Dichroism Research Articles

Structure Prediction and Expression of Modified rCTLA4-Ig as a Blocker for B7 Molecules.

CTLA4-Ig (Abatacept) has been produced to suppress immune response by inhibition of T cells functions in autoimmune disease. A new drug, which is called belatacept, has recently been recently developed that is more efficient. The development has been occurred by two substitutions (A29Y, L104E) in the extracellular domain of CTLA4. In the present study, the bioinformatics analysis was used in order to make a new structure that has a better function in comparison with belatacept. Firstly, eight different structures were designed. Thereafter, the secondary and 3D structures, mRNA structure, docking of chimeric proteins with CD80/CD86, antigenicity and affinity of designed chimeric molecules were predicted. Based on the criteria, a new candidate molecule was selected and its gene synthesized. The gene was cloned and expressed in E. coli BL21 (DE3) successfully. The purified rCTLA4-Ig was analyzed by SDS-PAGE, western blotting, and ELISA. Circular dichroism analysis (CD analysis) was used for characterization of the rCTLA4-Ig. Affinity of rCTLA4-Ig was also evaluated by the flow cytometry method. Finally, its biological activity was determined by T cell inhibition test. The results showed rCTLA4-Ig and the belatacept protein have some similarities in structure and function. In addition, rCTLA4-Ig was able to bind CD80/CD86 and inhibit T cell function. Although flow cytomery results showed that the standard protein (CTLA4-Ig), represented better affinity than rCTLA4-Ig, the recombinant protein was able to inhibit T cell proliferation as well as CTLA4-Ig.

Optimization of Buffer Additives for Efficient Recovery of hGM-CSF from Inclusion Bodies Using Response Surface Methodology.

Overexpression of human granulocyte-macrophage colony-stimulating factor (hGM-CSF) by Escherichia coli leads to formation of insoluble and inactive proteins, inclusion bodies. The aim of this study was to improve recovery of biologically active hGM-CSF from inclusion bodies. The effect of types, concentrations and pHs of denaturing agents and addition of reducing agents on the yield of inclusion bodies solubilization was evaluated. Next, various conditions were evaluated for refolding hGM-CSF using a two-step design of experiment (DOE) including primary screening by factorial design, and then optimization by response surface design. It was found that hGM-CSF inclusion bodies can be efficiently solubilized with 4 M urea and 4 mM β-mercaptoethanol, pH = 9. A response surface quadratic model was employed to predict the optimum refolding conditions and the accuracy of this model was confirmed by high value of R2 (0.99) and F-value of 0.64. DOE results revealed that sorbitol (0.235 M), imidazole (97 mM), and SDS (0.09%) would be the optimum buffer additives for refolding of hGM-CSF. Following refolding studies, the obtained protein was subjected to circular dichroism which confirmed correct secondary structure of the refolded hGM-CSF. The refolded hGM-CSF exhibited reasonable biological activity compared with standard protein. The approach developed in this work can be important to improve the refolding of other proteins with similar structural features.

Dispersion Forces Drive the Formation of Uranium-Alkane Adducts.

Single-crystal cryogenic X-ray diffraction at 6 K, electron paramagnetic resonance spectroscopy, and correlated electronic structure calculations are combined to shed light on the nature of the metal-tris(aryloxide) and η2-H, C metal-alkane interactions in the [((t·BuArO)3tacn)UIII(Mecy-C6)]·(Mecy-C6) adduct. An analysis of the ligand field experienced by the uranium center using ab initio ligand field theory in combination with the angular overlap model yields rather unusual U-OArO and U-Ntacn bonding parameters for the metal-tris(aryloxide) interaction. These parameters are incompatible with the concept of σ and π metal-ligand overlap. For that reason, it is deduced that metal-ligand bonding in the [((t·BuArO)3tacn)UIII] moiety is predominantly ionic. The bonding interaction within the [((t·BuArO)3tacn)UIII] moiety is shown to be dispersive in nature and essentially supported by the upper-rim tBu groups of the (t·BuArO)3tacn3- ligand. Our findings indicate that the axial alkane molecule is held in place by the guest-host effect rather than direct metal-alkane ionic or covalent interactions.

