Intermolecular interactions probed by rotational dynamics in gas-phase clusters.

The rotational dynamics of a molecule is sensitive to neighboring atoms or molecules, which can be used to probe the intermolecular interactions in the gas phase. Here, we real-time track the laser-driven rotational dynamics of a single N molecule affected by neighboring Ar atoms using coincident Coulomb explosion imaging. We find that the alignment trace of N-N axis decays fast and only persists for a few picoseconds when an Ar atom is nearby.

Ultrafast photoinduced C-H bond formation from two small inorganic molecules.

The formation of carbon-hydrogen (C-H) bonds via the reaction of small inorganic molecules is of great significance for understanding the fundamental transition from inorganic to organic matter, and thus the origin of life. Yet, the detailed mechanism of the C-H bond formation, particularly the time scale and molecular-level control of the dynamics, remain elusive. Here, we investigate the light-induced bimolecular reaction starting from a van der Waals molecular dimer composed of two small inorganic molecules, H and CO.

Femtosecond Collisional Dissipation of Vibrating D_{2}^{+} in Helium Nanodroplets.

We explored the collision-induced vibrational decoherence of singly ionized D_{2} molecules inside a helium nanodroplet. By using the pump-probe reaction microscopy with few-cycle laser pulses, we captured in real time the collision-induced ultrafast dissipation of vibrational nuclear wave packet dynamics of D_{2}^{+} ion embedded in the droplet. Because of the strong coupling of excited molecular cations with the surrounding solvent, the vibrational coherence of D_{2}^{+} in the droplet interior only lasts for a few vibrational periods and completely collapses within 140 fs.

Wave-Packet Surface Propagation for Light-Induced Molecular Dynamics.

Recent advances in laser technology have enabled tremendous progress in light-induced molecular reactions, at the heart of which the breaking and formation of chemical bonds are located. Such progress has been greatly facilitated by the development of an accurate quantum-mechanical simulation method, which, however, does not necessarily accompany clear dynamical scenarios and is rather computationally heavy. Here, we develop a wave-packet surface propagation (WASP) approach to describe the molecular bond-breaking dynamics from a hybrid quantum-classical perspective.

NatD epigenetically activates FOXA2 expression to promote breast cancer progression by facilitating MMP14 expression.

N-α-acetyltransferase D (NatD) mediates N-α-terminal acetylation of histone H4 (Nt-Ac-H4), but its role in breast cancer metastasis remains unknown. Here, we show that depletion of NatD directly represses the expression of FOXA2, and is accompanied by a significant reduction in Nt-Ac-H4 enrichment at the FOXA2 promoter. We show that NatD is commonly upregulated in primary breast cancer tissues, where its expression level correlates with FOXA2 expression, enhanced invasiveness, and poor clinical outcomes.

Tunnelling of electrons via the neighboring atom.

As compared to the intuitive process that the electron emits straight to the continuum from its parent ion, there is an alternative route that the electron may transfer to and be trapped by a neighboring ionic core before the eventual release. Here, we demonstrate that electron tunnelling via the neighboring atomic core is a pronounced process in light-induced tunnelling ionization of molecules by absorbing multiple near-infrared photons. We devised a site-resolved tunnelling experiment using an Ar-Kr ion as a prototype system to track the electron tunnelling dynamics from the Ar atom towards the neighboring Kr by monitoring its transverse momentum distribution, which is temporally captured into the resonant excited states of the Ar-Kr before its eventual releasing.

Probing and Steering Attosecond Electron Motion Using Tailored Ultrafast Laser Fields.

An ultrafast intense laser field is one of the most important tools to observe and manipulate electronic and nuclear dynamics with subcycle precision in highly nonlinear light-matter interactions, which provides access to attosecond chemistry and physics. In this review, we briefly summarize the protocol of attosecond chronoscopy and its application in probing the attosecond photoemission dynamics from atoms and molecules. We also review the control schemes of attosecond electron motion in atoms and molecules as well as molecular bond formation and cleavage with the assistance of tailored femtosecond laser fields.

FOXA2 activates HIF2α expression to promote tumor progression and is regulated by the E3 ubiquitin ligase VHL in renal cell carcinoma.

Renal cell carcinoma (RCC) is a frequent malignancy of the urinary system with high mortality and morbidity. However, the molecular mechanisms underlying RCC progression are still largely unknown. In this study, we identified FOXA2, a pioneer transcription factor, as a driver oncogene for RCC.

