No abstract

In the past few years, conjugated polymer nanoparticles (CPNs) have been successfully prepared and applied in the biological field because of their unique opto-electronic properties. The rapid development of CPNs is mainly attributed to their simple synthesis procedures and easy separation steps. The advantages of CPNs include high brightness, excellent photostability, low cytotoxicity, high quantum yield and versatile surface modification. The functionalization of CPNs with specific recognition elements imparts them good ability for targeted recognition and imaging in vitro and in vivo. CPNs can be applied to deliver drug and gene, and simultaneously to real-time monitor the release process due to their self-luminous characteristics. Moreover, CPNs can sensitize oxygen molecules to generate reactive oxygen species (ROS) which can kill adjacent bacteria and tumor cells. In this tutorial review, we provide a recent development of the preparation methods, properties, and functionalization strategies of CPNs, especially discussing their biological applications in targeted imaging, drug/gene delivery and biomedicine. The challenges and outlooks in this field will also be discussed.

Although the aetiology of systemic lupus erythematosus (SLE) is unclear, dysregulated B cell responses have been implicated. Here we show that an unusual CD11chiT-bet+ B cell subset, with a unique expression profile including chemokine receptors consistent with migration to target tissues, is expanded in SLE patients, present in nephrotic kidney, enriched for autoreactive specificities and correlates with defined clinical manifestations. IL-21 can potently induce CD11chiT-bet+ B cells and promote the differentiation of these cells into Ig-secreting autoreactive plasma cells. While murine studies have identified a role for T-bet-expressing B cells in autoimmunity, this study describes and exemplifies the importance of CD11chiT-bet+ B cells in human SLE.

Gold nanoparticles quench the fluorescence of cationic polyfluorene with Stern-Volmer constants (KSV) approaching 10 11 M ؊1 , several orders of magnitude larger than any previously reported conjugated polymer-quencher pair and 9 -10 orders of magnitude larger than small molecule dye-quencher pairs. The dependence of KSV on ionic strength, charge and conjugation length of the polymer, and the dimensions (and thus optical properties) of the nanoparticles suggests that three factors account for this extraordinary efficiency: (i) amplification of the quenching via rapid internal energy or electron transfer, (ii) electrostatic interactions between the cationic polymer and anionic nanoparticles, and (iii) the ability of gold nanoparticles to quench via efficient energy transfer. As a result of this extraordinarily high KSV, quenching can be observed even at subpicomolar concentrations of nanoparticles, suggesting that the combination of conjugated polymers with these nanomaterials can potentially lead to improved sensitivity in optical biosensors. (1). This is 5-6 orders of magnitude more efficient than the quenching of typical small molecule dye-quencher pairs (8), an effect that translates into greatly improved sensitivity in fluorescence-based assays (1, 2). Were further increases in K SV possible, they should thus translate directly into improved sensor performance.The observation that gold metal efficiently quenches the emission of many fluorophores (9-11) suggests that gold nanoparticles might serve as efficient quenchers of conjugated polymer fluorescence. Huang and Murray (12) have described the quenching of small molecule dyes by gold nanoparticles, and Dubertret et al. . This greatly increased K SV provides insights into the mechanisms that underlie the extraordinarily efficient quenching of these materials. More interestingly, versatile chemistry available for surface functionization of gold nanoparticles (14) makes the gold nanomaterials especially suitable for possible ligand tethering and therefore applicable for use in high-performance conjugated polymer-based sensors (1). Materials and MethodsThe water-soluble conjugated polymers and oligomers seen in Scheme 1 were synthesized at the University of California, Santa Barbara as described (15)(16)(17). Gold nanoparticles were obtained from either Sigma (5, 10, or 20 nm) or British Biocell International, Cardiff, U.K. (2 nm). Concentrations of gold nanoparticles were adapted from the data provided by the manufacturer. Absorption spectra were collected with a Shimadzu UV-2401PC UV-visible recording spectrophotometer, and photoluminescence (PL) spectra were collected with a PTI fluorometer (Photon Technology International, Lawrenceville, NJ). The quartz cuvettes were treated by hexamethyldisilazane to block nonspecific electrostatic absorption of cationic polymers to anionic quartz surfaces (18). The fluorescence spectra were obtained by exciting poly(9,9Ј-bis(6-N,N,N-trimethylammonium)-hexyl)-fluorene phenylene (PF) at 375 nm, oligofluorene at 320 nm, poly...

