Effects of Excluded Volume upon Protein Stability in Covalently Cross-Linked Proteins with Variable Linker Lengths

To explore the effects of molecular crowding and excluded volume upon protein stability, we used a series of cross-linking reagents with nine different single-cysteine mutants of staphylococcal nuclease to make covalently linked dimers. These cross-linkers ranged in length from 10.5 to 21.3 Å, compelling separations which would normally be found only in the most concentrated protein solutions. The stabilities of the dimeric proteins and monomeric controls were determined by guanidine hydrochloride and thermal denaturation. Dimers with short linkers tend to exhibit pronounced three-state denaturation behavior, as opposed to the two-state behavior of the monomeric controls. Increasing linker length leads to less pronounced three-state behavior. The three-state behavior is interpreted in a three-state model where cross-linked native protein dimer, N−N, interconverts in a two-state transition with a dimer where one protein subunit is denatured, N−D. The remaining native protein in turn can denature in another two-state transition to a state, D−D, in which both tethered proteins are denatured. Three-state behavior is best explained by excluded volume effects in the denatured state. For many dimers, linkers longer than 17 Å removed most three-state character. This sets a limit on the flexibility and size of the denatured state. Notably, in contradiction to theoretical predictions, these cross-linked dimers were not stabilized. The failure of these predictions is possibly due to neglect of the alteration in hydrophobic exposure that accompanies any significant reduction in the conformational space of the denatured state

Photoluminescence Properties of a Perfluorinated Supramolecular Columnar Liquid Crystal with a Pyrene Core: Effects of the Ordering and Orientation of the Columns

We investigated the effects of the alignment and ordering of π-conjugated perfluorinated dendrimers containing pyrene moieties in their cores on their photoluminescence (PL) properties. The pyrene molecules are stacked in columns surrounded by aromatic and semifluorinated tails, which can be conjugated and act as chromophores. Polarized light microscopy (PLM), cross-sectional scanning electron microscopy (SEM), and atomic force microscopy (AFM) results show that variation of the cooling rate of the dendrimers produces variation in their orientation and ordering:  Slow cooling (∼<0.5 °C/min) of the isotropic melt in a sandwich glass cell results in a high degree of ordering and the vertical alignment of the columns on the substrate, in which the stacked pyrene molecules are oriented parallel to the surface over large areas. In contrast, rapid cooling (∼>10 °C/min) leads to the planar alignment of the columns with significant disorder on the same substrate. UV−vis, PL, SEM, and AFM results show that the quenched columns with a planar orientation produce a broad emission band and a second weak shoulder, which indicates the presence of isolated molecules. However, the high degree of ordering of the columns with a vertical alignment produces a red-shift in the PL spectrum, with very few isolated molecules. By comparing two films with different alignments but similar ordering, we show that the ordering of this material has a greater influence on the PL spectrum than the alignment. This effect of the ordering of the columns was further verified by comparing the optical properties of the isolated dendrimers with those of small π-conjugated molecules in solution and solid films

Reduction of the Error in the Electrical Characterization of Organic Field-Effect Transistors Based on Donor–Acceptor Polymer Semiconductors

In terms of their electrical characteristics, organic field-effect transistors (OFETs) based on donor–acceptor (D–A) polymer semiconductors show a significant dependence on the materials used and measurement conditions. In this study, a variety of measurement methods for OFETs based on D–A polymer semiconductors are presented to reveal errors in electrical characterization including field-effect mobility and threshold voltage. By systematically evaluating the electrical characteristics under various measurement conditions, we can obtain adequate electrical parameters, providing accurate values for circuit designers and avoiding overestimation

Fabrication of 10 nm-Scale Complex 3D Nanopatterns with Multiple Shapes and Components by Secondary Sputtering Phenomenon

We introduce an advanced ultrahigh-resolution (∼15 nm) patterning technique that enables the fabrication of various 3D high aspect ratio multicomponents/shaped nanostructures. This methodology utilizes the repetitive secondary sputtering phenomenon under etching plasma conditions and prepatterned fabrication control. The secondary sputtering phenomenon repetitively generates an angular distribution of target particles during ion-bombardment. This method, advanced repetitive secondary sputtering lithography, provides many strategies to fabricate complex continuous patterns and multilayer/material patterns with 10 nm-scale resolution. To demonstrate the versatility of this method, we show induced vertical alignment of liquid crystals (LCs) on indium-tin-oxide (ITO) grid patterns without any alignment layers. The ITO grid pattern fabricated in this method is found to have not only an alignment capability but also electrode properties without electrical or optical damage

High birefringent reactive discotic liquid crystals based on asymmetrical triphenylene with phenyl-acetylene moieties

<p>Triphenylene (TP)-based liquid crystals, a category of discotic liquid crystals (DLCs), are easy to synthesise, thermally stable and can undergo self-assembly. A new DLC compound, 2,7,10-tris[4-(6-acryloyloxyhexyloxy)benzoate]-3,6,11-tris[(4-hexylphenyl)ethynyl]-triphenylene, was obtained with a 49% yield using catechol as a starting material and features acetylene groups on its TP core. This material can form films with high birefringence through its cross-linkable acrylate ends. Here, we synthesised this new compound and characterised it using nuclear magnetic resonance spectroscopy, mass spectrometry and elemental analysis. The thermal behaviour was also investigated using differential scanning calorimetry and polarised optical microscopy. This new asymmetric TP-based DLC compound exhibited a nematic liquid-crystalline phase between −20 and 170°C and formed an optical anisotropic film with a high birefringence (Δ<i>n</i> = 0.21–0.25).</p

