Computational Mechanistic and Stereochemical Studies of Single-Site Polymerisation Catalysts and Reactions

Computational investigations into four metal-centred polymerisation catalysts are presented. The work investigates how and why the catalysts behave as they do, focusing on specific interactions within the catalyst structure itself and also on the transition states involved in the polymerisation reactions. Density functional theory has been used to examine the effect of the metal, the role of the ligand and the interplay between the two. Each study addresses particular mechanistic and structural questions that have been raised during experimental investigations and that are difficult to answer experimentally. Chapter one provides a general overview of computational techniques used in chemical modelling. The specific methods used in this work are presented as well as a brief review of modern trends. Chapter two investigates an unusual pair of metal-hydrogen interactions in a tin bis(triazenide) complex. We have termed this double M-H interaction “bifurcated” and compared other systems in which this interaction is present (and often unidentified). A variety of computational techniques are used to analyse the nature of the interactions both in qualitative and quantitative terms. The third chapter investigates the mechanism of alkyl transfer in a magnesium bis(imino)pyridine complex. A number of mechanistic pathways are explored to explain the original report of non-electrophilic alkylation at a pyridine nitrogen. We consider in particular how the solvent and the role of other species in the reaction mixture may influence the mechanism. Chapter four describes the inversion of configuration occurring in a pseudo-C3- symmetric zirconium tris(phenolate) complex. Variable temperature NMR spectra and simulations complement DFT calculations to explore the mechanism of inversion. We question the long-held assumption that the inversion process is concerted. In chapter five, the polymerisation of rac-lactide by an aluminium salen-type system is investigated in detail through characterisation of the transition state structures. Specifically, we have aimed to explain the different behaviour of two structurally similar catalytic species’ which produce polymer of different tacticity. Application of a variety of additional computational techniques in a number of these studies supplements the density functional calculations. They provide insight into specific interactions in both starting materials and transition states and detailed information about the reaction mechanisms

Missed connections and silver linings: researching theatre for early years audience experience during the COVID-19 pandemic

Live performance designed for under 6s offers an out-of-the-ordinary aesthetic experience for very young children and the adults who bring them. This research draws on our knowledge of how children develop within the context of their closest relationships and brings a focus to how parents experience attending theatre for early years (TEY) with a child aged 12-36 months. Interviews and observations were analysed using Interpretive Phenomenological Analysis, which was found to be a supportive method to meeting the study aims. The digital context, necessitated by the COVID-19 pandemic, offered unique insights into a new form of presentation. The findings show that Zoom theatre offers some mitigation to much missed live performance whilst also highlighting the irreplicable qualities of live, in-person events for families with very young children. There was potential for parent-child bonding found in sharing valued time together, opportunities for empathy, and in connecting to others. In piloting the subject area for PhD, this study found the parent experience of the TEY performance space to be varied, meaningful and rich for further exploration. Further research could include the perspectives of performers and children and investigate relationships at live, in-person events.Live performance designed for under 6s offers an out-of-the-ordinary aesthetic experience for very young children and the adults who bring them. This research draws on our knowledge of how children develop within the context of their closest relationships and brings a focus to how parents experience attending theatre for early years (TEY) with a child aged 12-36 months. Interviews and observations were analysed using Interpretive Phenomenological Analysis, which was found to be a supportive method to meeting the study aims. The digital context, necessitated by the COVID-19 pandemic, offered unique insights into a new form of presentation. The findings show that Zoom theatre offers some mitigation to much missed live performance whilst also highlighting the irreplicable qualities of live, in-person events for families with very young children. There was potential for parent-child bonding found in sharing valued time together, opportunities for empathy, and in connecting to others. In piloting the subject area for PhD, this study found the parent experience of the TEY performance space to be varied, meaningful and rich for further exploration. Further research could include the perspectives of performers and children and investigate relationships at live, in-person events

Up and down : insights from a creative approach to online interaction with very young children

