Hydrophobic interactions leading to a complex interplay between bioelectrocatalytic properties and multilayer meso-organization in layer-by-layer assemblies

2014 ◽  
Vol 16 (38) ◽  
pp. 20844-20855 ◽  
Author(s):  
M. Lorena Cortez ◽  
Nicolás De Matteis ◽  
Marcelo Ceolín ◽  
Wolfgang Knoll ◽  
Fernando Battaglini ◽  
...  
Keyword(s):  
Hydrophobic Interactions ◽  
Layer By Layer ◽  
Complex Interplay

scholarly journals An in-silico layer-by-layer adsorption study of the interaction between Rebaudioside A and the T1R2 human sweet taste receptor: modelling and biosensing perspectives

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Olayide A. Arodola ◽  
Suvardhan Kanchi ◽  
Phathisanani Hloma ◽  
Krishna Bisetty ◽  
Abdullah M. Asiri ◽  
...  
Keyword(s):  
In Silico ◽  
Hydrophobic Interactions ◽  
Homology Modelling ◽  
Taste Receptor ◽  
Sweet Taste ◽  
Electrochemical Sensing ◽  
Hydroxyl Groups ◽  
Layer By Layer ◽  
Rebaudioside A ◽  
Sweet Taste Receptor

Abstract The human sweet taste receptor (T1R2) monomer—a member of the G-protein coupled receptor family that detects a wide variety of chemically and structurally diverse sweet tasting molecules, is known to pose a significant threat to human health. Protein that lack crystal structure is a challenge in structure-based protein design. This study focused on the interaction of the T1R2 monomer with rebaudioside A (Reb-A), a steviol glycoside with potential use as a natural sweetener using in-silico and biosensing methods. Herein, homology modelling, docking studies, and molecular dynamics simulations were applied to elucidate the interaction between Reb-A and the T1R2 monomer. In addition, the electrochemical sensing of the immobilised T1R2-Reb-A complex with zinc oxide nanoparticles (ZnONPs) and graphene oxide (GO) were assessed by testing the performance of multiwalled carbon nanotube (MWCNT) as an adsorbent experimentally. Results indicate a strong interaction between Reb-A and the T1R2 receptor, revealing the stabilizing interaction of the amino acids with the Reb-A by hydrogen bonds with the hydroxyl groups of the glucose moieties, along with a significant amount of hydrophobic interactions. Moreover, the presence of the MWCNT as an anchor confirms the adsorption strength of the T1R2-Reb-A complex onto the GO nanocomposite and supported with electrochemical measurements. Overall, this study could serve as a cornerstone in the development of electrochemical immunosensor for the detection of Reb-A, with applications in the food industry.

scholarly journals Viscoelastic Properties of Polyelectrolyte Multilayers Swollen with Ionic Liquid Solutions

Polymers ◽  
2019 ◽  
Vol 11 (8) ◽  
pp. 1285 ◽  
Author(s):  
Nagma Parveen ◽  
Pritam Kumar Jana ◽  
Monika Schönhoff
Keyword(s):  
Ionic Liquid ◽  
Hydrophobic Interactions ◽  
Salt Content ◽  
Water Soluble ◽  
Polyelectrolyte Multilayers ◽  
Layer By Layer ◽  
Organic Salts ◽  
Low Salt ◽  
Liquid Solutions ◽  
Voigt Model

Polyelectrolyte multilayers (PEM) obtained by layer-by-layer assembly can be doped with ionic liquid (IL) via the swelling of the films with IL solutions. In order to examine the mechanical properties of IL-containing PEM, we implement a Kelvin-Voigt model to obtain thickness, viscosity and elastic modulus from the frequency and dissipation shifts determined by a dissipative quartz crystal microbalance (QCM-D). We analyze the changes in the modeled thickness and viscoelasticity of PEI(PSS/PADMAC)4PSS and PEI(PSS/PAH)4PSS multilayers upon swelling by increasing the concentration of either 1-Ethyl-3-methylimidazolium chloride or 1-Hexyl-3-methylimidazolium chloride, which are water soluble ILs. The results show that the thickness of the multilayers changes monotonically up to a certain IL concentration, whereas the viscosity and elasticity change in a non-monotonic fashion with an increasing IL concentration. The changes in the modeled parameters can be divided into three concentration regimes of IL, a behavior specific to ILs (organic salts), which does not occur with swelling by simple inorganic salts such as NaCl. The existence of the regimes is attributed to a competition of the hydrophobic interactions of large hydrophobic ions, which enhance the layer stability at a low salt content, with the electrostatic screening, which dominates at a higher salt content and causes a film softening.