Resolving Quantum Interference Black Box through Attosecond Photoionization Spectroscopy.

Multiphoton light-matter interactions invoke a so-called "black box" in which the experimental observations contain the quantum interference between multiple pathways. Here, we employ polarization-controlled attosecond photoelectron metrology with a partial wave manipulator to deduce the pathway interference within this quantum 'black box" for the two-photon ionization of neon atoms. The angle-dependent and attosecond time-resolved photoelectron spectra are measured across a broad energy range.

Stereodynamical Control of D Formation from the Bimolecular Photoreaction in the D-D Dimer.

We report the stereodynamic control of D formation from the laser-induced bimolecular reaction in a weakly bound D-D dimer via impulsive molecular alignment. Using a linearly polarized moderately intense femtosecond pump pulse, the D molecules in the dimer were prealigned prior to the bimolecular reaction triggered by a delayed probe pulse. The rotationally excited D in the dimer was observed to rotate freely as if it were a monomer.

Identifying photoelectron releasing order in strong-field dissociative ionization of H.

Driven by intense laser fields, the outgoing photoelectrons in molecules possess a quiver motion, resulting in the rise of the effective ionization potential. The coupling of the field-dressed ionization potential with abundant molecular dynamics complicates the laser-molecule interactions. Here, we demonstrate an approach to resolve photoelectron releasing order in the dissociative and non-dissociative channels of multiphoton ionization driven by an orthogonally polarized two-color femtosecond laser pulse.

Ultrafast formation dynamics of D from the light-driven bimolecular reaction of the D-D dimer.

The light-driven formation of trihydrogen cation has been attracting considerable attention because of its important role as an initiator of chemical reactions in interstellar clouds. To understand the formation dynamics, most previous studies focused on creating H or D from unimolecular reactions of various organic molecules. Here we observe and characterize the ultrafast formation dynamics of D from a bimolecular reaction, using pump-probe experiments that employ ultrashort laser pulses to probe its formation from a D-D dimer.

Manipulating Parallel and Perpendicular Multiphoton Transitions in H_{2} Molecules.

We demonstrate that dissociative ionization of H_{2} can be fully manipulated in an angle-time-resolved fashion, employing a polarization-skewed (PS) laser pulse in which the polarization vector rotates. The leading and falling edges of the PS laser pulse, characterized by unfolded field polarization, trigger, sequentially, parallel and perpendicular transitions of stretching H_{2} molecules, respectively. These transitions result in counterintuitive proton ejections that deviate significantly from the laser polarization directions.

The SMARCA4 mutation facilitates chromatin remodeling and confers PRMT1/SMARCA4 inhibitors sensitivity in colorectal cancer.

Genomic studies have demonstrated a high frequency of genetic alterations in components of the SWI/SNF complex including the core subunit SMARCA4. However, the mechanisms of tumorigenesis driven by SMARCA4 mutations, particularly in colorectal cancer (CRC), remain largely unknown. In this study, we identified a specific, hotspot mutation in SMARCA4 (c.

Electron transfer in strong-field three-body fragmentation of ArKr trimers.

We experimentally studied the three-body fragmentation dynamics of a noble gas cluster (ArKr) upon its multiple ionization by an intense femtosecond laser pulse. The three-dimensional momentum vectors of correlated fragmental ions were measured in coincidence for each fragmentation event. A novel comet-like structure was observed in the Newton diagram of the quadruple-ionization-induced breakup channel of ArKr → Ar + Kr + Kr.

Enhancing Strong-Field Dissociation of H_{2}^{+} in Helium Nanodroplets.

We investigate the above-threshold multiphoton ionization of H_{2} embedded in superfluid He nanodroplets driven by ultraviolet femtosecond laser pulses. We find that the surrounding He atoms enhance the dissociation of in-droplet H_{2}^{+} from lower vibrational states as compared to that of isolated gas-phase molecules. As a result, the discrete peaks in the photoelectron energy spectrum correlated with the HHe^{+} from the dissociative in-droplet molecule shift to higher energies.

Rabi oscillations in a stretching molecule.

