Electric eels: Bizarre natural phenomena or inspiration for novel nanocomposite energy storage

The global rush to develop new high energy density, high power density electrical energy storage has motivated a variety of creative, alternative approaches to new technology development. We have adopted one such creative approach, looking to the electric eel as a model for how to manipulate and store electrical energy. These remarkable organisms are capable of repeatedly generating and discharging 1 Ampere of current at over 600V! The cellular machinery responsible for electrical energy storage in organisms like the electric eel is quite complex (Figure 1), but the driving force behind these sophisticated processes hinges on the relatively simple concept of controlled transmembrane ion transport. In specialized cells known as electrocytes, coordinated ion channels and protein pumps shuttle ions across a membrane to create, maintain, or release ion concentration gradients. The chemical potential of these concentration gradients can be translated to a voltage, and the transport of ions across a membrane generates current. Although the amount of current and voltage established across a single membrane is quite small, by assembling thousands of electrocytes both in series and in parallel within its electric organs, the electric eel can accumulate the remarkable voltages and current necessary for its lethal electrical discharge. In our work, we have established a simplified variation of Mother Nature’s scheme, still focusing on the concept of controllably and selectively pumping and gating ions to generate, maintain, or release electrical potentials. In particular, our simplified scheme utilizes two cooperating nanocomposite membranes: a pumping membrane and a gating membrane. The pumping membrane is a composite structure that relies on the light-activated proton pump bacteriorhodopsin (bR) as a one-directional ion (proton) pump, oriented within the membrane construct. When bR absorbs a photon, it responds by transporting one proton across a membrane, which means that an oriented array of bR is capable of using light to generate significant ion concentration gradients (and associated electrical potentials) across this “pump” membrane. In parallel, we are working to create a number of composite “gate” membrane structures that utilize, for example, electrochemically programmable chemistries applied to nanoporous substrates. These molecules, whose “gating state” is externally controllable with voltage, are expected to then maintain or release ion concentration gradients established by the bR pump membrane. We have discovered that by manipulating nanopore morphology, electrostatics, and solvation, these gate membranes can be used to rectify transmembrane ion transport, a critical capability needed to gate ions in this bio-inspired model system. Finally, we are working to address the concept of scalability, developing a system of microfluidic “cells” containing pump and gate membrane components in an artificial mimic of the series-parallel assembly of electrocytes in electric eels. In the course of this presentation, I will describe this biomimetic scheme, explore the strategies, chemistries, and materials employed in the development of our programmable nanocomposite membranes, and discuss our efforts to mimic the type of ion-based electrical energy management so “shockingly” effective in an electric eel

Design of ceramic-polymer optical composites for building energy efficiency: Infrared property control and transparent bulk thermal insulators

Of ~$1 trillion total U.S. energy use, 15$34 billion of energy waste annually. Materials design of windows, roofs and insulation is an opportunity for energy efficiency improvements, by optimizing solar absorption, transmission, infrared emission and thermal insulation. This presentation will discuss both static and dynamic/active approaches to improved energy efficiency in windows through materials design and performance improvements. Please click Additional Files below to see the full abstract

Supramolecular peptide composite assemblies: Mimicking biological form and function in synthetic systems

