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1. chinaXiv:201605.01808 [pdf]

Significant Expansion of Fluorescent Protein Sensing Ability through the Genetic Incorporation of Superior Photo-Induced Electron-Transfer Quenchers

Liu, Xiaohong; Jiang, Li; Li, Jiasong; Wang, Li; Zhou, Qing; Lv, Xiaoxuan; Gong, Weimin; Wang, Jiangyun; Lu, Yi; Lu, Yi; Yu, Yang
Subjects: Biology >> Biophysics

Photo-induced electron transfer (PET) is ubiquitous for photosynthesis and fluorescent sensor design. However, genetically coded PET sensors are underdeveloped, due to the lack of methods to site-specifically install PET probes on proteins. Here we describe a family of acid and Mn(III) turn-on fluorescent protein (FP) sensors, named iLovU, based on PET and the genetic incorporation of superior PET quenchers in the fluorescent flavoprotein iLov. Using the iLovU PET sensors, we monitored the cytoplasmic acidification process, and achieved Mn(III) fluorescence sensing for the first time. The iLovU sensors should be applicable for studying pH changes in living cells, monitoring biogentic Mn(III) in the environment, and screening for efficient manganese peroxidase, which is highly desirable for lignin degradation and biomass conversion. Our work establishes a platform for many more protein PET sensors, facilitates the de novo design of metalloenzymes harboring redox active residues, and expands our ability to probe protein conformational dynamics.

submitted time 2016-05-18 Hits1214Downloads558 Comment 0

2. chinaXiv:201605.01807 [pdf]

7T Transmit/Receive Arrays Using ICE Decoupling for Human Head MR Imaging

Yan, Xinqiang; Feng, Baotong; Ma, ChuangXin; Wei, Long; Yan, Xinqiang; Zhang, Xiaoliang; Zhang, Xiaoliang; Xue, Rong
Subjects: Biology >> Biophysics

In designing large-sized volume type phased array coils for human head imaging at ultrahigh fields, e.g., 7T, minimizing electromagnetic coupling among array elements is technically challenging. A new decoupling method based on induced current compensation or elimination (ICE) for a microstrip line planar array has recently been proposed. In this study, an eight-channel transmit/receive volume array with ICE-decoupled loop elements was built and investigated to demonstrate its feasibility and robustness for human head imaging at 7T. Isolation between adjacent loop elements was better than - 25 dB with a human head load. The worst-case of the isolation between all of the elements was about - 17.5 dB. All of the MRI experiments were performed on a 7T whole-body human MR scanner. Images of the phantom and human head were acquired and g-factor maps were measured and calculated to evaluate the performance of the coil array. Compared with the conventional capacitively decoupled array, the ICE-decoupled array demonstrated improved parallel imaging ability and had a higher SNR. The experimental results indicate that the transceiver array design with ICE decoupling technique might be a promising solution to designing high performance transmit/receive coil arrays for human head imaging at ultrahigh fields.

submitted time 2016-05-18 Hits1238Downloads557 Comment 0

3. chinaXiv:201605.01806 [pdf]

Polymer-Ag Nanocomposites with Enhanced Antimicrobial Activity against Bacterial Infection

Mei, Lin; Lu, Zhentan; Zhang, Xinge; Li, Chaoxing; Jia, Yanxia; Jia, Yanxia
Subjects: Biology >> Biophysics

Herein, a nontoxic nanocomposite is synthesized by reduction of silver nitrate in the presence of a cationic polymer displaying strong antimicrobial activity against bacterial infection. These nanocomposites with a large concentration of positive charge promote their adsorption to bacterial membranes through electrostatic interaction. Moreover, the synthesized nanocomposites with polyvalent and synergistic antimicrobial effects can effectively kill both Gram-positive and Gram-negative bacteria without the emergence of bacterial resistance. Morphological changes obtained by transmission electron microscope observation show that these nanocomposites can cause leakage and chaos of intracellular contents. Analysis of the antimicrobial mechanism confirms that the lethal action of nanocomposites against the bacteria started with disruption of the bacterial membrane, subsequent cellular internalization of the nanopartides, and inhibition of intracellular enzymatic activity. This novel antimicrobial material with good cytocompatibility promotes healing of infected wounds in diabetic rats, and has a promising future in the treatment of other infectious diseases.

