Elucidation of factors shaping reactivity of 5'-deoxyadenosyl - a prominent organic radical in biology.

This study investigates the factors modulating the reactivity of 5'-deoxyadenosyl (5'dAdo˙) radical, a potent hydrogen atom abstractor that forms in the active sites of radical SAM enzymes and that otherwise undergoes a rapid self-decay in aqueous solution. Here, we compare hydrogen atom abstraction (HAA) reactions between native substrates of radical SAM enzymes and 5'dAdo˙ in aqueous solution and in two enzymatic microenvironments. With that we reveal that HAA efficiency of 5'dAdo˙ is due to (i) the formation of 5'dAdo˙ in a pre-ordered complex with a substrate, which attenuates the unfavorable effect of substrate:5'dAdo˙ complex formation, and (ii) the prevention of the conformational changes associated with self-decay by a tight active-site cavity.

The evolution of organic material on Asteroid 162173 Ryugu and its delivery to Earth.

The recent return of samples from asteroid 162173 Ryugu provides a first insight into early Solar System prebiotic evolution from known planetary bodies. Ryugu's samples are CI chondrite-like, rich in water and organic material, and primarily composed of phyllosilicate. This phyllosilicate surrounds micron to submicron macromolecular organic particles known as insoluble organic matter.

Enhancing the Electrochemical Activity of 2D Materials Edges through Oriented Electric Fields.

The edges of 2D materials have emerged as promising electrochemical catalyst systems, yet their performance still lags behind that of noble metals. Here, we demonstrate the potential of oriented electric fields (OEFs) to enhance the electrochemical activity of 2D materials edges. By atomically engineering the edge of a fluorographene/graphene/MoS heterojunction nanoribbon, strong and localized OEFs were realized as confirmed by simulations and spatially resolved spectroscopy.

The valence electron affinity of uracil determined by anion cluster photoelectron spectroscopy.

The unoccupied π* orbitals of the nucleobases are considered to play important roles in low-energy electron attachment to DNA, inducing damage. While the lowest anionic valence state is vertically unbound in all neutral nucleobases, it remains unclear even for the simplest nucleobase, uracil (U), whether its valence anion (U) is adiabatically bound, which has important implications on the efficacy of damage processes. Using anion photoelectron spectroscopy, we demonstrate that the valence electron affinity (EA) of U can be accurately measured within weakly solvating clusters, U(Ar) and U(N).

Dissociative Electron Attachment Dynamics of a Promising Cancer Drug Indicates Its Radiosensitizing Potential.

2-Bromo-1-(3,3-dinitroazetidin-1-yl)ethan-1-one (RRx-001) is a hypoxic cell chemotherapeutics with already demonstrated synergism in combined chemo-radiation therapy. The interaction of the compound with secondary low-energy electrons formed in large amounts during the physico-chemical phase of the irradiation may lead to these synergistic effects. The present study focuses on the first step of RRx-001 interaction with low-energy electrons in which a transient anion is formed and fragmented.

Electron-induced ligand loss from iron tetracarbonyl methyl acrylate.

We probe the separation of ligands from iron tetracarbonyl methyl acrylate (Fe(CO)(CHO) or Fe(CO)MA) induced by the interaction with free electrons. The motivation comes from the possible use of this molecule as a nanofabrication precursor and from the corresponding need to understand its elementary reactions fundamental to the electron-induced deposition. We utilize two complementary electron collision setups and support the interpretation of data by quantum chemical calculations.

Water Dimer under Electric Fields: An Investigation up to Quantum Accuracy.

It is well-established that strong electric fields (EFs) can align water dipoles, partially order the H-bond network of liquid water, and induce water splitting and proton transfers. To illuminate the fundamental behavior of water under external EFs, we present the first benchmark, to the best of our knowledge, of DFT calculations of the water dimer exposed to intense EFs against coupled cluster calculations. The analyses of the vibrational Stark effect and electron density provide a consistent picture of the intermolecular charge transfer effects driven along the H-bond by the increasing applied field at all theory levels.

Highly Luminescent TCNQ in Melamine.

Optical properties of molecules change drastically as a result of interactions with surrounding environments as observed in solutions, clusters, and aggregates. Here, we make 7,7,8,8-tetracyanoquinodimethane (TCNQ) highly luminescent by encapsulating it in crystalline melamine. Colored single crystals are synthesized by slow evaporation of aqueous tetrahydrofuran solutions of melamine and TCNQ.