Modified sodium lignosulfonates (NaLS) with straight chain alcohols and their aggregation behavior and adsorption characteristics on solid surfaces

Holzforschung ◽  
2016 ◽  
Vol 70 (11) ◽  
pp. 1023-1030 ◽  
Author(s):  
Yuanyuan Li ◽  
Dongjie Yang ◽  
Qiuling Huang ◽  
Rong Li
Keyword(s):  
Polymer Brushes ◽  
Hydrophobic Interactions ◽  
Uv Spectroscopy ◽  
Solid Surfaces ◽  
Size Analysis ◽  
Layer By Layer ◽  
Quartz Surface ◽  
Straight Chain ◽  
Potential Measurement ◽  
Adsorption Characteristics

Abstract The aim of the present study is to reveal the effects of straight chain alcohols (CnOHs, 4<n<12) on the aggregation and adsorption behavior of sodium lignosulfonate (NaLS). The analytical methods zeta potential measurement and laser particle size analysis are in focus, while the adsorption characteristics of the samples are studied by means of electrostatic layer-by-layer self-assembly (LBL-SA), atomic force microscopy (AFM), UV spectroscopy, and a quartz crystal microbalance with dissipation (QCM-D) monitoring. The results indicated that the electronegative character of NaLS molecules increased and the aggregation degree of NaLS in solution diminished due to hydrophobic interactions between the hydrophobic core of NaLS and the alkyl chain of alcohols. The adsorption configuration of NaLS without CnOHs is a mushroom-like structure on the solid quartz surface, of which cation-π is the main driving force. In the presence of alcohols, the adsorption morphology of NaLS on the quartz surface changed from compact rigid to a less compact soft state. The adsorption configuration of NaLS with alcohols assumed the shape of polymer brushes, in which electrostatic interaction played an important role. Therefore, the adsorption amount of NaLS on solid surfaces significantly increases in the presence of alcohols, which facilitate the formation of more uniform and smooth adsorption films.

scholarly journals Voltammetric Detection of Caffeine in Beverages at Nafion/Graphite Nanoplatelets Layer-by-Layer Films

Nanomaterials ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 221 ◽  
Author(s):  
Sandra Hernandez-Aldave ◽  
Afshin Tarat ◽  
James D. McGettrick ◽  
Paolo Bertoncello
Keyword(s):  
Thin Films ◽  
Hydrogen Bonding ◽  
Hydrophobic Interactions ◽  
Carbon Electrodes ◽  
Layer By Layer ◽  
Graphite Nanoplatelets ◽  
Glassy Carbon Electrodes ◽  
X Ray ◽  
Voltammetric Detection ◽  
Lbl Films

