The assembly and use of tethered bilayer lipid membranes (tBLMs)

© Springer Science+Business Media New York 2015. Because they are firmly held in place, tethered bilayer lipid membranes (tBLMs) are considerably more robust than supported lipid bilayers such as black lipid membranes (BLMs) (Cornell et al. Nature 387(6633): 580–583, 1997). Here we describe the procedures required to assemble and test tethered lipid bilayers that can incorporate various lipid species, peptides, and ion channel proteins

The effect of tethers on artificial cell membranes: A coarse-grained molecular dynamics study

© 2016 Hoiles et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Tethered bilayer lipid membranes (tBLMs) provide a stable platform for modeling the dynamics and order of biological membranes where the tethers mimic the cytoskeletal supports present in biological cell membranes. In this paper coarse-grained molecular dynamics (CGMD) is applied to study the effects of tethers on lipid membrane properties. Using results from the CGMD model and the overdamped Fokker-Planck equation, we show that the diffusion tensor and particle density of water in the tBLM is spatially dependent. Further, it is shown that the membrane thickness, lipid diffusion, defect density, free energy of lipid flip-flop, and membrane dielectric permittivity are all dependent on the tether density. The numerically computed results from the CGMD model are in agreement with the experimentally measured results from tBLMs containing different tether densities and lipids derived from Archaebacteria. Additionally, using experimental measurements from Escherichia coli bacteria and Saccharomyces Cerevisiae yeast tethered membranes, we illustrate how previous molecular dynamics results can be combined with the proposed model to estimate the dielectric permittivity and defect density of these membranes as a function of tether density

The design of doctorate curricula for practising professionals

Expansion and changes in doctoral education globally have challenged universities to meet the needs of practising professionals. Values and purposes, structure and content and pedagogy of the provision are key considerations. This curriculum evaluation work investigated the views of 68 higher education staff mainly from Europe and North America involved in the development and delivery of professional doctorates on current issues in designing an appropriate curriculum for practitioners. Analysis of views from two international workshops suggested that while the social benefits of practitioner research were acknowledged, staff struggled with tensions in their higher education contexts to manage practitioner-focused elements, including the balance between theory and practice, recognition of practitioner methodologies and provision of appropriate supervision. The paper concludes that a wider understanding of the values and purpose of doctoral education within and beyond the academy is required that recognises the production of knowledge through practice, and supports ethical social action. Acknowledgements We would like to acknowledge the participants who took part in the two international workshops for their helpful contributions, and the reviewers for their helpful comments

An examination of microcystin-LR accumulation and toxicity using tethered bilayer lipid membranes (tBLMs)

© 2018 Elsevier Ltd Microcystin-LR (MC-LR) is a potent cyanobacterial toxin responsible for animal and human poisonings worldwide. MC-LR is found in organisms throughout the foodweb, however there is conjecture regarding whether it biomagnifies. Few studies have investigated how MC-LR interacts with lipid membranes, a determinant of biomagnification potential. We tested whether 1 μM MC-LR irreversibly associates with lipid bilayers or causes the creation of pore defects upon short and long-term exposure. Using tethered bilayer lipid membranes (tBLMs), we observed an increase in membrane conduction in tBLMs, representing an interaction of microcystin-LR with the lipid bilayer and a change in membrane packing properties. However, there were minimal changes in membrane capacitance upon short and long-term exposure, and MC-LR exhibited a rapid off-rate. Upon 24 h exposure to the toxin, no lipophilic multimeric complexes were detected capable of altering the toxin's off-rate. There was no evidence of the creation of new pores. This study demonstrates that MC-LR does not irreversibly imbed itself into lipids membranes after short or long-term exposure and suggests MC-LR does not biomagnify through the food web via lipid storage

Three reflections

Professor Cranfield contributes three short biblical reflections: considering points of contact between the parable of the Good Samaritan and an incident recorded in 2 Chronicles; some points of issue with Francis Watson’s Paul and the Hermeneutics of Faith; and thoughts on ‘the works of the law’ in Romans 3:20, and on Romans, rather than Galatians, being the best way into a study of Paul’s theology

New strategies to measure intracellular sodium concentrations

Fluorescent ion indicators are widely used to measure ion concentrations in living cells. However, despite considerable efforts in synthesizing new compounds, no ratiometric sodium indicator is available that can be excited at visible wavelengths. Ratiometric indicators have an advantage in that measured fluorescence intensities can be corrected for fluctuations of the indicator concentration and the illumination intensity, which is not possible when non-ratiometric indicators are used. One way to circumvent this problem is to measure fluorescence lifetimes, which are independent of these factors. Another way to overcome the disadvantages of a non-ratiometric indicator dye is to embed it, together with a reference dye, into nanoparticles. By relating the indicator fluorescence to the fluorescence of the reference dye, inhomogeneities in the nanosensor concentration or the illumination intensity can be cancelled out reliably. In this study we compare the benefits and drawbacks of these approaches. © 2010 Copyright SPIE - The International Society for Optical Engineering

The pivotal role of student assessment in work-integrated learning

Work-integrated learning (WIL) is proliferating in university courses across many countries. Like many educational practices, students’ experience of it is shaped by the assessment processes adopted. Does assessment support or inhibit what WIL seeks to foster? To explore how students experience assessment in WIL, a small-scale investigation was undertaken across faculties in a UK university. Students who had recently undertaken WIL in contexts where it was either tightly coupled or loosely coupled to their programme of study undertook a drawing-stimulated interview about their placement and the role of assessment within it. A thematic analysis was used to discern key themes in student responses. Key issues identified were the importance of assessment in scaffolding learning, the multiple roles of university and workplace staff in assessment, the extent to which assessment practices promote students seeing themselves as becoming practitioners and the reflexive effects of assessment on learning. The paper discusses the implications of these issues for the design of WIL activities

Women’s participation in organisationally-assigned expatriation: an assignment type effect?

This article examines women’s participation in long-term, short-term, rotational and commuter organisationally-assigned expatriation. It explores the effects of assignment length, pattern and accompanied/unaccompanied status on career contribution and home/family life outcomes. This triangulated research draws upon e-mail correspondence with 71 current female expatriates to learn about assignment types undertaken and future assignment intentions; and in-depth, semi-structured interviews with 26 of these assignees, and 14 Human Resource professionals in two case study oil and gas firms. This research is set within the theoretical frame of rational choice which suggests that couples engage co-operatively in their division of labour to maximise lifetime earnings, with women prioritising home and family over career prospects. The research finds that long-term assignments enable women to maximise or achieve high levels of both career and family outcomes. Alternative ‘flexpatriate’ assignments provide lower quality career potential and familial relationships, leading to career and/or family compromise/sacrifice. A model is presented to explain women’s assignment preferences in meeting career and family life objectives, extending rational choice theory into the expatriate context. Increasing use of flexpatriation may inhibit expatriate gender diversity