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Abstract Graphene is a promising material for applications as a channel in graphene field-effect transistors (GFETs) which may be used as a building block for optoelectronics, high-frequency devices and sensors. However, these devices require gate insulators which ideally should form atomically flat interfaces with graphene and at the same time contain small densities of traps to maintain high device stability. Previously used amorphous oxides, such as SiO2 and Al2O3, however, typically suffer from oxide dangling bonds at the interface, high surface roughness and numerous border oxide traps. In order to address these challenges, here we use 2 nm thick epitaxial CaF2 as a gate insulator in GFETs. By analyzing device-to-device variability for about 200 devices fabricated in two batches, we find that tens of them show similar gate transfer characteristics. Our statistical analysis of the hysteresis up to 175oC has revealed that while an ambient-sensitive counterclockwise hysteresis can be present in some devices, the dominant mechanism is thermally activated charge trapping by border defects in CaF2 which results in the conventional clockwise hysteresis. We demonstrate that both the hysteresis and bias-temperature instabilities in our GFETs with CaF2 are comparable to similar devices with SiO2 and Al2O3. In particular, we achieve a small hysteresis below 0.01 V for equivalent oxide thickness (EOT) of about 1 nm at the electric fields up to 15 MV cm−1 and sweep times in the kilosecond range. Thus, our results demonstrate that crystalline CaF2 is a promising insulator for highly-stable GFETs.

Abstract Recent advances in fabricating field-effect transistors with MoS2 and other related two-dimensional (2D) semiconductors have inspired the industry to begin with the integration of these emerging technologies into FAB-compatible process flows. Just like in the lab research on 2D devices performed in the last decade, focus during development is typically put on pure technology-related issues, such as low-temperature growth methods of large-area 2D films on target substrates, damage-free transfer from sacrificial substrates and growth of top-gate oxides. With maturing technology, the problem of stability limitations caused by oxide traps is gradually coming into focus now. Thus, here we report an in-depth analysis of hysteresis and bias-temperature instabilities for MoS2 FETs fabricated using a 300 mm FAB-compatible process. By performing a comprehensive statistical analysis on devices with top gate lengths ranging between 18 nm and 10 μm, we demonstrate that aggressive scaling results in additional stability problems, likely caused by defective edges of the scaled top gates, in particular at higher operation temperatures. These are important insights for understanding and addressing the stability limitations in future nanoscale 2D FETs produced using FAB process lines.

Electronics: encapsulated black phosphorous enables stable, long-lasting transistors Field effect transistors made of ultra-thin black phosphorous can retain long-term stability and reproducible electrical characteristics. A team led by Prof. Deji Akinwande at UT Austin developed a conformal encapsulation method of black phosphorous transistors with a 25 nm thick Al2O3 layer. Characterization of these devices by Dr. Yury Illarionov at TU Wien has shown that encapsulation results in a substantial improvement of device stability and reliability for at least 17 months in ambient conditions. The density of oxide traps that would cause deleterious variations of the device threshold voltage, thus hindering reproducibility, is as low as 1017 cm−3/eV at room temperature. This is comparable to values obtained for commercial silicon devices. Remarkably, the subthreshold slope of the black phosphorous field-effect transistors becomes steeper after several months, a signature of performance improvement that points towards a positive aging effect, despite extended storage and operation in the laboratory environment.

Contact resistance is a multifaceted challenge faced by the 2D materials community. Large Schottky barrier heights and gap-state pinning are active obstacles that require an integrated approach to achieve the development of high-performance electronic devices based on 2D materials. In this work, we present semiconducting PtSe 2 field effect transistors with all-van-der-Waals electrode and dielectric interfaces. We use graphite contacts, which enable high I ON / I OFF ratios up to 10 9 with currents above 100 μA μm -1 and mobilities of 50 cm 2  V -1  s -1 at room temperature and over 400 cm 2  V -1  s -1 at 10 K. The devices exhibit high stability with a maximum hysteresis width below 36 mV nm -1 . The contact resistance at the graphite-PtSe 2 interface is found to be below 700 Ω μm. Our results present PtSe 2 as a promising candidate for the realization of high-performance 2D circuits built solely with 2D materials.

