Production of lectin-affinity matrices for process-scale glycoprotein purification

A selection of prokaryotic lectins with a variety of glycan specificities and affinities have been identified, cloned, expressed in Eschericia coli and characterised. The aims of this project are to: - express the lectins at 1L scale to produce sufficient quantities for immobilisation studies (~100 mg) - immobilisethelectinsonSepharose - evaluate lectin performance on column by monitoring their ability toreproducibly capture and elute glycoprotein glycoforms

Genetically enhanced recombinant lectins for glyco-selective analysis and purification

- Generation of a library of recombinant prokaryotic lectins (RPL’s) through random mutagenesis of the carbohydrate binding sites of bacterial lectins. - Characterisation of mutant lectins with respect to structure and specificity - Provision of mutant RPL’s with enhanced affinity and/or altered specificity, alongside wild-type RPL’s, for glycoprotein analysis and purificatio

The investigation of a recombinant GalNAc binding protein from bacillus thuringiensis as a tool for glycan analysis and detection

Changes in the structures of glycans on the surfaces of eukaryotic cells can be important biomarkers for developmental or disease states. Improved methods are needed for the detection and analysis of alterations in glycan structures. Carbohydrate binding proteins such as lectins have potential for the recognition of changes in glycan structure. Host-pathogen interactions frequently involve the recognition of host carbohydrates by proteins of bacteria or viruses. Many bacterial toxins have evolved to interact with host cell receptors or with a specific tissue due to lectin like properties. The toxins from Bacillus thuringiensis have been shown to have carbohydrate binding abilities, in particular N-Acetylgalactosamine (GalNAc) has been shown to inhibit the binding of the toxin Cry1Ac. GalNAc has been shown to be an important marker in many diseases such as breast cancer and colon carcinogenesis. Moreover, changes in GalNAc glycosylation have been identified in many disorders such as cystic fibrosis, neuromuscular disorders and nephropathy. Here we describe the purification of a GalNAc binding protein of bacterial origin that may have potential in the development of diagnostic assays

Exploitation of siderophores for the speciation of iron

Iron is essential for life. It acts as an electron donor/acceptor in metabolic processes facilitated by its variable valency. Although vital, it is toxic at high levels due to Fe2+ oxidation. Iron toxicity is a concern as it can affect growth and product yields in animal cell culture. Siderophores are high affinity Fe3+ chelators produced by microorganisms. This affinity gives them the potential to be used as a basis in platforms to detect and speciate iron in industrial cell culture. Rhizobactin 1021 is of interest due to its decanoic acid “tail” that is not involved in chelation which makes it an ideal target for immobilisation

Regions of the Cry1Ac toxin predicted to be under positive selection are shown to be the carbohydrate binding sites and can be altered in their glycoprotein target specificity

The cry gene family, is a large family of homologous genes from Bacillus thuringiensis. Studies have examined the structural and functional relationships of the Cry proteins. They have revealed several residues in domains II and III that are important for target recognition and receptor attachment. In 2007 Wu, Jin-Yu et al employed a maximum likelihood method to detect evidence of adaptive evolution in Cry proteins. They identified positively selected residues, which are all located in Domain II or III. Figure 1 shows a protein sequence alignment between domain II and III of Cry1Ac and Cry1Aa. This highlights the areas which are thought to be under positive selection. Cry1Ac and Cry1Aa are structurally very similar and they both bind to a variety of N-aminopeptidases (APN’s) in different insect species. However Cry1Aa has a higher specificity for the cadherin like receptor HevCalP and Cry1Ac binds to N-acetylgalactosamine (GalNAc) on the surface of APN’s. Differences in the binding of the two toxins has been shown in an in-direct toxin-binding assay where GalNAc completely abolished toxin binding of Cry1Ac but had no effect on the binding of Cry1Aa. The binding site has been shown to be located in the third domain of Cry1Ac. Some of these sites correlate with the positively selected residues found by Wu et al 2007 in Cry1Aa. Our aim was to use the comparison of the toxins to analyse the potential to alter the binding specificity of Cry1Ac and its domains. In this work we identified critical amino acid residues for this objective

Evolution of extreme ontogenetic allometric diversity and heterochrony in pythons, a clade of giant and dwarf snakes