This paper offers guidance for remote communication with young children based on an interpretive study of participants engaged in an online Theatre for Early Years (TEY) event, Up and Down. Drawing on practices used for in-person performance, the theatre-makers engaged interactively with children aged 1 and 2 and their accompanying adults through a conference video call. Interpretive Phenomenological Analysis was used as an approach to generate themes from observation, and interviews with the parents. Three master themes were generated: Missing Live Performance, Unfiltered Response and Human Connection. The discussion was informed by relational pedagogies and the concept of cultural value. Those engaging with young children through video call software are encouraged to look for ways to create embodied, sensory, and ‘magical’ experiences; collaborate with the adults present; and take a strengths-based approach to the medium

Post-cancer treatment support program : an evaluation

Funding: This work was supported by the University of Aberdeen via research funds provided to CM and LB as part of their postgraduate studies. Acknowledgements: We thank Bethany Mills who collected study data and the staff and service users at Maggie’s who participated in this study.Peer reviewedPostprin

Biofilm formation under industrially-relevant conditions.

Biofilms are considered to be one of the most prevalent and successful modes of life on Earth, and the prevailing lifestyle for microorganisms. Enabling bacteria to adapt to an incredibly diverse array of environments and extreme conditions, biofilms are a major contaminant of both medical and industrial settings. Indeed, approximately 80% of microbial infections are associated with biofilm formation, whilst the damage caused by biofilms in industry is estimated at between 2 – 3% of global GDP per annum. In this body of work, the effect of two industrially-relevant shear conditions on biofilm formation by the reference Pseudomonas aeruginosa (Ps. a.) strains PA01 and PA14 was investigated, as well as the effect of growth conditions and growth medium components on curli gene expression in E. coli K12 PHL644. The CBC biofilm reactor was used to model low and high shear conditions at 75 RPM and 350 RPM respectively, and biofilms grown over a time period of 96 hours. High levels of the intracellular second messenger c-di-GMP are regarded as the determining factor for Ps. a. sessility and progression of the biofilm phenotype, thus the c-di-GMP-responsive cdrA::gfp reporter was used to measure intracellular c-di-GMP levels of PA01 and PA14 under low and high shear conditions. Biofilms were analysed via confocal laser scanning microscopy and staining of extracellular DNA (eDNA) and the exopolysaccharides Psl and Pel, which are all form crucial components of a self-produced and protective extracellular matrix that surrounds and enmeshes Ps. a. within a biofilm. Under high shear at 350 RPM, intracellular c-di-GMP levels of initially adhered (at 24 hours) bacteria were increased, resulting in increased production of exopolysaccharides and formation of early aggregative structures. Shear conditions were shown to impact upon biofilm development and maturation of three-dimensional structures: crucially, mushroom-shaped macrocolonies, which are archetypal of Ps. a. biofilm formation, did not form under high shear. Under low shear at 75 RPM, Psl and Pel were organised into networks of fibre-like structures that penetrated throughout well-established basal biofilms (> 72 hours), which is in agreement with the work of others (with respect to Psl), but is a novel observation of Pel morphology as produced by PA14. The work presented in this thesis therefore provides further insight on the variety of Psl and Pel morphologies that exhibit different structures, spatial and temporal organisation, and function across PA01 and PA14 biofilms in response to either low or high shear conditions. Whilst similarities were observed between the two strains, PA01 and PA14 exhibited distinct responses to the imposed shear regime, in terms of initial surface colonisation, time taken for mature structures to emerge, and exopolysaccharide production. Biofilms produced by E. coli PHL644 were grown using the Duran bottle model, via a method previously developed by the Overton laboratory. High levels of the transcriptional regulator CsgD are regarded as ‘master switch’ that determines biofilm formation in E. coli, thus the CsgD-responsive csgB::gfp reporter was used to measure curli gene expression in response to growth in LB broth (a rich medium) versus M63+ minimal medium, different concentrations of glucose (at 0 mM, 1 mM, 10 mM and 100 mM), and incubation at different temperatures (at 25 oC, 28 oC, 30 oC and 37 oC), and identify parameters which resulted in maximal expression of curli. Planktonic cell samples were taken from the tops of the Duran bottles, and sedimented cell samples taken from the bottom of the Duran bottles for comparative analysis of growth via spectrophotometry at OD600 and csgB::gfp fluorescence by flow cytometry. Curli gene expression was found to be highest in cultures grown in M63+ minimal medium, with a glucose concentration of 10 mM and at an incubation temperature of 30 oC, which is in agreement with comparable studies in the literature. Of interest was the fact that an inverse relationship between biomass concentration (as defined by OD600 values) and csgB::gfp fluorescence was observed. Curli gene expression in sedimented cell samples was consistently lower than that of planktonic cell cultures across all experimental subsets, suggesting that planktonic cells are physically more capable of surface attachment, and curli expression may be downregulated when in a sediment; exemplifying the importance and function of curli as the initial adhesin of E. coli K12. Overall, this body of work concludes that different shear conditions can impact upon Ps. a. biofilm development and induce distinct organisation of the ECM, and that the CBC biofilm reactor is a suitable experimental model for assessing the impact of turbulent flow regimes, akin to those experienced in industrial manufacturing plants, on biofilm formation and composition. Additionally, this body of work also demonstrated that the Duran bottle model is also a suitable method for biofilm formation, and for investigating the effect of a wide array of growth conditions on E. coli K12 biofilm formation and curli gene expression. Parameters that resulted in maximal curli gene expression in E. coli K12 PHL644 cultures grown via the Duran bottle method under the conditions tested were identified, and could be further used to optimise production of a physically robust E. coli biofilm for use in biocatalysis or certain industrial settings

