66 research outputs found
A protein knockdown strategy to study the function of β-catenin in tumorigenesis
BACKGROUND: The Wnt signaling pathway plays critical roles in cell proliferation and cell fate determination at many stages of development. A critical downstream target of Wnt signaling is the cytosolic β-catenin, which is stabilized upon Wnt activation and promotes transcription of a variety of target genes including c-myc and cyclin D. Aberrant Wnt signaling, which results from mutations of either β-catenin or adenomatous polyposis coli (APC), renders β-catenin resistant to degradation, and has been associated with multiple types of human cancers. RESULTS: A protein knockdown strategy was designed to reduce the cytosolic β-catenin levels through accelerating its turnover rate. By engineering a chimeric protein with the β-catenin binding domain of E-cadherin fused to βTrCP ubiquitin-protein ligase, the stable β-catenin mutant was recruited to the cellular SCF (Skp1, Cullin 1, and F-box-containing substrate receptor) ubiquitination machinery for ubiquitination and degradation. The DLD1 colon cancer cells express wild type β-catenin at abnormally high levels due to loss of APC. Remarkably, conditional expression of βTrCP-E-cadherin under the control of a tetracycline-repressive promoter in DLD1 cells selectively knocked down the cytosolic, but not membrane-associated subpopulation of β-catenin. As a result, DLD1 cells were impaired in their growth and clonogenic ability in vitro, and lost their tumorigenic potential in nude mice. CONCLUSION: We have designed a novel approach to induce degradation of stabilized/mutated β-catenin. Our results suggest that a high concentration of cytoplasmic β-catenin is critical for the growth of colorectal tumor cells. The protein knockdown strategy can be utilized not only as a novel method to dissect the role of oncoproteins in tumorigenesis, but also as a unique tool to delineate the function of a subpopulation of proteins localized to a specific subcellular compartment
Quantum Discord for Investigating Quantum Correlations without Entanglement in Solids
Quantum systems unfold diversified correlations which have no classical
counterparts. These quantum correlations have various different facets. Quantum
entanglement, as the most well known measure of quantum correlations, plays
essential roles in quantum information processing. However, it has recently
been pointed out that quantum entanglement cannot describe all the
nonclassicality in the correlations. Thus the study of quantum correlations in
separable states attracts widely attentions. Herein, we experimentally
investigate the quantum correlations of separable thermal states in terms of
quantum discord. The sudden change of quantum discord is observed, which
captures ambiguously the critical point associated with the behavior of
Hamiltonian. Our results display the potential applications of quantum
correlations in studying the fundamental properties of quantum system, such as
quantum criticality of non-zero temperature.Comment: 4 pages, 4 figure
Deterministic generation of polarization-entangled photon pairs in a cavity-QED system
We propose a cavity-QED scheme that can deterministically generate
Einstein-Podosky-Rosen polarization-entangled photon pairs. A four-level tripod
atom successively couples to two high-Q optical cavities possessing
polarization degeneracy, assisted by a classical -polarized pump field.
The stimulated Raman adiabatic passage process in the atom-cavity system is
used to produce the polarization-entangled photon pairs. The proposal is
particularly robust against atomic spontaneous decay, which should have
potential applications in quantum information processing.Comment: 15 pages, 4figure
Selectivity control in photocatalytic valorization of biomass-derived platform compounds by surface engineering of titanium oxide
化学化工学院王野教授课题组与程俊教授课题组合作,在生物质光催化选择转化方面取得重要突破。研究团队发展了一种调控TiO2表面结构以控制生物质转化途径的新方法,率先实现多种木质纤维素平台分子的光催化还原选择性调控,获得高产率的加氢产物(精细化学品)或偶联产物(燃料前驱体)。该论文第一作者为化学化工学院2015级博士毕业生吴雪娇、2015级博士毕业生李洁琼和固体表面物理化学国家重点实验室谢顺吉博士。【Abstract】Photocatalysis has offered a promising opportunity for selective transformation of biomass to high-value chemicals or fuels under mild conditions. Whereas titanium oxide has been widely used for photocatalytic pollutant degradation, H2 evolution, and CO2 reduction, few studies have been devoted to TiO2-based photocatalytic valorization of biomass or biomass-derived platform compounds. Here, we report on surface-controlled photocatalysis of TiO2 for selective valorization of furfurals and vanillin that are lignocellulose-derived key platform compounds. The reaction can be switched from hydrogenation of aldehyde group to C–C coupling by manipulating exposed facets; furanic and aromatic alcohols or coupling products, which are fine chemicals or jet-fuel precursors, could be produced with high selectivity. Our studies elucidate that the facet-dependent density of oxygen vacancies governs the charge distribution and adsorption strength of surface species and thus controls product selectivity. The present work offers an example of selectivity control by engineering TiO2 surfaces for valorization of biomass-derived feedstocks.This work was supported by the National Natural Science Foundation of China (nos. 21690082 and 21972115).
