Polymer-based microfluidic device for measuring membrane protein activities

Functional assays of membrane proteins are becoming increasingly important, both in research and drug discovery applications. The majority of current assays use the patch-clamp technology to measure the activity of ion channels which are over-expressed in cells. In future, in vitro assay systems will be available, which use reconstituted membrane proteins in free-standing lipid bilayers suspended in nano- or micrometer-sized pores. Such functional assays require (1) expression, purification and reconstitution of the membrane protein of interest, (2) a reliable method for lipid bilayer formation and membrane protein integration, and (3) a sensitive detection system. For practical applications, especially for automation, the reliable and controllable transport of fluids is essential. In order to achieve a stable free-standing lipid bilayer, a pore diameter in the micro- to nanometer range is essential. Novel microfluidic devices were developed by bonding a thick (300μm) polyether ether ketone foil, bearing a channel structure, to a thin (12μm) foil with a micropore of about 10μm diameter and then utilized for the formation of stable, free-standing lipid bilayers within the pore. A bacterial voltage-gated potassium channel is integrated therein by fusion and the ion channel activity detected by voltage clam

Specific Binding and Mineralization of Calcified Surfaces by Small Peptides

Several small (<25aa) peptides have been designed based on the sequence of the dentin phosphoprotein, one of the major noncollagenous proteins thought to be involved in the mineralization of the dentin extracellular matrix during tooth development. These peptides, consisting of multiple repeats of the tripeptide aspartate-serine-serine (DSS), bind with high affinity to calcium phosphate compounds and, when immobilized, can recruit calcium phosphate to peptide-derivatized polystyrene beads or to demineralized human dentin surfaces. The affinity of binding to hydroxyapatite surfaces increases with the number of (DSS)n repeats, and though similar repeated sequences—(NTT)n, (DTT)n, (ETT)n, (NSS)n, (ESS)n, (DAA)n, (ASS)n, and (NAA)n—also showed HA binding activity, it was generally not at the same level as the natural sequence. Binding of the (DSS)n peptides to sectioned human teeth was shown to be tissue-specific, with high levels of binding to the mantle dentin, lower levels of binding to the circumpulpal dentin, and little or no binding to healthy enamel. Phosphorylation of the serines of these peptides was found to affect the avidity, but not the affinity, of binding. The potential utility of these peptides in the detection of carious lesions, the delivery of therapeutic compounds to mineralized tissues, and the modulation of remineralization is discussed

The Main Belt Comets and ice in the Solar System

We review the evidence for buried ice in the asteroid belt; specifically the questions around the so-called Main Belt Comets (MBCs). We summarise the evidence for water throughout the Solar System, and describe the various methods for detecting it, including remote sensing from ultraviolet to radio wavelengths. We review progress in the first decade of study of MBCs, including observations, modelling of ice survival, and discussion on their origins. We then look at which methods will likely be most effective for further progress, including the key challenge of direct detection of (escaping) water in these bodies