Structural transitions of monoolein bicontinuous cubic phase induced by inclusion of protein lysozyme solutions

Inclusion of protein lysozyme molecules in lipidic monoolein cubic phase induces a transition from a $\rm Pn\bar{3}m$ structure to $\rm Im\bar{3}m$ one. Small-angle X-ray scattering (SAXS) method with high intensity synchrotron radiation enabled us to follow closely the transition depending on the conditions of lysozyme solutions. We showed that concentrated lysozyme solutions induced the appearance of the $\rm Im\bar{3}m$ structure coexisting with the $\rm Pn\bar{3}m$ structure. From the relation between the lattice parameters of these two structures it was shown that they were related by the Bonnet transformation of underlying triply periodic minimal surfaces. We found that the transition also occurred at lower lysozyme concentration when NaCl induced attraction between lysozyme molecules. The origin of the transition was considered as a frustration in the cubic phase where lysozyme molecules were highly confined. A simple estimation of the frustration was given, which took into account of the translational entropy of lysozyme molecules. At the highest concentration of lysozyme and NaCl the $\rm Im\bar{3}m$ structure was found to disappear and left only the $\rm Pn\bar{3}m$ structure. This was probably either due to the crystallization or phase separation of lysozyme solutions ongoing microscopically, which absorbed lysozyme molecules from channels of the cubic phase and thus removed the frustration.Comment: 8 pages, 5 figure

Biochemical applications of surface-enhanced infrared absorption spectroscopy

An overview is presented on the application of surface-enhanced infrared absorption (SEIRA) spectroscopy to biochemical problems. Use of SEIRA results in high surface sensitivity by enhancing the signal of the adsorbed molecule by approximately two orders of magnitude and has the potential to enable new studies, from fundamental aspects to applied sciences. This report surveys studies of DNA and nucleic acid adsorption to gold surfaces, development of immunoassays, electron transfer between metal electrodes and proteins, and protein–protein interactions. Because signal enhancement in SEIRA uses surface properties of the nano-structured metal, the biomaterial must be tethered to the metal without hampering its functionality. Because many biochemical reactions proceed vectorially, their functionality depends on proper orientation of the biomaterial. Thus, surface-modification techniques are addressed that enable control of the proper orientation of proteins on the metal surface. [Figure: see text

Fluorescence Imaging and Spectroscopy of Biomaterials in Air and Liquid by Scanning Near-Field Optical/Atomic Force Microscopy

We have developed scanning near-field optical/atomic force microscopy (SNOM/AFM). The SNOM/AFM uses a bent optical fiber simultaneously as a dynamic force AFM cantilever and a SNOM probe. Resonant frequency of the optical fiber cantilever is 15-40 kHz. Optical resolution of the SNOM/AFM images shows less than 50 nm. The SNOM/ AFM system contains photon counting system and polychrometer/intensified coupled charge devise (ICCD) system to observe fluorescence image and spectrograph of micro areas, respectively. Cultured cells were stained with fluorescein isothiocyanate (FITC)-labeled anti-keratin antibody or FITC-labeled phalloidin after treatment with Triton X-100. Fluorescence and topographic images were obtained in air and water. The fluorescence images showed clear images of keratin and actin filaments. The SNOM/AFM is perfect to observe biomaterials in liquid with a liquid chamber while the topographic Images showed subcellular structures which correspond to keratin and actin filaments

a Raman scattering study

The longitudinal optical phonon of metallic nanotubes shifts by 23 cm−1 to lower energies when the nanotubes are deposited from a solution onto a substrate. The linewidth increases by 13 cm−1. The changes are explained in terms of shifts in the Fermi energy that influence the Kohn anomaly in the longitudinal optical phonon branch in metallic nanotubes. Using in situ electrochemical Raman measurements we show that the Fermi energy is 0.16 eV below its intrinsic value in metallic nanotubes in solution. Our results impact the application of Raman spectroscopy to distinguish between metallic and semiconducting tubes by examining the high-energy mode line shape

