The Role of the Polyethylene Glycol in the Organization of Gold Nanorods at the Air-Water and Air-Solid Interfaces.

The organization of metallic nanoparticles into assembled films is a complex process. The type of nanoparticle stabilizing ligand and the method for creating an organized layer can profoundly affect the optical properties of the resulting nanoparticle assembly. Investigations of the ligand structure and nanoparticle interactions can provide a greater understanding of the design of the assembly process and the quality of the resulting materials. One of the functionalization methods in the preparation of specific gold nanorods is the utilization of thiol-terminated poly(ethylene glycol). This generates gold nanorods capable of forming stable monolayers at the air-water interface upon dispersion in a suitable organic solvent. Herein, we show that depending on the molecular weight of the poly(ethylene glycol), the structures obtained at the air-water and air-solid interfaces differ in the arrangement. The studied structures were characterized by using spectroscopic and microscopic techniques, and the structural type was correlated with the polymer type. Insoluble and stable Langmuir monolayers composed of higher-molecular-weight gold nanorods with poly(ethylene glycol) were formed only in the presence of an additional stabilizer that prevented the formation of gold nanorods in aqueous solutions. At the air-solid interface, conformational changes in poly(ethylene glycol) induced the aggregation of gold nanorods, which became closely packed under the influence of surface pressure. The presented results suggested that the arrangement of two-dimensional layers of gold nanorods could be tailored using poly(ethylene glycol) of various molecular weights.

The dynamic architecture of Map1- and NatB-ribosome complexes coordinates the sequential modifications of nascent polypeptide chains.

Cotranslational modification of the nascent polypeptide chain is one of the first events during the birth of a new protein. In eukaryotes, methionine aminopeptidases (MetAPs) cleave off the starter methionine, whereas N-acetyl-transferases (NATs) catalyze N-terminal acetylation. MetAPs and NATs compete with other cotranslationally acting chaperones, such as ribosome-associated complex (RAC), protein targeting and translocation factors (SRP and Sec61) for binding sites at the ribosomal tunnel exit. Yet, whereas well-resolved structures for ribosome-bound RAC, SRP and Sec61, are available, structural information on the mode of ribosome interaction of eukaryotic MetAPs or of the five cotranslationally active NATs is only available for NatA. Here, we present cryo-EM structures of yeast Map1 and NatB bound to ribosome-nascent chain complexes. Map1 is mainly associated with the dynamic rRNA expansion segment ES27a, thereby kept at an ideal position below the tunnel exit to act on the emerging substrate nascent chain. For NatB, we observe two copies of the NatB complex. NatB-1 binds directly below the tunnel exit, again involving ES27a, and NatB-2 is located below the second universal adapter site (eL31 and uL22). The binding mode of the two NatB complexes on the ribosome differs but overlaps with that of NatA and Map1, implying that NatB binds exclusively to the tunnel exit. We further observe that ES27a adopts distinct conformations when bound to NatA, NatB, or Map1, together suggesting a contribution to the coordination of a sequential activity of these factors on the emerging nascent chain at the ribosomal exit tunnel.

Structural basis for clearing of ribosome collisions by the RQT complex.

Translation of aberrant messenger RNAs can cause stalling of ribosomes resulting in ribosomal collisions. Collided ribosomes are specifically recognized to initiate stress responses and quality control pathways. Ribosome-associated quality control facilitates the degradation of incomplete translation products and requires dissociation of the stalled ribosomes. A central event is therefore the splitting of collided ribosomes by the ribosome quality control trigger complex, RQT, by an unknown mechanism. Here we show that RQT requires accessible mRNA and the presence of a neighboring ribosome. Cryogenic electron microscopy of RQT-ribosome complexes reveals that RQT engages the 40S subunit of the lead ribosome and can switch between two conformations. We propose that the Ski2-like helicase 1 (Slh1) subunit of RQT applies a pulling force on the mRNA, causing destabilizing conformational changes of the small ribosomal subunit, ultimately resulting in subunit dissociation. Our findings provide conceptual framework for a helicase-driven ribosomal splitting mechanism.

Photocatalytic degradation of sulfamethoxazole using TiO2-based materials - Perspectives for the development of a sustainable water treatment technology.

Heterogeneous photocatalysis using titanium dioxide-based materials is considered a promising and innovative solution to the water pollution problem. However, due to the limitations concerning the use of the developed materials and the applied photodegradation conditions, the research on photoremediation using TiO2 often stays behind the lab door. The challenge is to convert the basic research into a successful innovation, leading to the implementation of this process into wastewater treatment. For this purpose, the most active materials and optimal photodegradation conditions must be chosen. This article collects and compares the studies on photocatalytic degradation of an emerging pollutant - sulfamethoxazole, an antibacterial drug - and attempts to find the best approaches to be successfully applied on an industrial scale. Various types of TiO2-based photocatalysts are compared, including different nanoforms, doped or polymer-based composites, composites with graphene, activated carbon, dyes or natural compounds, as well as possible supporting materials for TiO2. The paper covers the impact of the irradiation source (natural sunlight, LED, mercury or xenon lamps) and water matrix on the photodegradation process, considering the ecological and economic sustainability of the process. Emphasis is put on the stability, ease of separation and reuse of the photocatalyst, power and safety of the irradiation source, identification of photodegradation intermediates and toxicity assays. The main approaches are critically discussed, main challenges and perspectives for an effective photocatalytic water treatment technology are pointed out.