Defects play a pivotal role in limiting the performance and reliability of nanoscale devices. Field-effect transistors (FETs) based on atomically thin two-dimensional (2D) semiconductors such as monolayer MoS 2 are no exception. Probing defect dynamics in 2D FETs is therefore of significant interest. Here, we present a comprehensive insight into various defect dynamics observed in monolayer MoS 2 FETs at varying gate biases and temperatures. The measured source-to-drain currents exhibit random telegraph signals (RTS) owing to the transfer of charges between the semiconducting channel and individual defects. Based on the modeled temperature and gate bias dependence, oxygen vacancies or aluminum interstitials are probable defect candidates. Several types of RTSs are observed including anomalous RTS and giant RTS indicating local current crowding effects and rich defect dynamics in monolayer MoS 2 FETs. This study explores defect dynamics in large area-grown monolayer MoS 2 with ALD-grown Al 2 O 3 as the gate dielectric.

Within the last decade, considerable efforts have been devoted to fabricating transistors utilizing 2D semiconductors. Also, small circuits consisting of a few transistors have been demonstrated, including inverters, ring oscillators, and static random access memory cells. However, for industrial applications, both time-zero and time-dependent variability in the performance of the transistors appear critical. While time-zero variability is primarily related to immature processing, time-dependent drifts are dominated by charge trapping at defects located at the channel/insulator interface and in the insulator itself, which can substantially degrade the stability of circuits. At the current state of the art, 2D transistors typically exhibit a few orders of magnitude higher trap densities than silicon devices, which considerably increases their time-dependent variability, resulting in stability and yield issues. Here, the stability of currently available 2D electronics is carefully evaluated using circuit simulations to determine the impact of transistor-related issues on the overall circuit performance. The results suggest that while the performance parameters of transistors based on certain material combinations are already getting close to being competitive with Si technologies, a reduction in variability and defect densities is required. Overall, the criteria for parameter variability serve as guidance for evaluating the future development of 2D technologies., (© 2022 The Authors. Advanced Materials published by Wiley-VCH GmbH.)

For ultra-scaled technology nodes at channel lengths below 12 nm, two-dimensional (2D) materials are a potential replacement for silicon since even atomically thin 2D semiconductors can maintain sizable mobilities and provide enhanced gate control in a stacked channel nanosheet transistor geometry. While theoretical projections and available experimental prototypes indicate great potential for 2D field effect transistors (FETs), several major challenges must be solved to realize CMOS logic circuits based on 2D materials at the wafer scale. This review discusses the most critical issues and benchmarks against the targets outlined for the 0.7 nm node in the International Roadmap for Devices and Systems scheduled for 2034. These issues are grouped into four areas; device scaling, the formation of low-resistive contacts to 2D semiconductors, gate stack design, and wafer-scale process integration. Here, we summarize recent developments in these areas and identify the most important future research questions which will have to be solved to allow for industrial adaptation of the 2D technology.

Electronic devices based on two-dimensional semiconductors suffer from limited electrical stability because charge carriers originating from the semiconductors interact with defects in the surrounding insulators. In field-effect transistors, the resulting trapped charges can lead to large hysteresis and device drifts, particularly when common amorphous gate oxides (such as silicon or hafnium dioxide) are used, hindering stable circuit operation. Here, we show that device stability in graphene-based field-effect transistors with amorphous gate oxides can be improved by Fermi-level tuning. We deliberately tune the Fermi level of the channel to maximize the energy distance between the charge carriers in the channel and the defect bands in the amorphous aluminium gate oxide. Charge trapping is highly sensitive to the energetic alignment of the Fermi level of the channel with the defect band in the insulator, and thus, our approach minimizes the amount of electrically active border traps without the need to reduce the total number of traps in the insulator., Competing Interests: Competing interestsThe authors declare no competing interests., (© The Author(s) 2022.)