We present the discovery of nine quasars at z ∼ 6 identified in the Sloan Digital Sky Survey (SDSS) imaging data. This completes our survey of z ∼ 6 quasars in the SDSS footprint. Our final sample consists of 52 quasars at 5.7 < z ≤ 6.4, including 29 quasars with z AB ≤ 20 mag selected from 11,240 deg 2 of the SDSS single-epoch imaging survey (the main survey), 10 quasars with 20 ≤ z AB ≤ 20.5 selected from 4223 deg 2 of the SDSS overlap regions (regions with two or more imaging scans), and 13 quasars down to z AB ≈ 22 mag from the 277 deg 2 in Stripe 82. They span a wide luminosity range of −29.0 ≤ M 1450 ≤ −24.5. This well-defined sample is used to derive the quasar luminosity function (QLF) at z ∼ 6. After combining our SDSS sample with two faint (M 1450 ≥ −23 mag) quasars from the literature, we obtain the parameters for a double power-law fit to the QLF. The bright-end slope β of the QLF is well constrained to be β = −2.8 ± 0.2. Due to the small number of low-luminosity quasars, the faint-end slope α and the characteristic magnitude M * 1450 are less well constrained, with α = −1.90The spatial density of luminous quasars, parametrized as ρ(M 1450 < −26, z) = ρ(z = 6) 10 k(z−6) , drops rapidly from z ∼ 5 to 6, with k = −0.72 ± 0.11. Based on our fitted QLF and assuming an IGM clumping factor of C = 3, we find that the observed quasar population cannot provide enough photons to ionize the z ∼ 6 IGM at ∼ 90% confidence. Quasars may still provide a significant fraction of the required photons, although much larger samples of faint quasars are needed for more stringent constraints on the quasar contribution to reionization.

Summary In animals, Hox transcription factors define regional identity in distinct anatomical domains. How Hox genes encode this specificity is a paradox, because different Hox proteins bind with high affinity in vitro to similar DNA sequences. Here, we demonstrate that the Hox protein Ultrabithorax (Ubx) in complex with its cofactor Extradenticle (Exd) bound specifically to clusters of very low affinity sites in enhancers of the shavenbaby gene of Drosophila. These low affinity sites conferred specificity for Ubx binding in vivo, but multiple clustered sites were required for robust expression when embryos developed in variable environments. Although most individual Ubx binding sites are not evolutionarily conserved, the overall enhancer architecture—clusters of low affinity binding sites—is maintained and required for enhancer function. Natural selection therefore works at the level of the enhancer, requiring a particular density of low affinity Ubx sites to confer both specific and robust expression.

Innate immunity plays a crucial role in the response to sterile inflammation such as liver ischemia/reperfusion (I/R) injury. The initiation of liver I/R injury results in the release of damage associated molecular patterns (DAMPs), which trigger innate immune and inflammatory cascade via pattern recognition receptors. Neutrophils are recruited to the liver after I/R and contribute to the organ damage, innate immune and inflammatory responses. Formation of neutrophil extracellular trap (NET) has been recently found in response to various stimuli. However, the role of NETs during liver I/R injury remains unknown. We show that NETs form in the sinusoids of ischemic liver lobes in vivo. This was associated with increased NET markers, serum level of myeloperoxidase (MPO)-DNA complexes and tissue level of citrullinated-histone H3 compared to control mice. Treatment with peptidyl-arginine-deiminase (PAD) 4 inhibitor or DNase I significantly protected hepatocytes and reduced inflammation after liver I/R as evidenced by inhibition of NET formation, indicating the pathophysiological role of NETs in liver I/R injury. In vitro, NETs increase hepatocyte death and induce Kupffer cells to release proinflammatory cytokines. DAMPs, such as HMGB1 and histones, released by injured hepatocytes stimulate NET formation through Toll-like receptor (TLR4)- and TLR9-MyD88 signaling pathways. After neutrophil depletion in mice, the adoptive transfer of TLR4 knockout (KO) or TLR9 KO neutrophils confers significant protection from liver I/R injury with significant decrease in NET formation. In addition, we found inhibition of NET formation by PAD4 inhibitor or DNase I reduces HMGB1 and histone-mediated liver I/R injury. Conclusion DAMPs released during liver I/R promotes NET formation through TLRs signaling pathway. Development of NETs subsequently exacerbates organ damage and initiates inflammatory responses during liver I/R.

Amphotericin has remained the powerful but highly toxic last line of defense in treating life-threatening fungal infections in humans for over 50 years with minimal development of microbial resistance. Understanding how this small molecule kills yeast is thus critical for guiding development of derivatives with an improved therapeutic index and other resistance-refractory antimicrobial agents. In the widely accepted ion channel model for its mechanism of cytocidal action, amphotericin forms aggregates inside lipid bilayers that permeabilize and kill cells. In contrast, we report that amphotericin exists primarily in the form of large, extramembranous aggregates that kill yeast by extracting ergosterol from lipid bilayers. These findings reveal that extraction of a polyfunctional lipid underlies the resistance-refractory antimicrobial action of amphotericin and suggests a roadmap for separating its cytocidal and membrane-permeabilizing activities. This new mechanistic understanding is also guiding development of the first derivatives of amphotericin that kill yeast but not human cells.