Plasma-etching is a powerful tool in the determination of the resistance of the sublayer of skinned asymmetric hollow fiber membranes of poly (2,6-dimethyl-1,4-phenylene oxide). Using a resistance model and data provided by etched hollow PPO fiber membranes it is possible to predict the ultimate selectivity of the total membrane for helium over nitrogen and oxygen over nitrogen. From this model...

For the development of a high-performance software system of membrane protein prediction, we analyzed the distribution of hydrophobicity and the amphiphilicity around transmembrane helices, using dataset of membrane proteins whose 3D structures or topologies are known. The moving average of 7 residues showed that there are a hydrophobicity peak in the center of a transmembrane helix and two amp...

BACKGROUND Asymmetric cell division (ACD) is a key process that allows different cell types to be generated at precisely defined times and positions. In Drosophila, neural precursor cells rely heavily on ACD to generate the different cell types in the nervous system. A conserved protein machinery that regulates ACD has been identified in Drosophila, but how this machinery acts to allow the esta...

In eukaryotic cells, the membranes of different intracellular organelles have different lipid composition, and various biomembranes show an asymmetric distribution of lipid types across the membrane bilayer. Membrane lipid organization reflects a dynamic equilibrium of lipids moving across the bilayer in both directions. In this review, we summarize data supporting the role of specific membrane...

( Asymmetric cellulose acetate membranes have been prepared and characterized in the laboratory with a view to use them in membrane bio-reactors. Enzymatic hydrolysis of sucrose has been investigated in a dead-end stirred cell type membrane bio-reactor using these membranes. Effect of different operating variables such as substrate concentration, enzyme loading, flow rate and working volume hav...

Asymmetric cell division is common in biology and plays critical roles in differentiation and development. Unicellular organisms are often used as model systems for understanding the origins and consequences of asymmetry during cell division. Although basic as compared to mammalian cells, these are already quite complex. We report complete budding and asymmetric fission of very simple nonliving...

Membrane proteins reside in a highly asymmetric environment compared to their cytosolic counterparts which gives them unique properties. Rather than being in a homogeneous aqueous solvent, the "solvent" that surrounds membrane proteins consists of the aqueous region outside the membrane, the ionic region of the membrane surface and the oily region of the membrane interior. These differing diele...

Over the past two decades a variety of mechanisms regulating cellular differentiation have been uncovered. These include signaling by morphogens or membrane-associated ligands and asymmetric segregation of cytoplasmic components. Most of these processes are driven by protein coding genes. Here I describe another possible cellular differentiation mechanism that involves asymmetric segregation of...

The resemblance of lipid membrane models to physiological membranes determines how well molecular dynamics (MD) simulations imitate the dynamic behavior of cell membranes and membrane proteins. Physiological lipid membranes are composed of multiple types of phospholipids, and the leaflet compositions are generally asymmetric. Here we describe an approach for self-assembly of a Coarse-Grained (C...

Past work has shown that ions can pass through a membrane more readily in one direction than the other. We demonstrate here in a model and an experiment that for a mixture of small and large particles such asymmetric diffusion can arise solely from an asymmetry in the geometry of the pores of the membrane. Our deterministic simulation considers a two-dimensional gas of elastic disks of two size...