Nanocomposites of Titanium Dioxide and Peripherally Substituted Phthalocyanines for the Photocatalytic Degradation of Sulfamethoxazole.

Phthalocyanines (Pcs) are often used in photosensitization of titanium(IV) oxide, a commonly employed photocatalyst, as such an approach holds the promise of obtaining highly stable and efficient visible light-harvesting materials. Herein, we report on the preparation, characterization and photoactivity of a series of composites based on TiO2 and peripherally modified metallophthalocyanines: either tetrasulfonated or 4,4',4'',4'''-tetraazaphthalocyanines, with either copper(II), nickel(II) or zinc(II) as the central metal ion. Physicochemical characterization was performed using UV-Vis diffuse reflectance spectroscopy, hydrodynamic particle-size analysis, surface-area analysis using N2 adsorption-desorption measurements and thermogravimetry combined with differential scanning calorimetry. The band-gap energy values were lower for the composites with peripherally modified phthalocyanines than for the commercial TiO2 P25 or the unsubstituted zinc(II) phthalocyanine-grafted TiO2. TG-DSC results confirmed that the chemical deposition, used for the preparation of Pc/TiO2 composites, is a simple and efficient method for TiO2 surface modification, as all the Pc load was successfully grafted on TiO2. The photocatalytic potential of the Pc/TiO2 materials was assessed in the photocatalytic removal of sulfamethoxazole-a commonly used antibacterial drug of emerging ecological concern. To compare the activity of the materials in different conditions, photodegradation tests were conducted both in water and in an organic medium.

Inhibition of SRP-dependent protein secretion by the bacterial alarmone (p)ppGpp.

The stringent response enables bacteria to respond to nutrient limitation and other stress conditions through production of the nucleotide-based second messengers ppGpp and pppGpp, collectively known as (p)ppGpp. Here, we report that (p)ppGpp inhibits the signal recognition particle (SRP)-dependent protein targeting pathway, which is essential for membrane protein biogenesis and protein secretion. More specifically, (p)ppGpp binds to the SRP GTPases Ffh and FtsY, and inhibits the formation of the SRP receptor-targeting complex, which is central for the coordinated binding of the translating ribosome to the SecYEG translocon. Cryo-EM analysis of SRP bound to translating ribosomes suggests that (p)ppGpp may induce a distinct conformational stabilization of the NG domain of Ffh and FtsY in Bacillus subtilis but not in E. coli.

A quantitative polymerase chain reaction based method for molecular subtype classification of urinary bladder cancer-Stromal gene expressions show higher prognostic values than intrinsic tumor genes.

Transcriptome-based molecular subtypes of muscle-invasive bladder cancer (MIBC) have been shown to be both prognostic and predictive, but are not used in routine clinical practice. We aimed to develop a feasible, reverse transcription quantitative polymerase chain reaction (RT-qPCR)-based method for molecular subtyping. First, we defined a 68-gene set covering tumor intrinsic (luminal, basal, squamous, neuronal, epithelial-to-mesenchymal, in situ carcinoma) and stromal (immune, extracellular matrix, p53-like) signatures. Then, classifier methods with this 68-gene panel were developed in silico and validated on public data sets with available subtype class information (MD Anderson [MDA], The Cancer Genome Atlas [TCGA], Lund, Consensus). Finally, expression of the selected 68 genes was determined in 104 frozen tissue samples of our MIBC cohort by RT-qPCR using the TaqMan Array Card platform and samples were classified by our newly developed classifiers. The prognostic value of each subtype classification system and molecular signature scores were assessed. We found that the reduced marker set combined with the developed classifiers were able to reproduce the TCGA II, MDA, Lund and Consensus subtype classification systems with an overlap of 79%, 76%, 69% and 64%, respectively. Importantly, we could successfully classify 96% (100/104) of our MIBC samples by using RT-qPCR. Neuronal and luminal subtypes and low stromal gene expressions were associated with poor survival. In conclusion, we developed a robust and feasible method for the molecular subtyping according to the TCGA II, MDA, Lund and Consensus classifications. Our results suggest that stromal signatures have a superior prognostic value compared to tumor intrinsic signatures and therefore underline the importance of tumor-stroma interaction during the progression of MIBC.

Solid-State Stability Profiling of Ramipril to Optimize Its Quality Efficiency and Safety.

