Biophysical investigations of the mechanism of colicin translocation

Colicins are a family of bacterial toxins, which kill Escherichia coli cells and other closely related species. Their mode of action requires binding to an outer membrane receptor, translocation across the outer membrane and periplasm and cytotoxic action on a specific target. Colicins usually kill cells either by attacking the bacterial RNA or DNA or by forming pores in the inner membrane of the cell. Their cytotoxic activity can be inhibited by the high affinity binding of an immunity protein. For Group A colicins, translocation requires interaction between the N-terminal domain of the colicin and a series of membrane bound and periplasmic proteins called the Tol system (TolB, TolR, TolA, TolQ and Pal). Three residues of colicin E9 have previously been shown to be essential for an interaction with TolB. This study suggests that these residues play differing roles in the interaction with TolB. Other residues surrounding these previously identified residues are also shown to be involved in the interaction with TolB. In order to allow cytotoxicity, the immunity protein of colicins E3 and E9 must be lost on entry of the colicin to a target cell. This work has demonstrated by Surface Plasmon Resonance and Atomic Force Microscopy that the affinity of colicins E3 and E9 for TolB is increased when the immunity protein is removed. This observation has implications for the mechanism by which the immunity protein dissociates from the colicin. Finally this study has used Surface Plasmon Resonance to explore differences between pore-forming and enzymatic colicins in their interactions with Tol proteins. Although the pore-former colicin A interacts with TolR, TolA and TolB, the endonuclease colicins E3 and E9 were shown only to interact with TolB. This suggests that pore-forming and endonuclease colicins use the Tol system in different ways in order to translocate across the periplasm

Biophysical investigations of the mechanism of colicin translocation

Colicins are a family of bacterial toxins, which kill Escherichia coli cells and other closely related species. Their mode of action requires binding to an outer membrane receptor, translocation across the outer membrane and periplasm and cytotoxic action on a specific target. Colicins usually kill cells either by attacking the bacterial RNA or DNA or by forming pores in the inner membrane of the cell. Their cytotoxic activity can be inhibited by the high affinity binding of an immunity protein. For Group A colicins, translocation requires interaction between the N-terminal domain of the colicin and a series of membrane bound and periplasmic proteins called the Tol system (TolB, TolR, TolA, TolQ and Pal). Three residues of colicin E9 have previously been shown to be essential for an interaction with TolB. This study suggests that these residues play differing roles in the interaction with TolB. Other residues surrounding these previously identified residues are also shown to be involved in the interaction with TolB. In order to allow cytotoxicity, the immunity protein of colicins E3 and E9 must be lost on entry of the colicin to a target cell. This work has demonstrated by Surface Plasmon Resonance and Atomic Force Microscopy that the affinity of colicins E3 and E9 for TolB is increased when the immunity protein is removed. This observation has implications for the mechanism by which the immunity protein dissociates from the colicin. Finally this study has used Surface Plasmon Resonance to explore differences between pore-forming and enzymatic colicins in their interactions with Tol proteins. Although the pore-former colicin A interacts with TolR, TolA and TolB, the endonuclease colicins E3 and E9 were shown only to interact with TolB. This suggests that pore-forming and endonuclease colicins use the Tol system in different ways in order to translocate across the periplasm

Exploring disruption through the lens of an adapted Five Senses Framework

This quasi-experimental research design surveyed 688 students through a self-administered online survey to specifically explore relations between student self-assessed capabilities (Lizzio Five Senses, 2006), overall program satisfaction, withdrawal behaviours, demographics and year of study in their university courses during an emergency COVID-19 lockdown experience. Importantly, this research offers a more nuanced view of the Five Senses and confirms their importance as a university strategy for student success. These findings offer further granularity into the complex set of relations that impact decisions around satisfaction, persistence, and capability in higher education and support previous research by Lizzio and Wilson (2008) indicating students’ perceptions of purpose is the strongest predictor of satisfaction, lower anxiety and lower course withdrawal. Ultimately, the paper suggests as higher education looks towards future possible disruptions due to climate, health or political realities, equipping and fostering a strong sense of purpose, connectedness, and resourcefulness as well as sense of capability and academic culture will buffer and support students to persevere. In addition, this research suggests that those students who may have weak associations with these senses merit additional attention