Kinematic Control and Obstacle Avoidance for Soft Inflatable Manipulator

© Springer Nature Switzerland AG 2019. In this paper, we present a kinematic control and obstacle avoidance for the soft inflatable manipulator which combines pressure and tendons as an actuating mechanism. The position control and obstacle avoidance took inspiration from the phenomena of a magnetic field in nature. The redundancy in the manipulator combined with a planar mobile base is exploited to help the actuators stay under their maximum capability. The navigation algorithm is shown to outperform the potential-field-based navigation in its ability to smoothly and reactively avoid obstacles and reach the goal in simulation scenarios

Reconstitution of [Fe]-hydrogenase using model complexes

[Fe]-Hydrogenase catalyses the reversible hydrogenation of a methenyltetrahydromethanopterin substrate, which is an intermediate step during the methanogenesis from CO2 and H-2. The active site contains an iron-guanylylpyridinol cofactor, in which Fe2+ is coordinated by two CO ligands, as well as an acyl carbon atom and a pyridinyl nitrogen atom from a 3,4,5,6-substituted 2-pyridinol ligand. However, the mechanism of H-2 activation by [Fe]-hydrogenase is unclear. Here we report the reconstitution of [Fe]-hydrogenase from an apoenzyme using two FeGP cofactor mimics to create semisynthetic enzymes. The small-molecule mimics reproduce the ligand environment of the active site, but are inactive towards H-2 binding and activation on their own. We show that reconstituting the enzyme using a mimic that contains a 2-hydroxypyridine group restores activity, whereas an analogous enzyme with a 2-methoxypyridine complex was essentially inactive. These findings, together with density functional theory computations, support a mechanism in which the 2-hydroxy group is deprotonated before it serves as an internal base for heterolytic H-2 cleavage

A Cilia-inspired Closed-loop Sensor-actuator Array

© 2018, Jilin University. Cilia are finger-like cell-surface organelles that are used by certain varieties of aquatic unicellular organisms for motility, sensing and object manipulation. Initiated by internal generators and external mechanical and chemical stimuli, coordinated undulations of cilia lead to the motion of a fluid surrounding the organism. This motion transports micro-particles towards an oral cavity and provides motile force. Inspired by the emergent properties of cilia possessed by the pond organism P. caudatum, we propose a novel smart surface with closed-loop control using sensor-actuators pairings that can manipulate objects. Each vibrating motor actuator is controlled by a localised microcontroller which utilises proximity sensor information to initiate actuation. The circuit boards are designed to be plug-and-play and are infinitely up-scalable and reconfigurable. The smart surface is capable of moving objects at a speed of 7.2 millimetres per second in forward or reverse direction. Further development of this platform will include more anatomically similar biomimetic cilia and control

Nucleated polymerisation in the presence of pre-formed seed filaments

We revisit the classical problem of nucleated polymerisation and derive a range of exact results describing polymerisation in systems intermediate between the well-known limiting cases of a reaction starting from purely soluble material and for a reaction where no new growth nuclei are formed

The role of formic acid/formate equilibria in the oxidation of formic acid on Pt(111)

[EN] The formic acid oxidation reaction has been studied in concentrated perchloric acid solutions (up to 9.14M (60%)) on the Pt (111) surface to explore the relationships between interfacial properties and kinetics. It is found that, as the concentration of perchloric acid in the supporting electrolyte increases, the current markedly decreases, making it possible to detect adsorbed formate on the surface by voltammetric methods. With the aid of DFT calculations, it is shown that the diminution in current is the result of two opposing factors: the reduction in the concentration of free formate in solution and electrode charge effects which encourage the adsorption of formate in a particular configuration. Additionally, the electrochemical behavior under highly acidic conditions suggests the formation of clathrate structures and emphasizes the relevance of the water structure effect in electrode adsorption processes.This work has been financially supported by the Ministerio de Economia, Industria y Competitividad through the project CTQ2016-76221-P. CBR also thanks his Postdoctoral fellowship to Generalitat Valenciana (APOSTD/2017/010).Busó-Rogero, C.; Ferre-Vilaplana, A.; Herrero, E.; Feliu, JM. (2019). The role of formic acid/formate equilibria in the oxidation of formic acid on Pt(111). Electrochemistry Communications. 98:10-14. https://doi.org/10.1016/j.elecom.2018.11.011S10149