Antioxidant mechanism, spectroscopic and pharmacological properties of four flavonoids: DFT, docking and molecular dynamics.

Myricetin (1), quercetin (2), kaempferol (3) and kaempferide (4) were flavonoids with phenolic hydroxyl groups. The antioxidant and pharmacological mechanisms of them were investigated in detail. The lowest hydroxyl dissociation enthalpies of 1, 2, 3 and 4 were calculated by DFT, respectively. The hydroxyl dissociation enthalpies of the four flavonoids at the O2 site are the highest. By analyzing the intramolecular hydrogen bonds and HOMO-LUMO orbitals of the four flavonoids, the reasons for their divergence of hydroxyl dissociation enthalpies and antioxidant mechanisms were further investigated. The UV-vis and IR spectra of four flavonoids were compared. The interactions about electrostatic attraction, p-π conjugation and hydrogen bond combined the flavonoid with the target protein closely. The root mean square deviation of peroxisome proliferator-activated receptor γ combined with 1, 2 and 3 increased, while that of PPARγ combined with 4 decreased.

Quantum metric and metrology with parametrically-driven Tavis-Cummings models.

We study the quantum metric in a driven Tavis-Cummings model, comprised of multiple qubits interacting with a quantized photonic field. The parametrical driving of the photonic field breaks the system's U(1) symmetry down to a Z2 symmetry, whose spontaneous breaking initiates a superradiant phase transition. We analytically solved the eigenenergies and eigenstates, and numerically simulated the system behaviors near the critical point. The critical behaviors near the superradiant phase transition are characterized by the quantum metric, defined in terms of the response of the quantum state to variation of the control parameter. In addition, a quantum metrological protocol based on the critical behaviors of the quantum metric near the superradiant phase transition is proposed, which enables greatly the achievable measurement precision.

Observation of a Superradiant Phase Transition with Emergent Cat States.

Superradiant phase transitions (SPTs) are important for understanding light-matter interactions at the quantum level, and play a central role in criticality-enhanced quantum sensing. So far, SPTs have been observed in driven-dissipative systems, but the emergent light fields did not show any nonclassical characteristic due to the presence of strong dissipation. Here we report an experimental demonstration of the SPT featuring the emergence of a highly nonclassical photonic field, realized with a resonator coupled to a superconducting qubit, implementing the quantum Rabi model. We fully characterize the light-matter state by Wigner matrix tomography. The measured matrix elements exhibit quantum interference intrinsic of a photonic mesoscopic superposition, and reveal light-matter entanglement.

Design, Synthesis, and Molecular Docking Study of Novel 3-Cyanopyridine Derivatives for the Anti-Cancer Drug Target Survivin Protein.

Survivin is an important member of the antiapoptotic protein family and controls the cell's life cycle. Overexpression of survivin in tumor cells leads to inhibition of apoptosis, thus contributing to cancer cell proliferation. The largest binding pocket in the survivin dimer was located in the BIR domain. The key to the efficacy of 3-cyanopyridines was their surface interaction with the survivin amino acid Ile74. METHODS: Through the optimization of the 3-cyanopyridine, 29 new compounds with a 3- Cyanopyridine structure were designed, synthesized, and characterized by NMR, IR, and mass spectrometry. The antitumor activity of the compounds in vitro was detected by the MTT method. RESULTS: In vitro anti-tumor experiments showed that some compounds exhibited good anti-cancer effects. The IC50 values of the compound 2-amino-6-(2,4-difluorophenyl)-4-(4-hydroxyphenyl) nicotinonitrile (10n) against human liver cancer (Huh7), human glioma (U251), and human melanoma (A375) cells were 5.9, 6.0 and 7.2 µM, respectively. The IC50 values of the compound 6-(2,4-difluorophenyl)- 4-(4-hydroxyphenyl)-2-oxo-1,2-dihydropyridine-3-carbonitrile (9o) against Huh7, U251 and A375 cells were 2.4, 17.5 and 7.2 µM, respectively, which were better than those of 10- hydroxycamptothecin and 5-fluorouracil. Analysis of the results of molecular dynamics simulation established that the BIR domain is the optimal binding site on the survivin protein, and the fingerprints of the eight most active compounds and the molecular docking to the survivin protein are analyzed. CONCLUSION: 3-Cyanopyridine is an excellent backbone for antitumor lead compounds, 10n and 9o, as derivatives of 3-Cyanopyridine are excellent survivin protein-targeting inhibitors worthy of further study. The key factor in inhibiting survivin protein through the action of amino acid Ile74.