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Biotic-Abiotic Interactions: Factors that Influence Peptide-Graphene Interactions.

Understanding the factors that influence the interaction between biomolecules and abiotic surfaces is of utmost interest in biosensing and biomedical research. Through phage display technology, several peptides have been identified as specific binders to abiotic material surfaces, such as gold, graphene, silver, and so forth. Using graphene-peptide as our model abiotic-biotic pair, we investigate the effect of graphene quality, number of layers, and the underlying support substrate effect on graphene-peptide interactions using both experiments and computation. Our results indicate that graphene quality plays a significant role in graphene-peptide interactions. The graphene-biomolecule interaction appears to show no significant dependency on the number of graphene layers or the underlying support substrate.

Insight on Structure of Water and Ice Next to Graphene Using Surface-Sensitive Spectroscopy

The water/graphene interface has received considerable attention in the past decade due to its relevance in various potential applications including energy storage, sensing, desalination, and catalysis. Most of our knowledge about the interfacial water structure next to graphene stems from simulations, which use experimentally measured water contact angles (WCAs) on graphene (or graphite) to estimate the water-graphene interaction strength. However, the existence of a wide spectrum of reported WCAs on supported graphene and graphitic surfaces makes it difficult to interpret the water-graphene interactions. Here, we have used surface-sensitive infrared-visible sum frequency generation (SFG) spectroscopy to probe the interfacial water structure next to graphene supported on a sapphire substrate. In addition, the ice nucleation properties of graphene have been explored by performing in situ freezing experiments as graphitic surfaces are considered good ice nucleators. For graphene supported on sapphire, we observed a strong SFG peak associated with highly coordinated, ordered water next to graphene. Similar ordering was not detected next to bare sapphire, implying that the observed ordering of water molecules in the former case is a consequence of the presence of graphene. Our analysis indicates that graphene behaves like a hydrophobic (or negatively charged) surface, leading to enhanced ordering of water molecules. Although liquid water orders next to graphene, the ice formed is proton disordered. This research sheds light on water-graphene interactions relevant in optimizing the performance of graphene in various applications.

Peptide interactions with zigzag edges in graphene

Recognition and manipulation of graphene edges enable the control of physical properties of graphene-based devices. Recently, the authors have identified a peptide that preferentially binds to graphene edges from a combinatorial peptide library. In this study, the authors examine the functional basis for the edge binding peptide using experimental and computational methods. The effect of amino acid substitution, sequence context, and solution pH value on the binding of the peptide to graphene has been investigated. The N-terminus glutamic acid residue plays a key role in recognizing and binding to graphene edges. The protonation, substitution, and positional context of the glutamic acid residue impact graphene edge-binding. Our findings provide insights into the binding mechanisms and the design of peptides for recognizing and functionalizing graphene edges.

Investigation of a DNA nucleobase as a gate dielectric for potential application in a graphene-based field effect transistor

In this study, we investigated the effect of substrates on the electrical properties of transferred graphene. A wide range of substrates such as silicon carbide (SiC), glass, kapton, photo-print paper, polydimethylsiloxane (PDMS) and Willow glass were selected based on their surface properties, flexibility and lattice match. Four monolayers of graphene were transferred onto each of these substrates. A comparative study of the electrical characteristics of the transferred graphene film only and graphene/guanine film on the different substrates was undertaken.

Chemically Enhanced Polymer-Coated Carbon Nanotube Electronic Gas Sensor for Isopropyl Alcohol Detection

Breathing-air quality within commercial airline cabins has come under increased scrutiny because of the identification of volatile organic compounds (VOCs) from the engine bleed air used to provide oxygen to cabins. Ideally, a sensor would be placed within the bleed air pipe itself, enabling detection before it permeated through and contaminated the entire cabin. Current gas-phase sensors suffer from issues with selectivity, do not have the appropriate form factor, or are too complex for commercial deployment. Here, we chose isopropyl alcohol (IPA), a main component of de-icer spray used in the aerospace community, as a target analyte: IPA exposure has been hypothesized to be a key component of aerotoxic syndrome in pre, during, and postflight. IPAs proposed mechanism of action is that of an anesthetic and central nervous system depressant. In this work, we describe IPA sensor development by showing (1) the integration of a polymer as an IPA capture matrix, (2) the adoption of a redox chemical additives as an IPA oxidizer, and (3) the application of carbon nanotubes as an electronic sensing conduit. We demonstrate the ability to not only detect IPA at 100–10 000 ppm in unfiltered, laboratory air but also discriminate among IPA, isoprene, and acetone, especially in comparison to a typical photoionization detector. Overall, we show an electronic device that operates at room temperature and responds preferentially to IPA, where the increase in the resistance corresponds directly to the concentration of IPA. Ultimately, this study opens up the pathway to selective electronic sensors that can enable real-time monitoring in a variety of environments for the force health prevention and protection, and the potential through future work to enable low parts-per-million and possibly high parts-per-billion selective detection of gas-phase VOCs of interest.

Visualization of peptide-peptide interactions in FET biosensors with liquid-cell TEM

Graphene-based field effect transistor (g-FET) sensors have been broadly applied in detection of biological macromolecules, such as RNA, DNA, peptides, and small toxic compounds [1]. The specificity and selectivity rely heavily on graphene-functionalization with biological recognizing elements (BREs) and the characterization of BRE engagement with target molecule is therefore one of the critical steps in sensor development. Transmission electron microscopy (TEM), because of its ability to offer high spatial resolution in compared to other image-based approaches, is a useful tool for examining the dynamic process involved in sensor detection. Here we present our TEM studies on a Neuropeptide Y specific g-FET biosensor in a liquid environment.

Three-dimensional structure of neuropeptide Y pre-pro-peptide to reveal its interaction with lipid membrane

Neuropeptide Y (NPY) is one of the abundant proteins within brain [1], and it is involved in regulation of important biological and pathophysiological functions such as food uptake, energy homeostasis, circadian rhythm and cognition. NPY also serves as a major neurochemical component in stress response and a key element in modulation of emotional-affective behavior. NPY is therefore a potential drug for the disease condition characterized by dysregulation of NPY-dependent physiological pathway(s), eg, resilience from traumatic conditions, or an indicator of susceptibility to stressful or threat-related events.