Freshwater harmful algal blooms (HABs) are a major environmental health problem worldwide. HABs are caused by a predominance of cyanobacteria, some of which produce potent toxins. The most ubiquitous cyanotoxin is microcystin (MC) and the congener MC-LR is the most studied due to its toxicity. Short-term exposure to toxins can cause gut microbiome disturbances, but this has not been well described with MC-LR exposure. This study investigated the gut microbial communities of mice from a prior study, which identified significant liver toxicity from ingestion of MC-LR daily for 8 days. CD-1 mice were divided into three dosage groups: control, low exposure (sub-lethal MC-LR concentration), and high exposure (near-lethal MC-LR concentration). Fecal samples were analyzed using 16S rRNA sequencing. Results revealed that at population level, there were no significant shifts in bacterial diversity or the microbial community structure over the exposure period. However, there were significant differences between male and female mice. Predictive functional gene analysis indicated that several metabolic pathways were significantly different in the high dose group before exposure and following 7 doses of MC-LR, as well as between the control and high dose groups on Day 8. Significant differentially abundant taxa were also identified contributing to these pathways. Several pathways, including superpathway of N-acetylneuraminate degradation, were related to liver and gut inflammation. The outcome of this study suggests a need for in-depth investigation of metabolic activity and other functions in the gut in future studies, as well as potential consideration of the role of sex in MC-LR toxicity., (Copyright © 2021 The Authors. Published by Elsevier Inc. All rights reserved.)

Microcystins (MCs) are the most prevalent cyanotoxins reported in freshwater. While numerous studies have examined the toxicological impacts of MCs on mammalian systems, very few have examined the chronic impacts of MCs on the gut microbiome of exposed organisms. Our understanding of the relationship of MCs, especially lysed toxic cyanobacteria, and the gut microbiota is very limited. The objective of this study was to determine the impacts of MC-LR and Microcystis lysate ingestion on the gut microbiome in a hepatocellular carcinoma mouse model, simulating a high-risk population and exposure at an environmentally relevant MC level. Mice were assigned to 4 groups (MC-LR; Microcystis lysate; Negative control; Positive (liver carcinogen) control). Fecal samples were collected every 8 weeks. Bacterial community and colony counts were analyzed. The abundance of Firmicutes in the positive control and lysate group was higher than the negative control and MC group. Exposure to MC-LR or lysate was associated with significantly decreased bacterial diversity. A distinct separation of the three groups (MC-LR/lysate/carcinogen) from the negative was much more apparent in their gut microbiome as the exposure time increased. The MC-LR and lysate groups showed gut microbiome structure responding to lipid metabolism disturbance and high stress. Bacterial colony count was significantly lower in all the treated groups than the negative control. Our study highlights that chronic exposure to MC-LR and Microcystis lysate negatively impacts gut microbiome succession and altered the bacterial community structure into the one similar to the carcinogen group, which may indicate that the change favors progression of hepatocellular carcinoma. In a future study, more in-depth investigation is warranted to better understand the liver-gut nexus in promoting liver cancer among those exposed to MC and toxic cyanobacteria., (Copyright © 2020. Published by Elsevier Inc.)

Chemoproteomics is a key technology to characterize the mode of action of drugs, as it directly identifies the protein targets of bioactive compounds and aids in the development of optimized small-molecule compounds. Current approaches cannot identify the protein targets of a compound and also detect the interaction surfaces between ligands and protein targets without prior labeling or modification. To address this limitation, we here develop LiP-Quant, a drug target deconvolution pipeline based on limited proteolysis coupled with mass spectrometry that works across species, including in human cells. We use machine learning to discern features indicative of drug binding and integrate them into a single score to identify protein targets of small molecules and approximate their binding sites. We demonstrate drug target identification across compound classes, including drugs targeting kinases, phosphatases and membrane proteins. LiP-Quant estimates the half maximal effective concentration of compound binding sites in whole cell lysates, correctly discriminating drug binding to homologous proteins and identifying the so far unknown targets of a fungicide research compound.

Mechanically exfoliated 2D hexagonal boron nitride (h-BN) is currently the preferred dielectric material to interact with graphene and 2D transition metal dichalcogenides in nanoelectronic devices, as they form a clean van der Waals interface. However, h-BN has a low dielectric constant (≈3.9), which in ultrascaled devices results in high leakage current and premature dielectric breakdown. Furthermore, the synthesis of h-BN using scalable methods, such as chemical vapor deposition, requires very high temperatures (>900 °C) , and the resulting h-BN stacks contain abundant few-atoms-wide amorphous regions that decrease its homogeneity and dielectric strength. Here it is shown that ultrathin calcium fluoride (CaF 2 ) ionic crystals could be an excellent solution to mitigate these problems. By applying >3000 ramped voltage stresses and several current maps at different locations of the samples via conductive atomic force microscopy, it is statistically demonstrated that ultrathin CaF 2 shows much better dielectric performance (i.e., homogeneity, leakage current, and dielectric strength) than SiO 2 , TiO 2 , and h-BN. The main reason behind this behavior is that the cubic crystalline structure of CaF 2 is continuous and free of defects over large regions, which prevents the formation of electrically weak spots., (© 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Nanoelectronic devices based on 2D materials are far from delivering their full theoretical performance potential due to the lack of scalable insulators. Amorphous oxides that work well in silicon technology have ill-defined interfaces with 2D materials and numerous defects, while 2D hexagonal boron nitride does not meet required dielectric specifications. The list of suitable alternative insulators is currently very limited. Thus, a radically different mindset with respect to suitable insulators for 2D technologies may be required. We review possible solution scenarios like the creation of clean interfaces, production of native oxides from 2D semiconductors and more intensive studies on crystalline insulators.

