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The work done in this thesis aims to visualize multivalent binding events of proteins and their ligands, more specifically lectins and sugar moieties. This visualization is done by single channel recording (SCR) via stochastic sensing. Herein, the binding is studied at a single molecular level. Two mannose moieties are covalently connected by linker molecules to an ion channel forming protein, forming bivalent mannopores. These bivalent mannopores are used in a SCR set-up, wherein different lectins are added to study their binding behaviour. The lectins differ in their valency, with monovalent, bivalent, trivalent and tetravalent lectins being used. For each of these lectins, a binding model was derived that shows the dynamic nature of a multivalent binding event. This work shows that lectin-sugar binding is much more dynamic than previous theories would suggest.

SARS-CoV-2 infections have been reported in all age groups including infants, children, and adolescents. However, the role of children in the COVID-19 pandemic is still uncertain. This systematic review of early studies synthesises evidence on the susceptibility of children to SARS-CoV-2 infection, the severity and clinical outcomes in children with SARS-CoV-2 infection, and the transmissibility of SARS-CoV-2 by children. A systematic literature review was conducted in PubMed. Reviewers extracted data from relevant, peer-reviewed studies published during the first wave of the SARS-CoV-2 outbreak using a standardised form and assessed quality using the NIH Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. For studies included in the meta-analysis, we used a random effects model to calculate pooled estimates of the proportion of children considered asymptomatic or in a severe or critical state. We identified 2,775 potential studies of which 128 studies met our inclusion criteria; data were extracted from 99, which were then quality assessed. Finally, 29 studies were considered for the meta-analysis that included information of symptoms and/or severity, these were further assessed based on patient recruitment. Our pooled estimate of the proportion of test positive children who were asymptomatic was 21.1% (95% CI: 14.0 - 28.1%), based on 13 included studies, and the proportion of children with severe or critical symptoms was 3.8% (95% CI: 1.5 - 6.0%), based on 14 included studies. We did not identify any studies designed to assess transmissibility in children and found that susceptibility to infection in children was highly variable across studies. Children’s susceptibility to infection and onward transmissibility relative to adults is still unclear and varied widely between studies. However, it is evident that most children experience clinically mild disease or remain asymptomatically infected. More comprehensive contact-tracing studies combined with serosurveys are needed to quantify children’s transmissibility relative to adults. With children back in schools, testing regimes and study protocols that will allow us to better understand the role of children in this pandemic are critical.

Protein bacteriocins are potent narrow spectrum antibiotics that exploit outer membrane porins to kill bacteria by poorly understood mechanisms. Here, we determine how colicins, bacteriocins specific for Escherichia coli, engage the trimeric porin OmpF to initiate toxin entry. The N-terminal ~80 residues of the nuclease colicin ColE9 are intrinsically unstructured and house two OmpF binding sites (OBS1 and OBS2) that reside within the pores of OmpF and which flank an epitope that binds periplasmic TolB. Using a combination of molecular dynamics simulations, chemical trimerization, isothermal titration calorimetry, fluorescence microscopy and single channel recording planar lipid bilayer measurements, we show that this arrangement is achieved by OBS2 binding from the extracellular face of OmpF, whilst the interaction of OBS1 occurs from the periplasmic face of OmpF. Our study shows how the narrow pores of oligomeric porins are exploited by colicin disordered regions for direction-specific binding, which ensures the constrained presentation of an activating signal within the bacterial periplasm.

A decade ago, ‘nano’ was a word of tomorrow, signifying the promise of a future enhanced and streamlined by the torrent of possibilities that would come from single-atom control over the material world. Apple had just blazed a now well-worn path of cashing in on this cultural sentiment, releasing its firstgeneration iPod Nano in September 2005. Nanotechnology was hailed as a panacea to the economic and ecological malaise of the early 2000s, with the promise of cost-effective and relatively easy-to-produce solutions to problems as diverse as the energy crisis, chemotherapy and cybersecurity.

The cavity within the cap domain of the transmembrane staphylococcal alpha-hemolysin (alphaHL) pore is roughly a sphere of diameter approximately 45 A (molecular surface volume approximately 39,500 A(3)). We tested the ability of the cavity to accommodate exogenous polypeptide chains. Concatemerized Gly/Ser-containing sequences ("loops", L; number of repeats = n; number of residues = 10n + 5, n = 0-21) were inserted at a position located within the cavity of the fully assembled heptameric alphaHL pore. Homomeric pores containing 25 or less residues in each loop (n or= 7, only one L subunit was incorporated. As the inserted loop was lengthened, transient closures were observed in planar bilayer experiments with single pores. However, L(1)W(6) pores with very long loops (n = 14 and 21) had unitary conductance values close to those of W(7), suggesting that the loop is extruded through the opening in the cap of the pore into the external medium. Further analysis of bilayer recordings and electrophoretic migration patterns indicates that the upper capacity of the cavity is approximately 175 amino acids. The findings suggest that small functional peptides or proteins might be assembled within the alphaHL pore.

The effects of ethanol on a number of electrophysiological parameters were examined in 10 different voltage-gated potassium channels expressed in Xenopus oocytes. None of the channels examined was highly sensitive to ethanol, but there was significant variability among the channels tested at concentrations of ethanol of 200 mM and greater. The response to ethanol was not determined exclusively by membership in a genetic subfamily. In addition, the relative sensitivity among different channels could vary independently for different electrical parameters. For example, current amplitude in DRK1 was insensitive to ethanol, even at concentrations as high as 600 mM, whereas this was one of the more sensitive channels with respect to the kinetics of current inactivation. The opposite situation was true for ShA1. Therefore, ethanol at high concentrations may selectively perturb discrete regions of channel proteins. This is supported by the finding that removal of 318 amino acids from the cytoplasmic carboxyl terminus of DRK1 results in a channel whose current amplitude shows greater sensitivity to ethanol than does DRK1. Thus, the effects of ethanol on the channel may not be limited to interactions at the lipid-protein interface.

Background Although mother-to-child transmission (MTCT) rates are at an all-time low in Western Europe, potentially preventable transmissions continue to occur. Duration of antenatal combination antiretroviral therapy (ART) is strongly associated with MTCT risk. Methods Data on pregnant HIV-infected women enrolled in the Western and Central European sites of the European Collaborative Study between January 2000 and July 2009 were analysed. The proportion of women receiving no antenatal ART or 1–13 days of treatment was investigated, and associated factors explored using logistic regression models. Results Of 2,148 women, 142 (7%) received no antenatal ART, decreasing from 8% in 2000–2003 to 5% in 2004– 2009 (χ2=8.73; PConclusions Over the last 10 years, around one in 11 women in this study received insufficient antenatal ART, accounting for 40% of MTCTs. One-half of these women were diagnosed before conception, suggesting disengagement from care.