Ontogenetic allometry, how species change with size through their lives, and heterochony, a decoupling between shape, size, and age, are major contributors to biological diversity. However, macroevolutionary allometric and heterochronic trends remain poorly understood because previous studies have focused on small groups of closely related species. Here, we focus on testing hypotheses about the evolution of allometry and how allometry and heterochrony drive morphological diversification at the level of an entire species‐rich and diverse clade. Pythons are a useful system due to their remarkably diverse and well‐adapted phenotypes and extreme size disparity. We collected detailed phenotype data on 40 of the 44 species of python from 1191 specimens. We used a suite of analyses to test for shifts in allometric trajectories that modify morphological diversity. Heterochrony is the main driver of initial divergence within python clades, and shifts in the slopes of allometric trajectories make exploration of novel phenotypes possible later in divergence history. We found that allometric coefficients are highly evolvable and there is an association between ontogenetic allometry and ecology, suggesting that allometry is both labile and adaptive rather than a constraint on possible phenotypes.This study was funded by the Peter Rankin Trust Fund for Herpetology, the ACT Herpetological Association, the American Museum of Natural History, the Australian National University, the Australian Society of Herpetologists, and the Australian Research Council (ARC DP150102403 to JSK). DE is supported by a Becas Chile—CONICYT scholarshi

Ontogenetic drivers of morphological evolution in monitor lizards and allies (Squamata: Paleoanguimorpha), a clade with extreme body size disparity

Background Heterochrony, change in the rate or timing of development, is thought to be one of the main drivers of morphological evolution, and allometry, trait scaling patterns imposed by size, is traditionally thought to represent an evolutionary constraint. However, recent studies suggest that the ontogenetic allometric trajectories describing how organisms change as they grow may be labile and adaptive. Here we investigated the role of postnatal ontogenetic development in the morphological diversification of Paleoanguimorpha, the monitor lizards and allies, a clade with extreme body size disparity. We obtained linear and geometric morphometric data for more than 1,600 specimens belonging to three families and 60 species, representing ~ 72% of extant paleoanguimorph diversity. We used these data to undertake one of the largest comparative studies of ontogenetic allometry to date. Results Heterochrony is likely dictating morphological divergence at shallow evolutionary scales, while changes in the magnitude and direction of ontogenetic change are found mainly between major clades. Some patterns of ontogenetic variation and morphological disparity appear to reflect ontogenetic transitions in habitat use. Generally, juveniles are more similar to each other than adults, possibly because species that differ in ecology as adults are arboreal as juveniles. The magnitude of ontogenetic change follows evolutionary models where variation is constrained around an optimal value. Conversely, the direction of ontogenetic change may follow models with different adaptive optima per habitat use category or models where interspecific interactions influence its evolution. Finally, we found that the evolutionary rates of the ontogenetic allometric trajectories are phylogenetically variable. Conclusions The attributes of ontogenetic allometric trajectories and their evolutionary rates are phylogenetically heterogeneous in Paleoanguimorpha. Both allometric constraints and ecological factors have shaped ontogeny in the group. Our study highlights the evolutionary lability and adaptability of postnatal ontogeny, and teases apart how different evolutionary shifts in ontogeny contribute to the generation of morphological diversity at different evolutionary scales

The development and validation of a scoring tool to predict the operative duration of elective laparoscopic cholecystectomy

Background: The ability to accurately predict operative duration has the potential to optimise theatre efficiency and utilisation, thus reducing costs and increasing staff and patient satisfaction. With laparoscopic cholecystectomy being one of the most commonly performed procedures worldwide, a tool to predict operative duration could be extremely beneficial to healthcare organisations. Methods: Data collected from the CholeS study on patients undergoing cholecystectomy in UK and Irish hospitals between 04/2014 and 05/2014 were used to study operative duration. A multivariable binary logistic regression model was produced in order to identify significant independent predictors of long (> 90 min) operations. The resulting model was converted to a risk score, which was subsequently validated on second cohort of patients using ROC curves. Results: After exclusions, data were available for 7227 patients in the derivation (CholeS) cohort. The median operative duration was 60 min (interquartile range 45–85), with 17.7% of operations lasting longer than 90 min. Ten factors were found to be significant independent predictors of operative durations > 90 min, including ASA, age, previous surgical admissions, BMI, gallbladder wall thickness and CBD diameter. A risk score was then produced from these factors, and applied to a cohort of 2405 patients from a tertiary centre for external validation. This returned an area under the ROC curve of 0.708 (SE = 0.013, p  90 min increasing more than eightfold from 5.1 to 41.8% in the extremes of the score. Conclusion: The scoring tool produced in this study was found to be significantly predictive of long operative durations on validation in an external cohort. As such, the tool may have the potential to enable organisations to better organise theatre lists and deliver greater efficiencies in care

Extracorporeal Membrane Oxygenation for Severe Acute Respiratory Distress Syndrome associated with COVID-19: An Emulated Target Trial Analysis.