Rabi oscillation is an elementary laser-driven physical process in atoms and artificial atoms from solid-state systems, while it is rarely demonstrated in molecules. Here, we investigate the bond-length-dependent Rabi oscillations with varying Rabi frequencies in strong-laser-field dissociation of H. The coupling of the bond stretching and Rabi oscillations makes the nuclei gain different kinetic energies while the electron is alternatively absorbing and emitting photons.

Probing Resonant Photoionization Time Delay by Self-Referenced Molecular Attoclock.

Attosecond time-resolved electron tunneling dynamics have been investigated by using attosecond angular streaking spectroscopy, where a clock reference to the laser field vector is required in atomic strong-field ionization and the situation becomes complicated in molecules. Here we reveal a resonant ionization process via a transient state by developing an electron-tunneling-site-resolved molecular attoclock in Ar-Kr^{+}. Two distinct deflection angles are observed in the photoelectron angular distribution in the molecular frame, corresponding to the direct and resonant ionization pathways.

Atomic partial wave meter by attosecond coincidence metrology.

Attosecond chronoscopy is central to the understanding of ultrafast electron dynamics in matter from gas to the condensed phase with attosecond temporal resolution. It has, however, not yet been possible to determine the timing of individual partial waves, and steering their contribution has been a substantial challenge. Here, we develop a polarization-skewed attosecond chronoscopy serving as a partial wave meter to reveal the role of each partial wave from the angle-resolved photoionization phase shifts in rare gas atoms.

Femtosecond Rotational Dynamics of D_{2} Molecules in Superfluid Helium Nanodroplets.

Rotational dynamics of D_{2} molecules inside helium nanodroplets is induced by a moderately intense femtosecond pump pulse and measured as a function of time by recording the yield of HeD^{+} ions, created through strong-field dissociative ionization with a delayed femtosecond probe pulse. The yield oscillates with a period of 185 fs, reflecting field-free rotational wave packet dynamics, and the oscillation persists for more than 500 periods. Within the experimental uncertainty, the rotational constant B_{He} of the in-droplet D_{2} molecule, determined by Fourier analysis, is the same as B_{gas} for an isolated D_{2} molecule.

Light-Induced Ultrafast Molecular Dynamics: From Photochemistry to Optochemistry.

By precisely controlling the waveform of ultrashort laser fields, electronic and nuclear motions in molecules can be steered on extremely short time scales, even in the attosecond regime. This new research field, termed "optochemistry", presents the light field in the time-frequency domain and opens new avenues for tailoring molecular reactions beyond photochemistry. This Perspective summarizes the ultrafast laser techniques employed in recent years for manipulating the molecular reactions based on waveform control of intense ultrashort laser pulses, where the chemical reactions can take place in isolated molecules, clusters, and various nanosystems.

DDX21 Interacts with WDR5 to Promote Colorectal Cancer Cell Proliferation by Activating CDK1 Expression.

DEAD-box RNA helicase 21 (DDX21), is a nucleolar protein harboring ATP-dependent double-stranded RNA unwinding activities, essential in rRNA processing and ribosome biogenesis. However, its role in colorectal cancer (CRC) progression remains unclear. In this study, we show that knockdown of DDX21 significantly inhibited CRC cell proliferation and blocked cell cycle at the G2/M phase.

Transient Valence Charge Localization in Strong-Field Dissociative Ionization of HCl Molecules.

Probing transient charge localization in the innershell orbital of atoms and molecules has been made possible by the recent progress of advanced light sources. Here, we demonstrate that the ultrafast electron tunneling ionization by an intense femtosecond laser pulse could induce an asymmetric transient charge localization in the valence shell of the HCl molecule during the dissociative ionization process. The transient charge localization is encoded in the laser impulse acquired by the outgoing ionic fragments, and the asymmetry is revealed by carefully examining the electron tunneling-site distinguished momentum angular distribution of the ejected H^{+} fragments.

Transcriptional silencing of fetal hemoglobin expression by NonO.

Human fetal globin (γ-globin) genes are developmentally silenced after birth, and reactivation of γ-globin expression in adulthood ameliorates symptoms of hemoglobin disorders, such as sickle cell disease (SCD) and β-thalassemia. However, the mechanisms by which γ-globin expression is precisely regulated are still incompletely understood. Here, we found that NonO (non-POU domain-containing octamer-binding protein) interacted directly with SOX6, and repressed the expression of γ-globin gene in human erythroid cells.