ETD151, an analogue of the antifungal insect defensin heliomicin, is an antifungal peptide active against yeasts and filamentous fungi. To decipher the mechanisms underlying its molecular action on the phytopathogenic fungus Botrytis cinerea , a necrotrophic pathogen responsible for gray mold disease, we investigated the changes in 3 day-old mycelia upon treatment with different concentrations of ETD151. Optical and fluorescence microscopies were used prior to establishing the peptide/protein profiles through two mass spectrometry approaches: MALDI profiling, to generate molecular mass fingerprints as peptide signatures, and a gel-free bottom-up proteomics approach. Our results show that a concentration of ETD151 above the half-maximal inhibitory concentration can alter the integrity of the mycelial structure of B. cinerea . Furthermore, reproducible modifications of the peptide/protein composition were demonstrated in the presence of ETD151 within a 1500-16,000 mass ( m/z ) range. After the robustness of LC-ESI-MS/MS analysis on B. cinerea mycelial extracts was confirmed, our analyses highlighted 340 significantly modulated proteins upon treatment with ETD151 within a 4.8-466 kDa mass range. Finally, data mapping on KEGG pathways revealed the molecular impact of ETD151 on at least six pathways, namely, spliceosome, ribosome, protein processing in endoplasmic reticulum, endocytosis, MAPK signaling pathway, and oxidative phosphorylation.

RNAi mediated by small-interfering RNAs (siRNAs) operates via transcriptional (TGS) and posttranscriptional gene silencing (PTGS). In Arabidopsis thaliana , TGS relies on DICER-LIKE-3 (DCL3)-dependent 24-nt siRNAs loaded into AGO4-clade ARGONAUTE effector proteins. PTGS operates via DCL4-dependent 21-nt siRNAs loaded into AGO1-clade proteins. We set up and validated a medium-throughput, semi-automatized procedure enabling chemical screening, in a 96-well in vitro format, of Arabidopsis transgenic seedlings expressing an inverted-repeat construct from the phloem companion cells. The ensuing quantitative PTGS phenotype was exploited to identify molecules, which, upon topical application, either inhibit or enhance siRNA biogenesis/activities. The vast majority of identified modifiers were enhancers, among which Sortin1, Isoxazolone, and [5-(3,4-dichlorophenyl)furan-2-yl]-piperidine-1-ylmethanethione (DFPM) provided the most robust and consistent results, including upon their application onto soil-grown plants in which their effect was nonautonomous and long lasting. The three molecules increased the RNAi potency of the inverted-repeat construct, in large part by enhancing 21-nt siRNA accumulation and loading into AGO1, and concomitantly reducing AGO4 and DCL3 levels in planta. A similar, albeit not identical effect, was observed on 22-nt siRNAs produced from a naturally occurring inverted-repeat locus, demonstrating that the molecules also enhance endogenous PTGS. In standardized assays conducted in seedling extracts, the three enhancers selectively increased DCL4-mediated processing of in vitro-synthesized double-stranded RNAs, indicating the targeting of a hitherto unknown PTGS component probably independent of the DCL4-cofactor DOUBLE-STRANDED RNA-BINDING 4 (DRB4). This study establishes the proof-of-concept that RNAi efficacy can be modulated by chemicals in a whole organism. Their potential applications and the associated future research are discussed., (© 2019 Jay et al.; Published by Cold Spring Harbor Laboratory Press for the RNA Society.)

