited on the 111 surface. A smaller degree of facet dependence is seen for silver with the peptide behaving similar on both of these. The difference in the facet dependence can be related to the difference between direct adsorption onto the gold 111 surface, with a preference towards indirect (water mediated) adsorption onto the other surfaces. This new information on the behaviour of an amyloidogenic peptide on metal surfaces can give insight into the size-dependent effect of nanoparticles on fibril formation and the use of surfaces to control fibrillation.
Are substitutes to Cd-based quantum dots in displays more sustainable, effective, and cost competitive? An alternatives assessment approach
Authors: Bechu Aude , Ghoshal Subhasis , Moores Audrey , Basu Niladri
Published: February 2022

Light emissive organics and inorganic nanoparticles are substance classes competing for applications in displays in the form of organic LEDs (OLEDs) and quantum LEDs (QLEDs), respectively. Upcoming substance classes (perovskites) and Q-OLED displays also contain novel nanomaterials and organics for these applications. However, the sustainability of these emissive substances is difficult to assess quickly and broadly because of their complexity, their inherently different structures, and their rapid evolution in the literature. We propose the use of an alternatives assessment to compare the hazard, cost, and performance of these competing substances, with a focus on replacing cadmium-containing quantum dots. The cost assessment highlights competitiveness of OLEDs because of their low amounts needed per display, but performance assessments do not identify a preferred alternative. The hazard results indicate there is no clear alternative either, with each novel nanomaterial or organic substance having different negative aspects. These results identify the need for a low-hazard high-performing alternative substance, and the assessment provides a framework for researchers to evaluate their own novel substances.
Drug Repurposing 57 well-known drugs for three COVID-19 targets: Mpro, Spike, RdRp
Authors: Nelakuditi Bhavishya , Shrivastava Awantika
Published: February 2022

The pandemic that we are currently living through, caused by SARS COVID-19, changed the way we perceive deadly diseases along with our comprehension of efficacious drugs. In this project, we compare 57 repurposable drugs from different categories like anti-inflammatory, anticancer, anticoagulant, antiviral, anti-parasitic, antidepressant, Parkinson’s disease drugs, and discontinued drugs, to identify the best drugs with strongest binding affinities, that can be considered for treating COVID-19. We identified three target proteins- Main protease (PDB ID: 6LU7), Spike Glycoprotein with human receptor ACE2 (PDB ID: 6M0J), and RNA-dependent RNA polymerase (RdRp) in complex with Remdesivir (PDB ID: 7BV2) which are responsible for transcription, entrance into host’s cell and viral replication respectively. We used AutoDock Vina for docking, and based our results on the binding affinity and hydrogen bond interactions. We shortlisted 15 drugs- Vilazodone, Lopinavir, Ritonavir, Darunavir, Selinexor, Etoposide, Nintedanib, Methylprednisolone, Hydrocortisone, Tolcapone, Apixaban, Rivaroxaban, Dabigatran, Betrixaban, and Amprenavir- that showcased comparable or higher affinity than Remdesivir with all of our three target proteins, and recommend these for further studies.
Resonantly-Enhanced Difference-Frequency Generation in the Core X-ray Absorption of Molecules
Authors: Serrat Carles
Published: February 2022

We use real-time time-dependent density functional theory simulations to numerically demonstrate that resonantly-enhanced difference-frequency generation (re-DFG) involving intense ultrashort coherent X-ray pulses can selectively excite core states of atoms in molecules. As a model case, we evaluate the spectral selectivity of re-DFG excitation of the oxygen K-edge by illumination of a single gas-phase water molecule with two-color X-ray pulses of different photon energies and durations. The re-DFG excitation is further probed by a small delayed pulse with central photon energy resonant with the oxygen K-edge peak absorption line. Based on these results, we anticipate that highly selective excitation by re-DFG X-ray nonlinear processes might be achieved in more complex molecular systems and bulk materials by using highly penetrating two-color hard X-ray pulses, with extensive applications.
Pt(II)-Coordinated Tricomponent Self-Assemblies of Tetrapyridyl Porphyrin and Dicarboxylate Ligands: Are They 3D Prisms or 2D Bow Ties?
Authors: Benavides Paola , Gordillo Monica A. , Yadav Ashok , Joaqui-Joaqui M. Andrey , Saha Sourav
Published: February 2022

