Selective ion-permeable membranes by insertion of biopores into polymersomes

In nature there are various specific reactions for which highly selective detection or support is required to preserve their bio-specificity or/and functionality. In this respect, mimics of cell membranes and bio-compartments are essential for developing tailored applications in therapeutic diagnostics. Being inspired by nature, we present here biomimetic nanocompartments with ion-selective membrane permeability engineered by insertion of ionomycin into polymersomes with sizes less than 250 nm. As a marker to assess the proper insertion and functionality of ionomycin inside the synthetic membrane, we used a Ca2+-sensitive dye encapsulated inside the polymersome cavity prior to inserting the biopore. The calcium sensitive dye, ionomycin, and Ca2+ did not influence the architecture and the size of polymersomes. Successful ionomycin functionality inside the synthetic membrane with a thickness of 10.7 nm was established by a combination of fluorescence spectroscopy and stopped-flow spectroscopy. Polymersomes equipped with ion selective membranes are ideal candidates for the development of medical applications, such as cellular ion nanosensors or nanoreactors in which ion exchange is required to support in situ reactions

Lateral diffusion processes in biomimetic polymer membranes

Molecular self-assembly offers an important bottom-up approach to generate new materials with great potential for applications in nano-, life- and medical- sciences and engineering. The interest in “soft” materials suitable for the generation of artificial, biomimetic membranes has increased rapidly over the last years. These membranes combine the advantages of specificity and efficiency found in nature and the robustness and stability of synthetic materials from polymer science. There are currently two approaches to design biomimetic membranes. One uses natural phospholipids, while the other ones uses synthetic lipid mimics as the advanced alternative, which have shown great mechanical and chemical stability compared to their natural counterparts. This is important for technological application where durable devices are required. Biological membrane proteins, which provide selective and very efficient membrane transport, can be inserted into these synthetic block copolymer membranes. This combination of a synthetic membrane with biological membrane proteins is an intriguing phenomenon because the fundamental requirements for successful insertion are still matter of debate. One important issue is that polymeric membranes have thicknesses that exceed the height of the membrane proteins by several factors and the two lengths actually do not match. However, this significant height mismatch can be overcome by choosing a polymer with high flexibility, which has been shown to allow membrane proteins insertion in their active conformation. Flexibility and fluidity are essential membrane properties allowing successful generation of biomimetic membranes. In this thesis, the fluid properties of synthetic membranes composed of synthetic amphiphiles are studied based on a large library of block copolymers. These consist of poly(2-methyloxazoline) (PMOXA) and poly(dimethylsiloxane) (PDMS) and are used as diblock (PMOXA-b-PDMS, AB) and triblock (PMOXA-b-PDMS-b-PMOXA, ABA) copolymers. Variation of the molecular weight induces changes in the membrane thickness and thus the fluidity of the membrane. The diffusion of membrane proteins within synthetic triblock copolymer membranes was investigated. The study revealed that the membrane proteins are mobile even at hydrophobic mismatches of up to 7 nm, which is a factor of seven compared to mismatches existing in biological membranes. The advantage of PDMS-containing block copolymers is their enormous flexibility even at high molecular weights, which provides a similar membrane environment compared to biological phospholipid membranes. This explains and displays the ability of PDMS to compress in contact to membrane proteins. Their diffusion decreases steadily with increasing thickness mismatch. The importance of a very flexible polymer for the generation of biomimetic membranes was elucidated for membrane protein insertion, such as PDMS, which offers high fluidity and high membrane stability within membranes with even large thicknesses. The properties of these synthetic membranes investigated here, i.e. fluidity, lateral diffusion and membrane thickness, are important for the generation of biomimetic membranes for technological applications

Professionelle Sprachförderkompetenz frühpädagogischer Fachkräfte : eine empirische Analyse von Wissen und Handeln in dialogischen Interaktionskontexten

Wie erfolgreich sich Kinder sprachlich entwickeln, hängt im Bereich der Frühpädagogik im Wesentlichen von der Sprachförderkompetenz der frühpädagogischen Fachkraft ab. Eine professionelle Sprachförderkompetenz zeichnet sich u. a. durch die Fähigkeit einer sprachanregenden Interaktionsgestaltung aus, die durch sogenannte Sprachfördertechniken beeinflusst wird. Diese gilt es in der Aus- und Weiterbildung zu schulen, wobei Kompetenzmodelle von einer Verbindung zwischen den Kompetenzfacetten des Wissens und des Handelns ausgehen. Im Bereich der Frühpädagogik fehlt es allerdings an domänenspezifischen Kompetenzuntersuchungen, die diese Verbindung für die sprachanregende Interaktionsgestaltung bestätigen. An dieser explorativ ausgerichteten Studie zur Untersuchung eines Zusammenhangs zwischen handlungsnahem sprachförderspezifischem Wissen und dem sprachförderlichen Handeln nahmen 47 frühpädagogische Fachkräfte aus der Schweiz und aus Deutschland teil. Das handlungsnahe Wissen wurde mittels eines Filmvignetteninterviews und das Handeln mittels einer Videobeobachtung erhoben. Die deskriptiven Ergebnisse zeigen, dass handlungsnahes Wissen basierend auf verschiedenen als sprachförderwirksam angesehenen Sprachförderdimensionen unterschiedlich differenziert erfasst werden konnte. Auch in der Häufigkeit der Anwendung von spezifischen Sprachfördertechniken im Handeln zeichnen sich grosse Unterschiede innerhalb der Stichprobe ab. Ein statistischer Zusammenhang konnte zwischen spezifischen, auf einer Mikroebene der Sprachförderung angesiedelten Wissensaspekten (Dialogvertiefung, Fragen und korrigierendes Verhalten) gefunden werden. Wissensbereiche, die auf einer übergeordneten Ebene der Sprachförderung anzusiedeln sind (Dialog- und Beziehungsgestaltung), stehen nicht mit dem Handeln in Verbindung. Die Ergebnisse werden in Bezug auf das methodische Vorgehen und die inhaltliche Strukturierung von sprachförderspezifischem handlungsnahem Wissen in eine Mikro- und in eine Makroebene kritisch diskutiert