MoS 2 has received a lot of attention lately as a semiconducting channel material for electronic devices, in part due to its large band gap as compared to that of other 2D materials. Yet, the performance and reliability of these devices are still severely limited by defects which act as traps for charge carriers, causing severely reduced mobilities, hysteresis, and long-term drift. Despite their importance, these defects are only poorly understood. One fundamental problem in defect characterization is that due to the large defect concentration only the average response to bias changes can be measured. On the basis of such averaged data, a detailed analysis of their properties and identification of particular defect types are difficult. To overcome this limitation, we here characterize single defects on MoS 2 devices by performing measurements on ultrascaled transistors (∼65 × 50 nm) which contain only a few defects. These single defects are characterized electrically at varying gate biases and temperatures. The measured currents contain random telegraph noise, which is due to the transfer of charge between the channel of the transistors and individual defects, visible only due to the large impact of a single elementary charge on the local electrostatics in these small devices. Using hidden Markov models for statistical analysis, we extract the charge capture and emission times of a number of defects. By comparing the bias-dependence of the measured capture and emission times to the prediction of theoretical models, we provide simple rules to distinguish oxide traps from adsorbates on these back-gated devices. In addition, we give simple expressions to estimate the vertical and energetic positions of the defects. Using the methods presented in this work, it is possible to locate the sources of performance and reliability limitations in 2D devices and to probe defect distributions in oxide materials with 2D channel materials.

A combination of mutasynthesis, precursor-directed biosynthesis and semisynthesis provides access to new ansamitocin derivatives including new nanostructured particle-drug conjugates. These conjugates are based on the toxin ansamitocin and superparamagnetic iron oxide-silica core shell particles. New ansamitocin derivatives that are functionalized either with alkynyl- or azido groups in the ester side chain at C-3 are attached to nanostructured iron oxide core-silica shell particles. Upon exposure to an oscillating electromagnetic field these conjugates heat up and the ansamitocin derivatives are released by a retro-Diels-Alder reaction. For example, one ansamitocin derivative exerts strong antiproliferative activity against various cancer cell lines in the lower nanomolar range while the corresponding nanostructured particle-drug conjugate is not toxic. Therefore, these new conjugates can serve as dormant toxins that can be employed simultaneously in hyperthermia and chemotherapy when external inductive heating is applied., (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Purpose: In this study, the contrasting properties of human serum albumin nanoparticles (HSA-NPs) loaded with gadolinium-diethylenetriamine pentaacetic acid (Gd-DTPA) and coated with transferrin in MRI in mice are evaluated., Procedures: HSA-NPs were conjugated with Gd-DTPA (Gd-HSA-NPs) and coupled with transferrin (Gd-HSA-NP-Tf). Mice underwent MRI before or after injection of Gd-DTPA, Gd-HSA-NP, or Gd-HSA-NP-Tf., Results: All the studied contrast agents provided a contrast enhancement (CE) in the blood, heart muscle, and liver. Compared to Gd-DTPA, CE with HSA-NP was achieved at lower Gd doses. Gd-HSA-NP-Tf yielded significantly higher CE than Gd-HSA-NP in the skeletal muscle, blood, cardiac muscle, and liver (p < 0.05). Gd-HSA-NP-Tf achieved a significantly higher CE than Gd-HSA-NP and Gd-DTPA in the blood, cardiac muscle, and liver (p < 0.05). In the brain, only Gd-HSA-NP-Tf was found to cause a significant CE (p < 0.05)., Conclusions: The Gd-HSA nanoparticles have potential as MRI contrast agents. In particular, Gd-HSA-NP-Tf has a potential as a specific contrast agent for the brain, while the blood-brain barrier is still intact, as well as in the heart, liver, and skeletal muscle.

