Chemical protein synthesis has emerged as a powerful approach for producing ubiquitin (Ub) and ubiquitin-like modifiers (Ubls) in both their free and conjugated forms, particularly when recombinant or enzymatic strategies are challenging. By providing precise control over the assembly of Ub and Ubls, chemical synthesis enables the generation of complex constructs with site-specific modifications that facilitate detailed functional and structural studies. Ub and Ubls are central regulators of protein homeostasis, regulating a wide range of cellular processes such as cell cycle progression, transcription, DNA repair, and apoptosis. Ubls share an evolutionary link with Ub, resembling its structure and following a parallel conjugation pathway that results in a covalent isopeptide bond with their cellular substrates. Despite their structural similarities and sequence homology, Ub and Ubls exhibit distinct functional differences. Understanding Ubl biology is essential for unraveling how cells maintain their regulatory networks and how disruptions in these pathways contribute to various diseases. In this review, we highlight the chemical methodologies and strategies available for studying Ubls and advancing our comprehensive understanding of the Ubl system in health and disease.

We demonstrate that calculating the spontaneous emission decay rate from metastable resonance states (states with finite lifetimes embedded in the continuum) requires considering transitions to all continuum states, not just to lower states. This holds even when the lifetimes of the metastable states are very long and might be effectively considered as bound states in the continuum. However, employing complex-scaling transformations, this computationally prohibitive task becomes feasible by utilizing methods originally designed for excited bound states for calculation of complex poles of the scattering matrix. As an illustrative example, these methods are applied to calculate the spontaneous emission decay rates of metastable resonance states in a double-barrier potential. The rapid numerical convergence of this approach highlights a new avenue for studying spontaneous emission from metastable states in real-life systems, particularly in many-electron systems, where calculation of the spontaneous emission decay rate from metastable resonances (e.g., autoionization states) is computationally difficult, if not impossible, using the standard (Hermitian) formalism of quantum mechanics.

CO2-containing synthesis gas is a relevant feedstock for the production of synthetic fuels using Fischer-Tropsch Synthesis. We report the role of CO2 in CO2, CO and H2 mixed feeds over a cobalt-based catalyst at 220 °C and 21 bar in a packed bed reactor. The C5+ selectivity remains above 78 % even for CO2-rich synthesis gas with 75 % CO2/(CO+CO2). Using 13CO2 isotopic labeling, the increase in methane selectivity is attributed to both CO and CO2 methanation, which is limited by maintaining a H2/CO outlet ratio below 10 and an outlet CO partial pressure above 0.2 bar, respectively. Operando modulated DRIFTS confirms a positive relationship between CO surface coverage and CO partial pressure. From DFT and microkinetic modeling, enhanced CO and CO2 methanation could be attributed to a lower CO surface coverage and a higher H2 surface coverage. This work identifies boundaries for efficient cobalt-catalyzed mixed-feed FTS for synthetic fuels production.

Plastic pollution poses a significant threat to soil ecosystems, yet the role of volatile organic compounds (VOCs) in plastic degradation is not well-studied. The present research focuses on the impact of polyethylene (PE), polylactic acid (PLA), and poly(butylene-adipate-co-terephthalate) (PBAT) residues on soil in a 12-week long lab-scale aerobic experiment. The study focused on the dynamics of VOC profiles, soil physicochemical properties, and microbial communities. PBAT, known for its biodegradability, produced a distinct VOC profile with hazardous compounds such as 1,3-butadiene, which is consistently associated with cardiovascular diseases and leukemia. Microbial analysis of PBAT revealed distinct bacterial and fungal diversity responses, along with unique KEGG pathway profiles compared to PE and PLA, suggesting its biodegradation process may involve biofilm formation and quorum sensing. Correlation analysis based on the relevant abundance of specific microbes exhibited strong positive correlations, such as Streptomyces with propyne emission and Hydrogenispora with ethylene emission. These results demonstrated distinct biodegradation patterns of various plastics in soil, identified through the combination of VOC detection and microbiome analysis.

The analysis of symmetries is extremely useful across science. In Physics, symmetries are used to derive conservation laws and selection rules for transitions in interacting systems. In the early days of nonlinear optics (NLO), symmetries were used to formulate a set of rules for photonic processes according to the medium's symmetries that are reflected in the NLO coefficient tensor. While this approach was believed to be complete and closed, the field has recently reignited as multi-color ultrashort laser pulses with tailored polarization and spatiotemporal structures become standard in NLO. A more complete theory has been recently emerging, which aims to incorporate all possible dynamical degrees of freedom of light: spin and orbital angular momentum, spatial structure, time-dependent polarizations, temporal envelopes, etc., in addition to the symmetries of the medium. This theoretical development is also accompanied by experimental advances that rely on tailored light beams that can now be generated with ever-increasing complexity, including topologies in real and a variety of synthetic dimensions, carrying poly-chromatic carrier waves, time-dependent varying angular momenta, local-chirality, and more. The nonlinear interactions between light fields with unique symmetries (or asymmetries) and matter is especially appealing, since that holds the key for developing new ultrafast spectroscopies with sub-femtosecond resolution, for exerting exact control over matter, and improving our fundamental understanding of how light and matter interact. We review these recent advances in this expanding field, focusing on the theory, its implications, and seminal experiments. We aim to establish a comprehensive database of symmetries and selection rules governing NLO light-matter interactions within the emerging new formalism, and invite the scientific community to contribute to this effort.

