Signaling Recognition Events with Fluorescent Sensors and Switches.

9.2. Protein-Based Hg(II) Detectors 3467 9.3. Oligonucleotide-Based Hg(II) Detector 3467 9.4. DNAzyme-Based Hg(II) Detectors 3469 9.5. Antibody-Based Hg(II) Detector 3469 10. Mercury Detectors Based on Materials 3469 10.1. Soluble and Fluorescent Polymers 3469 10.2. Membranes, Films, and Fibers 3471 10.3. Micelles 3473 10.4. Nanoparticles 3473 11. Perspectives 3474 12. Addendum 3475 12.1. Small Molecules 3475 12.2. Biomolecules 3477 12.3. Materials 3477 13. List of Abbreviations 3477 14. Acknowledgments 3478 15. References 3478

Tools and tactics for the optical detection of mercuric ion.

An analyte monitor includes a sensor, a sensor control unit, and a display unit. The sensor has, for example, a substrate, a recessed channel formed in the substrate, and conductive material disposed in the recessed channel to form a working electrode. The sensor control unit typically has a housing adapted for placement on skin and is adapted to receive a portion of an electrochemical sensor. The sensor control unit also includes two or more conductive contacts disposed on the housing and configured for coupling to two or more contact pads on the sensor. A transmitter is disposed in the housing and coupled to the plurality of conductive contacts for transmitting data obtained using the sensor. The display unit has a receiver for receiving data transmitted by the transmitter of the sensor control unit and a display coupled to the receiver for displaying an indication of a level of an analyte. The analyte monitor may also be part of a drug delivery system to alter the level of the analyte based on the data obtained using the sensor.

Analyte Monitoring Device And Methods Of Use

Developing highly efficient catalysts for the oxygen reduction reaction (ORR) is key to the fabrication of commercially viable fuel cell devices and metal–air batteries for future energy applications. Herein, we review the most recent advances in the development of Pt-based and Pt-free materials in the field of fuel cell ORR catalysis. This review covers catalyst material selection, design, synthesis, and characterization, as well as the theoretical understanding of the catalysis process and mechanisms. The integration of these catalysts into fuel cell operations and the resulting performance/durability are also discussed. Finally, we provide insights into the remaining challenges and directions for future perspectives and research.

Recent advancements in Pt and Pt-free catalysts for oxygen reduction reaction

Molecular imprinting technology (MIT), often described as a method of making a molecular lock to match a molecular key, is a technique for the creation of molecularly imprinted polymers (MIPs) with tailor-made binding sites complementary to the template molecules in shape, size and functional groups. Owing to their unique features of structure predictability, recognition specificity and application universality, MIPs have found a wide range of applications in various fields. Herein, we propose to comprehensively review the recent advances in molecular imprinting including versatile perspectives and applications, concerning novel preparation technologies and strategies of MIT, and highlight the applications of MIPs. The fundamentals of MIPs involving essential elements, preparation procedures and characterization methods are briefly outlined. Smart MIT for MIPs is especially highlighted including ingenious MIT (surface imprinting, nanoimprinting, etc.), special strategies of MIT (dummy imprinting, segment imprinting, etc.) and stimuli-responsive MIT (single/dual/multi-responsive technology). By virtue of smart MIT, new formatted MIPs gain popularity for versatile applications, including sample pretreatment/chromatographic separation (solid phase extraction, monolithic column chromatography, etc.) and chemical/biological sensing (electrochemical sensing, fluorescence sensing, etc.). Finally, we propose the remaining challenges and future perspectives to accelerate the development of MIT, and to utilize it for further developing versatile MIPs with a wide range of applications (650 references).

http://ir.yic.ac.cn/bitstream/133337/17045/1/Molecular%20imprinting%20perspectives%20and%20applications.pdf

Molecular imprinting: perspectives and applications

Cell membranes consist of a fluidic medium of lipids and proteins that organize into specific submicron scale structures for signaling and molecular trafficking processes. These organized molecular assemblies form as a result of the structure and chemistry of the membrane components as well as the interactions of those components with analytes from solution. Although considerable research has focused on the structure and chemistry of membrane components and their ability to form organized assemblies, less attention has been paid toward the influence that chemical recognition has upon membrane reorganization. This review focuses on the recognition and binding of metal ions, small molecules, polyelectrolytes, and proteins on model membrane systems to assess the effects of long- and short-range interactions upon the molecular organization of the membrane. Chemical recognition can induce dramatic changes on the membrane's phase transition temperature and the clustering or dispersion of membrane components.

Control of membrane structure and organization through chemical recognition.