High global expenditure on out-of-label-date drugs, along with safety concerns associated with the accumulation of degradation impurities, justify the need for stability profiling. In this article, a comprehensive study on the solid-state stability of ramipril (RAM) was performed via isothermal methods under stress conditions. A validated stability-indicating HPLC protocol was used. The effects of various factors on the rate of RAM degradation were investigated, including: temperature, relative air humidity (RH), excipients (talc, starch, methylcellulose and hydroxypropyl methylcellulose), mode of tablet storage, and immediate packaging. The degradation impurities were also identified by HPLC-MS. It was found that RAM was unstable, and temperature accelerated its degradation. RAM was also vulnerable to RH changes, suggesting that it must be protected from moisture. The reaction followed first-order kinetics. The studied excipients stabilized RAM as a pure substance. The tableting process deteriorated its stability, explaining the need for appropriate immediate packaging. RAM in the form of tablets must be stored in blisters, and it cannot be crushed into two halves. The degradation impurities were ramiprilat and the diketopiperazine derivative.

Titanium Dioxide Nanoparticles in Food and Personal Care Products-What Do We Know about Their Safety?

Titanium dioxide (TiO2) is a material of diverse applications commonly used as a food additive or cosmetic ingredient. Its prevalence in products of everyday use, especially in nanosize, raises concerns about safety. Current findings on the safety of titanium dioxide nanoparticles (TiO2 NPs) used as a food additive or a sunscreen compound are reviewed and systematized in this publication. Although some studies state that TiO2 NPs are not harmful to humans through ingestion or via dermal exposure, there is a considerable number of data that demonstrated their toxic effects in animal models. The final agreement on the safety of this nanomaterial has not yet been reached among researchers. There is also a lack of official, standardized guidelines for thorough characterization of TiO2 NPs in food and cosmetic products, provided by international authorities. Recent advances in the application of 'green-synthesized' TiO2 NPs, as well as comparative studies of the properties of 'biogenic' and 'traditional' nanoparticles, are presented. To conclude, perspectives and directions for further studies on the toxicity of TiO2 NPs are proposed.

Costs and effectiveness of pharmacist-led group medical visits for type-2 diabetes: A multi-center randomized controlled trial.

OBJECTIVES: The effectiveness and costs associated with addition of pharmacist-led group medical visits to standard care for patients with Type-2 Diabetes Mellitus (T2DM) is unknown. METHODS: Randomized-controlled-trial in three US Veteran Health Administration (VHA) Hospitals, where 250 patients with T2DM, HbA1c >7% and either hypertension, active smoking or hyperlipidemia were randomized to either (1) addition of pharmacist-led group-medical-visits or (2) standard care alone for 13 months. Group (4-6 patients) visits consisted of 2-hour, education and comprehensive medication management sessions once weekly for 4 weeks, followed by quarterly visits. Change from baseline in cardiovascular risk estimated by the UKPDS-risk-score, health-related quality-of-life (SF36v) and institutional healthcare costs were compared between study arms. RESULTS: After 13 months, both groups had similar and significant improvements from baseline in UKPDS-risk-score (-0.02 ±0.09 and -0.04 ±0.09, group visit and standard care respectively, adjusted p<0.05 for both); however, there was no significant difference between the study arms (adjusted p = 0.45). There were no significant differences on improvement from baseline in A1c, systolic-blood-pressure, and LDL as well as health-related quality-of-life measures between the study arms. Compared to 13 months prior, the increase in per-person outpatient expenditure from baseline was significantly lower in the group visit versus the standard care arm, both during the study intervention period and at 13-months after study interventions. The overall VHA healthcare costs/person were comparable between the study arms during the study period (p = 0.15); then decreased by 6% for the group visit but increased by 13% for the standard care arm 13 months post-study (p<0.01). CONCLUSIONS: Addition of pharmacist-led group medical visits in T2DM achieved similar improvements from baseline in cardiovascular risk factors than usual care, but with reduction in the healthcare costs in the group visit arm 13 months after completion compared to the steady rise in cost for the usual care arm. TRIAL REGISTRATION: NCT00554671 ClinicalTrials.gov.

Reconstitution of Isotopically Labeled Ribosomal Protein L29 in the 50S Large Ribosomal Subunit for Solution-State and Solid-State NMR.

Solid-state nuclear magnetic resonance (NMR) has recently emerged as a method of choice to study structural and dynamic properties of large biomolecular complexes at atomic resolution. Indeed, recent technological and methodological developments have enabled the study of ever more complex systems in the solid-state. However, to explore multicomponent protein complexes by NMR, specific labeling schemes need to be developed that are dependent on the biological question to be answered. We show here how to reconstitute an isotopically labeled protein within the unlabeled 50S or 70S ribosomal subunit. In particular, we focus on the 63-residue ribosomal protein L29 (~7 kDa), which is located at the exit of the tunnel of the large 50S ribosomal subunit (~1.5 MDa). The aim of this work is the preparation of a suitable sample to investigate allosteric conformational changes in a ribosomal protein that are induced by the nascent polypeptide chain and that trigger the interaction with different chaperones (e.g., trigger factor or SRP).