Stress-induced absorption of a birefringence-reduced polymer optical fiber with doped core

A poly[(methyl methacrylate/2,2,2-trifluoroethyl methacrylate/benzyl methacrylate) = 52/42/6 (w/w/w)] copolymer was used to form the core of a polymer optical fiber (POF) with the purpose of fabricating a birefringence-reduced core (BRC). The fabricated POF showed almost no phase shift, regardless of the stress that was applied to the fiber. Therefore, it is possible to maintain the polarization in the POF core, which is an important factor for detection of the direction in which stress is applied to the POF. To detect the stress direction, the core of a BRC–POF was doped with dichroic dye. A doped BRC–POF that was fabricated using magenta dye showed variations in its output under operating conditions where the stress vector and the incident polarization formed different angular relationships. The results presented here are considered to be applicable to detailed structural monitoring using POFs.

Electrohydrodynamic instabilities for smart window applications

ABSTRACT Electrohydrodynamic instability in liquid crystals is investigated for smart window applications. By comparing different species of ions doped in liquid crystals, the positive charge of the organic part of the salt is the origin of the generation of vortexes and leads to the activation of electrohydrodynamic instability. By replacing conventional electrolytes with zwitterions, compared to electrolyte-doped liquid crystals, zwitterion-doped liquid crystals have a broader range of optimal frequency from 10 Hz to 5 kHz. The devices can be switched between the transparent state and the light scattering state for thousands of times without showing any fatigue. A scattering colour is obtained by incorporating a dichroic dye in zwitterion-doped liquid crystal. A patterned device is designed and shows a localised light scattering and colour effect in the presence of an electric field. This strategy will make electrohydrodynamic instability possible to enrich the applications across smart windows, projection screens and information displays.

Preparation and electrooptic study of reverse mode polymer dispersed liquid crystal: Performance augmentation with the doping of nanoparticles and dichroic dye

ABSTRACTReported herein, the preparation, morphological, and electrooptic (EO) characterization of reverse mode polymer dispersed liquid crystals (PDLCs) with nematic liquid crystal (LC) and UV curable polymer optical adhesive using polymerization induced phase separation method. The PDLCs are switchable between transparent and opaque states due to the homeotropic and planar alignment of LC in their OFF and ON states of applied voltage, respectively. Further, effect of doping of a fixed concentration of azo dye and silica nanoparticles (NPs) on morphological, EO and response characteristics of same PDLC sample was also analyzed. Experimental results showed that doped reverse mode PDLCs have the higher OFF state optical transmission and boost up in the scattering ON state compared with pristine reverse mode PDLC. The phenomenon is also supported by extinction coefficient and absorption study based on Beer's law. The threshold and operating voltages were found reduced ~1.56 and ~1.73 times for NPs and (NPs + dye) doped reverse mode PDLCs, respectively, along with better contrasts to the pristine reverse mode PDLC. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48745.

Effect of Concentration of the Guest Dichroic Dye in Guest-Host Liquid Crystal Panel for Viewing Angle Controller of Display

Effect of Concentration of the Guest Dichroic Dye in Guest-Host Liquid Crystal Panel for Viewing Angle Controller of Display

Effect of Concentration of the Guest Dichroic Dye in Guest-Host Liquid Crystal Panel for Viewing Angle Controller of Display

Effect of Concentration of the Guest Dichroic Dye in Guest-Host Liquid Crystal Panel for Viewing Angle Controller of Display

Methanesulfonyl Iodide

Methanesulfonyl iodide is produced in aqueous solutions from the reaction of triiodide with methanesulfinate. Dichroic crystals of (CH3SO2I)4·KI3·2I2 are formed from KI/I2 solutions with high concentrations of CH3SO2-, while dichroic crystals of (CH3SO2I)2·RbI3 are formed from RbI/I2 solutions. X-ray crystallography of these two compounds shows that the CH3SO2I molecules coordinate through their oxygen atoms to the metal cations and that the S-I bond length is 2.44 Å. At low concentrations of CH3SO2-, the solutions remain homogeneous and the sulfonyl iodide is formed in a rapid equilibrium: CH3SO2- + I3- ⇌ CH3SO2I + 2I-, KMSI = 1.07 ± 0.01 M at 25 °C (μ = 0.1 M, NaClO4). The sulfonyl iodide solutions display an absorbance maximum at 309 nm with a molar absorptivity of 667 M-1 cm-1. Stopped-flow studies reveal that the equilibrium is established within the dead time of the instrument (∼2 ms). Solutions of CH3SO2I decompose slowly to form the sulfonate: CH3SO2I + H2O → CH3SO3- + I- + 2H+, khyd. In dilute phosphate buffer, this decomposition occurs with khyd = 2.0 × 10-4 s-1; the decomposition rate shows an inverse-squared dependence on [I-] because of the KMSI equilibrium.