Different from regular small molecule contrast agents, nanoparticle-based contrast agents have a longer circulation time and can be modified with ligands to confer tissue-specific contrasting properties. We evaluated the tissue distribution of polymeric nanoparticles (NPs) prepared from human serum albumin (HSA), loaded with gadolinium-diethylenetriaminepentaacetic acid (Gd-DTPA) (Gd-HSA-NP), and coated with folic acid (FA) (Gd-HSA-NP-FA) in mice by magnetic resonance imaging (MRI). FA increases the affinity of the Gd-HSA-NP to FA receptor-expressing cells. Clinical 3 T MRI was used to evaluate the signal intensities in the different organs of mice injected with Gd-DTPA, Gd-HSA-NP, or Gd-HSA-NP-FA. Signal intensities were measured and standardized by calculating the signal to noise ratios. In general, the NP-based contrast agents provided stronger contrasting than Gd-DTPA. Gd-HSA-NP-FA provided a significant contrast enhancement (CE) in the brain (p  =  .0032), whereas Gd-DTPA or Gd-HSA-NP did not. All studied MRI contrast agents showed significant CE in the blood, kidney, and liver (p < .05). Gd-HSA-NP-FA elicited significantly higher CE in the blood than Gd-HSA-NP (p  =  .0069); Gd-HSA-NP and Gd-HSA-NP-FA did not show CE in skeletal muscle and gallbladder; Gd-HSA-NP, but not Gd-HSA-NP-FA, showed CE in the cardiac muscle. Gd-HSA-NP-FA has potential as an MRI contrast agent in the brain.

We describe the unprecedented formation of six ansamitocin derivatives that are deoxygenated at C-7 of the ansamitocin core, obtained during fermentation experiments by employing a variety of Actinosynnema pretiosum mutants and mutasynthetic approaches. We suggest that the formation of these derivatives is based on elimination at C-7/C-8 followed by reduction(s) of the intermediate enone. In bioactivity tests, only ansamitocin derivatives bearing an ester side chain at C-3 showed strong antiproliferative activity.

The second generation photosensitizer mTHPC was approved by the European Medicines Agency (EMA) for the palliative treatment of advanced head and neck cancer in October 2001. It is known that mTHPC possesses a significant phototoxicity against a variety of human cancer cells in vitro but also exhibits dark toxicity and can cause adverse effects (especially skin photosensitization). Due to its poor water solubility, the administration of hydrophobic photosensitizer still presents several difficulties. To overcome the administration problems, the use of nanoparticles as drug carrier systems is much investigated. Nanoparticles based on poly(lactic-co-glycolic acid) (PLGA) have been extensively studied as delivery systems into tumours due to their biocompatibility and biodegradability. The goal of this study was the comparison of free mTHPC and mTHPC-loaded PLGA nanoparticles concerning cytotoxicity and intracellular accumulation in human colon carcinoma cells (HT29). The nanoparticles delivered the photosensitizer to the colon carcinoma cells and enabled drug release without losing its activity. The cytotoxicity assays showed a time- and concentration-dependent decrease in cell proliferation and viability after illumination. However, first and foremost mTHPC lost its dark toxic effects using the PLGA nanoparticles as a drug carrier system. Therefore, PLGA nanoparticles are a promising drug carrier system for the hydrophobic photosensitizer mTHPC.

Folic acid has been previously demonstrated to mediate intracellular nanoparticle uptake. Here, we investigated cellular uptake of folic acid-conjugated human serum albumin nanoparticles (HSA NPs). HSA NPs were prepared by desolvation and stabilised by chemical cross-linking with glutaraldehyde. Folic acid was covalently coupled to amino groups on the surface of HSA NPs by carbodiimide reaction. Preparation resulted in spherical HSA NPs with diameters of 239 ± 26 nm. As shown by size exclusion chromatography, 7.40 ± 0.90 μg folate was bound per mg HSA NPs. Cellular NP binding and uptake were studied in primary normal human foreskin fibroblasts (HFFs), the human neuroblastoma cell line UKF-NB-3, and the rat glioblastoma cell line 101/8 by fluorescence spectrophotometry, flow cytometry, and confocal laser scanning microscopy. Covalent conjugation of folic acid to HSA NPs increased NP uptake into cancer cells but not into HFFs. Free folic acid interfered with cancer cell uptake of folic acid-conjugated HSA NPs but not with uptake of folic acid-conjugated HSA NPs into HFFs. These data suggest that covalent linkage of folic acid can specifically increase cancer cell HSA NP uptake., (Copyright © 2011 Elsevier B.V. All rights reserved.)

