Bioinspired Network Analysis Enabled Divergent Syntheses and Structure Revision of Pentacyclic Cytochalasans.

We accomplished the divergent total syntheses of ten pentacyclic cytochalasans (aspergillin PZ, trichodermone, trichoderones, flavipesines, and flavichalasines) from a common precursor aspochalasin D and revised the structures of trichoderone B, spicochalasin A, flavichalasine C, aspergilluchalasin based on structure network analysis of the cytochalasans biosynthetic pathways and DFT calculations. The key steps of the syntheses include transannular alkene/epoxyalkene and carbonyl-ene cyclizations to establish the C/D ring of pentacyclic aspochalasans. Our bioinspired approach to these pentacyclic cytochalasans validate the proposed biosynthetic speculation from a chemical view and provide a platform for the synthesis of more than 400 valuable cytochalasans bearing different macrocycles and amino-acid residues.

Spin Squeezing with Short-Range Spin-Exchange Interactions.

We investigate many-body spin squeezing dynamics in an XXZ model with interactions that fall off with distance r as 1/r^{α} in D=2 and 3 spatial dimensions. In stark contrast to the Ising model, we find a broad parameter regime where spin squeezing comparable to the infinite-range α=0 limit is achievable even when interactions are short ranged, α>D. A region of "collective" behavior in which optimal squeezing grows with system size extends all the way to the α→∞ limit of nearest-neighbor interactions. Our predictions, made using the discrete truncated Wigner approximation, are testable in a variety of experimental cold atomic, molecular, and optical platforms.

Biomimetic Total Synthesis of (±)-Carbocyclinone-534 Reveals Its Biosynthetic Pathway.

Carbocyclinone-534 is a new antibiotic produced after the metabolism of tapinarof. We identify a biomimetic total synthesis of carbocyclinone-534 in eight steps by taking advantage of an intermolecular Diels-Alder homodimerization/dehydrogenation/intramolecular Diels-Alder cycloaddition cascade. This synthetic sequence provides direct experimental evidence for revealing the biosynthetic pathway of carbocyclinone-534.

Total Synthesis of (-)-Perezoperezone through an Intermolecular [5+2] Homodimerization of Hydroxy p-Quinone.

The first copper-catalyzed intermolecular [5+2] homodimerization of hydroxy p-quinone is presented, furnishing bicyclo[3.2.1]octadienone core structures in typically good yields and excellent diastereoselectivities. Applying this synthetic approach enables a concise nine-step total synthesis of (-)-perezoperezone from commercially available 3,5-dimethoxytoluene.

PTPN9 induces cell apoptosis by mitigating the activation of Stat3 and acts as a tumor suppressor in colorectal cancer.

BACKGROUND: Accumulating evidence has shown that protein tyrosine phosphatases (PTPs) are involved in regulating the transduction of many signaling pathways and play important roles in modulating the progression of some cancers, but the functions of PTPs in cancers have not been well elucidated until now. Here, we aimed to identify the roles of protein tyrosine phosphatase nonreceptor type 9 (PTPN9), a cytoplasmic PTP, in the development of colorectal cancer and elucidate the regulatory mechanism involved. MATERIALS AND METHODS: Cell viability assessment, colony formation assay, caspase-3 and caspase-9 activity assay, real-time PCR, and Western blot analysis were applied. RESULTS: Our results showed that PTPN9 expression was frequently downregulated in colorectal cancer tissues compared with adjacent normal tissues. Overexpression of PTPN9 mitigated cell growth and colony formation and induced cell apoptosis in colorectal cancer. Conversely, PTPN9 knockdown promoted cell growth and survival. Moreover, PTPN9 negatively regulated the activation of Stat3 and depressed its nuclear translocation in colorectal cancer. The effects of PTPN9 knockdown on cell apoptosis were attenuated by inhibition of the Stat3 pathway. CONCLUSION: These results indicate that PTPN9 inhibits cell growth and survival by repressing the activation of Stat3 in colorectal cancer, which suggests an important underlying mechanism of regulating cell growth and provides a novel candidate therapeutic target for colorectal cancer.

Spin current generation and relaxation in a quenched spin-orbit-coupled Bose-Einstein condensate.

Understanding the effects of spin-orbit coupling (SOC) and many-body interactions on spin transport is important in condensed matter physics and spintronics. This topic has been intensively studied for spin carriers such as electrons but barely explored for charge-neutral bosonic quasiparticles (including their condensates), which hold promises for coherent spin transport over macroscopic distances. Here, we explore the effects of synthetic SOC (induced by optical Raman coupling) and atomic interactions on the spin transport in an atomic Bose-Einstein condensate (BEC), where the spin-dipole mode (SDM, actuated by quenching the Raman coupling) of two interacting spin components constitutes an alternating spin current. We experimentally observe that SOC significantly enhances the SDM damping while reducing the thermalization (the reduction of the condensate fraction). We also observe generation of BEC collective excitations such as shape oscillations. Our theory reveals that the SOC-modified interference, immiscibility, and interaction between the spin components can play crucial roles in spin transport.

Observation of Spin Superfluidity in a Bose Gas Mixture.