Thermodynamically favored heteroleptic coordination of Pt(II) ions with one aza- and another oxo-coordinating ligand yield tricomponent supramolecular coordination complexes (SCCs), which possess much greater structural complexity and functional diversity than traditional bicomponent SCCs containing only one of the ligands. Through X-ray crystallography, 1H, 31P, and 2D NMR spectroscopies, mass spectrometry, and computational studies, herein, we demonstrated that heteroleptic coordination of tetrapyridyl porphyrins (MTPP, M = Zn or H2) and various dicarboxylate ligands (XDC) having different lengths and rigidity with cis-(Et3P)2PtII corners yielded bow-tie (⋈)-shaped tricomponent [{cis-(Et3P)2Pt}4(MTPP)(XDC)2]4+ complexes featuring a MTPP core and two parallel XDC linkers held together by four heteroligated PtII(N,O) corners and ruled out the MTPP-based tetragonal prism formation. Irrespective of the rigidity and length of the XDC linkers within a certain range (~7–11 Å), they intramolecularly bridged two adjacent pyridyl tips of an MTPP ligand via PtII(N,O) corners, which led to the formation of bow-tie complexes instead of prisms. This happened because the angles of projection between the adjacent pyridyl rings of MTPP cores adapted to accommodate the bridging XDC linkers having different lengths, and the bow-tie formation was entropically favored over tetragonal prisms. This work not only unveiled novel bow-tie-shaped coordination complexes, but also accurately defined the actual structures and compositions of MTPP-based tricomponent SCCs. Furthermore, a representative bow-tie complex containing an electron-rich ZnTPP core selectively formed a charge-transfer (CT) complex with highly electron deficient 1,4,5,8,9,12-hexaazatriphenylene-2,3,6,7,10,11-heaxacarbonitrile (HATHCN) but not with π-donors like pyrene.
A microelectrode-based sensor for measuring operando active species concentrations in redox flow cells
Authors: Neyhouse Bertrand , Tenny Kevin , Chiang Yet-Ming , Brushett Fikile
Published: February 2022

The assessment of candidate materials for redox flow batteries requires effective diagnostic techniques for monitoring the evolution of electrolyte state of charge and state of health to interrogate time-dependent changes in system behavior. Further, such tools can be applied in practical embodiments to inform maintenance schedules and optimize energy utilization. In this work, we develop and test a flow-through, microelectrode-based electrochemical sensor to continuously measure active species concentrations in redox flow cells. A gold microelectrode (working electrode) and platinum wire (pseudo-reference electrode) are sealed into a stainless-steel fitting (counter electrode), and three-electrode electroanalytical techniques (i.e., voltammetry, chronoamperometry) are performed to correlate steady-state current to concentration. To validate transport and thermodynamics that govern the sensing mechanism, we combine multiphysics simulation with ex situ experimental testing, confirming the device is capable of accurately determining individual species concentrations. We then evaluate the microelectrode sensor in a symmetric redox flow cell, demonstrating the utility of this approach for measuring operando concentrations, and discuss additional considerations for successful implementation (e.g., measurement protocol, material selection, flow cell design). Assembled from commercially available, off-the-shelf components, the sensor can be readily adopted by research laboratories and integrated into existing experimental workflows, making it a promising tool for studying novel flow battery materials.
Photoconductivity of Intrinsic Semiconductor Phthalocyanine-Based Covalent Organic Polymer with Benzimidazole Linkage
Authors: Duygulu Ercan , Alev Onur , Chumakov Yurii , Öztürk Zafer Ziya , AYHAN MEHMET MENAF , Yüksel Fatma
Published: February 2022

Novel phthalocyanine-based benzimidazole linked conjugated covalent organic polymer (NiPc-COP1) have been synthesized with multiple randomly ordered crystalline morphology. This unique alignment leads to significantly enhanced panchromatic light-absorption capability, thus high photoconductivity with high photoresponce speed.
A first-principles study of hydrogen surface coverage on δ-Pu (100), (111), and (110) surfaces
Authors: Mullen Ryan , Goldman Nir
Published: February 2022