Pupils’ emotional experience in human-technology interactions

The experience of human emotion is a central topic in the research field of product design and human interactions. Emotions have the ability to affect pupils’ experience deeply since the elicitation of emotion has the ability to affect attention, behaviour and attitude towards man-made artefacts. The qualitative study presented in this paper is part of ongoing research intended to develop a framework for modelling pupils’ emotional experiences when interacting with technological artefacts. This paper underlines how the elicitation of emotion is itself a consequence of the interaction between the human individual and the technological artefact. These conceptualisations underline the necessity to study the attributes both human and technological artefacts responsible for the elicitation of emotion. The study presented in this paper focuses on the human element. The participants in this study were students undertaking an undergraduate programme in technical design and technology offered by the Department of Technology and Entrepreneurship Education at the University of Malta. The study reveals that 43% of the subjects are concerned with being provided proper guidance and mentoring particularly when interacting with technological artefacts which are novel to the pupils. In addition, the study reveals that the inherent simplicity of a technological artefact and the ability to provide an immediate visual feedback, as factors which contribute to render the interaction between pupils and technological artefacts more enjoyable. The results emerging from the empirical study are discussed in light of how pupils’ concerns and emotional experiences influence attitudes towards technological artefacts.peer-reviewe

Radiation effects on satellites during extreme space weather events

High‐energy trapped electrons in the Van Allen belts pose a threat to the survivability of orbiting spacecraft. Two key radiation effects are total ionising dose (TID) and displacement damage dose (DDD) in components and materials, both of which cause cumulative and largely irreversible damage. During an extreme space weather event, trapped electron fluxes in the Van Allen belts can increase by several orders of magnitude in intensity, leading to an enhanced risk of satellite failure. We use extreme environments generated by modelling and statistical analyses to estimate the consequences for satellites in terms of the radiation effects described above. A worst‐case event could lead to significant losses in power generating capability ‐ up to almost 8% ‐ and cause up to four years’ worth of ionising dose degradation, leading to component damage and a life‐shortening effect on satellites. The consequences of such losses are hugely significant given our increasing reliance on satellites for a vast array of services, including communication, navigation, defence and critical infrastructure

Evaluation of the Antimicrobial Activity of Cationic Polymers against Mycobacteria: Toward Antitubercular Macromolecules.

Antimicrobial resistance is a global healthcare problem with a dwindling arsenal of usable drugs. Tuberculosis, caused by Mycobacterium tuberculosis, requires long-term combination therapy and multi- and totally drug resistant strains have emerged. This study reports the antibacterial activity of cationic polymers against mycobacteria, which are distinguished from other Gram-positive bacteria by their unique cell wall comprising a covalently linked mycolic acid-arabinogalactan-peptidoglycan complex (mAGP), interspersed with additional complex lipids which helps them persist in their host. The present study finds that poly(dimethylaminoethyl methacrylate) has particularly potent antimycobacterial activity and high selectivity over two Gram-negative strains. Removal of the backbone methyl group (poly(dimethylaminoethyl acrylate)) decreased antimycobacterial activity, and poly(aminoethyl methacrylate) also had no activity against mycobacteria. Hemolysis assays revealed poly(dimethylaminoethyl methacrylate) did not disrupt red blood cell membranes. Interestingly, poly(dimethylaminoethyl methacrylate) was not found to permeabilize mycobacterial membranes, as judged by dye exclusion assays, suggesting the mode of action is not simple membrane disruption, supported by electron microscopy analysis. These results demonstrate that synthetic polycations, with the correctly tuned structure are useful tools against mycobacterial infections, for which new drugs are urgently required

Realistic worst case for a severe space weather event driven by a fast solar wind stream

Satellite charging is one of the most important risks for satellites on orbit. Satellite charging can lead to an electrostatic discharge resulting in component damage, phantom commands, and loss of service and in exceptional cases total satellite loss. Here we construct a realistic worst case for a fast solar wind stream event lasting 5 days or more and use a physical model to calculate the maximum electron flux greater than 2 MeV for geostationary orbit. We find that the flux tends toward a value of 106 cm−2·s−1·sr−1 after 5 days and remains high for another 5 days. The resulting flux is comparable to a 1 in 150‐year event found from an independent statistical analysis of electron data. Approximately 2.5 mm of Al shielding would be required to reduce the internal charging current to below the National Aeronautics and Space Administration‐recommended guidelines, much more than is currently used. Thus, we would expect many satellites to report electrostatic discharge anomalies during such an event with a strong likelihood of service outage and total satellite loss. We conclude that satellites at geostationary orbit are more likely to be at risk from fast solar wind stream event than a Carrington‐type storm

Associations of body mass index and waist circumference with: energy intake and percentage energy from macronutrients, in a cohort of australian children