Synergistic Effect of Fluorination and Molecular Orientational Order on the Dielectric Properties of Low‑κ Liquid Crystal Polymer Films

With the rapid advancement in 5G and 6G communication technology, the demand for fast transmission and reception speed, high-capacity communication, and simultaneous multiterminal access without delay has become extremely important. Here, we fabricated liquid crystal polymer (LCP) films by judiciously controlling fluorine contents and the degree of orientational order. LCPs with fluorinated additives have garnered significant attention due to low dielectric properties and low moisture uptake compared to the current polymeric materials like polyimide, thereby anticipating to minimize signal loss in the high-frequency band of 28 GHz. The optimum fluorine content is determined under a low loading condition of 2.0 wt %. More fluorine can lead to a sharp decline in orientational order and deteriorate the dielectric properties. Similarly, the rubbing process renders uniaxially aligned molecules, which induce low dielectric loss due to the restricted chain motions upon polymerization. Additionally, theoretical values obtained from DFT calculations provide fundamental insights into understanding the relationship between fluorine moieties and dielectric properties

Control of Interfacial Defect States in the Flexible InGaZnO Thin Film Transistor with a 6FDA-MDA Gate Insulator by Using an Al₂O₃ Interlayer

Recently, the high-mobility flexible thin film transistor (TFT) has been reported by using an organic–inorganic heterojunction structure to enhance the flexibility. This study investigates the origin of enhancement in an In–Ga–Zn–O (IGZO)-based TFT, utilizing 6FDA-based polyimide (6FDA-MDA) as the gate insulator (GI) to achieve a high-mobility flexible TFT. 6FDA-MDA has great advantages to apply to a flexible TFT as a gate insulator, such as a low leakage current, high mechanical stability, a room-temperature process, and smooth surface topographies. Through qualitative/quantitative defect analysis of the IGZO/GI interface, we find the origin of enhancement in the IGZO/6FDA-MDA TFT and suggest a facile method by applying an Al2O3 interlayer. By analyzing the physical properties of the IGZO TFT with a 6FDA-MDA GI, we find that diffused fluorine atoms from the 6FDA-MDA in the active area modulate the Fermi level toward the valence band in the interface. To prevent the diffusion of fluorine, we used the Al2O3 layer as a blocking layer, and it is confirmed by quantitative defect analysis that the defect states in the active/GI interface region are reduced by inserting the Al2O3 interlayer. By applying an Al2O3 interlayer between the GI and the active layer, the performance has been improved in terms of mobility, bias stability, and on/off ratio. Precisely, the field-effect mobility increased about 5 times from 0.05 to 14.57 cm2/(V s), the positive biased threshold voltage decreased to 8.0 from 14.42 V, and the on/off ratio increased to 2.62 × 108 from 3.77 × 106. Moreover, the TFT device with Al2O3 blocking can operate over 2000 times. Due to sputtering damage, fluorine could be diffused from 6FDA-MDA to the IGZO active area and generate defects in a channel. The formation energy and energy level in the band gap of the IGZO film with fluorine are obtained by density functional theory calculations. Fluorine causes the defect states in the IGZO/6FDA-MDA interface, and the energy level of each defect state is lowered to the conduction band by fluorine diffusion

Surface Modification of a Polyimide Gate Insulator with an Yttrium Oxide Interlayer for Aqueous-Solution-Processed ZnO Thin-Film Transistors

We report a simple approach to modify the surface of a polyimide gate insulator with an yttrium oxide interlayer for aqueous-solution-processed ZnO thin-film transistors. It is expected that the yttrium oxide interlayer will provide a surface that is more chemically compatible with the ZnO semiconductor than is bare polyimde. The field-effect mobility and the on/off current ratio of the ZnO TFT with the YO_<i>x</i>/polyimide gate insulator were 0.456 cm²/V·s and 2.12 × 10⁶, respectively, whereas the ZnO TFT with the polyimide gate insulator was inactive

Direct Observation of Highly Ordered Dendrimer Soft Building Blocks over a Large Area

Developing large-area, single domain of organic soft-building blocks such as block copolymers, colloids, and supramolecular materials is one of the most important issues in the materials science and nanotechnology. Owing to their small sizes, complex molecular architectures, and high mobility, supramolecular materials are not well-suited for building large area, single domain structures. In the described study, a single domain of supramolecular columnar dendrimers was created over large area. The columnar structures in these domains have smaller (4.5 nm) diameters, higher area densities (ca. 36 Tera-dots/in²) and larger domains (>0.1 × 0.1 mm²) than those of all existing BCP and colloidal assemblies. By simply annealing dendrimer thin films between two flat solid surfaces, single domains of hexagonal columnar structures are created over large macroscopic areas. Observations made in this effort should serve as the foundation for the design of new routes for bottom-up lithography based on supramolecular building blocks