Methane activation by B5 + yields CB5H2 + through H2 elimination. Electronic-structure calculations connect the nascent dehydrogenation product to a low-lying isomer containing a planar tetracoordinate carbon atom. ABSTRACT Planar tetracoordinate carbon (ptC) motifs have been identified predominantly in the global-minimum structures of gas-phase clusters generated through laser ablation, limiting access to alternative kinetically persistent structures. Here, gas-phase reactions of mass-selected B5 + clusters with methane at room temperature yield CB5H2 + through H2 elimination, as established by time-of-flight mass spectrometry, isotope labeling, and kinetic measurements. Electronic-structure calculations identify a low-lying ptC-containing isomer accessible from the nascent dehydrogenation product through a multistep rearrangement pathway. Microcanonical analysis indicates that a fraction of the nascent dehydrogenation product population can overcome the highest barrier before collisional deactivation. Once collisionally stabilized, this species is predicted to be kinetically persistent under the experimental conditions. Its bonding pattern combines localized C–B interactions with multicenter σ and π delocalization across the CB5 framework. These results establish CB5H2 + formation and provide computational support for access to a low-lying ptC-containing system.

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The HCO$^+$/HOC$^+$ abundance ratio has been observed to vary significantly in different astrophysical environments, making it an important diagnostic tool for exploring the interstellar medium.…

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Background: In medicine, ionizing radiation can damage cells by generating free radicals, harming healthy tissues during radiotherapy. Radioprotectors help mitigate this damage, but current options often have low efficacy, high cost, or side effects.Objective: This study aimed to investigate α-Tocotrienol, a vitamin E isomer with antioxidant and anti-cancer properties, as a potential radioprotector for brain radiotherapy patients and radiation workers. While its protective effects on normal brain tissue are promising, its potential impact on tumor cells remains a critical consideration for future studies.Material and Methods: This randomized controlled experimental animal study was conducted on healthy male Wistar rats maintained under standardized laboratory conditions. The animals were randomly divided into groups and pretreated with α-Tocotrienol prior to localized brain irradiation. Following irradiation, brain tissues were harvested and evaluated for histopathological alterations and biochemical markers of oxidative stress.Results: Pretreated rats with α-Tocotrienol showed fewer nerve cell injuries compared to untreated irradiated rats. Biochemically, irradiated rats had increased malondialdehyde (oxidative stress marker) and decreased antioxidant enzymes (superoxide dismutase, catalase, glutathione peroxidase), while α-Tocotrienol-treated rats maintained higher enzyme activity. Conclusion: α-Tocotrienol enhances radiation resistance by boosting antioxidant defenses and reducing neuronal damage. However, given the possibility of parallel protection of tumor cells, its clinical translation requires careful evaluation and optimization. Further studies are needed to determine selective dosing strategies and timing that maximize neuroprotection without compromising tumor control.