Effect of N Atom Substitution on Electronic Resonances: A 2D Photoelectron Spectroscopic and Computational Study of Anthracene, Acridine, and Phenazine Anions.

The accommodation of an excess electron by polycyclic aromatic hydrocarbons (PAHs) has important chemical and technological implications ranging from molecular electronics to charge balance in interstellar molecular clouds. Here, we use two-dimensional photoelectron spectroscopy and equation-of-motion coupled-cluster calculations of the radical anions of acridine (CHN) and phenazine (CHN) and compare our results for these species to those for the anthracene anion (CH). The calculations predict the observed resonances and additionally find low-energy two-particle-one-hole states, which are not immediately apparent in the spectra, and offer a slightly revised interpretation of the resonances in anthracene.

Decomposition of HCN during Experimental Impacts in Dry and Wet Planetary Atmospheres.

Hydrogen cyanide (HCN), a key molecule of significant importance in contemporary perspectives on prebiotic chemistry, originates in planetary atmospheres from various processes, such as photochemistry, thermochemistry, and impact chemistry, as well as from delivery by impacts. The resilience of HCN during periods of heavy bombardment, a phenomenon caused by an influx of material on unstable trajectories after accretion, remains relatively understudied. This study extensively investigates the stability of HCN under impact conditions simulated using a laboratory Nd:YAG laser in the ELISE experimental setup.

Radical ligand transfer: mechanism and reactivity governed by three-component thermodynamics.

Here, we demonstrate that the relationship between reactivity and thermodynamics in radical ligand transfer chemistry can be understood if this chemistry is dissected as concerted ion-electron transfer (cIET). Namely, we investigate radical ligand transfer reactions from the perspective of thermodynamic contributions to the reaction barrier: the diagonal effect of the free energy of the reaction, and the off-diagonal effect resulting from asynchronicity and frustration, which we originally derived from the thermodynamic cycle for concerted proton-electron transfer (cPET). This study on the OH transfer reaction shows that the three-component thermodynamic model goes beyond cPET chemistry, successfully capturing the changes in radical ligand transfer reactivity in a series of model Fe-OH⋯(diflouro)cyclohexadienyl systems.

Condensed Matter Systems Exposed to Radiation: Multiscale Theory, Simulations, and Experiment.

This roadmap reviews the new, highly interdisciplinary research field studying the behavior of condensed matter systems exposed to radiation. The Review highlights several recent advances in the field and provides a roadmap for the development of the field over the next decade. Condensed matter systems exposed to radiation can be inorganic, organic, or biological, finite or infinite, composed of different molecular species or materials, exist in different phases, and operate under different thermodynamic conditions.

Lipid conjugate dissociation analysis improves the in vivo understanding of lipid-based nanomedicine.

Lipid conjugates have advanced the field of lipid-based nanomedicine by promoting active-targeting (ligand, peptide, antibody), stability (PEGylation), controlled release (lipoid prodrug), and probe-based tracking (fluorophore). Recent findings indicate lipid conjugates dissociating from nanomedicine upon encountering a biological environment. Yet, implications for (pre)clinical outcomes remain unclear.

Are Redox-Active Centers Bridged by Saturated Flexible Linkers Systematically Electrochemically Independent?

The extent to which electrophores covalently bridged by a saturated linker are electrochemically independent was investigated considering the charge/spin duality of the electron and functionality of the electrophore as a spin carrier upon reduction. By combining computational modeling with electrochemical experiments, we investigated the mechanism by which tethered electrophores react together within 4,4'-oligo[n]methylene-bipyridinium assemblies (with n=2 to 5). We show that native dicationic electrophores (redox state Z=+2) are folded prior to electron injection into the system, allowing the emergence of supra-molecular orbitals (supra-MOs) likely to support the process of the reductive σ bond formation giving cyclomers.

Dynamics of collisions and uptake of alcohol molecules with hydrated nitric acid clusters.

We investigate the collisions of different alcohol molecules with hydrated nitric acid clusters using a molecular beam experiment and molecular dynamics simulations. The uptake cross sections for the molecules evaluated from the experiment are in excellent agreement with the simulations. This suggests that (i) the nontrivial assumptions implemented in the evaluation procedure of the experimental data are valid, and (ii) the simulations describe correctly the major processes in the molecule-cluster collisions.

Gas-phase ion mobility of protonated aldehydes in helium measured using a selected ion flow-drift tube.