The spin dynamics of a harmonically trapped Bose-Einstein condensed binary mixture of sodium atoms is experimentally investigated at finite temperature. In the collisional regime the motion of the thermal component is shown to be damped because of spin drag, while the two condensates exhibit a counterflow oscillation without friction, thereby providing direct evidence for spin superfluidity. Results are also reported in the collisionless regime where the spin components of both the condensate and thermal part oscillate without damping, their relative motion being driven by a mean-field effect. We also measure the static polarizability of the condensed and thermal parts and we find a large increase of the condensate polarizability with respect to the T=0 value, in agreement with the predictions of theory.

Angular Momentum of a Bose-Einstein Condensate in a Synthetic Rotational Field.

By applying a position-dependent detuning to a spin-orbit-coupled Hamiltonian with equal Rashba and Dresselhaus coupling, we exploit the behavior of the angular momentum of a harmonically trapped Bose-Einstein condensed atomic gas and discuss the distinctive role of its canonical and spin components. By developing the formalism of spinor hydrodynamics, we predict the precession of the dipole oscillation caused by the synthetic rotational field, in analogy with the precession of the Foucault pendulum, the excitation of the scissors mode, following the sudden switching off of the detuning, and the occurrence of Hall-like effects. When the detuning exceeds a critical value, we observe a transition from a vortex free, rigidly rotating quantum gas to a gas containing vortices with negative circulation which results in a significant reduction of the total angular momentum.

Magnetic Solitons in a Binary Bose-Einstein Condensate.

We study solitary waves of polarization (magnetic solitons) in a two-component Bose gas with slightly unequal repulsive intra- and interspin interactions. In experimentally relevant conditions we obtain an analytical solution which reveals that the width and the velocity of magnetic solitons are explicitly related to the spin healing length and the spin sound velocity of the Bose mixture, respectively. We calculate the profiles, the energy, and the effective mass of the solitons in the absence of external fields and investigate their oscillation in a harmonic trap where the oscillation period is calculated as a function of the oscillation amplitude. The stability of magnetic solitons in two dimensions and the conditions for their experimental observation are also briefly discussed.

Fulde-Ferrell Superfluids without Spin Imbalance in Driven Optical Lattices.

Spin-imbalanced ultracold Fermi gases have been widely studied recently as a platform for exploring the long-sought Fulde-Ferrell-Larkin-Ovchinnikov superfluid phases, but so far conclusive evidence has not been found. Here we propose to realize an Fulde-Ferrell (FF) superfluid without spin imbalance in a three-dimensional fermionic cold atom optical lattice, where s- and p-orbital bands of the lattice are coupled by another weak moving optical lattice. Such coupling leads to a spin-independent asymmetric Fermi surface, which, together with the s-wave scattering interaction between two spins, yields an FF type of superfluid pairing. Unlike traditional schemes, our proposal does not rely on the spin imbalance (or an equivalent Zeeman field) to induce the Fermi surface mismatch and provides a completely new route for realizing FF superfluids.

Spin-momentum coupled Bose-Einstein condensates with lattice band pseudospins.

The quantum emulation of spin-momentum coupling, a crucial ingredient for the emergence of topological phases, is currently drawing considerable interest. In previous quantum gas experiments, typically two atomic hyperfine states were chosen as pseudospins. Here, we report the observation of a spin-momentum coupling achieved by loading a Bose-Einstein condensate into periodically driven optical lattices. The s and p bands of a static lattice, which act as pseudospins, are coupled through an additional moving lattice that induces a momentum-dependent coupling between the two pseudospins, resulting in s-p hybrid Floquet-Bloch bands. We investigate the band structures by measuring the quasimomentum of the Bose-Einstein condensate for different velocities and strengths of the moving lattice, and compare our measurements to theoretical predictions. The realization of spin-momentum coupling with lattice bands as pseudospins paves the way for engineering novel quantum matter using hybrid orbital bands.

Dicke-type phase transition in a spin-orbit-coupled Bose-Einstein condensate.

Spin-orbit-coupled Bose-Einstein condensates (BECs) provide a powerful tool to investigate interesting gauge field-related phenomena. Here we study the ground state properties of such a system and show that it can be mapped to the well-known Dicke model in quantum optics, which describes the interactions between an ensemble of atoms and an optical field. A central prediction of the Dicke model is a quantum phase transition between a superradiant phase and a normal phase. We detect this transition in a spin-orbit-coupled BEC by measuring various physical quantities across the phase transition. These quantities include the spin polarization, the relative occupation of the nearly degenerate single-particle states, the quantity analogous to the photon field occupation and the period of a collective oscillation (quadrupole mode). The applicability of the Dicke model to spin-orbit-coupled BECs may lead to interesting applications in quantum optics and quantum information science.

Topological superfluids with finite-momentum pairing and Majorana fermions.

Majorana fermions (MFs), quantum particles that are their own antiparticles, are not only of fundamental importance in elementary particle physics and dark matter, but also building blocks for fault-tolerant quantum computation. Recently MFs have been intensively studied in solid state and cold atomic systems. These studies are generally based on superconducting pairing with zero total momentum. On the other hand, finite total momentum Cooper pairings, known as Fulde-Ferrell (FF) Larkin-Ovchinnikov (LO) states, were widely studied in many branches of physics. However, whether FF and LO superconductors can support MFs has not been explored. Here we show that MFs can exist in certain types of gapped FF states, yielding a new quantum matter: topological FF superfluids/superconductors. We demonstrate the existence of such topological FF superfluids and the associated MFs using spin-orbit-coupled degenerate Fermi gases and derive their parameter regions. The implementation of topological FF superconductors in semiconductor/superconductor heterostructures is also discussed.