Tale of two alkaloids : pH-controlled electrochemiluminescence for differentiation of structurally similar compounds

Electrochemiluminescence (ECL) has increased in popularity as a result of its inherent advantages, including but not limited to portability, simplicity of use, and low reagent consumption. However, its significant advantages are often over shadowed as a result of its limited specificity. ECL emissions are intrinsically broad and lack the definition of other available analytical techniques. Furthermore, species with similar functional groups have almost identical electrochemical behavior and thus typically emit within approximately the same potential region. Within this contribution we have demonstrate the use of pH controlled ECL to prove the presence of two individual species within a mixed sample. Analysis at a single pH would not provide this information. We have illustrated the potential of this methodology to quantify scopolamine alongside sister tropane alkaloid atropine, a known ECL interferent. Previously the two alkaloids could not be distinguished from one another using a single technique which did not involve a separation strategy. pH controlled ECL is a simple approach to improve the specificity of a basic [Ru(bpy)3]2+ film based sensor. By exploiting molecular characteristics, such as pKa, we have been able to fine-tune our methodology to facilitate identification of analytes previously exhibiting indistinguishable ECL emission. Thus, by improving specificity, while maintaining operational simplicity and inexpensive design, we have been able to highlight the potential power of ECL for identification of structurally similar compounds. Further improvements of specificity, such as demonstrated within this contribution, will only further future applications of ECL sensors across a range of different fields

Electrochemiluminescent sensors as a screening strategy for psychoactive substances within biological matrices

With the rapid growth and appearance of novel psychoactive substances (NPS) onto the global drug market, the need for alternative screening methodologies for implementation within clinical environments is substantial. The immunoassay methods currently in use are inadequate for this new drug trend with the potential for misdiagnosis and subsequent administration of incorrect patient treatment increased. This contribution illustrates a strong proof-of-concept for the use of electrochemiluminescence (ECL) as a screening methodology for NPS within biological fluids, using the hallucinogen scopolamine as a model compound. A low cost, easy-to-use and portable sensor has been developed and successfully employed for the detection of scopolamine at clinically relevant concentrations within a variety of biological matrices, including human pooled serum, urine, artificial saliva and sweat, without any prior sample preparation required. Moreover, assessment of the sensor's potential as a point-of-care wearable device was performed with sample collection from the surface of skin, demonstrating its capability for the qualitative identification of scopolamine despite collection of only minimal volumes off the skins surface. The developed sensor described herein exhibits a strong proof-of-concept for the employment of such ECL sensors as point-of-care devices, where the sensors ease of use and removal of time-consuming and complex sample preparation methods will ultimately increase its usability by physicians, widening the avenues where ECL sensors could be employed