Efficiency improvements in a dichroic dye-doped liquid crystal Fresnel lens.

A dichroic dye-doped liquid crystal Fresnel lens was fabricated and investigated to observe the combination of phase and amplitude modulation based focusing. An anthraquinone dichroic dye was doped into a liquid crystal host, which when in the Fresnel lens configuration, generates a Fresnel zone plate with alternating "transparent" and "opaque" zones. The zones were induced by using photo-alignment of a light-sensitive alignment layer to generate the alternating pattern. The voltage dependency of efficiency for the dye-doped and pure liquid crystal Fresnel devices were investigated. Incorporation of dyes into the device yielded a significant 4% improvement in relative efficiency in the lens, giving a maximum of 37% achieved in the device, much closer to the theoretical 41% limit when compared with the non-dye-doped device. The input polarization dependence of efficiency was also investigated, showing very small fluctuations (±1.5%), allowing further insight into the effect of fabrication method on these liquid crystal Fresnel devices.

Static and Dynamic Control of Fingerprint Landscapes of Liquid Crystal Network Coatings.

Surface topography variations of liquid crystal networks in their functional coatings provide unique properties in these systems. Chiral-nematic polymer coatings self-organize in a fingerprint texture with the molecular helices parallel to the substrate with alternating domains of molecular units with parallel and perpendicular director orientation as controlled by the concentration of a reactive chiral additive. Driven by surface-tension differences and altered by anisotropic polymerization shrinkage, the coating may form hills and valleys hundreds of nanometers in size with different molecular alignment. The director orientation in the corrugations could be controlled by monomer diffusion during polymerization. Polymerization in the presence of a dichroic dye gives topographic elevations in which the molecules are oriented along the normal. Polymerization by means of a dichroic photoinitiator gives topographic elevations in which the molecules align parallel to the surface. By balancing the monomer diffusion and anisotropic polymerization shrinkage, relatively flat surfaces are also achieved. The different surfaces exhibit distinct topographical deformations when subjected to external stimuli, such as an AC electric field. This method can be universally extended to LC polymers with other alignment configurations.

Dependence of the viewing angle control property of a guest-host liquid crystal cell on the extinction coefficient of the mixture.

The theoretical prediction of a display viewing angle control using a guest-host (GH) liquid crystal (LC) cell has been reported by Chen etal. [Jpn. J. Appl. Phys.48, 062401 (2009)JJAPA50021-492210.1143/JJAP.48.062401]. We experimentally confirmed the viewing angle control property of the GH cell and also investigated its dependence on the extinction coefficient of the GH mixture. The GH cell with a negative dielectric anisotropy and a vertical orientation was attached on front of the display panel, resulting in narrow viewing (NV) property at the field-off state. The GH molecules were switched to a planar orientation, which is also orthogonal to the polarization direction of light at the field-on state, showing wide viewing (WV) property. We varied the concentration of a guest dichroic dye in a host LC and measured the extinction coefficients of the mixtures. We simulated the viewing control property using the measured extinction coefficients and found that the horizontal viewing angle can be controlled using the GH cell, but the vertical viewing angle cannot be controlled. Then, we experimentally confirmed the horizontal viewing angle control using the GH cell. The extinction between the NV and the WV states was increased with a greater extinction coefficient of the GH molecules, but the transmittance was decreased.