Hydriding corrosion of plutonium leads to surface cracking, pitting, and ultimately structural failure. Laboratory experiments demonstrate that hydriding begins on the surface or near subsurface of plutonium. However there has not yet been a systematic evaluation of hydrogen surface coverage on plutonium. In this work, we compute the surface energies of the low facet surfaces of face-centered cubic δ-Pu. The adsorption free energies of expected hydrogen structures at low and high coverage are presented, along with the likely progression for filling sites as the H2 partial pressure increases. Implications for near-equilibrium pressure hydride nucleation and non-equilibrium millibar pressure hydriding are discussed.
Local Electric Fields Dictate Function: The Different Product Selectivity Observed for Fatty Acids Oxidation by Two Deceptively Very Similar P450-Peroxygenases OleT and BSbeta
Authors: Yadav Shalini , Shaik Sason , Siddiqui Shakir Ali , Kalita Surajit , Dubey Kshatresh
Published: February 2022

Cytochrome P450 peroxygenases use hydrogen peroxide to hydroxylate long-chain fatty acids by bypassing the use of O 2 and a redox partner. Among the peroxygenases, P450 OleT uniquely performs decarboxylation of fatty acids and production of terminal olefins. This root taken by P450 OleT is intriguing, and its importance is augmented by the practical importance of olefin production. As such, this mechanistic choice merits elucidation. To address this puzzle we use hybrid QM/MM calculations and MD simulations for the OleT enzyme as well as for the structurally analogous enzyme, P450 BSβ . The study of P450 OleT reveals that the protonated His85 in the wild-type P450 OleT , plays a crucial role in steering decarboxylation activity by stabilizing the corresponding hydroxoiron(IV) intermediate (Cpd II). In contrast, for P450 BSβ in which Q85 replaces H85, the respective Cpd II species is unstable and it reacts readily with the substrate radical by rebound, producing hydroxylation products. As we show, this single-site difference creates in P450 OleT a local electric field (LEF), which is significantly higher than that in P450 BSβ . In turn, these LEF differences are responsible for the different stabilities of the respective Cpd II/radical intermediates, and hence for different functions of the two enzymes. P450 BSβ uses the common rebound mechanism and leads to hydroxylation, whereas P450 OleT proceeds via decarboxylation and generates terminal olefins. Olefin production projects the power of a single residue to alter the LEF and the enzyme’s function!
Room-Level Ventilation in Schools and Universities
Authors: McNeill V. Faye , Corsi Richard , Huffman J. Alex , Maeng Do Young , King Cathleen , Klein Robert , Lamore Michael , Miller Shelly , Ng Nga Lee , Olsiewski Paula , Pollitt Krystal , Segalman Rachel , Sessions Alex , Squires Todd , Westgate Sabrina
Published: February 2022

Ventilation is of primary concern for maintaining healthy indoor air quality and reducing the spread of airborne infectious disease, including COVID-19. In addition to building-level guidelines, increased attention is being placed on room-level ventilation. However, for many universities and schools, ventilation data on a room-by-room basis are not available for classrooms and other key spaces. We present an overview of approaches for measuring ventilation along with their advantages and disadvantages. We also present data from recent case studies for a variety of institutions across the United States, with various building ages, types, locations, and climates, highlighting their commonalities and differences, and examples of the use of this data to support decision making.
A system for the evolution of protein-protein interaction inducers
Authors: Dewey Jeffrey , Azizi Saara-Anne , Lu Vivian , Dickinson Bryan
Published: February 2022

Molecules that induce interactions between proteins, often referred to as “molecular glues”, are increasingly recognized as important therapeutic modalities and as entry points for rewiring cellular signaling networks. Here, we report a new PACE-based method to rapidly select and evolve molecules that mediate interactions between otherwise non-interacting proteins: rapid evolution of Protein-Protein Interaction Glues (rePPI-G). Proof-of-concept evolutions demonstrated that rePPI-G reduces the “hook” effect of the engineered molecular glues, due at least in part to tuning the interaction affinities of each individual component of the bifunctional molecule. Altogether, this work validates rePPI-G as a continuous, phage-based evolutionary technology for optimizing molecular glues, providing a strategy for developing molecules that reprogram protein-protein interactions.
Direct Synthesis and Applications of Solid Silylzinc Reagents
Authors: Rasappan Ramesh , Chandrasekaran Revathi , Thomas Pulikkottil Feba , Suresh Krishna
Published: February 2022