Rationale: In soft chemical ionization mass spectrometry, analyte ions are produced via ion-molecule reactions in the reactor. When an electric field E is imposed, the ion drift velocity v determines the reaction time and the effective ion temperature. Agreement between experimental ion mobilities and theoretical predictions confirms the accuracy of the ion residence time measurement procedure.

Selected ice nanoparticle accelerator hypervelocity impact mass spectrometer (SELINA-HIMS): features and impacts of charged particles.

The selected ice nanoparticle accelerator, SELINA, was used to prepare beams of single ice particles with positive or negative charge. Positively charged particles were prepared from deionized water and 0.05-0.

Synergistic photogeneration of nitric oxide and singlet oxygen by nanofiber membranes via blue and/or red-light irradiation: Strong antibacterial action.

New functionalities were added to biocompatible polycaprolactone nanofiber materials through the co-encapsulation of chlorin e6 trimethyl ester (Ce6) photogenerating singlet oxygen and absorbing light both in the blue and red regions, and using 4-(N-(aminopropyl)-3-(trifluoromethyl)-4-nitrobenzenamine)-7-nitrobenzofurazan, NO-photodonor (NOP), absorbing light in the blue region of visible light. Time-resolved and steady-state luminescence, as well as absorption spectroscopy, were used to monitor both photoactive compounds. The nanofiber material exhibited photogeneration of antibacterial species, specifically nitric oxide and singlet oxygen, upon visible light excitation.

Influence of proline and hydroxyproline as antimicrobial and anticancer peptide components on the silver(I) ion activity: structural and biological evaluation with a new theoretical and experimental SAR approach.

Silver(I) complexes with proline and hydroxyproline were synthesized and structurally characterized and crystal structure analysis shows that the formulas of the compounds are {[Ag(Pro)(NO)]NO} (AgPro) (Pro = L-proline) and {[Ag(Hyp)(NO)]NO} (AgHyp) (Hyp = -4-hydroxy-L-proline). Both complexes crystallize in the monoclinic lattice with space group 2 with a carboxylate bidentate-bridging coordination mode of the organic ligands Pro and Hyp (with NH and COO groups in zwitterionic form). Both complexes have a distorted seesaw (C) geometry around one silver(I) ion with values of 58% (AgPro) and 51% (AgHyp).

A Novel Abiotic Pathway for Phosphine Synthesis over Acidic Dust in Venus' Atmosphere.

Recent ground-based observations of Venus have detected a single spectral feature consistent with phosphine (PH) in the middle atmosphere, a gas which has been suggested as a biosignature on rocky planets. The presence of PH in the oxidized atmosphere of Venus has not yet been explained by any abiotic process. However, state-of-the-art experimental and theoretical research published in previous works demonstrated a photochemical origin of another potential biosignature-the hydride methane-from carbon dioxide over acidic mineral surfaces on Mars.

Transition metal complexes of the (2,2,2-trifluoroethyl)phosphinate NOTA analogue as potential contrast agents for F magnetic resonance imaging.

A new hexadentate 1,4,7-triazacyclononane-based ligand bearing three coordinating methylene-(2,2,2-trifluoroethyl)phosphinate pendant arms was synthesized and its coordination behaviour towards selected divalent (Mg, Ca, Mn, Fe, Co, Ni, Cu, Zn) and trivalent (Cr, Fe, Co) transition metal ions was studied. The ligand forms stable complexes with late divalent transition metal ions (from Co to Zn) and the complexes of these metal ions are formed above pH ∼3. A number of complexes with divalent metal ions were structurally characterized by means of single-crystal X-ray diffraction.

Photoelectron spectroscopy of the deprotonated tryptophan anion: the contribution of deprotomers to its photodetachment channels.

Photoelectron spectroscopy and electronic structure calculations are used to investigate the electronic structure of the deprotonated anionic form of the aromatic amino acid tryptophan, and its chromophore, indole. The photoelectron spectra of tryptophan, recorded at different wavelengths across the UV, consist of two direct detachment channels and thermionic emission, whereas the = 4.66 eV spectrum of indole consists of two direct detachment features.

The Enigma of Methanol Synthesis by Cu/ZnO/AlO-Based Catalysts.

The activity and durability of the Cu/ZnO/AlO (CZA) catalyst formulation for methanol synthesis from CO/CO/H feeds far exceed the sum of its individual components. As such, this ternary catalytic system is a prime example of synergy in catalysis, one that has been employed for the large scale commercial production of methanol since its inception in the mid 1960s with precious little alteration to its original formulation. Methanol is a key building block of the chemical industry.