RATIONALE: Whether COVID patients may benefit from extracorporeal membrane oxygenation (ECMO) compared with conventional invasive mechanical ventilation (IMV) remains unknown. OBJECTIVES: To estimate the effect of ECMO on 90-Day mortality vs IMV only Methods: Among 4,244 critically ill adult patients with COVID-19 included in a multicenter cohort study, we emulated a target trial comparing the treatment strategies of initiating ECMO vs. no ECMO within 7 days of IMV in patients with severe acute respiratory distress syndrome (PaO2/FiO2 <80 or PaCO2 ≥60 mmHg). We controlled for confounding using a multivariable Cox model based on predefined variables. MAIN RESULTS: 1,235 patients met the full eligibility criteria for the emulated trial, among whom 164 patients initiated ECMO. The ECMO strategy had a higher survival probability at Day-7 from the onset of eligibility criteria (87% vs 83%, risk difference: 4%, 95% CI 0;9%) which decreased during follow-up (survival at Day-90: 63% vs 65%, risk difference: -2%, 95% CI -10;5%). However, ECMO was associated with higher survival when performed in high-volume ECMO centers or in regions where a specific ECMO network organization was set up to handle high demand, and when initiated within the first 4 days of MV and in profoundly hypoxemic patients. CONCLUSIONS: In an emulated trial based on a nationwide COVID-19 cohort, we found differential survival over time of an ECMO compared with a no-ECMO strategy. However, ECMO was consistently associated with better outcomes when performed in high-volume centers and in regions with ECMO capacities specifically organized to handle high demand. This article is open access and distributed under the terms of the Creative Commons Attribution Non-Commercial No Derivatives License 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

Haem and xenosiderophore mediated iron acquisition by sinorhizobium meliloti and pseudomonas aeruginosa

The bacterial cell membrane is the principal barrier for the acquisition of essential nutrients such as iron. Although critical to the survival of bacteria, iron is extremely limited in the environment due to the formation of insoluble hydroxides at physiological pH. To surmount these obstacles bacteria have evolved several mechanisms of iron acquisition. Sinorhizobium meliloti 2011, the endosymbiont of Medicago sativa, is capable of utilising several xenosiderophores and the haem compounds haemoglobin and haemin to overcome conditions of iron limitation. The high demand for iron in the nodule makes the study of S. meliloti 2011 biologically significant. Two putative hydroxamate siderophore outer membrane receptors were identified on the S. meliloti 2011 chromosome. Insertional inactivation indicated that FhuA1 and FhuA2 function in the utilisation of ferrichrome and ferrioxamine B respectively. Analysis of the region directly downstream of FhuA2 resulted in the identification of a ferrioxamine B specific ferric iron reductase, fhuF (smc01658), and a periplasmic siderophore binding protein, fhuP (smc01659). FhuP was found to function with the inner membrane haem permease and ATPase, HmuU and HmuV respectively, to effect ferrichrome and ferrioxamine B utilisation. Insertions in hmuPSTUV resulted in a reduction in haem utilisation suggesting the presence of a secondary haem utlilisation system. Heterologous expression of HmuTUV but not HmuUV in an E. coli dppF mutant restored haem utilisation suggesting that all three proteins are required for haem utilisation and that HmuUV can function with two separate periplasmic binding proteins. Orthologues of HmuUV were cloned from Rhizobium leguminosarum bv. vicae 3841 and found to restore ferrichrome, ferrioxamine B and haem utlilisation in a S. meliloti hmuU mutant. Previously it was demonstrated that Pseudomonas aeruginosa PAO1 is capable of utilising the xenosiderophores ferrichrome, ferrioxamine B and schizokinen. An inner membrane transporter, FoxB, was identified by heterologous expression in a S. meliloti siderophore transport deficient background. The expression and purification of full-length recombinant His-tagged FoxB was achieved