Microtubules (MTs) are dynamic, multifunctional biomaterials that facilitate a range of complex biological process in cells ranging from regulation of cell morphology to separation of chromosomes during cell division to directing the intracellular transport of molecular cargo.1 The remarkable precision, versatility, and dynamic nature of these non-equilibrium structures has motivated our desire to mimic their structure and function in synthetic materials. Here, I will identify a number of the key attributes responsible for MT form and function, and describe our efforts to merge computation and experiment to design, synthesize, and study a family of self-assembling peptides intended to mimic MTs. MTs are self-assembled biological filaments assembled from tightly bound heterodimers of α and β tubulin. These dimers assemble head-to-tail into protofilaments that associate laterally into closed sheets forming the characteristic tubular morphology of the MTs. These tubules are approximately 25 nm in diameter and can be many micrometers long, though the length of the MTs is subject to their dynamic assembly and disassembly within a cell (dynamic instability). Ultimately, both the initial assembly and dynamic instability of MTs are governed by complex electrostatic and hydrogen bonding interactions between tubulin heterodimers and other functional biomolecules within the cell. These interactions allow biology to effectively program MT form and function to meet the dynamic and evolving needs of a cell. From a synthetic materials perspective, we aim to create simplified peptide or composite peptide molecules capable of similar programmable functional assembly that could similarly be used to facilitate dynamic or adaptable organization of nanomaterials. To guide the design and facilitate understanding of these peptide systems, we utilize a combination of density functional theory (DFT) and self-consistent field theory (SCFT) that can reveal simplified or distilled molecular characteristics needed in an artificial MT scheme. These computational studies have provided insight into the necessary molecular geometries, peptide compositions, and even targeted intermolecular interactions built into our MT-mimetic designs. In particular here, I will describe a collection of simulation-inspired peptides in which we demonstrate that molecular shape, electrostatic interactions, hydrogen bonding, and solvent interactions influence peptide self assembly into sheets, fibers, ribbons, vesicles and tubules (Figure 1).2,3 Moreover, we show that by creating hybrid or composite compositions containing multiple functionalities, it is possible to control molecular self-assembly through interactions with secondary molecules. For example, select bola-peptide compositions are shown to undergo unique self-assembly in collaboration with the surfactant sodium dodecylsulfate, creating a composite structure that is resistant to enzymatic degradation. In another example, molecules comprising self assembling peptides, such as diphenylalanine, and boronic acid form ribbon-structures whose reversible self-assembly is mediated by binding of polysaccharides to the boronic acids. Just as in the natural MT system, the self-assembly (and disassembly) in these hybrid systems is regulated by molecular shape, electrostatic and hydrogen bonding interactions, and the programmable response of these molecules to chemical stimuli. Continued development of these hybrid, composite peptide systems is aimed at developing a new class of biomimetic molecular materials which mimic not only the form, but also the underlying function of some of Nature’s most compelling supramolecular creations

Adding some Dirt to Clean energy: Applying clay nanocomposites in solar cells

Polymer clay nanocomposite (PCN) thin films have found application across a number of applications, ranging from oxygen barriers to flame retardants, where their resistance to molecular gas diffusion has proven remarkably effective, even in films only a few hundred nanometers thick. Deposited using a layer-by-layer processing approach that takes advantage of self-assembly of the constituent components, these composite thin films comprise highly organized, alternating molecular layers of functional polymers and exfoliated clay platelets, commonly montmorillonite or vermiculite. Here, we explore the potential application and utility of PCN thin films in solar cells, where they serve as conformal, transparent barrier films with the potential to impact solar cell lifetime, reliability, and safety. Solar cell failures commonly result when environmental moisture and corrosive or reactive gases penetrate a cell’s encapsulant. Moreover, such cell degradation can manifest as a gradual decline in solar cell performance or, in the case when degradation leads to significantly damaged electrical elements, much more dramatic arc-faults that can lead to complete and dramatic module failure, even igniting module fires. Here, we describe how the unique nanostructure, materials chemistry, and gas barrier properties of PCNs offer promise toward addressing these challenges. Applying the PCN coatings to various elements of a solar cell module, we demonstrate the efficacy of PCNs as gas barriers, corrosion inhibitors, and arc-fault flammability mitigators. I will discuss here not only the results of our studies but also potential mechanisms for effective PCN function and present some apparent limitations of select approaches to PCN integration. These results reveal significant potential for PCNs to impact photovoltaic and other energy-related technologies, and our work highlights how these diverse, highly functional thin films may offer tremendous new opportunities for other next generation materials advances. Please click Additional Files below to see the full abstract

EGO-1 is related to RNA-directed RNA polymerase and functions in germ-line development and RNA interference in C. elegans

AbstractBackground: Cell-fate determination requires that cells choose between alternative developmental pathways. For example, germ cells in the nematode worm Caenorhabditis elegans choose between mitotic and meiotic division, and between oogenesis and spermatogenesis. Germ-line mitosis depends on a somatic signal that is mediated by a Notch-type signaling pathway. The ego-1 gene was originally identified on the basis of genetic interactions with the receptor in this pathway and was also shown to be required for oogenesis. Here, we provide more insight into the role of ego-1 in germ-line development.Results: We have determined the ego-1 gene structure and the molecular basis of ego-1 alleles. Putative ego-1 null mutants had multiple, previously unreported defects in germ-line development. The ego-1 transcript was found predominantly in the germ line. The predicted EGO-1 protein was found to be related to the tomato RNA-directed RNA polymerase (RdRP) and to Neurospora crassa QDE-1, two proteins implicated in post-transcriptional gene silencing (PTGS). For a number of germ-line-expressed genes, ego-1 mutants were resistant to a form of PTGS called RNA interference.Conclusions: The ego-1 gene is the first example of a gene encoding an RdRP-related protein with an essential developmental function. The ego-1 gene is also required for a robust response to RNA interference by certain genes. Hence, a protein required for germ-line development in C. elegans may be a component of the RNA interference/PTGS machinery

