A new and facile method to prepare large‐area silver‐coated silicon nanowire arrays for surface‐enhanced Raman spectroscopy (SERS)‐based sensing is introduced. High‐quality silicon nanowire arrays are prepared by a chemical etching method and used as a template for the generation of SERS‐active silver‐coated silicon nanowire arrays. The morphologies of the silicon nanowire arrays and the type of silver‐plating solution are two key factors determining the magnitude of SERS signal enhancement and the sensitivity of detection; they are investigated in detail for the purpose of optimization. The optimized silver‐coated silicon nanowire arrays exhibit great potential for ultrasensitive molecular sensing in terms of high SERS signal enhancement ability, good stability, and reproducibility. Their further applications in rapidly detecting molecules relating to human health and safety are discussed. A 10 s data acquisition time is capable of achieving a limit of detection of approximately 4 × 10−6 M calcium dipicolinate (CaDPA), a biomarker for anthrax. This value is 1/15 the infectious dose of spores (6 × 10−5 M required), revealing that the optimized silver‐coated silicon nanowire arrays as SERS‐based ultrasensitive sensors are extremely suitable for detecting Bacillus anthracis spores.

E2F transcription factors play a major role in controlling mammalian cell cycle progression. We recently reported that a potential tumor suppressor, prohibitin, which interacts with retinoblastoma protein (Rb), regulates E2F function and this activity correlates with its growth-suppressive activity. We show here that prohibitin recruits Brg-1/Brm to E2F-responsive promoters, and that this recruitment is required for the repression of E2F-mediated transcription by prohibitin. Expression of a dominantnegative Brg-1 or Brm releases prohibitin-mediated repression of E2F and relieves prohibitin-mediated growth suppression. Although prohibitin associates with, and recruits, Brg-1 and Brm independently of Rb, prohibitin/Brg-1/Brm-mediated transcriptional repression requires Rb. A viral oncoprotein, SV40 large T antigen, can reverse prohibitin-mediated suppression of E2F-mediated gene transcription, and targets prohibitin through interruption of the association between prohibitin and Brg-1/Brm without affecting the prohibitin±E2F interaction. Keywords: Brg-1/Brm/E2F/prohibitin/SV40 T antigen IntroductionProhibitin is a potential tumor suppressor gene that has been linked to human cancers. The prohibitin gene encodes a protein of 275 amino acids that is highly evolutionarily conserved. The prohibitin gene is located at 17q21, close to the BRCA1 locus, and four mutations have been reported in a screen of 23 sporadic breast cancers, suggesting a role for prohibitin in breast cancer (Sato et al., 1992(Sato et al., , 1993. The prohibitin gene was originally cloned based on its anti-proliferative activity, causing cell cycle arrest at G 1 /S (McClung et al., 1992(McClung et al., , 1995Asamoto and Cohen, 1994;Ikonen et al., 1995;Dell'Orco et al., 1996;Coates et al., 1997). We recently reported that prohibitin physically interacts with E2F and regulates E2F function, and that this interaction is necessary for the growth-suppressive activity of prohibitin (Wang et al., 1999a,b).The E2F family of transcription factors plays a major role in regulating mammalian cell cycle progression and is involved in differentiation, transformation and apoptosis (Chellappan et al., 1991;Nevins, 1992Nevins, , 1998 Kaelin, 1995, 1996;Harbour and Dean, 2000;Muller and Helin, 2000). Many cellular genes required for progression through the S phase contain E2F-binding sites in their promoters, and E2F activity is essential for their expression (Adams and Kaelin, 1995). It has been established that the retinoblastoma protein (Rb) family of tumor suppressors interacts with E2F and regulates their function (Chellappan et al., 1991). Recent studies have shown that Rb represses E2F-mediated transcriptional activation through recruitment of chromatin-remodeling complexes, such as histone deacetylase (HDAC) and Brg-1/Brm (Dunaief et al., 1994;Brehm et al., 1998;.We have found that prohibitin interacts with all members of the Rb family (Wang et al., 1999a) and demonstrated important functional and mechanistic differences between Rb-and prohibitin-mediated ...