Polybenzenoid hydrocarbons (PBHs) are widely studied for their semiconductive properties and potential applications in organic electronics and photochemistry. Understanding their behavior in excited states is crucial for optimizing their performance in these applications. Here, we computationally investigate a dataset of 43 unbranched cata-condensed PBHs in their first singlet excited state (S₁), revealing clear correlations between molecular structure and electronic properties. By analyzing these molecules through their annulation patterns—specifically the arrangement of linear (L) and angular (A) tricyclic subunits and tetracyclic zigzag (Z) and curve (C) motifs—we establish a predictive hierarchy (L > Z > C > A) for the location of unpaired electrons and Baird-antiaromaticity. This structural approach enables semiquantitative prediction of key properties, including excitation energies, magnetic response, and singlet fission capability. Notably, we find that singlet fission propensity is dependent on both the length of the Longest L sequence and the position of the L motifs within the sequence. These insights, derived from the analysis of small tri- and tetracyclic components and validated on larger systems, provide a practical framework for understanding and designing PBH-based materials.

Chiral systems exhibit unique properties traditionally linked to their asymmetric spatial arrangement. Recently, multiple laser pulses were shown to induce purely electronic chiral states without altering the nuclear configuration. Here we propose and numerically demonstrate a simpler realization of light-induced electronic chirality that is long-lived and occurs much before the onset of nuclear motion. Specifically, a single monochromatic circularly-polarized laser pulse can induce electronic chiral currents in an oriented achiral molecule. We analyze this effect with state-of-the-art ab-initio theory and connect the induced electronic chiral currents directly to induced magnetic dipole moments, which are detectable using attosecond transient absorption electronic circular dichroism spectroscopy. Our findings show that the chiral electronic wavepacket rapidly oscillates in handedness at frequencies corresponding to higher-order harmonics of the pump laser's carrier frequency, and the currents survive well after the laser pulse has turned off. Therefore, we propose a light-induced chiral molecular-current analogue to high harmonic generation, paving the way to attosecond transient chirality controlled by a single laser pulse. Such ultrafast chiral transients could enable emerging technologies such as enhanced spintronics, coherent control of chemical reactions, and more.

Incorporation of a BN pair into polycyclic aro- matic hydrocarbons is a common approach for modulating their electronic properties. However, a conceptual and quantitative framework rationalizing the observed effects has not been developed, and general structure-property relationships remain elusive. In this work, we perform a data-driven investigation that leads to concrete principles for rational design of (BN)1-PBHs with targeted properties. We construct a new chemical database, COMPAS-4, which contains the geometries and properties of all possible (BN)1-PBH isomers up to 6 rings, calculated at both the GFN1-xTB and DFT (CAM-B3LYP/def2-SVP) levels of theory. We investigate the influence of BN-substitution on various molecular properties, including their molecular orbital energies and aromaticity, and define specific structural features that determine these properties. Notably, all of these features are chemically intuitive and simple to extract from the structure of the molecule, without any prior computation. We find that the most influential feature is the number of rings whose cyclic delocalization is disturbed as a result of the substitution

Biological membranes play a major role in diffusing protons on their surfaces between transmembrane protein complexes. The retention of protons on the membrane's surface is commonly described by a membrane-associated proton barrier that determines the efficiency of protons escaping from surface to bulk, which correlates with the proton diffusion (PD) dimensionality at the membrane's surface. Here, we explore the role of the membrane's biophysical properties and its ability to accept a proton from a light-triggered proton donor situated on the membrane's surface and to support PD around the probe. By changing lipid composition and temperature, while going through the melting point of the membrane, we directly investigate the role of the membrane phase in PD. We show that the proton transfer process from the proton donor to the membrane is more efficient in the liquid phase of the membrane than in the gel phase, with very low calculated activation energies that are also dependent on the lipid composition of the membrane. We further show that the liquid phase of the membrane allows higher dimensionalities (close to 3) of PD around the probe, indicating lower membrane proton barriers. In the gel phase, we show that the dimensionality of PD is lower, in some cases reaching values closer to 1, thus implying specific pathways for PD, which results in a higher proton recombination rate with the membrane-tethered probe. Computational simulations indicate that the change in PD between the two phases can be correlated to the membrane's ‘stiffness’ and ‘looseness’ at each phase.

The underline physics of resonance high harmonic generation in plasma plumes is still not well understood. A simple model, which is an extension of the well-known three step model predict the capture of the re-colliding electron into an autoionization state and only then return to the ground state while emitting the HHG photon. Another explanation is a better phase matching due to strong variation of the refractive index near resonance. Here we first rule out the second option. Next, we theocratically study the physical mechanism of high-order harmonic generation (HHG) from chromium ions irradiated by intense laser pulses. By performing a combination of state-of-the-art ab-initio and model simulations that agree with well-known experimental observations, we uncover the fundamental physical picture for HHG in Cr⁺. We found that the main contribution to resonance enhancement originates from initially occupied spin-down 3p states, while spin-up 3d electrons negligibly contribute to resonance HHG. We studied the phase and emission time of each harmonic and compare it to experimental results.