submitted time 2016-05-18 Hits1132Downloads504 Comment 0

4. chinaXiv:201605.01804 [pdf]

An Iron-Containing Dodecameric Heptosyltransferase Family Modifies Bacterial Autotransporters in Pathogenesis

Lu, Qiuhe; Yao, Qing; Xu, Yue; Li, Lin; Li, Shan; Gao, Wenqing; Niu, Miao; Chen, She; Shao, Feng; Xu, Yue; Liu, Yanhua; Liu, Xiaoyun; Liu, Yanhua; Liu, Xiaoyun; Sharon, Michal; Ben-Nissan, Gili; Zamyatina, Alla; Shao, Feng; Shao, Feng
Subjects: Biology >> Biophysics

Autotransporters deliver virulence factors to the bacterial surface by translocating an effector passenger domain through a membrane-anchored barrel structure. Although passenger domains are diverse, those found in enteric bacteria autotransporters, including AIDA-I in diffusely adhering Escherichia coli (DAEC) and TibA in enterotoxigenic E. coli, are commonly glycosylated. We show that AIDA-I is heptosylated within the bacterial cytoplasm by autotransporter adhesin heptosyltransferase (AAH) and its paralogue AAH2. AIDA-I heptosylation determines DAEC adhesion to host cells. AAH/AAH2 define a bacterial autotransporter heptosyltransferase (BAHT) family that contains ferric ion and adopts a dodecamer assembly. Structural analyses of the heptosylated TibA passenger domain reveal 35 heptose conjugates forming patterned and solenoid-like arrays on the surface of a beta helix. Additionally, CARC, the AIDA-like autotransporter from Citrobacter rodentium, is essential for colonization in mice and requires heptosylation by its cognate BAHT. Our study establishes a bacterial glycosylation system that regulates virulence and is essential for pathogenesis.

submitted time 2016-05-18 Hits1166Downloads516 Comment 0

5. chinaXiv:201605.01802 [pdf]

Environmentally responsive polymeric materials: effect of the topological structure on self-assembly

Wang, Hui; Zhang, Pei; Shi, Xuefeng; Yu, Danfeng; Wang, Jinben; Yan, Haike; Ji, Gang
Subjects: Biology >> Biophysics

A novel amphiphilic homopolymer (PAGC(8)), containing two hydrophilic head groups and double hydrophobic tails in each repeat unit, has been prepared by solution polymerization and named as "a geminized amphiphilic homopolymer" in this paper, which is capable of self-assembling into various nanoobjects depending on the solution concentration and solvent properties. Characterization of the self-assembly behaviors was carried out by steady-state fluorescence, transmission electron microscopy and nuclear magnetic resonance techniques. Particular emphasis was dedicated to the environmental responsiveness of the assemblies. The morphologies were observed to transform from micelle-type to vesicles on adding a certain amount of ethanol. It is noteworthy that the assemblies were able to trap hydrophilic (rhodamine B) and hydrophobic (Sudan Red) molecules. Subsequently different nanoobjects were found after the encapsulation. To probe the effect of the topological structure on the self-assembly behaviors, the properties of an additional homopolymer with single charge pendant architecture on the backbone were investigated for comparison. Significant differences in structure between the two architectures brought out remarkable variations in aggregates, which were non-responsive to the solvent environment, or encapsulation of molecules. Based on the experimental results, we proposed a possible mechanism of the morphological transitions of the assemblies.

submitted time 2016-05-18 Hits1030Downloads439 Comment 0

6. chinaXiv:201605.01801 [pdf]

