Fungal Origins of the Bicyclo[2.2.2]diazaoctane Ring System of Prenylated Indole Alkaloids

Over eight different families of natural products, consisting of nearly seventy secondary metabolites, which contain the bicyclo[2.2.2]diazaoctane ring system, have been isolated from various Aspergillus, Penicillium, and Malbranchea species. Since 1968, these secondary metabolites have been the focus of numerous biogenetic, synthetic, taxonomic, and biological studies, and, as such, have made a lasting impact across multiple scientific disciplines. This review covers the isolation, biosynthesis, and biological activity of these unique secondary metabolites containing the bridging bicyclo[2.2.2]diazaoctane ring system. Furthermore, the diverse fungal origin of these natural products is closely examined and, in many cases, updated to reflect the currently accepted fungal taxonomy

Genetic Selection of Low Fertile Onchocerca volvulus by Ivermectin Treatment

Onchocerca volvulus is the causative agent of onchocerciasis, or “river blindness”. Ivermectin has been used for mass treatment of onchocerciasis for up to 18 years, and recently there have been reports of poor parasitological responses to the drug and evidence of drug resistance. Drug resistance has a genetic basis. In this study, genetic changes in β-tubulin, a gene associated with ivermectin resistance in nematodes, were seen in parasites obtained from the patients exposed to repeated ivermectin treatment compared with parasites obtained from the same patients before any exposure to ivermectin. Furthermore, the extent of the genetic changes was dependent on the level of ivermectin treatment exposure. This genetic selection was associated with a lower reproductive rate in the female parasites. The data indicates that this genetic selection is for a population of O. volvulus that is more tolerant to ivermectin. This selection could have implications for the development of ivermectin resistance in O. volvulus and for the ongoing onchocerciasis control programmes. Monitoring for the possible development and spread of ivermectin resistance, as part of the control programmes, should be implemented so that any foci of resistant parasites can be treated by alternative control measures

The successes and challenges of harmonising juvenile idiopathic arthritis (JIA) datasets to create a large-scale JIA data resource

Background CLUSTER is a UK consortium focussed on precision medicine research in JIA/JIA-Uveitis. As part of this programme, a large-scale JIA data resource was created by harmonizing and pooling existing real-world studies. Here we present challenges and progress towards creation of this unique large JIA dataset. Methods Four real-world studies contributed data; two clinical datasets of JIA patients starting first-line methotrexate (MTX) or tumour necrosis factor inhibitors (TNFi) were created. Variables were selected based on a previously developed core dataset, and encrypted NHS numbers were used to identify children contributing similar data across multiple studies. Results Of 7013 records (from 5435 individuals), 2882 (1304 individuals) represented the same child across studies. The final datasets contain 2899 (MTX) and 2401 (TNFi) unique patients; 1018 are in both datasets. Missingness ranged from 10 to 60% and was not improved through harmonisation. Conclusions Combining data across studies has achieved dataset sizes rarely seen in JIA, invaluable to progressing research. Losing variable specificity and missingness, and their impact on future analyses requires further consideration

Engineered Single-Domain Antibodies with High Protease Resistance and Thermal Stability

The extreme pH and protease-rich environment of the upper gastrointestinal tract is a major obstacle facing orally-administered protein therapeutics, including antibodies. Through protein engineering, several Clostridium difficile toxin A-specific heavy chain antibody variable domains (VHHs) were expressed with an additional disulfide bond by introducing Ala/Gly54Cys and Ile78Cys mutations. Mutant antibodies were compared to their wild-type counterparts with respect to expression yield, non-aggregation status, affinity for toxin A, circular dichroism (CD) structural signatures, thermal stability, protease resistance, and toxin A-neutralizing capacity. The mutant VHHs were found to be well expressed, although with lower yields compared to wild-type counterparts, were non-aggregating monomers, retained low nM affinity for toxin A, albeit the majority showed somewhat reduced affinity compared to wild-type counterparts, and were capable of in vitro toxin A neutralization in cell-based assays. Far-UV and near-UV CD spectroscopy consistently showed shifts in peak intensity and selective peak minima for wild-type and mutant VHH pairs; however, the overall CD profile remained very similar. A significant increase in the thermal unfolding midpoint temperature was observed for all mutants at both neutral and acidic pH. Digestion of the VHHs with the major gastrointestinal proteases, at biologically relevant concentrations, revealed a significant increase in pepsin resistance for all mutants and an increase in chymotrypsin resistance for the majority of mutants. Mutant VHH trypsin resistance was similar to that of wild-type VHHs, although the trypsin resistance of one VHH mutant was significantly reduced. Therefore, the introduction of a second disulfide bond in the hydrophobic core not only increases VHH thermal stability at neutral pH, as previously shown, but also represents a generic strategy to increase VHH stability at low pH and impart protease resistance, with only minor perturbations in target binding affinities. These are all desirable characteristics for the design of protein-based oral therapeutics

Optical error diffusion coding for analog-to-digital conversion

We propose an alternative to classical interferometric optical analog-to-digital conversion based on oversampling and error diffusion coding techniques that employs optical threshold and arithmetic operators, and describe a noninterferometric realization using multiple quantum well SEED devices, photodetectors, common optical components, and a novel approach to achieve noninterferometric optical subtraction. The analog input signal is first optically sampled at a rate much greater than the Nyquist frequency and is then quantized by a modulator that incorporates one-bit quantizers and linear filters in a negative feedback architecture for the purpose of reducing the in-band quantization noise. The output of the modulator is subsequently processed by a digital decimation filter that removes the out-of-band noise and generates a high resolution digital approximation to the analog input signal at the signal’s Nyquist rate. In the proposed realization, quantization is performed by optically bistable S-SEEDs while noninterferometric optical subtraction is accomplished by SEEDs using a technique known as optical level shifting.</jats:p

Optical oversampled analog-to-digital conversion

Previously,1 we introduced a new method of optical analog-to-digital conversion based on oversampling and error diffusion coding that offers the potential to extend resolution and conversion rates beyond that currently possible with other electronic or optical converters. In this new approach, the analog input signal is first optically sampled at a rate much greater than the Nyquist frequency and is then quantized by a modulator that incorporates one-bit quantizers and linear filters in a negative feedback architecture for the purpose of reducing in-band quantization noise. The output of the modulator is subsequently processed by a digital decimation filter, which removes the out-of-band noise and generates a high resolution digital approximation to the analog input signal at the signal's Nyquist rate. In this paper, we present experimental results from the first demonstration of an optical first-order noninterferometric modulator and discuss both spatial and temporal extensions of this optical error diffusion technique to multidimensional applications.</jats:p