We report for the first time a procedure in which Nafion/Graphite nanoplatelets (GNPs) thin films are fabricated using a modified layer-by-layer (LbL) method. The method consists of dipping a substrate (quartz and/or glassy carbon electrodes) into a composite solution made of Nafion and GNPs dissolved together in ethanol, followed by washing steps in water. This procedure allowed the fabrication of multilayer films of (Nafion/GNPs)n by means of hydrogen bonding and hydrophobic‒hydrophobic interactions between Nafion, GNPs, and the corresponding solid substrate. The average thickness of each layer evaluated using profilometer corresponds to ca. 50 nm. The as-prepared Nafion/GNPs LbL films were characterized using various spectroscopic techniques such as X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray spectroscopy (EDS), FTIR, and optical microscopy. This characterization highlights the presence of oxygen functionalities that support a mechanism of self-assembly via hydrogen bonding interactions, along with hydrophobic interactions between the carbon groups of GNPs and the Teflon-like (carbon‒fluorine backbone) of Nafion. We showed that Nafion/GNPs LbL films can be deposited onto glassy carbon electrodes and utilized for the voltammetric detection of caffeine in beverages. The results showed that Nafion/GNPs LbL films can achieve a limit of detection for caffeine (LoD) of 0.032 μM and linear range between 20‒250 μM using differential pulse voltammetry, whereas, using cyclic voltammetry LoD and linear range were found to be 24 μM and 50‒5000 μM, respectively. Voltammetric detection of caffeine in beverages showed good agreement between the values found experimentally and those reported by the beverage producers. The values found are also in agreement with those obtained using a standard spectrophotometric method. The proposed method is appealing because it allows the fabrication of Nafion/GNPs thin films in a simple fashion using a single-step procedure, rather than using composite solutions with opposite electrostatic charge, and also allows the detection of caffeine in beverages without any pre-treatment or dilution of the real samples. The proposed method is characterized by a fast response time without apparent interference, and the results were competitive with those obtained with other materials reported in the literature.

scholarly journals Heterogeneous Impacts of Protein-Stabilizing Osmolytes on Hydrophobic Interaction

2018 ◽  
Author(s):  
Mrinmoy Mukherjee ◽  
Jagannath Mondal
Keyword(s):  
Hydrophobic Interaction ◽  
Driving Force ◽  
Hydrophobic Interactions ◽  
Interaction Analysis ◽  
Protein Sequences ◽  
Methyl Groups ◽  
Complex Interplay ◽  
Diverse Range ◽  
Hydrophobic Collapse ◽  
Preferential Binding

AbstractOsmolytes’ mechanism of protecting proteins against denaturation is a longstanding puzzle, further complicated by the complex diversities inherent in protein sequences. An emergent approach in understanding osmolytes’ mechanism of action towards biopolymer has been to investigate osmolytes’ interplay with hydrophobic interaction, the major driving force of protein folding. However, the crucial question is whether all these protein-stabilizing osmolytes display a single unified mechanism towards hydrophobic interactions. By simulating the hydrophobic collapse of a macromolecule in aqueous solutions of two such osmoprotectants, Glycine and Trimethyl N-oxide (TMAO), both of which are known to stabilize protein’s folded conformation, we here demonstrate that these two osmolytes can impart mutually contrasting effects towards hydrophobic interaction. While TMAO preserves its protectant nature across diverse range of polymer-osmolyte interactions, glycine is found to display an interesting cross-over from being a protectant at weaker polymer-osmolyte interaction to a denaturant of hydrophobicity at stronger polymer-osmolyte interactions. A preferential-interaction analysis reveals that a subtle balance of conformation-dependent exclusion/binding of osmolyte molecules from/to the macromolecule holds the key to overall heterogenous behavior. Specifically, TMAO’s consistent stabilization of collapsed configuration of macromolecule is found to be a result of TMAO’s preferential binding to polymer via hydrophobic methyl groups. However, polar Glycine’s cross-over from being a protectant to denaturant across polymer-osmolyte interaction is rooted in its switch from preferential exclusion to preferential binding to the polymer with increasing interaction. Overall, by highlighting the complex interplay of osmolytes with hydrophobic interaction, this work puts forward the necessity of quantitative categorization of osmolytes’ action in protein.