Expanding the genetic code for site-specific labelling of tobacco mosaic virus coat protein and building biotin-functionalized virus-like particles

Wu, F. C.; Zhou, Q.; Wu, M.; Tian, Y.; Niu, Z. W.; Huang, Y.; Wu, F. C.; Zhou, Q.; Wu, F. C.; Ballard, Z.; Zhang, H.; Wang, J. Y.
Subjects: Biology >> Biophysics

A method for site-specific and high yield modification of tobacco mosaic virus coat protein (TMVCP) utilizing a genetic code expanding technology and copper free cycloaddition reaction has been established, and biotin-functionalized virus-like particles were built by the self-assembly of the protein monomers.

submitted time 2016-05-18 Hits1012Downloads433 Comment 0

7. chinaXiv:201605.01737 [pdf]

Baicalin Inhibits the Lethality of Shiga-Like Toxin 2 in Mice

Dong, Jing; Zhang, Yong; Zhang, Yu; Deng, Xuming; Dong, Jing; Chen, Yutao; Wang, Quan; Li, Xuemei; Niu, Xiaodi; Yang, Cheng
Subjects: Biology >> Biophysics

Shiga-like toxins (Stxs), produced by pathogenic Escherichia coli, are a major virulence factor involved in severe diseases in human and animals. These toxins are ribosome-inactivating proteins, and treatment for diseases caused by them is not available. Therefore, there is an urgent need for agents capable of effectively targeting this lethal toxin. In this study, we identified baicalin, a flavonoid compound used in Chinese traditional medicine, as a compound against Shiga-like toxin 2 (Stx2). We found that baicalin significantly improves renal function and reduces Stx2-induced lethality in mice. Further experiments revealed that baicalin induces the formation of oligomers by the toxin by direct binding. We also identified the residues important for such interactions and analyzed their roles in binding baicalin by biophysical and biochemical analyses. Our results establish baicalin as a candidate compound for the development of therapeutics against diseases caused by Stxs.

submitted time 2016-05-15 Hits968Downloads399 Comment 0

8. chinaXiv:201605.01736 [pdf]

Retinotopic Changes in the Gray Matter Volume and Cerebral Blood Flow in the Primary Visual Cortex of Patients With Primary Open-Angle Glaucoma

Zhang, Shaodan; Zhang, Chun; Zhang, Shaodan; Wang, Bo; Zhu, SenHua; Xie, Yuan; Qing, Guoping; Wang, Ningli; Thomas, Ravi; Thomas, Ravi
Subjects: Biology >> Biophysics

PURPOSE. To assess the cortical structure and cerebral blood flow changes in the brain of patients with primary open-angle glaucoma (POAG). METHODS. High-resolution anatomical magnetic resonance imaging (MRI) and arterial spin labeling (ASL)-MRI were performed in 23 POAG patients and 29 controls. Patients were further divided into early-moderate and advanced groups based on mean deviation (MD) cutoff of 12 dB. A baseline scan was obtained and repeated during visual stimulation to the central preserved visual field in the more affected eye of POAG patients and a randomly selected eye of controls. Gray matter volume (GMV) and cerebral blood flow (CBF) throughout the whole brain were compared between patients and controls. RESULTS. Compared to controls, a region with significant reduction of GMV was detected in the anterior calcarine fissure of advanced POAG patients (P < 0.001, voxels = 503, 1698 mm3). Patients with early-moderate POAG had resting CBF similar to that of controls. However, a region with marked CBF decrease was detected in the anterior calcarine fissure of advanced POAG patients (P < 0.001, voxels = 1687, 13,496 mm(3)). The region with CBF reduction in advanced POAG showed good colocalization with the region with GMV decrease in this group. Following visual stimulation, patients with advanced POAG showed significantly lower increase in CBF in the occipital lobes (P < 0.001, voxels = 112, 896 mm(3)) as compared to controls (P < 0.001, voxels = 1880, 15,040 mm(3)) and early-moderate POAG (P < 0.001, voxels = 2233, 17,864 mm(3)). CONCLUSIONS. Primary open-angle glaucoma patients demonstrate a disease severity-dependent retinotopic pattern of cortical atrophy and CBF abnormalities in the visual cortex. Cerebral blood flow may be a potential biomarker for the brain involvement in glaucoma.