Violencia conyugal en las madres del programa del vaso de leche del distrito de Sapallaga - Huancayo

La violencia conyugal es un problema muy álgido en todos los niveles sociales, esto se evidencia en la problemática enmarcada en salud pública. La investigación tuvo como objetivo conocer si existe violencia física y psicológica en las madres del programa vaso de leche del distrito de Sapallanga que reportaron sus casos en la DEMUNA del distrito de Sapallanga. La investigación es de tipo básico, de nivel descriptivo, a su vez se utilizó el método inductivo y deductivo. La conducta violenta se aprende y la primera oportunidad para aprender a comportarse agresivamente surge en el hogar observando e imitando la conducta agresiva de los padres, de familiares, y de otros familiares e incluso personajes que aparecen en los medios de comunicación. Las reacciones de los padres que premian la conducta agresiva de sus hijos y el maltrato infantil por parte de ellos, son algunos de los mecanismos mediante los cuales los niños aprenden a una temprana edad a expresarse en forma violenta. Para abordar esta problemática se debe intensificar investigaciones donde se identifiquen las causas con la finalidad de establecer estrategias que se consideren a la educación como pilar fundamental para hacer frente a la violencia. Asimismo se conoció denuncias de 69 madres de familia del PVL, las que reportaron que han vivido experiencias de violencia física y psicológica; a quienes se aplicó un cuestionario con 39 preguntas y se obtuvo testimonios de algunas de ellas. Los resultados de la investigación evidencian que las madres de familia son víctimas de violencia física manifestado en golpes, quemaduras, fracturas y psicológica presentados por insultos, indiferencia, humillaciones y amenazas. En Conclusión en los hallazgos se evidenciaron que estas madres del programa vaso de leche sufrieron violencia física y psicológica.Tesi

Durable vesicles for reconstitution of membrane proteins in biotechnology

The application of membrane proteins in biotechnology requires robust, durable reconstitution systems that enhance their stability and support their functionality in a range of working environments. Vesicular architectures are highly desirable to provide the compartmentalisation to utilise the functional transmembrane transport and signalling properties of membrane proteins. Proteoliposomes provide a native-like membrane environment to support membrane protein function, but can lack the required chemical and physical stability. Amphiphilic block copolymers can also self-assemble into polymersomes: tough vesicles with improved stability compared with liposomes. This review discusses the reconstitution of membrane proteins into polymersomes and the more recent development of hybrid vesicles, which blend the robust nature of block copolymers with the biofunctionality of lipids. These novel synthetic vesicles hold great promise for enabling membrane proteins within biotechnologies by supporting their enhanced in vitro performance and could also contribute to fundamental biochemical and biophysical research by improving the stability of membrane proteins that are challenging to work with

Water channel pore size determines exclusion properties but not solute selectivity

Aquaporins (AQPs) are a ubiquitous family of transmembrane water channel proteins. A subgroup of AQP water channels also facilitates transmembrane diffusion of small, polar solutes. A constriction within the pore, the aromatic/arginine (ar/R) selectivity filter, is thought to control solute permeability: previous studies on single representative water channel proteins suggest narrow channels conduct water, whilst wider channels permit passage of solutes. To assess this model of selectivity, we used mutagenesis, permeability measurements and in silico comparisons of water-specific as well as glycerol-permeable human AQPs. Our studies show that single amino acid substitutions in the selectivity filters of AQP1, AQP4 and AQP3 differentially affect glycerol and urea permeability in an AQP-specific manner. Comparison between in silico-calculated channel cross-sectional areas and in vitro permeability measurements suggests that selectivity filter cross-sectional area predicts urea but not glycerol permeability. Our data show that substrate discrimination in water channels depends on a complex interplay between the solute, pore size, and polarity, and that using single water channel proteins as representative models has led to an underestimation of this complexity

Gas-tight triblock-copolymer membranes are converted to CO2 permeable by insertion of plant aquaporins

We demonstrate that membranes consisting of certain triblock-copolymers were tight for CO2. Using a novel approach, we provide evidence for aquaporin facilitated CO2 diffusion. Plant aquaporins obtained from heterologous expression were inserted into triblock copolymer membranes. These were employed to separate a chamber with a solution maintaining high CO2 concentrations from one with depleted CO2 concentrations. CO2 diffusion was detected by measuring the pH change resulting from membrane CO2 diffusion from one chamber to the other. An up to 21 fold increase in diffusion rate was determined. Besides the supply of this proof of principle, we could provide additional arguments in favour of protein facilitated CO2 diffusion to the vivid on-going debate about the principles of membrane gas diffusion in living cells