No abstract

The study of pathophysiological mechanisms in human liver disease has been constrained by the inability to expand primary hepatocytes in vitro while maintaining proliferative capacity and metabolic function. We and others have previously shown that mouse mature hepatocytes can be converted to liver progenitor-like cells in vitro with defined chemical factors. Here we describe a protocol achieving efficient conversion of human primary hepatocytes into liver progenitor-like cells (HepLPCs) through delivery of developmentally relevant cues, including NAD + -dependent deacetylase SIRT1 signaling. These HepLPCs could be expanded significantly during in vitro passage. The expanded cells can readily be converted back into metabolically functional hepatocytes in vitro and upon transplantation in vivo. Under three-dimensional culture conditions, differentiated cells generated from HepLPCs regained the ability to support infection or reactivation of hepatitis B virus (HBV). Our work demonstrates the utility of the conversion between hepatocyte and liver progenitor-like cells for studying HBV biology and antiviral therapies. These findings will facilitate the study of liver diseases and regenerative medicine.

In situ cross-linking of nano-objects with controllable morphologies in polymerization-induced self-assembly (PISA) has been a challenge because cross-linking lowers chain mobility and hence inhibits morphology transition. Herein, we propose a novel strategy that allows in situ cross-linking of vesicles in PISA in an aqueous dispersion polymerization formulation. This is realized by utilizing an asymmetric cross-linker bearing two vinyl groups of differing reactivities such that cross-linking is delayed to the late stage of polymerization when morphology transition has completed. Cross-linked vesicles with varying degrees (1–5 mol %) of cross-links were prepared, and their resistance to solvent dissolution and surfactant disruption was investigated. It was found that vesicles with ≥2 mol % cross-links were able to retain their structural integrity and colloidal stability when dispersed in DMF or in the presence of 1% of an anionic surfactant sodium dodecyl sulfate.

Biocatalysis is promising for sustainable production of polymers. Enzyme-initiated reversible addition− fragmentation chain transfer (RAFT) polymerization is reported. Horseradish peroxidase (HRP) catalyzes oxidation of acetylacetone (ACAC) by hydrogen peroxide to generate ACAC radicals, which in the presence of a suitable chain transfer agent initiate efficient and well-controlled RAFT polymerization in aqueous buffer solution at room temperature. The versatility of HRP-initiated RAFT polymerization was demonstrated by controlled polymerization of a wide range of monomers, including both more and less activated monomers, under a variety of conditions, including both homogeneous solution polymerization and heterogeneous dispersion polymerization conditions. In all cases, the polymerization afforded excellent pseudo-first-order kinetics, predictable molecular weights, and narrow molecular weight distributions. Operation via RAFT mechanism of this HRP-initiated polymerization was confirmed by a combination of MALDI-ToF, NMR, and UV−vis as well as by chain extension to make well-defined block copolymers. The mildness, specificity, and biocompatibility of HRP-initiated RAFT polymerization were illustrated by controlled polymerization in undiluted fetal bovine serum (FBS) solution. RAFT polymerization initiated by glucose oxidase (GOx)−HRP enzymatic cascade catalysis was developed, opening up a new avenue to potential green synthesis of precision polymers by controlled radical polymerization in air.

As a single-atom-thick carbon material with high surface area and conductivity, graphene provides an ideal platform for designing composite nanomaterials for high-performance electrocatalytic or electrochemical devices. Herein, we demonstrated a facile strategy for controllably growing high-quality Prussian blue nanocubes on the surface of reduced graphene oxide (PBNCs/rGO), which represents a new type of graphene/transition metal complex heterostructure. The merit of this method is that the composite nanomaterials could be produced directly from GO in an in situ wet-chemical reaction, where the reduction of GO and the deposition of PBNCs occurred simultaneously. The obtained composite nanomaterials were characterized by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Raman spectroscopy, and electrochemical techniques. It was found that uniform PBNCs with controlled size and good dispersion were directly grown on the surface of graphene nanosheets. Moreover, we also investigated the performance of PBNCs/rGO nanocomposites as amperometric sensor toward reduction of H(2)O(2). Such a sensor showed a rapid and highly sensitive response to H(2)O(2) with a low detection limit (45 nM), which might find promising applications in developing a new type of enzymeless biosensor.

Sensoren für Sporen: Mit einem organischen Farbstoff beschichtete Siliciumoxidnanopartikel und ein Europiumkomplex wurden in einem Sensor kombiniert, der einen Anthrax‐Biomarker schnell und hoch empfindlich nachweisen kann (siehe Bild; gelbe Punkte: Siliciumoxidnanopartikel, äußere Schale: EuIII‐Komplex). Das Verfahren ist der Detektion mit herkömmlichen Sensoren auf Terbiumbasis überlegen.