论文中相关研究工作得到国家自然科学基金(21690082、21972115)等项目的资助
Contralateral C7 transfer to lower trunk via a subcutaneous tunnel across the anterior surface of the chest and neck for total brachial plexus root avulsion: a cadaveric study
Abstract Background Restoration of hand function after total brachial plexus root avulsion (tBPRA) is a difficult problem in surgical management. A new modified approach in repairing tBPRA is to use a subcutaneous tunnel across the anterior surface of the chest and neck, and then transfer the contralateral C7 root (cC7) to the lower trunk. However, the anatomical details of this method have not yet been fully described and assessed. The objective of this study was to quantitatively describe the nerve transfer using a cadaveric surgical simulation. Materials and methods Brachial plexuses were dissected from 12 adult cadavers, producing 24 sides of brachial plexuses for nerve transfer experiments. We performed simulated cC7 transfers to the lower trunk via a subcutaneous tunnel across the anterior surface of the chest and neck. Measurements of the nerves were made and transfers quantitatively documented. Results With the affected shoulder and arm in a neutral position, cC7 and C8-T1 could be sutured directly together in 75% of the cadavers. A nerve graft length of 4.6 ± 1.18 cm was needed to bridge the gap in the remaining cadavers. For cadavers where distal cC7 was directly connected with the lower trunk, 54.17% could be sutured, and an average nerve graft length of 3.9 cm was needed in the remains. Conclusions For surgical management of total tBPRA, transfer of the cC7 nerve to the C8-T1 or lower trunk via a subcutaneous tunnel across the chest and neck will likely be superior to a conventional cC7 root transfer in the clinic. This approach shortens the nerve graft needed and nerve regeneration distance, decreases the number of neurorrhaphy sites, and makes full use of the donor nerves, which may benefit hand flexion restoration
Design and Development of Collaborative Office Automation System Based on Hierarchical Structure
In order to improve the work efficiency, this paper introduces a collaborative office automation system, and describes the main functional modules of the collaborative office automation system. It also describes the demand analysis and hierarchical system architecture design of the collaborative office automation system. The system has the characteristics of continuous and stable operation, which improves the work efficiency of the team and saves resources
Non-generative Generalized Zero-shot Learning via Task-correlated Disentanglement and Controllable Samples Synthesis
Synthesizing pseudo samples is currently the most effective way to solve the
Generalized Zero-Shot Learning (GZSL) problem. Most models achieve competitive
performance but still suffer from two problems: (1) Feature confounding, the
overall representations confound task-correlated and task-independent features,
and existing models disentangle them in a generative way, but they are
unreasonable to synthesize reliable pseudo samples with limited samples; (2)
Distribution uncertainty, that massive data is needed when existing models
synthesize samples from the uncertain distribution, which causes poor
performance in limited samples of seen classes. In this paper, we propose a
non-generative model to address these problems correspondingly in two modules:
(1) Task-correlated feature disentanglement, to exclude the task-correlated
features from task-independent ones by adversarial learning of domain adaption
towards reasonable synthesis; (2) Controllable pseudo sample synthesis, to
synthesize edge-pseudo and center-pseudo samples with certain characteristics
towards more diversity generated and intuitive transfer. In addation, to
describe the new scene that is the limit seen class samples in the training
process, we further formulate a new ZSL task named the 'Few-shot Seen class and
Zero-shot Unseen class learning' (FSZU). Extensive experiments on four
benchmarks verify that the proposed method is competitive in the GZSL and the
FSZU tasks.Comment: 12 pages, 5 figure
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