Despite major progress in the investigation of boron cluster anions, direct experimental study of neutral boron clusters remains a significant challenge because of the difficulty in size selection. Here we report a size-specific study of the neutral B9 cluster using threshold photoionization with a tunable vacuum ultraviolet free electron laser. The ionization potential of B9 is measured to be 8.45 ± 0.02 eV and it is found to have a heptagonal bipyramid D7h structure, quite different from the planar molecular wheel of the B9- anionic cluster. Chemical bonding analyses reveal superior stability of the bipyramidal structure arising from delocalized s and p bonding interactions within the B7 ring and between the B7 ring and the capping atoms. Photoionization of B9 breaks the single-electron B-B bond of the capping atoms, which undergo off-axis distortion to enhance interactions with the B7 ring in the singlet ground state of B9+. The single-electron B-B bond of the capping atoms appears to be crucial in stabilizing the D7h structure of B9. This work opens avenues for direct size-dependent experimental studies of a large variety of neutral boron clusters to explore the stepwise development of network structures.
We have studied the interaction of hydrogen with small neutral and anionic carbon clusters using density functional calculations. The geometry, stability, and electronic structure of these clusters show an odd–even alternation originating in the bonding nature of the carbon atoms. Our mass spectrometric measurements of the abundance of CnH− (n⩽10) cluster anions produced by gas-feed Cs sputtering from different crystallographic forms of carbon display similar odd–even alternation with the even-n clusters being relatively more abundant. The calculated trend in the adiabatic electron affinities shows a behavior similar to the experimental abundance pattern. We discuss a possible partial suppression of the chain-to-ring transformation (which normally occurs at n=10 in Cn−) in CnH− and compare it with our density functional calculations as well as observations in CnN−. We also observe that the size dependence of the abundance of CnH− clusters sputter ejected from a fullerene target exhibits a distinctly different power-law decline compared to crystalline and amorphous carbon.
Abstract Melanoma, the most aggressive skin cancer type, is challenging to treat due to its high metastatic potential and low response to conventional therapies. Innovative approaches, including combination therapies, are crucial for enhancing treatment efficacy while minimizing side effects. It is developed boronophenylalanine‐containing polydopaine (B‐PDA) nanoparticles by encapsulating boronophenylalanine in polydopamine through nitrogen‐boronate coordination, targeting both boron neutron capture therapy (BNCT) and photothermal therapy (PTT). With stability and biocompatibility under physiological conditions, these nanoparticles utilize the phenylalanine residues in BPA to target the overexpressed neutral amino acid transporter 1 (LAT1) in melanoma cells, resulting in enhanced cell‐specific targeting. B‐PDA nanoparticles demonstrated significant photothermal effects under external stimulation, inducing localized heating and triggering heterogeneous tumor cell death, thereby enhancing sensitivity to BNCT. Combining BNCT and PTT, the B‐PDA nanoparticles offer a promising strategy for melanoma treatment.
Abstract Despite the growing application of tetrazine bioorthogonal chemistry, it is still challenging to access tetrazines conveniently from easily available materials. Described here is the de novo formation of tetrazine from nitriles and hydrazine hydrate using a broad array of thiol‐containing catalysts, including peptides. Using this facile methodology, the syntheses of 14 unsymmetric tetrazines, containing a range of reactive functional groups, on the gram scale were achieved with satisfactory yields. Using tetrazine methylphosphonate as a building block, a highly efficient Horner–Wadsworth–Emmons reaction was developed for further derivatization under mild reaction conditions. Tetrazine probes with diverse functions can be scalably produced in yields of 87–93 %. This methodology may facilitate the widespread application of tetrazine bioorthogonal chemistry.
Despite major progress in the investigation of boron cluster anions, direct experimental study of neutral boron clusters remains a significant challenge because of the difficulty in size selection. Here we report a size‐specific study of the neutral B9 cluster using threshold photoionization with a tunable vacuum ultraviolet free electron laser. The ionization potential of B9 is measured to be 8.45 ± 0.02 eV and it is found to have a heptagonal bipyramid D7h structure, quite different from the planar molecular wheel of the B9‐ anionic cluster. Chemical bonding analyses reveal superior stability of the bipyramidal structure arising from delocalized s and p bonding interactions within the B7 ring and between the B7 ring and the capping atoms. Photoionization of B9 breaks the single‐electron B‐B bond of the capping atoms, which undergo off‐axis distortion to enhance interactions with the B7 ring in the singlet ground state of B9+. The single‐electron B‐B bond of the capping atoms appears to be crucial in stabilizing the D7h structure of B9. This work opens avenues for direct size‐dependent experimental studies of a large variety of neutral boron clusters to explore the stepwise development of network structures.
Recent studies have proven that the purinergic signaling pathway plays a key role in neurotransmission and neuromodulation, and is involved in various neurodegenerative diseases and psychiatric disorders. With the characterization of the subtypes of receptors in purinergic signaling, i.e. the P1 (adenosine), P2X (ion channel) and P2Y (G protein-coupled), more attention has been paid to the pathophysiology and therapeutic potential of purinergic signaling in the central nervous system disorders. Alzheimer’s disease (AD) is a progressive and deadly neurodegenerative disease that is characterized by memory loss, cognitive impairment and dementia. However, as drug development aimed to prevent or control AD has series of failures in recent years, more researchers have focused on the neuroprotection-related mechanisms such as purinergic signaling in AD patients to find a potential cure. This article reviews the recent discoveries of purinergic signaling in AD, and summarizes the potential agents as modulators for the receptors of purinergic signaling in AD-related research and treatments. Thus, our paper provides an insight into purinergic signaling in the development of anti- AD therapies.
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