Engineering topics
Jin, Rui
Publications and source records attributed to Jin, Rui.
Time-resolving state-specific molecular dissociation with XUV broadband absorption spectroscopy
The electronic and nuclear dynamics inside molecules are essential for chemical reactions, where different pathways typically unfold on ultrafast timescales. Extreme ultraviolet (XUV) light pulses generated by free-electron lasers (FELs) allow atomic-site and electronic-state selectivity, triggering specific molecular dynamics while providing femtosecond resolution. Yet, time-resolved experiments are either blind to neutral fragments or limited by the spectral bandwidth of FEL pulses. Here, we combine a broadband XUV probe pulse from high-order harmonic generation with an FEL pump pulse to observe dissociation pathways leading to fragments in different quantum states. We temporally resolve the dissociation of a specific O 2 + state into two competing channels by measuring the resonances of ionic and neutral fragments. This scheme can be applied to investigate convoluted dynamics in larger molecules relevant to diverse science fields.
X-ray multiphoton-induced Coulomb explosion images complex single molecules
Following structural dynamics in real time is a fundamental goal towards a better understanding of chemical reactions. Recording snapshots of individual molecules with ultrashort exposure times is a key ingredient towards this goal, as atoms move on femtosecond (10 -15 s) timescales. For condensed-phase samples, ultrafast, atomically resolved structure determination has been demonstrated using X-ray and electron diffraction. Pioneering experiments have also started addressing gaseous samples. However, they face the problem of low target densities, low scattering cross sections and random spatial orientation of the molecules. Therefore, obtaining images of entire, isolated molecules capturing all constituents, including hydrogen atoms, remains challenging. Here we demonstrate that intense femtosecond pulses from an X-ray free-electron laser trigger rapid and complete Coulomb explosions of 2-iodopyridine and 2-iodopyrazine molecules. We obtain intriguingly clear momentum images depicting ten or eleven atoms, including all the hydrogens, and thus overcome a so-far impregnable barrier for complete Coulomb explosion imaging—its limitation on molecules consisting of three to five atoms. In combination with state-of-the-art multi-coincidence techniques and elaborate theoretical modelling, this allows tracing ultrafast hydrogen emission and obtaining information on the result of intramolecular electron rearrangement. Our work represents an important step towards imaging femtosecond chemistry via Coulomb explosion.
Involvement of TFAP2A in the activation of GSDMD gene promoter in hyperoxia-induced ALI
Highlights: • Hyperoxia exposure increases GSDMD expression in rat lung tissue and A549 cells. • The core promoter region of GSDMD located in −98/-12 bp relative to TSS. • E2F4 and TFAP2A positively regulate the basal transcriptional activity of GSDMD by directly binding to its promoter. • TFAP2A directly drives the expression of GSDMD in hyperoxia-inducedA549 cells. • TFAP2A expression is increased in lung tissues of rats with hyperoxia-induced ALI and linearly correlated with GSDMD. Oxygen therapy is a common treatment in neonatal intensive care units, but long-term continuous hyperoxia ventilation may induce acute lung injury (ALI). Gasdermin D (GSDMD)-mediated pyroptosis participates in various diseases including ALI, but the role of GSDMD in hyperoxia-induced ALI is yet understood. Here, we showed a significant increase in GSDMD after exposure to high oxygen. To elucidate the molecular mechanisms involved in GSDMD regulation, we identified the core promoter of GSDMD, −98 ~ −12 bp relative to the transcriptional start site (TSS). The results of mutational analysis, overexpression or siRNA interference, EMSA and ChIP demonstrated that E2F4 and TFAP2A positively regulate the transcriptional activity of the GSDMD by binding to its promoter. However, only TFAP2A showed a regulatory effect on the expression of GSDMD. Moreover, TFAP2A was increased in the lung tissues of rats exposed to hyperoxia and showed a strong linear correlation with GSDMD. Our results indicated that TFAP2A positively regulates the GSDMD expression via binding to the promoter region of GSDMD.