Darryl Y. Sasaki

Bio: Darryl Y. Sasaki is an academic researcher from Sandia National Laboratories. The author has contributed to research in topics: Lipid bilayer & Membrane. The author has an hindex of 37, co-authored 128 publications receiving 4933 citations. Previous affiliations of Darryl Y. Sasaki include United States Air Force Academy & University of New Mexico.

Self-assembly of mesoscopically ordered chromatic polydiacetylene/silica nanocomposites

Abstract: Nature abounds with intricate composite architectures composed of hard and soft materials synergistically intertwined to provide both useful functionality and mechanical integrity. Recent synthetic efforts to mimic such natural designs have focused on nanocomposites, prepared mainly by slow procedures like monomer or polymer infiltration of inorganic nanostructures or sequential deposition. Here we report the self-assembly of conjugated polymer/silica nanocomposite films with hexagonal, cubic or lamellar mesoscopic order using polymerizable amphiphilic diacetylene molecules as both structure-directing agents and monomers. The self-assembly procedure is rapid and incorporates the organic monomers uniformly within a highly ordered, inorganic environment. Polymerization results in polydiacetylene/silica nanocomposites that are optically transparent and mechanically robust. Compared to ordered diacetylene-containing films prepared as Langmuir monolayers or by Langmuir-Blodgett deposition, the nanostructured inorganic host alters the diacetylene polymerization behaviour, and the resulting nanocomposite exhibits unusual chromatic changes in response to thermal, mechanical and chemical stimuli. The inorganic framework serves to protect, stabilize, and orient the polymer, and to mediate its function. The nanocomposite architecture also provides sufficient mechanical integrity to enable integration into devices and microsystems.

Membrane bending by protein-protein crowding

Abstract: Membrane deformation is necessary to generate endocytic vesicles, but the molecular mechanisms proposed to drive membrane bending are controversial. Stachowiak and Schmid et al. report that crowding of proteins at the membrane is sufficient to induce curvature in vitro.

Steric confinement of proteins on lipid membranes can drive curvature and tubulation

Abstract: Deformation of lipid membranes into curved structures such as buds and tubules is essential to many cellular structures including endocytic pits and filopodia. Binding of specific proteins to lipid membranes has been shown to promote membrane bending during endocytosis and transport vesicle formation. Additionally, specific lipid species are found to colocalize with many curved membrane structures, inspiring ongoing exploration of a variety of roles for lipid domains in membrane bending. However, the specific mechanisms by which lipids and proteins collaborate to induce curvature remain unknown. Here we demonstrate a new mechanism for induction and amplification of lipid membrane curvature that relies on steric confinement of protein binding on membrane surfaces. Using giant lipid vesicles that contain domains with high affinity for his-tagged proteins, we show that protein crowding on lipid domain surfaces creates a protein layer that buckles outward, spontaneously bending the domain into stable buds and tubules. In contrast to previously described bending mechanisms relying on local steric interactions between proteins and lipids (i.e. helix insertion into membranes), this mechanism produces tubules whose dimensions are defined by global parameters: domain size and membrane tension. Our results suggest the intriguing possibility that confining structures, such as lipid domains and protein lattices, can amplify membrane bending by concentrating the steric interactions between bound proteins. This observation highlights a fundamental physical mechanism for initiation and control of membrane bending that may help explain how lipids and proteins collaborate to create the highly curved structures observed in vivo.

First observation of mechanochromism at the nanometer scale

Abstract: A mechanically-induced color transition (''mechanochromism'') in polydiacetylene thin films has been generated at the nanometer scale using the tips of two different scanning probe microscopes. A blue-to-red chromatic transition in polydiacetylene molecular trilayer films, polymerized from 10,12-pentacosadiynoic acid (poly-PCDA), was found to result from shear forces acting between the tip and the poly-PCDA molecules, as independently observed with near-field scanning optical microscopy and atomic force microscopy (AFM). Red domains were identified by a fluorescence emission signature. Transformed regions as small as 30 nm in width were observed with AFM. The irreversibly transformed domains preferentially grow along the polymer backbone direction. Significant rearrangement of poly-PCDA bilayer segments is observed by AFM in transformed regions. The removal of these segments appears to be a characteristic feature of the transition. To our knowledge, this is the first observation of nanometer-scale mechanochromism in any material.

Polydiacetylene films: a review of recent investigations into chromogenic transitions and nanomechanical properties

Abstract: Polydiacetylenes (PDAs) form a unique class of polymeric materials that couple highly aligned and conjugated backbones with tailorable pendant sidegroups and terminal functionalities. They can be structured in the form of bulk materials, multilayer and monolayer films, polymerized vesicles, and even incorporated into inorganic host matrices to form nanocomposites. The resulting materials exhibit an array of spectacular properties, beginning most notably with dramatic chromogenic transitions that can be activated optically, thermally, chemically, and mechanically. Recent studies have shown that these transitions can even be controlled and observed at the nanometre scale. These transitions have been harnessed for the purpose of chemical and biomolecular sensors, and on a more fundamental level have led to new insights regarding chromogenic phenomena in polymers. Other recent studies have explored how the strong structural anisotropy that thes em aterials possess leads to anisotropic nanomechanical behaviour. These recen ta dvances suggest that PDAs could be considered as a potential component in nanostructured devices due to the large number of tunable properties. In this paper, we provide a succinct review of the latest insights and applications involving PDA. We then focus in more detail on our work concerning ultrathin films, specifically structural properties, mechanochromism, thermochromism, and in-plane mechanical anisotropy of PDA monolayers. Atomic force microscopy (AFM) and fluorescence microscopy confirm that films 1–3 monolayers thick can be organized into highly ordered domains,with the conjugated backbones parallel to the substrate. The number of stable layers is controlled by the head-group functionality. Local mechanical stress applied by AFM an dn ear-field optical probes induces the chromogenic transition in the film at the nanometre scale. The transition

Tools and tactics for the optical detection of mercuric ion.

Abstract: 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

Analyte Monitoring Device And Methods Of Use

Abstract: 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.

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

Abstract: 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.

Molecular imprinting: perspectives and applications

Abstract: 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).