New ansamitocin derivatives were prepared by feeding aminobenzoic acid derivatives to cultures of Actinosynnema pretiosum HGF073, a mutant strain blocked in the biosynthesis of the required 3-amino-5-hydroxybenzoic acid (AHBA) starter unit. Use of several aminobenzoic acids as precursors led to a spectrum of products, reflecting the sequence of post-PKS tailoring steps involved in the generation of ansamitocins and adding novel aspects to the published suggestion model of post-PKS tailoring logic and flexibility. The studies provide insights into the substrate flexibility of the enzymes required for ansamitocin biosynthesis in A. pretiosum, whereas preliminary biological testing of the derivatives isolated and fully characterized by NMR spectroscopy allowed structure-activity relationship assignments to be made for a variety of intermediates occurring during the post-PKS tailoring sequence in ansamitocin biosynthesis., (Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Human serum albumin (HSA) nanoparticles (NP) were prepared by desolvation. Insulin or an anti-insulin receptor monoclonal antibody (29B4) were covalently coupled to the HSA NP, using the NHS-PEG-MAL-5000 crosslinker. Loperamide-loaded HSA NP with covalently bound insulin or the 29B4 antibodies induced significant antinociceptive effects in the tail-flick test in ICR (CD-1) mice after intravenous injection, demonstrating that insulin or these antibodies covalently coupled to HSA NP are able to transport loperamide across the blood-brain barrier (BBB) which it normally is unable to cross. Control loperamide-loaded HSA NP with immunoglobulin G antibodies yielded only marginal effects. The loperamide transport across the BBB using the NP with covalently attached insulin could be totally inhibited by the pretreatment with the antibody 29B4.

The timing of introduction of the unusually placed Delta(11,13) diene system in ansamitocin (AP) biosynthesis was probed by synthesizing optically active potential tri- and tetraketide intermediates as their SNAC thioesters. An AP-nonproducing mutant Actinosynnema pretiosum was complemented by the R enantiomer of the triketide and by the tetraketide with rearranged double bonds, but not by the tetraketide carrying the double bonds in conjugation to the thioester function. The results show that the double bonds are installed in their final positions during processing of the nascent polyketide on module 3 of the asm PKS and that KS4 of the PKS acts as a gatekeeper which accepts only a tetraketide with shifted double bonds as substrate for further processing.

Physical therapies and exercise are beneficial not only for physiological recovery in inflamed or injured joints, but also for promoting a homeostatic equilibrium in healthy joints. Human joints provide the pivot points and physiological hinges essential for ambulation and movement to the body, and it is this mobility that in return promotes the health of the joints. But how mobilization regulates the joint microenvironment at the molecular level has remained enigmatic for many years. Recent advances in joint biomechanics and molecular approaches have facilitated an enriched understanding of how joints operate. Consequently, the mechanisms active during joint inflammation that lead to arthritic conditions, both in vivo in animal models, and in vitro at cell and tissue levels, have become increasingly detailed and defined. These efforts have produced mounting evidences supporting the premise that biomechanical signals play a fundamental role in both the etiopathogenesis of arthritic diseases and in the physiological restoration of joints. This report aims to summarize current peer-reviewed literature and available experimental data to explain how the signals generated by mechanical forces/joint mobilization generate beneficial effects on inflamed articular cartilage, and to propose the basis for using appropriate physical therapies for the optimal benefit to the patient suffering from joint associated injuries.

Secondary metabolites are an extremely diverse and important group of natural products with industrial and biomedical implications. Advances in metabolic engineering of both native and heterologous secondary metabolite producing organisms have allowed the directed synthesis of desired novel products by exploiting their biosynthetic potentials. Metabolic engineering utilises knowledge of cellular metabolism to alter biosynthetic pathways. An important technique that combines chemical synthesis with metabolic engineering is mutasynthesis (mutational biosynthesis; MBS), which advanced from precursor-directed biosynthesis (PDB). Both techniques are based on the cellular uptake of modified biosynthetic intermediates and their incorporation into complex secondary metabolites. Mutasynthesis utilises genetically engineered organisms in conjunction with feeding of chemically modified intermediates. From a synthetic chemist's point of view the concept of mutasynthesis is highly attractive, as the method combines chemical expertise with Nature's synthetic machinery and thus can be exploited to rapidly create small libraries of secondary metabolites. However, in each case, the method has to be critically compared with semi- and total synthesis in terms of practicability and efficiency. Recent developments in metabolic engineering promise to further broaden the scope of outsourcing chemically demanding steps to biological systems.