Highly polarized absorption and emission from polymer-stabilized smectic guest-host systems

ABSTRACTThe optical properties of luminescent molecules dissolved in liquid crystals have led to their proposed use in luminescent thin-film polarizers. These molecules are typically required to fulfil a range of criteria related to their absorption and emission properties, degree of alignment and stability; however, concurrently satisfying these requirements has proven a barrier in their practical use. We obtained highly polarized absorption and emission luminescent thin-film polarizer using reactive liquid crystalline monomers and highly dichroic luminescent dyes, both of which have polymerizable end groups. In situ photopolymerization of the liquid crystalline mixtures in the highly ordered SmB phase resulted in the formation of cross-linked polymeric networks in which the anisotropic absorption and emission of the film were fixed. The as-obtained product exhibited a high dichroic ratio (DR = 30) with a large fluorescence quantum yield (ϕF = 0.77). The device is both cheap and easy to fabricate and has the potential to be used in practical electro-optic applications.

Research progress in the characterization of protein adsorption on biomaterial surface

The characterization methods in the field of protein adsorption on biological materials in recent years were reviewed from the aspects of protein adsorption amount, adsorption layer thickness, molecular conformational change after protein adsorption, molecular morphology after protein adsorption, and protein molecule adsorption process simulation. These methods include biochemical analysis, surface plasmon resonance (SPR), dissipative quartz crystal microbalance (QCM-D), ellipsometry (ELM), optical interference reflection (RIFS), attenuated total reflection Fourier transformed infrared spectroscopy (ATR-FTIR), circular dichroism (CD), atomic force microscopy (AFM) and computer molecular simulation techniques. In this paper, the basic principles, the advantages and disadvantages of the above characterization methods and related researches were reviewed. This paper provides a comprehensive and reliable basis for the selection of protein experimental characterization methods in protein adsorption, biomaterial design and other research, and provides new ideas for research in the field of protein. Key words: Protein; Adsorption; Biomaterial; Characterization

Photo- and electrical-responsive liquid crystal smart dimmer for augmented reality displays.

A dual-stimuli polarizer-free dye-doped liquid crystal (LC) dimmer is demonstrated. The LC composition consists of photo-stable chiral agent, photosensitive azobenzene, and dichroic dye in a nematic host with positive dielectric anisotropy. Upon UV exposure, the LC directors and dye molecules turn from initially vertical alignment (high transmittance state) to twisted fingerprint structure (low transmittance state). The reversal process is accelerated by combining a longitudinal electric field to unwind the LC directors from twisted fingerprint to homeotropic state, and a red light to transform the cis azobenzene back to trans. This device can be used as a smart dimmer to enhance the ambient contrast ratio for augmented reality displays.

Fabrication of highly efficient coatable polarizer from tolane-based smectic reactive mesogen

This work is aimed to fabricate ultra-thin coatable polarizers on a single substrate based on “host-guest” effect between highly ordered smectic reactive mesogen (RM) and dichroic dye. We designed and synthesized a new tolane-based RM with a highly ordered smectic A phase at room temperature. Polymerizable “host-guest” mixture was formulated from the host RM, dichroic dye and additives, then spin-coated on a single substrate having an alignment layer. Subsequent in-situ photopolymerization by UV irradiation successfully resulted in a coatable polarizer with good polarizing properties. The fabricated coatable polarizer showed a dichroic ratio (DR) of 16.4 and a degree of polarization (DOP) of 99.3% with the thickness of 4 μm. The resulting coatable polarizer possessed a considerable solvent resistance, good thermal stability and robust mechanical properties. Moreover, we prepared a TN-mode LC cell by using the prepared coatable polarizers inside the cell (in-cell), in which the coatable polarizers acted as a polarizer and an alignment layer, simultaneously. The resulting TN cell with in-cell polarizers exhibited a decent electro-optical behavior. We believe that the coatable polarizer proposed in this study possesses practical application potential in ultra-thin LCDs or flexible OLEDs.

