Thermotropic phase behavior and headgroup interactions of the nonbilayer lipids phosphatidylethanolamine and monogalactosyldiacylglycerol in the dry state

<p>Abstract</p> <p>Background</p> <p>Although biological membranes are organized as lipid bilayers, they contain a substantial fraction of lipids that have a strong tendency to adopt a nonlamellar, most often inverted hexagonal (H_II) phase. The polymorphic phase behavior of such nonbilayer lipids has been studied previously with a variety of methods in the fully hydrated state or at different degrees of dehydration. Here, we present a study of the thermotropic phase behavior of the nonbilayer lipids egg phosphatidylethanolamine (EPE) and monogalactosyldiacylglycerol (MGDG) with a focus on interactions between the lipid molecules in the interfacial and headgroup regions.</p> <p>Results</p> <p>Liposomes were investigated in the dry state by Fourier-transform Infrared (FTIR) spectroscopy and Differential Scanning Calorimetry (DSC). Dry EPE showed a gel to liquid-crystalline phase transition below 0°C and a liquid-crystalline to H_IItransition at 100°C. MGDG, on the other hand, was in the liquid-crystalline phase down to -30°C and showed a nonbilayer transition at about 85°C. Mixtures (1:1 by mass) with two different phosphatidylcholines (PC) formed bilayers with no evidence for nonbilayer transitions up to 120°C. FTIR spectroscopy revealed complex interactions between the nonbilayer lipids and PC. Strong H-bonding interactions occurred between the sugar headgroup of MGDG and the phosphate, carbonyl and choline groups of PC. Similarly, the ethanolamine moiety of EPE was H-bonded to the carbonyl and choline groups of PC and probably interacted through charge pairing with the phosphate group.</p> <p>Conclusions</p> <p>This study provides a comprehensive characterization of dry membranes containing the two most important nonbilayer lipids (PE and MGDG) in living cells. These data will be of particular relevance for the analysis of interactions between membranes and low molecular weight solutes or soluble proteins that are presumably involved in cellular protection during anhydrobiosis.</p

‘The project cannot be approved in its current form’: feminist visual research meets the human research ethics committee

This article reflects on a university human research ethics committee&rsquo;s unease regarding a feminist visual pilot study within the field of education. The small exploratory study proposed to explore a migrant mother&rsquo;s production of her son&rsquo;s identity through her family photograph collection. The committee requested substantial changes to the research design which centred primarily on their concerns regarding risk of harm to pre-existing relationships, and also issues of anonymity and consent. I consider the combined liberal individualist, utilitarian and positivist biomedical basis for the ethics committee&rsquo;s discomfort with the proposed research which was to involve members of my family. I draw on my experience of the review process to critique the human research ethics committee paradigm which constructs the ideal researcher as an objective and disinterested observer, hinges on a weighing of risks and benefits, and considers humans to be independent and equal. I demonstrate how the blanket application of these values acts to problematise some kinds of research, and how these values can be inappropriate, incompatible and even destructive when applied to research proposals that are exploratory, visual, and/or involve the researcher&rsquo;s family members as participants

A paired conceptual framework integrating information systems research and democracy theory

Anastasiadou, M., dos Santos, V. D., & Evans, A. M. (2020). A paired conceptual framework integrating information systems research and democracy theory. In H. Santos, G. V. Pereira, M. Budde, S. F. Lopes, & P. Nikolic (Eds.), Science and Technologies for Smart Cities: 5th EAI International Summit, SmartCity360, Braga, Portugal, December 4-6, 2019, Proceedings (pp. 217-235). (Lecture Notes of the Institute for Computer Sciences, Social-Informatics and Telecommunications Engineering, LNICST; Vol. 323 LNICST). Springer. https://doi.org/10.1007/978-3-030-51005-3_20Information systems (IS) play an important role in contemporary society, but critical questions remain on their impact on democracy. This study aims to contribute to a better understanding of this phenomenon. In order to do so, the study develops an innovative methodological approach. Drawing from Design Science Research (DSR), we build conceptual pairs between core preoccupations explored by critical thought on democracy and available problem-solving information technologies. The study does not aim at an exhaustive analysis of problems and solutions; this would be unfeasible, considering the limitations of journal article format. Rather, it aims at early-stage methodology incorporation across disciplines that draw from different research paradigms. The findings will offer a preliminary probe on the analytical input of DSR conceptual artefacts in examining functional links between information systems and political outcomes.authorsversionpublishe

Serum-free transfection of CHO-cells with tailor-made unilamellar vesicles

At present, a number of transfection techniques are available to introduce foreign DNA into cells, but still minimal intrusion or interference with normal cell physiology, low toxicity, reproducibility, cost efficiency and successful creation of stable transfectants are highly desirable properties for improved transfection techniques