The interaction of biomacromolecules with dense packed lipid layers is of great interest for biotechnology in the areas of biocompatibility, medicine, sensors, and biomolecular devices. Such interactions are also important for understanding certain biochemical processes such as cell signaling and toxin assault on cells. One important goal is to understand how various types of fundamental interactions and their spatial distribution affect the conformation of an adsorbed protein. Important aspects include the orientation of the adsorbed protein (end-on versus side-on) and single layer versus multilayer adsorption. The orientation of an enzyme, for example, can affect access to an active site and thus activity. Another important question is whether rearrangement of protein structure or even denaturation occurs upon adsorption. Indeed, the protein myoglobin has been shown to undergo a dramatic conformational change in solution under certain conditions,1 and it is important to know whether significant conformational changes may occur upon adsorption to a substrate as well. Furthermore, it is important to understand changes that occur in the conformation of an adsorbed protein for varying solution conditions. Much work has been reported regarding protein adsorption to solid surfaces, where methods such as scanning probes, the surface forces apparatus, linear and circular dichroism, Fourier transform infrared spectroscopy, and X-ray and neutron scattering are readily available to probe the density and structure of the adsorbed layer.2-5 Much less work has been reported at fluid-fluid interfaces. For biomimetic studies, lipid membranes at fluid-fluid interfaces offer the advantage of greater in-plane mobility of the lipids, thus better mimicking the surface of a cell. Studies of protein adsorption to lipid monolayers at the liquid-air interface have involved mainly surface pressure isotherms, ellipsometry, and fluorescence and Brewster angle microscopies,6-11 much of the work focusing on lipid reorganization and protein-protein interactions in the two-dimensional (2-D) plane. Additional information on the dimension normal to the interface would provide further depth into the mode of protein interaction with functionalized films. Information regarding monolayer or multilayer adsorption as well as protein structure (i.e., denaturation, conformational change) would provide finer detail of molecular-level interactions of host-guest complexation systems. Recently, several studies probing the structure of proteins bound to functionalized lipid films have been reported. Losche et al. demonstrated the power of neutron reflectivity in examining the conformation of streptavidin adsorbed to monolayers of biotin-functionalized lipids and binary lipid mixtures.12 Most recently, grazing incidence X-ray diffraction has been used to examine 2-D protein crystals formed upon adsorption to lipid monolayers13,14 and the effect of the binding of a lung surfactant specific protein SP-B on the structure of palmitic acid monolayers.15 Toourknowledge,all of thestudies reportingdetailed structural information on proteins bound to fluid membranes thus far have involved proteins which form twodimensional crystals. Information on amorphous structures of proteins bound to fluid membranes, which encompass most of the biological protein-membrane interactions, is almost nonexistent. We report here the use of neutron reflection to examine the segment conformation profile of myoglobin adsorbed to a Langmuir monolayer containing a metal ion chelating lipid that targets histidine residues. The metal-chelating lipid is PSIDA, shown in Figure 1, which has an iminodiacetate headgroup for metal ion chelation and a pyrene group on one of the tails to enable fluorescence studies of metal ion9,16 and protein8,17 adsorption. The use of metal ion coordination to target the adsorption of proteins to lipid membranes has been studied extensively by

Segment concentration profile of myoglobin adsorbed to metal ion chelating lipid monolayers at the air-water interface by neutron reflection

A series of functionalized lipid membranes were shown to respond selectively to Fe3+, Cr3+, Cu2+, and Fe2+ with a distinctive change in bilayer fluorescence. The optical response is due to a change in the aggregational state of functionalized, pyrene-labeled lipids as they recognize and bind to the metal ion. Two new lipids are introduced with 2,2′-bipyridine (PSBiPy) and N-methylamide (PSMA) headgroups. These functionalized lipids, along with two other lipids having hydroxyl (PSOH) and iminodiacetic acid (PSIDA) headgroups, were incorporated into bilayers of distearylphosphatidylcholine (DSPC) producing materials that exhibited an excellent range of sensitivity for the metal ions at low pH. At neutral pH the metal ion sensitivities were lost for PSOH and PSMA while the sensitivity and selectivity for Cu2+ increased for PSBiPy. In addition to optical sensing, the bilayers also can undergo restructuring of the membrane architecture. Dynamic light scattering and transmission electron microscope images show that for the majority of the bilayers, metal ion addition caused only aggregation of the vesicles. However, for the PSBiPy/DSPC membranes extraordinary square-shaped assemblies of planar bilayers formed in the presence of 100 µM Cu2+.

Selective fluorescence detection of divalent and trivalent metal ions with functionalized lipid membranes.

Poly(tetrahydrofuran), poly(oxacyclobutane), and poly(ethylene oxide) were epixially grown on the basal plane of graphite via in situ polymerization and ther intra- and interchain structures as well as epixial orientations were examined by scanning tunneling microscopy (STM). STM images indicated these polymer chains in a planar, all trans conformation commensurate with the graphite lattice. Different polymer lattices can be constructed by mutually shifting a chain with respect to the adjacent chain along the backbone direction, in units of the graphite haxagon. Most of the STM images can be explained by moire patterns generated through rotations of the polymer lattice on top of the graphite lattice

Structural study of polyethers on graphite by scanning tunneling microscopy. Polymerization-induced epitaxy

We demonstrate the construction of novel protein-lipid assemblies through the design of a lipid-like molecule, DPIDA, endowed with tail-driven affinity for specific lipid membrane phases and head-driven affinity for specific proteins. In studies performed on giant unilamellar vesicles (GUVs) with varying mole fractions of dipalymitoylphosphatidylcholine (DPPC), cholesterol, and diphytanoylphosphatidyl choline (DPhPC), DPIDA selectively partitioned into the more ordered phases, either solid or liquid-ordered (L(o)) depending on membrane composition. Fluorescence imaging established the phase behavior of the resulting quaternary lipid system. Fluorescence correlation spectroscopy confirmed the fluidity of the L(o) phase containing DPIDA. In the presence of CuCl(2), the iminodiacetic acid (IDA) headgroup of DPIDA forms the Cu(II)-IDA complex that exhibits a high affinity for histidine residues. His-tagged proteins were bound specifically to domains enriched in DPIDA, demonstrating the capacity to target protein binding selectively to both solid and L(o) phases. Steric pressure from the crowding of surface-bound proteins transformed the domains into tubules with persistence lengths that depended on the phase state of the lipid domains.

Darryl Y. Sasaki

Papers

Control of membrane structure and organization through chemical recognition.

Segment concentration profile of myoglobin adsorbed to metal ion chelating lipid monolayers at the air-water interface by neutron reflection

Selective fluorescence detection of divalent and trivalent metal ions with functionalized lipid membranes.

Structural study of polyethers on graphite by scanning tunneling microscopy. Polymerization-induced epitaxy

Targeting proteins to liquid-ordered domains in lipid membranes.