Microstructural characterization of CoPtCr/Cr thin film disks by cross-section TEM and elongated probe micro-diffraction

1991 ◽  
Vol 49 ◽  
pp. 762-763
Author(s):  
M.A. Parker ◽  
K.E. Johnson ◽  
C. Hwang ◽  
A. Bermea
Keyword(s):  
Magnetic Recording ◽  
Electron Probe ◽  
Microstructural Characterization ◽  
Crystallographic Structure ◽  
Recording Media ◽  
Layer By Layer ◽  
Cross Sectional ◽  
New Techniques ◽  
Polished Side

We have reported the dependence of the magnetic and recording properties of CoPtCr recording media on the thickness of the Cr underlayer. It was inferred from XRD data that grain-to-grain epitaxy of the Cr with the CoPtCr was responsible for the interaction observed between these layers. However, no cross-sectional TEM (XTEM) work was performed to confirm this inference. In this paper, we report the application of new techniques for preparing XTEM specimens from actual magnetic recording disks, and for layer-by-layer micro-diffraction with an electron probe elongated parallel to the surface of the deposited structure which elucidate the effect of the crystallographic structure of the Cr on that of the CoPtCr.XTEM specimens were prepared from magnetic recording disks by modifying a technique used to prepare semiconductor specimens. After 3mm disks were prepared per the standard XTEM procedure, these disks were then lapped using a tripod polishing device. A grid with a single 1mmx2mm hole was then glued with M-bond 610 to the polished side of the disk.

Epitaxial growth manner and structure of superconducting oxide films

1990 ◽  
Vol 48 (4) ◽  
pp. 2-3
Author(s):  
Yoshichika Bando ◽  
Takahito Terashima ◽  
Kenji Iijima ◽  
Kazunuki Yamamoto ◽  
Kazuto Hirata ◽  
...  
Keyword(s):  
Ultrathin Films ◽  
Film Surface ◽  
High Energy ◽  
Epitaxial Films ◽  
Layer By Layer ◽  
Initial Growth ◽  
In Situ Growth ◽  
High Quality ◽  
Activated Reactive Evaporation

The high quality thin films of high-Tc superconducting oxide are necessary for elucidating the superconducting mechanism and for device application. The recent trend in the preparation of high-Tc films has been toward “in-situ” growth of the superconducting phase at relatively low temperatures. The purpose of “in-situ” growth is to attain surface smoothness suitable for fabricating film devices but also to obtain high quality film. We present the investigation on the initial growth manner of YBCO by in-situ reflective high energy electron diffraction (RHEED) technique and on the structural and superconducting properties of the resulting ultrathin films below 100Å. The epitaxial films have been grown on (100) plane of MgO and SrTiO, heated below 650°C by activated reactive evaporation. The in-situ RHEED observation and the intensity measurement was carried out during deposition of YBCO on the substrate at 650°C. The deposition rate was 0.8Å/s. Fig. 1 shows the RHEED patterns at every stage of deposition of YBCO on MgO(100). All the patterns exhibit the sharp streaks, indicating that the film surface is atomically smooth and the growth manner is layer-by-layer.

Compact back-scattered electrons' energy analyzer for standard SEM

1994 ◽  
Vol 52 ◽  
pp. 488-489
Author(s):  
S. Likharev ◽  
A. Kramarenko ◽  
V. Vybornov
Keyword(s):  
Depth Resolution ◽  
High Energy ◽  
Primary Beam ◽  
Layer By Layer ◽  
Energy Analyzer ◽  
High Energy Part ◽  
Small Window ◽  
Energy Part ◽  
Wide Range ◽  
High Voltage Supply

At present time the interest is growing considerably for theoretical and experimental analysis of back-scattered electrons (BSE) energy spectra. It was discovered that a special angle and energy nitration of BSE flow could be used for increasing a spatial resolution of BSE mode, sample topography investigations and for layer-by layer visualizing of a depth structure. In the last case it was shown theoretically that in order to obtain suitable depth resolution it is necessary to select a part of BSE flow with the directions of velocities close to inverse to the primary beam and energies within a small window in the high-energy part of the whole spectrum.A wide range of such devices has been developed earlier, but all of them have considerable demerit: they can hardly be used with a standard SEM due to the necessity of sufficient SEM modifications like installation of large accessories in or out SEM chamber, mounting of specialized detector systems, input wires for high voltage supply, screening a primary beam from additional electromagnetic field, etc. In this report we present a new scheme of a compact BSE energy analyzer that is free of imperfections mentioned above.

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