The increased synthetic utility of organosilanes motivates researchers to develop a milder and more practical synthetic methods. Silylzinc reagents, which are typically the most functional group tolerant, are notoriously difficult to synthesize because they are obtained by a pyrophoric reaction of silyllithium, particularly Me3 SiLi itself prepared by the reaction of MeLi and disilane. Furthermore, the dissolved LiCl in silylzinc may have a detrimental effect. A synthetic method that can avoid silyllithium and involves a direct synthesis of silylzinc reagents from silyl halides is arguably the simplest and economical strategy. We describe for the first time, the direct synthesis of PhMe2 SiZnI and Me3 SiZnI reagents by employing a coordinating TMEDA ligand, as well as single crystal XRD structures. Importantly, they can be obtained as solid and stored for longer periods of time. We demonstrate their significance in cross-coupling of various free alkyl/aryl/alkenyl carboxylic acids with broader functional group tolerance and API derivatives. The general applicability and efficiency of solid Me3 SiZnI are shown in a wide variety of reactions including alkylation, arylation, allylation, 1,4-addition, acylation and more.
Copper/nickel-Decorated Olive Pit Biochar: One Pot Solid State Synthesis for Environmental Remediation
Authors: Khalil Ahmed M. , Michely Laurent , Pires Rémy , Bastide Stéphane , Jlassi Khouloud , Ammar Souad , Jaziri Mohamed , Chehimi Mohamed
Published: February 2022

Developing micro- and nanomaterials for environmental pollution remediation is hot topic presently. Among the plethora of strategies, designing supported nanocatalysts for the degradation of pollutants witnessed constant renewal. In this context, we are addressing one of the UN Sustainable Development Goals by valorizing agrowaste as a source of biochar which serves as support for bimetallic nanocatalysts. Herein, Olive pit powder particles were impregnated with copper and nickel nitrates and pyrolyzed at 400 °C. The resulting material consists of bimetallic CuNi-decorated biochar. CuNi nanocatalysts were found to be as small as 10 nm and very well dispersed over biochar with zero valent copper and nickel and formation of copper-nickel solid solutions. The biochar@CuNi exhibited typical soft ferromagnet hysteresis loops with zero remanence and zero coercivity. The biochar@CuNi was found to be efficient catalyst of the reduction of methyl orange (MO) dye, taken as model pollutant. To sum up, the one pot method devised in this work provided unique CuNi-decorated biochar and opens new horizons for the emerging topic of biochar-supported nanocatalysts.
Twin-emitter design strategy for use in solution-processable thermally activated delayed fluorescence organic light-emitting diodes
Authors: Crovini Ettore , Zhang Zhen , Kusakabe Yu , Ren Yongxia , Wada Yoshimasa , Naqvi Bilal , Sahay Prakhar , Bruetting Wolfgang , Suzuki Katsuaki , Kaji Hironori , Bräse Stefan , Zysman-Colman Eli
Published: February 2022

In this work we showcase the emitter DICzTRZ in which we employed a twin-emitter design of our previously reported material, ICzTRZ. This new system presented a red-shifted emission at 488 nm compared to that of ICzTRZ at 475 nm and showed a comparable photoluminescence quantum yield of 57.1% in a 20 wt% CzSi film versus 63.3% for ICzTRZ. The emitter was then incorporated within a solution-processed organic light-emitting diode that showed a maximum external quantum efficiency of 8%, with Commision Internationale de l’Éclairage coordinate of (0.21, 0.47), at 10 cd m−2.
Co-harvesting Solar Energy with Ambient Heat and On-Demand Release of Thermal Energy Below 0 oC Through Visible-Light-Controlled Photochemical Phase Transitions of Azopyrazoles
Authors: Shangguan Zhichun , Sun Wenjin , Zhang Zhao-yang , Fang Dong , Wu Si , Deng Chao , Huang Xianhui , He Yixin , Wang Ruzhu , Li Tingxian , Li Tao
Published: February 2022

