分类: 生物学 >> 生物物理学 >> 细胞生物学 提交时间: 2016-05-12
摘要: p53 is an important tumor suppressor and stress response mediator. Proper control of p53 level and activity is tightly associated with its function. Posttranslational modifications and the interactions with Mdm2 and Mdm4 are major mechanisms controlling p53 activity and stability. As p53 protein is short-lived and hardly detectable in unstressed situations, less is known on its basal level expression and the corresponding controlling mechanisms in vivo. In addition, it also remains obscure how p53 expression might contribute to its functional regulation. In this study, we established bacterial artificial chromosome transgenic E.coli beta-galactosidase Z gene reporter mice to monitor p53 expression in mouse tissues and identify important regulatory elements critical for the expression in vivo. We revealed preferentially high level of p53 reporter expressions in the proliferating, but not the differentiated compartments of the majority of tissues during development and tissue homeostasis. In addition, tumors as well as regenerating tissues in the p53 reporter mice also expressed high level of beta-gal. Furthermore, both the enhancer box sequence (CANNTG) in the p53 promoter and the 3' terminal untranslated region element were critical in mediating the high-level expression of the reporter. We also provided evidence that cellular myelocytomatosis oncogene was a critical player regulating p53 mRNA expression in proliferating cells and tissues. Finally, we found robust p53 activation preferentially in the proliferating compartment of mouse tissues upon DNA damage and the proliferating cells exhibited an enhanced p53 response as compared with cells in a quiescent state. Together, these results suggested a highly regulated expression pattern of p53 in the proliferating compartment controlled by both transcriptional and posttranscriptional mechanisms, and such regulated p53 expression may impose functional significance upon stress by setting up a precautionary mode in defense of cellular transformation and tumorigenesis.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Based on a bio-inspiration polydopamine reaction platform, hollow Ag/carbon microporous spheres were facilely prepared through a template-assisted method. The hollow Ag/carbon spheres, with a uniform shell thickness of 30 nm and a high Ag loading, show high catalytic activity for the reduction of 4-nitrophenol by NaBH4 to 4-aminophenol. It is found that the 4-nitrophenol (10 mL, 1 10 3 M) can be completely converted to 4-aminophenol in 2 min by adding 20 mg of hollow Ag/carbon catalysts. The catalytic activity of the hollow Ag/carbon microporous spheres is also confirmed by CO oxidation. At 200 C, 100% CO conversions can be achieved by using hollow Ag/carbon microporous spheres as catalysts, which is promising to replace other noble metal catalysts in metal catalyzed reactions.
提交时间: 2017-05-02
摘要: Cathode interlayer is essential to inverted bulk heterojunction polymer solar cells [PSCs]. A series of zwitterionic ammonium and neutral amino organic molecules are introduced into inverted PSCs as cathode interlayer and power conversion efficiency [PCE]
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: The preparation of lightweight materials with electromagnetic interference-shielding effect- iveness higher than 30dB is critical for most industrial and consumer applications. Compounding polymer resin with conductive filler can generate excellent electromagnetic interference-shielding effectiveness but usually leads to a high-sample density, while the foaming of polymer composite suffers from the significant-reduced electromagnetic inter- ference-shielding effectiveness. In this study, polyetherimide composite foams with loading of 10–80 phr (parts per hundred of resins) nickel particles were fabricated to meet the gap. The polyetherimide/nickel composite foams possessed uniform cell structure and low- sample density such as 0.86 g/cm3 at 70 phr nickel. The coupling effects of gravity settle- ment and cell-structure solidification led to the formation of gradient distribution of nickel particles across the foams. The formed novel structure facilitated the enhancement of multi-reflection and multi-scattering among nickel particles and cells. As a consequence, polyetherimide/nickel foam with 70 phr nickel (PEIN70) possessed a high-electromagnetic interference shielding effectiveness of 86.7–106.5 dB over a frequency range of 50–3000MHz. When the sample density was considered, the specific electromagnetic interference shielding effectiveness of PEIN70 foam was as high as 121.3 dB/(g/cm3) at 1 GHz, which was higher than the reported electromagnetic interference-shielding materials. The excellent electromagnetic interference-shielding properties, lightweight, well-defined resin proper- ties ensure polyetherimide/nickel composite foams useful in many advanced applications.
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: Many chemotherapeutics used for cancer treatments encounter issues during delivery to tumors in vivo and have high levels of systemic toxicity. One of the most prominent progresses in improving drug delivery efficiency is through exploring various types of nanoparticles (NPs) as drug carriers. Recent studies have demonstrated that titanium dioxide (TiO2) nanocarriers have potential for drug delivery and therapy even in multidrug resistant cancers in vitro. Moreover, it was proved that the anticancer activity of doxorubicin (DOX) was enhanced by loading onto TiO2 nanoparticles in breast cancer cells in vitro. However, there is no evidence from the animal model in vivo, which is a critical step for their further clinical applications. The aim of this study was to explore novel TiO2–PEG–DOX nanoparticles, the DOX loaded polyethylene glycol (PEG) coated TiO2 nanocarriers, and investigate their potential application in enabling controlled drug release and enhancing the chemotherapeutic efficacy of DOX in the orthotopic breast tumor bearing mice. The tumor growth and drug treatment efficacy were dynamically monitored by bioluminescence imaging (BLI), and the safety of NPs for in vivo usage was also evaluated. It was found that TiO2–PEG–DOX nanoparticles possessed improved antitumor efficacy without observable side effects compared to the free DOX treatment. Our study suggested that the PEG coated TiO2 nanocarrier is a safe and potential platform for the efficient drug delivery and minimizing the systemic toxicity of chemotherapeutic agents. It has been proved for the first time that TiO2-based nanocarriers enhance the chemotherapeutic effects of doxorubicin in vivo.
提交时间: 2017-05-02
摘要: Various low ratios of triplet iridium complexes [0, 0.5, 1, 1.5, 2.5, and 5 mol%] are conjugated to the backbone of the famous champion donor polymer PTB7. At the same conditions, the power conversion efficiency for polymer containing 1% of Ir increases b
分类: 物理学 >> 普通物理:统计和量子力学,量子信息等 提交时间: 2017-05-02
摘要: A green facile scalable method inspired by polymeric dental restorative composite is developed to synthesize TiO2/carbon nanocomposites for manipulation of the intercala- tion potential of TiO2 as lithium-ion battery anode. Poorly crystallized TiO2 nanoparticles with average sizes of 4−6 nm are homogeneously embedded in carbon matrix with the TiO2 mass content varied between 28 and 65%. Characteristic discharge/ charge plateaus of TiO2 are significantly diminished and voltage continues to change along with proceeding discharge/charge process. The tap density, gravimetric and volumetric capacities, and cyclic and rate performance of the TiO2/C composites are effectively improved.