Objective: While the effects of biomechanical signals in the form of joint movement and exercise are known to be beneficial to inflamed joints, limited information is available regarding the intracellular mechanisms of their actions. This study was undertaken to examine the intracellular mechanisms by which biomechanical signals suppress proinflammatory gene induction by the interleukin-1-beta (IL-1beta)-induced NF-kappaB signaling cascade in articular chondrocytes., Methods: Primary rat articular chondrocytes were exposed to biomechanical signals in the form of cyclic tensile strain, and the effects on the NF-kappaB signaling cascade were examined by Western blot analysis, real-time polymerase chain reaction, and immunofluorescence., Results: Cyclic tensile strain rapidly inhibited the IL-1beta-induced nuclear translocation of NF-kappaB, but not its IL-1beta-induced phosphorylation at serine 276 and serine 536, which are necessary for its transactivation and transcriptional efficacy, respectively. Examination of upstream events revealed that cyclic tensile strain also inhibited the cytoplasmic protein degradation of IkappaBbeta and IkappaBalpha, as well as repressed their gene transcription. Additionally, cyclic tensile strain induced a rapid nuclear translocation of IkappaBalpha to potentially prevent NF-kappaB binding to DNA. Furthermore, the inhibition of IL-1beta-induced degradation of IkappaB by cyclic tensile strain was mediated by down-regulation of IkappaB kinase activity., Conclusion: These results indicate that the signals generated by cyclic tensile strain act at multiple sites within the NF-kappaB signaling cascade to inhibit IL-1beta-induced proinflammatory gene induction. Taken together, these findings provide insight into how biomechanical signals regulate and reduce inflammation, and underscore their potential in enhancing the ability of chondrocytes to curb inflammation in diseased joints.

Nd:YAG, argon and diode lasers have been used in neurosurgical procedures including neuroendoscopy. However, many neurosurgeons are reluctant to use these lasers because of their inappropriate wavelength and uncontrollable tissue interaction, which has the potential to cause serious complications. Recently, a 2.0-microm near infrared laser with adequate wavelength and minimal tissue penetration became available. This laser was developed for endoscopic neurosurgical procedures. It is the aim of the study to report the initial experiences with this laser in neuroendoscopic procedures. We have performed 43 laser-assisted neuroendoscopic procedures [multicompartmental congenital, posthaemorrhagic or postinfectious hydrocephalus (n = 17), tumour biopsies (n = 6), rescue of fixed and allocated ventricular catheters (n = 2), endoscopic third ventriculostomy (ETV, n = 17) and aqueductoplasty (n = 1)] in 41 patients aged between 3 months and 80 years. The laser beam was delivered through a 365-microm bare silica fibre introduced through the working channel of a rigid endoscope. It was used for the opening of cysts, perforating the third ventricular floor, and for coagulation prior to and after biopsy. The therapeutic goals [creating unhindered cerebrospinal fluid (CSF) flow between cysts, ventricles and cisterns, sufficient tissue samples for histopathological diagnosis and catheter rescue] were achieved in 40 patients by the first and in 2 patients by a second neuroendoscopic operation. In one child, a CSF shunt was later required despite patency of the created stoma proven by magnetic resonance imaging (MRI). In another patient ETV was abandoned due to a tiny third ventricle. There was neither mortality nor transient or permanent morbidity. The authors conclude that the use of the 2.0-microm near infrared laser enables safe and effective procedures in neuroendoscopy.

Expression of the fibroblast growth factor 4 (FGF-4) gene is tightly regulated during mammalian development. Dysregulation of FGF-4 gene expression results in cell transformation and tumorigenesis. It is therefore pertinent to investigate the regulatory mechanisms which control expression of FGF-4. In an initial attempt to identify exogenous factors other than retinoic acid which might control FGF-4 expression, we have investigated the response of endogenous FGF-4 to serum in a number of embryonal carcinoma and embryonic stem cell lines. We have identified a human embryonal carcinoma cell line (Tera-2) in which the FGF-4 gene can be induced by serum. In Tera-2 cells made quiescent by serum deprivation, expression of the FGF-4 gene is repressed. Subsequent addition of serum reactivates FGF-LC expression and further addition of cycloheximide results in superinduction of mRNA suggesting that FGF-4 may be classified as an early response gene. It is suggested that this observation may be explained, at least in part, by the stage of differentiation of the Tera-2 cells.