Study of Fluorescent Dichroic Liquid Crystal Dyes for Wearable and Flexible Device

There is growing attention and rapid development on flexible electronic devices with electronic materials and sensing technology innovations. In particular, strain sensors with high elasticity and stretchability are needed for several potential applications including human entertainment technology, human–machine interface, personal healthcare, and sports performance monitoring, etc. Significant advancements in wearable and flexible electronic and photonic technologies, are materials science of new and alternative materials and methods of coating and deposition, characterization of flexible and transparent or display electronic devices, the electronics behind new sensor development for wearables and flexible technology, and new device design concepts.The anisotropic properties of a system comprising a guest dye dissolved in an aligned liquid-crystalline host were reported, arising from the combination of the bulk liquid crystal host alignment and the anisotropic shape and absorption characteristics of the dye molecules. For many applications, it is also desirable for a guest–host mixture to exhibit a long useable lifetime in addition to the optical properties described above. Many of the proposed applications involve exposure of the systems to wearable and flexible device, polarisers, smart windows and lasers. The stability of a dye molecule may be strongly dependent on its chemical environment, so the stabilityof a guest–host system may depend on the nature of the host mixture as well as that of the dye. A series of new fluorescent dichroic dyes which included phenylacetylene substituent group to 4-site of the 1,8-dicyanonaphthene were synthesized. All dyes were characterized by nuclear magnetism and high resolution mass spectrum. The dicyanonaphthene fluorescent dichroic dyes meet the application conditions of ‘Guest-host’ display. Phenylacetylene bridge bond is often used for liquid crystal molecular design and synthesis to improve the liquid crystal birefringence because of its excellence stability, optical anisotropy.On the one hand, the addition of the phenylacetylene bond increases the molecular linearity and the aspect ratio, which is more favorable for the arrangement of the dye molecules in the main liquid crystal, thereby increasing the ordered parameters of the dye molecules in the liquid crystal; On the other hand, phenylacetylene bonds can increase the molecular conjugation system and optimize the optical properties of dye molecules. Ester groups as a class of important linking groups have been widely used in the synthesis of diamodal dyes4.The 1,8-naphthalene dinitrile is regarded as the precursor, introduced p-ethynylbenzoic acid at its 4-position and then through the acylation reaction to introduce the alkoxy chain, in order to obtain a greater degree of conjugation, in the main liquid crystal has good solubility and high dichroic dye. Acknowledgements We are grateful to the National Natural Science Foundation of China (21576043), supported by the Fundamental Research Funds for the Central Universities.

Circular Dichroism in Cholesteric Liquid Crystals

The circular dichroism in cholesteric liquid crystals (CLCs) has been studied in the absorption bands of dissolved dichroic dyes possessing both the positive and negative linear dichroism. The circular dichroism is studied depending on the position of CLC selective reflection band with respect to the dye absorption band. The induced circular dichroism due to dye absorption is compared to intrinsic CLC circular dichroism due to the light diffraction from the periodic chiral structure.

Electroconvection characterization of guest-host nematic liquid crystals for dynamic scattering mode applications

ABSTRACTThe threshold voltage for electro-hydrodynamic convection (EHC) in nematic liquid crystals in the low-frequency convective regime is examined. The addition of dopant species is known to strongly effect the frequency response of this regime. In this work, we investigate the effect of adding optically anisotropic species on the low-frequency threshold, and, demonstrate that certain dichroic dyes have a marked effect. We have measured electrical transport properties of suitably doped liquid crystal mixtures in order to make a comparison with theoretical predictions based upon linear stability considerations. Our results show satisfactory agreement with these predictions. Our findings indicate future directions for new applications of dynamic scattering mode technologies with more accessible operating parameters previously known.

Dye-Doped Electrically Smart Windows Based on Polymer-Stabilized Liquid Crystal.

Here we report the fabrication of dye-doped polymer-stabilized liquid crystals (PSLC)-based smart windows. The effect of dye doping on PSLC contrast was investigated. Non-dichroic dye tints the PSLC sample in both off- and on-state, which is not beneficial for increasing its off/on contrast. The sample doped with dichroic dye shows a slight color in the off-state and strong color in the on-state, resulting in an enhanced contrast, which attributed to orientation dependent absorption of dichroic dyes. Furthermore, we blended non-dichroic dye and dichroic dye who have complementary absorption together into PSLC mixture. The sample is almost colorless in the off-state due to the subtractive process, while colored in the on-state. The contrast is further enhanced. The results show that the proposed multi-dye-doped PSLC device has high visual contrast and fast response time, making it attractive for applications in light management and architectural aesthetics.