om92, a glp-1 enhancer mutation, is an allele of ekl-1

Germline stem cell proliferation in C. elegans requires activation of the GLP-1/Notch receptor, which is located on the germline plasma membrane and encoded by the glp-1 gene. We previously identified several genes whose products directly or indirectly promote activity of the GLP-1 signaling pathway by finding mutations that enhance the germline phenotype of a glp-1(ts) allele, glp-1(bn18) . Here, we report phenotypic and molecular analysis of a new ekl-1 allele, ekl-1(om92) , that enhances the glp-1(bn18) phenotype. ekl-1(om92) is a 244 bp deletion predicted to generate a frameshift and premature termination codon, yielding a severely truncated protein, suggesting it is a null allele

The ion seeps tonight: Assessing ionic transport in multilayered nanocomposites

Figure 6 – Schematic of cation (M+) transport through an organized multilayered composite. Controlling ion transport across membranes and interfaces is one of the central themes challenging technological pursuits ranging from corrosion to energy storage and chemical separations. Here, we present several examples in which we have studied the application of multilayer nanocomposites to regulate ion transport. These composites comprise organized layers of functional or structural elements, integrated within composites such that the specific nanostructure and composition of the materials play important roles in defining ionic interactions and mobility. In cases such as corrosion inhibition, thin film composite coatings are intended to block ionic transport, retarding deleterious corrosion reactions. We show that by manipulating the materials chemistry of highly organized polymer clay nanocomposite thin film barriers, it is possible to significantly increase corrosion resistance of steel samples in a simulated sea water environment. In contrast, for energy storage applications such as batteries, composite separators capable of rapid ionic diffusion are desired for high current performance. We explore how layered composite structures may provide effective ion diffusion planes, leading to promising ionic conductivity in new solid state separators. Finally, in chemical separations, the selective transport of ions becomes important. We examine how manipulating the chemical and electrostatic composition of layered polyelectrolyte materials leads to preferential cation transport through these composite structures, a key property for an effective separations membrane. These different technologies exemplify how the principles governing ion transport through multilayered materials can be adapted for widely varied applications, and they illustrate the potential for this materials development strategy to enable new classes of functional composite materials. Please click Additional Files below to see the full abstract

The National Lung Matrix Trial: translating the biology of stratification in advanced non-small-cell lung cancer

© The Author 2015.Background: The management of NSCLC has been transformed by stratified medicine. The National Lung Matrix Trial (NLMT) is a UK-wide study exploring the activity of rationally selected biomarker/targeted therapy combinations. Patients and methods: The Cancer Research UK (CRUK) Stratified Medicine Programme 2 is undertaking the large volume national molecular pre-screening which integrates with the NLMT. At study initiation, there are eight drugs being used to target 18 molecular cohorts. The aim is to determine whether there is sufficient signal of activity in any drug-biomarker combination to warrant further investigation. A Bayesian adaptive design that gives a more realistic approach to decision making and flexibility to make conclusions without fixing the sample size was chosen. The screening platform is an adaptable 28-gene Nextera next-generation sequencing platform designed by Illumina, covering the range of molecular abnormalities being targeted. The adaptive design allows new biomarker-drug combination cohorts to be incorporated by substantial amendment. The pre-clinical justification for each biomarker-drug combination has been rigorously assessed creating molecular exclusion rules and a trumping strategy in patients harbouring concomitant actionable genetic abnormalities. Discrete routes of pathway activation or inactivation determined by cancer genome aberrations are treated as separate cohorts. Key translational analyses include the deep genomic analysis of pre- and post-treatment biopsies, the establishment of patient-derived xenograft models and longitudinal ctDNA collection, in order to define predictive biomarkers, mechanisms of resistance and early markers of response and relapse. Conclusion: The SMP2 platform will provide large scale genetic screening to inform entry into the NLMT, a trial explicitly aimed at discovering novel actionable cohorts in NSCLC

The microcirculation: linking trauma and coagulopathy

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/96284/1/trf12034.pd