Helvetica Chimica Acta最新文献

Native mass spectrometry ionizes biomolecules from aqueous buffered solutions using electrospray ionization. Collisions and lasers are often used to study the structures of such native biomolecular ions. While structural changes upon collisions have been studied in more detail, interactions with photons mostly comprise fragmentation. It remains unclear to what degree biomolecular ions undergo unfolding until cleavage. Here, gas-phase Förster resonance energy transfer (FRET) is used to study fluorescence lifetimes of a 32-residue α-helical peptide to monitor peptide unfolding. Increases in lifetime of up to 1.2 ns per charge are observed for different charge states, showing that a low charge is necessary for peptides to retain a compact structure. Increases in lifetime by up to 0.5 ns are observed upon collisional and laser-based activation and show that the peptide is partially unfolding upon activation. The results contribute to understanding the unfolding dynamics of biomolecules upon activation in mass spectrometry experiments.

The hydrolysis of dihydrazides was studied at different pH values in water at 25 °C. The resulting species were analyzed by HPLC, ¹H-NMR, and MALDI-TOF mass spectrometry. Among these species, unexpected molecules bearing carboxylate moieties were detected. Based on this analysis, a 2-step hydrolysis mechanism was proposed involving the formation of cyclic and linear intermediates before the addition of a water molecule to lead to carboxylate moieties. The first step was shown to be rate-determining and catalyzed in acidic conditions. To the best of our knowledge, this study shows for the first time that the hydrolysis of some dihydrazides can spontaneously occur in mild aqueous conditions, contrary to monohydrazides which do not reveal such a hydrolysis in same conditions. This draws attention to an overlooked degradation which might need more consideration, and possibly highlights new ways of soft hydrolysis conditions.

We present electric dipole polarizability calculations employing atomic-orbitals based linear response theory within the Kohn-Sham Density Functional Theory (KS-DFT) framework, considering both non-periodic and periodic boundary conditions. We adopt the optimization scheme introduced by T. Helgaker et al. in Chemical Physics Letters 327, 397 (2000) for the single-electron atomic-orbitals density matrix. We conduct a comparative analysis between the static polarizability computed using atomic orbitals-based and previously implemented molecular orbitals-based methods. In our calculations involving periodic boundary conditions, we implement polarizability calculation using velocity representation of the electric dipole operator in atomic orbitals-based algorithm, subsequently comparing the results with those computed using the Berry-phase formulation and velocity representation in molecular orbitals-based algorithm. We investigate 10 small and medium-sized molecules in the gas phase, analyze liquid-phase systems with up to 256 water molecules, and the solid-state structures of anatase TiO₂ and bulk WO₃. All polarizability results obtained from the AO-based solver exhibit good agreement with MO-based results. From our example calculations, we find that the AO-based solver exhibits better computational scaling and less memory demand than the MO-based solvers, which makes it better suited for very large systems.

The beginning of 2025 marks the completion of our first 3-year mandate as Editors-in-Chief of Helvetica Chimica Acta. This has been an exciting and intensive period of time, which has allowed us to drive forward our vision for the journal. We are now delighted to renew our commitment with Helvetica for a second (and last) three year mandate. Having said that, we also feel that now it is the right time to reflect on what we have achieved so far and to give new impulses for the future.

Thermoresponsive polymers, which undergo phase transitions within physiologically tolerated temperatures, are key to developing drug delivery systems (DDS) with precise spatial and temporal control, potentially addressing challenges associated with the treatment of complex diseases. Inorganic nanoparticles with unique optical, electronic, and magnetic properties serve as efficient transducers, converting external stimuli into localized heat to trigger thermoresponsive nanocarriers. This review explores the design and application of thermoresponsive nanocarriers transduced by inorganic nanoparticles as DDS. Following a brief description of temperature-triggered phase transition of polymers and heat generation mechanisms by inorganic nanoparticles, strategies to integrate these components into hybrid systems are described. Examples demonstrating the utility of these hybrid systems as advanced DDS are discussed, highlighting their potential for precise drug release alongside theranostic capabilities by combining therapy with imaging. Despite the challenges in design, synthesis, and biological applications, thermoresponsive polymer-inorganic hybrids hold immense promise for transforming drug delivery and biomedical innovations.

Carbonyl-tethered alkylidenecyclopropanes can react with aryl isocyanates in presence of Pd(0)-phosphoramidite catalysts to give seven-membered heterobicyclic products in a formal [3+2+2] cycloaddition process. The reaction involves the formation of a palladium π-allyl complex intermediate (A), which behaves as a formal 1,5-dipole, and can be trapped by externally added isocyanates. This report also includes preliminary assays of asymmetric variants, as well as DFT computational studies that shed some light on the nature of the catalytic cycle.

We report two catalytic enantioselective borylation/oxidation sequences that streamline access to either enantioenriched 1,2- or 1,3-diols starting from O-benzyl-protected allylic alcohols as a single precursor. The approach takes advantage of the complementary regioselectivity of the Cu-catalyzed protoboration and the Cu-catalyzed hydroboration of disubstituted alkenes, which effectively install a borane function and a hydrogen atom on opposite C(sp²) carbon atoms of a carbon–carbon double bond. The two methods feature broad substrate scope and are amenable to large scale without measurable loss of the catalytic efficiency. Both protocols display high levels of regioselectivity and enantioselectivity.

The integration of sustainable practices, such as employing renewable light sources for synthesizing valuable synthetic scaffolds, has been progressing over the past few decades. Among these noteworthy organic frameworks, lactams, particularly γ-lactams, have established their prominence due to their extensive applications in the pharmaceutical, agricultural, and medicinal domains. This growing significance of γ-lactams has spurred considerable interest in their synthesis, especially via milder, more sustainable, and environmentally friendly methods. In recent years, numerous innovative reaction mechanisms have been explored, highlighting how photocatalysis can enable the formation of γ-lactams from readily accessible precursors through C−N bond formation and cyclization processes. This review emphasizes the potential of photocatalytic strategies to not only enhance current synthetic methods for γ-lactams but also foster the development of greener and more sustainable chemical processes for the future.