submitted time 2016-05-15 Hits1152Downloads617 Comment 0

9. chinaXiv:201605.01735 [pdf]

PTEN deficiency reprogrammes human neural stem cells towards a glioblastoma stem cell-like phenotype

Duan, Shunlei; Yuan, Guohong; Ren, Ruotong; Xu, Xiuling; Fu, Lina; Li, Ying; Yang, Jiping; Zhang, Weiqi; Liu, Guang-Hui; Liu, Xiaomeng; Li, Jingyi; Tang, Fuchou; Ren, Ruotong; Bai, Ruijun; Liu, Guang-Hui; Ren, Ruotong; Bai, Ruijun; Qu, Jing; Zhang, Weizhou; Wu, Jun
Subjects: Biology >> Biophysics

PTEN is a tumour suppressor frequently mutated in many types of cancers. Here we show that targeted disruption of PTEN leads to neoplastic transformation of human neural stem cells (NSCs), but not mesenchymal stem cells. PTEN-deficient NSCs display neoplasm-associated metabolic and gene expression profiles and generate intracranial tumours in immunodeficientmice. PTEN is localized to the nucleus in NSCs, binds to the PAX7 promoter through association with cAMP responsive element binding protein 1 (CREB)/CREB binding protein (CBP) and inhibits PAX7 transcription. PTEN deficiency leads to the upregulation of PAX7, which in turn promotes oncogenic transformation of NSCs and instates 'aggressiveness' in human glioblastoma stem cells. In a large clinical database, we find increased PAX7 levels in PTEN-deficient glioblastoma. Furthermore, we identify that mitomycin C selectively triggers apoptosis in NSCs with PTEN deficiency. Together, we uncover a potential mechanism of how PTEN safeguards NSCs, and establish a cellular platform to identify factors involved in NSC transformation, potentially permitting personalized treatment of glioblastoma.

submitted time 2016-05-15 Hits1112Downloads469 Comment 0

10. chinaXiv:201605.01734 [pdf]

Real-Time Monitoring Surface Chemistry-Dependent In Vivo Behaviors of Protein Nanocages via Encapsulating an NIR-II Ag2S Quantum Dot

Li, Chunyan; Zhang, Yejun; Wang, Qiangbin; Li, Feng; Zhang, Wenjing; Zhang, Xian-En
Subjects: Biology >> Biophysics

Protein nanocages (PNCs) have been recognized as a promising platform for nanomedicine innovation. Real-time in vivo tracking of PNCs can provide critically important information for the development of PNC-based diagnostics and therapeutics. Here we demonstrate a general strategy for monitoring the behaviors of PNCs in vivo by encapsulating a Ag2S quantum dot (QD) with fluorescence in the second near-infrared window (NIR-II, 1000-1700 nm) inside the PNC, using simian virus 40 (SV40) PNC (PNCSV40) as a model. Benefiting from the high spatiotemporal resolution and deep tissue penetration of NIR-II fluorescence imaging, the dynamic distribution of the PNCSV40 in living mice was tracked in real time with high fidelity, and adopting the PEGylation strategy, surface chemistry-dependent in vivo behaviors of PNCSV40 were clearly revealed. This study represents the first evidence of real-time tracking of the intrinsic behaviors of PNCs in vivo without interference in PNC-host interactions by encapsulating nanoprobes inside. The as-described imaging strategy will facilitate the study of interactions between exogenously introduced PNCs and host body and prompt the development of future protein-based drugs, sensors, and high-efficacy targeted delivery systems.

submitted time 2016-05-15 Hits1031Downloads465 Comment 0

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