Background: It is evident from previous research that the role of dietary composition in relation to the development of childhood obesity remains inconclusive. Several studies investigating the relationship between body mass index (BMI), waist circumference (WC) and/or skin fold measurements with energy intake have suggested that the macronutrient composition of the diet (protein, carbohydrate, fat) may play an important contributing role to obesity in childhood as it does in adults. This study investigated the possible relationship between BMI and WC with energy intake and percentage energy intake from macronutrients in Australian children and adolescents

Disruption of arterial perivascular drainage of amyloid-β from the brains of mice expressing the human APOE ε4 allele

Failure of elimination of amyloid-β (Aβ) from the brain and vasculature appears to be a key factor in the etiology of sporadic Alzheimer’s disease (AD) and cerebral amyloid angiopathy (CAA). In addition to age, possession of an apolipoprotein E (APOE) ε4 allele is a strong risk factor for the development of sporadic AD. The present study tested the hypothesis that possession of the APOE ε4 allele is associated with disruption of perivascular drainage of Aβ from the brain and with changes in cerebrovascular basement membrane protein levels. Targeted replacement (TR) mice expressing the human APOE3 (TRE3) or APOE4 (TRE4) genes and wildtype mice received intracerebral injections of human Aβ40. Aβ40 aggregated in peri-arterial drainage pathways in TRE4 mice, but not in TRE3 or wildtype mice. The number of Aβ deposits was significantly higher in the hippocampi of TRE4 mice than in the TRE3 mice, at both 3- and 16-months of age, suggesting that clearance of Aβ was disrupted in the brains of TRE4 mice. Immunocytochemical and Western blot analysis of vascular basement membrane proteins demonstrated significantly raised levels of collagen IV in 3-month-old TRE4 mice compared with TRE3 and wild type mice. In 16-month-old mice, collagen IV and laminin levels were unchanged between wild type and TRE3 mice, but were lower in TRE4 mice. The results of this study suggest that APOE4 may increase the risk for AD through disruption and impedance of perivascular drainage of soluble Aβ from the brain. This effect may be mediated, in part, by changes in age-related expression of basement membrane proteins in the cerebral vasculature

BHPR research: qualitative1. Complex reasoning determines patients' perception of outcome following foot surgery in rheumatoid arhtritis

Background: Foot surgery is common in patients with RA but research into surgical outcomes is limited and conceptually flawed as current outcome measures lack face validity: to date no one has asked patients what is important to them. This study aimed to determine which factors are important to patients when evaluating the success of foot surgery in RA Methods: Semi structured interviews of RA patients who had undergone foot surgery were conducted and transcribed verbatim. Thematic analysis of interviews was conducted to explore issues that were important to patients. Results: 11 RA patients (9 ♂, mean age 59, dis dur = 22yrs, mean of 3 yrs post op) with mixed experiences of foot surgery were interviewed. Patients interpreted outcome in respect to a multitude of factors, frequently positive change in one aspect contrasted with negative opinions about another. Overall, four major themes emerged. Function: Functional ability & participation in valued activities were very important to patients. Walking ability was a key concern but patients interpreted levels of activity in light of other aspects of their disease, reflecting on change in functional ability more than overall level. Positive feelings of improved mobility were often moderated by negative self perception ("I mean, I still walk like a waddling duck”). Appearance: Appearance was important to almost all patients but perhaps the most complex theme of all. Physical appearance, foot shape, and footwear were closely interlinked, yet patients saw these as distinct separate concepts. Patients need to legitimize these feelings was clear and they frequently entered into a defensive repertoire ("it's not cosmetic surgery; it's something that's more important than that, you know?”). Clinician opinion: Surgeons' post operative evaluation of the procedure was very influential. The impact of this appraisal continued to affect patients' lasting impression irrespective of how the outcome compared to their initial goals ("when he'd done it ... he said that hasn't worked as good as he'd wanted to ... but the pain has gone”). Pain: Whilst pain was important to almost all patients, it appeared to be less important than the other themes. Pain was predominately raised when it influenced other themes, such as function; many still felt the need to legitimize their foot pain in order for health professionals to take it seriously ("in the end I went to my GP because it had happened a few times and I went to an orthopaedic surgeon who was quite dismissive of it, it was like what are you complaining about”). Conclusions: Patients interpret the outcome of foot surgery using a multitude of interrelated factors, particularly functional ability, appearance and surgeons' appraisal of the procedure. While pain was often noted, this appeared less important than other factors in the overall outcome of the surgery. Future research into foot surgery should incorporate the complexity of how patients determine their outcome Disclosure statement: All authors have declared no conflicts of interes