Photochemical crystal-to-liquid transition generally needs UV light as a stimulus and it is even more challenging to carry out below 0 oC. Here, we design a series of 4-alkylthioarylazopyrazoles as molecular solar thermal batteries, which show bidirectional visible-light-triggered photochemical trans-crystal ↔ cis-liquid transitions below ice point (-1 oC). Through co-harvesting visible-light energy and low-temperature ambient heat, high energy density (0.25 MJ kg-1) is achieved. Further, the rechargeable solar thermal batteries devices are fabricated, which can be charged by blue light (400 nm) at -1 oC. Then, the charged devices can release energy on demand in the form of high-temperature heat. Under green light (532 nm) irradiation, the temperature difference between the charged devices and the ice-cold surrounding is up to 13.5 oC. This study paves the way for the design of advanced molecular solar thermal batteries that store both natural sunlight and ambient heat over a wide temperature range.
Oxidation state variation in bis-calix[4]arene supported decametallic Mn clusters
Authors: Brechin Euan , Dalgarno Scott , Wilson Lucinda , Coletta Marco , Rajaraman Gopalan , Jose Reshma
Published: February 2022

The reaction of MnCl2·4H2O, H8L (2,2’-bis-p-tBu-calix[4]arene) and NEt3 in a dmf/MeOH solvent mixture results in the formation of a mixed valent decametallic cluster of formula [MnII6MnIII4(L)2(µ3-OH)4(µ-OH)4(MeOH)4(dmf)4(MeCN)2]·MeCN (3). Complex 3 crystallises in the monoclinic space group P21/n with the asymmetric unit comprising half of the compound. Structure solution reveals that the bis-calix[4]arene ligands are arranged such that one TBC[4] moiety in each has undergone inversion in order to accommodate a [MnIII4MnII6] metallic skeleton that describes three vertex-sharing [MnIII2MnII2] butterflies. The structure is closely related to the species [MnIII6MnII4(L)2(μ3-O)2(μ3-OH)2(μ-OMe)4(H2O)4(dmf)8]·4dmf (4), the major difference being the oxidation level of the Mn ions in the core of the compound. DFT calculations on the full structures reveal that replacing the MnIII ions in 4 for MnII ions in 3 results in a significant decrease in the magnitude of some antiferromagnetic exchange contributions, a switch from ferromagnetic to antiferromagnetic in others, and the loss of significant spin frustration.
Silver cation-mediated dual-emissive Au–Ag bimetallic nanoclusters for pH ratiometric sensing
Authors: Peng Po , Zheng Liu-Xi , Wang Pan-Yue , Zhou Jia-Feng , Ding Meng , Sun Hao-Di , Shan Bing-Qian , zhang kun
Published: February 2022

Metal nanoclusters (NCs) with intrinsic dual-emission are not only significant for fundamental research but also for accurate ratiometric sensing and imaging. Using 1-dodecanethiol (DT) as protected-cum-reduced ligand, the core-shell structured Au-Ag bimetallic NCs with well-resolved dual-emission bands centered at 440 nm and at 630 nm were successfully synthesized by a facile one-pot approach.A combined characterizations of X-ray photoelectron spectroscopy(XPS), transmission rlectron microscope (TEM) and optical spectrum revealed that the Au-Ag bimetallic NCs had a core-shell structure with a metallic Au(0) core coated by a shell of Au(I)- and Ag(I)-thiolate motifs, and very interestingly, the dual-emissive Au-Ag NCs exhibited unique ratiometric pH-dependent emissions, which could be used an ideal pH ratiometric nanosensors. Most importantly, our observed Ag+ mediated pH-dependent dual-emissive behavior suggests that the metal NCs core is not real emitter center, while structural water molecules (SWs) confined at the nanoscale interface of metal core are true luminous centers, which answers that the optical properties of metal NCs are very sensitive to the delicate change of surrounding microenvironment of metal NCs, including the dosing of Ag+, pH and packing mode of surface ligands. Our discovery not only opens up new possibilities for the design of ultrasmall ratiometric pH nanoindicators, but also provides new insights on the origin of photoluminscent (PL) emission of metal NCs.