High Solution Viscosity Research Articles

Flow Activation Energy of High-Concentration Monoclonal Antibody Solutions and Protein-Protein Interactions Influenced by NaCl and Sucrose.

The solution viscosity and protein-protein interactions (PPIs) as a function of temperature (4-40 °C) were measured at a series of protein concentrations for a monoclonal antibody (mAb) with different formulation conditions, which include NaCl and sucrose. The flow activation energy (Eη) was extracted from the temperature dependence of solution viscosity using the Arrhenius equation. PPIs were quantified via the protein diffusion interaction parameter (kD) measured by dynamic light scattering, together with the osmotic second virial coefficient and the structure factor obtained through small-angle X-ray scattering. Both viscosity and PPIs were found to vary with the formulation conditions. Adding NaCl introduces an attractive interaction but leads to a significant reduction in the viscosity. However, adding sucrose enhances an overall repulsive effect and leads to a slight decrease in viscosity. Thus, the averaged (attractive or repulsive) PPI information is not a good indicator of viscosity at high protein concentrations for the mAb studied here. Instead, a correlation based on the temperature dependence of viscosity (i.e., Eη) and the temperature sensitivity in PPIs was observed for this specific mAb. When kD is more sensitive to the temperature variation, it corresponds to a larger value of Eη and thus a higher viscosity in concentrated protein solutions. When kD is less sensitive to temperature change, it corresponds to a smaller value of Eη and thus a lower viscosity at high protein concentrations. Rather than the absolute value of PPIs at a given temperature, our results show that the temperature sensitivity of PPIs may be a more useful metric for predicting issues with high viscosity of concentrated solutions. In addition, we also demonstrate that caution is required in choosing a proper protein concentration range to extract kD. In some excipient conditions studied here, the appropriate protein concentration range needs to be less than 4 mg/mL, remarkably lower than the typical concentration range used in the literature.

Stable Lithium Metal Batteries Enabled by Dilute Cationic Additives

Conventional Li-ion electrolytes consist of carbonate solvents and Li-ion salts that were made for carbonaceous negative electrodes. When the electrolytes are used with metallic lithium anodes, carbonate electrolytes lead to low charge-discharge cycle stability due to adverse reactive species at the anode surface.1-4 This reactive species are called the solid electrolyte interface (SEI).1 SEI instabilities/inhomogeneities result in its continuous thickening and formation of electronically non-active dead lithium.2 SEI composition and structure are affected by both solvent and electrolyte chemistry in bulk solution and, more importantly, at the electrode-electrolyte interface.4 Current research studies suggest that X-rich (where X is a halogen) SEI yields superior performance compared to halogen-free SEI.1,5 Electrolytes that have large volume fractions of halogenated species have statistically higher probability to be reduced at the electrode surface and yield X-rich SEI layers.6 Therefore, the use of halogenated solvent and/or high concentrated (> 1 M) lithium salt with halogenated anions has been actively explored for LiMBs. However, the high cost of Li salts and high viscosity of the electrolyte at high salt concentration make the concentrated electrolytes unrealistic for commercial battery applications. In search of a cost-effective solution for high performance LiMBs, halogenated electrolyte additives could serve as an ideal approach since only a small amount of the additive would be potentially required to induce similar X-rich interface that can be seen in the case of the halogenated ether electrolyte. In this meeting abstract, we present a new concept that leverages favorable electrostatic interactions with the electrolyte additive to drive the formation of robust SEI layers even at low additive content. Specifically, custom-designed additives can be electrostatically attracted to the negatively charged electrode, creating a high population of halogenated species at the anode surface even at a dilute Li salt concentration. Effective SEI formation with a low-concentration additive circumvents the challenges associated with the current state-of-the-art approach of using halogenated species at high concentration (i.e., unfavorably high solution viscosity and high cost). Reference 1 Louli, A. J. et al. Diagnosing and correcting anode-free cell failure via electrolyte and morphological analysis. Nature Energy 5, 693-702, (2020).2 Chen, K.-H. et al. Dead lithium: mass transport effects on voltage, capacity, and failure of lithium metal anodes. Journal of Materials Chemistry A 5, 11671-11681, (2017).3 Lin, D. et al. Three-dimensional stable lithium metal anode with nanoscale lithium islands embedded in ionically conductive solid matrix. Proc Natl Acad Sci U S A 114, 4613-4618, (2017).4 Lin, D., Liu, Y. & Cui, Y. Reviving the lithium metal anode for high-energy batteries. Nat Nanotechnol 12, 194-206, (2017).5 Yu, Z. et al. Molecular design for electrolyte solvents enabling energy-dense and long-cycling lithium metal batteries. Nature Energy 5, 526-533, (2020).6 Yamada, Y., Wang, J., Ko, S., Watanabe, E. & Yamada, A. Advances and issues in developing salt-concentrated battery electrolytes. Nature Energy 4, 269-280, (2019).

A Scalable and Surfactant-Free Emulsion Method for Producing Microbeads from Varied Biomass Feedstocks.

Despite national and international regulations, plastic microbeads are still widely used in personal care and consumer products (PCCPs). These exfoliants and rheological modifiers cause significant microplastic pollution in natural aquatic environments. Microbeads from nonderivatized biomass like cellulose and lignin can offer a sustainable alternative to these nondegradable microplastics, but processing this biomass into microbeads is challenging due to limited viable solvents and high biomass solution viscosities. To produce biomass microbeads of the appropriate size range for PCCPs (ca. 200-800 μm diameter) with shapes and mechanical properties comparable to those of commercial plastic microbeads, we used a surfactant-free emulsion/precipitation method, mixing biomass solutions in 1-ethyl-3-methylimidazolium acetate (EMImAc) with various oils and precipitating with ethanol. While yield of microbeads within the target size range highly depends on purification conditions, optimized protocols led to >90% yield of cellulose microbeads. Kraft lignin was then successfully incorporated into beads at up to 20 wt %; however, higher lignin contents result in emulsion destabilization unless surfactant is added. Finally, the microbead shape and surface morphology can be tuned using oils of varying viscosities and interfacial tensions. Dripping measurements and pendant drop tensiometry confirmed that the higher affinity of cellulose for certain oil/IL interfaces largely controlled the observed surface morphology. This work thus outlines how biomass composition, oil viscosity, and interfacial properties can be altered to produce more sustainable microbeads for use in PCCPs, which have desirable mechanical properties and can be produced over a wide range of shapes and surface morphologies.

Comparison of Different Extraction and Purification Methods of Lime Peel Pectin and Evaluation of Physiochemical, Rheological, and Textural Properties

Background:: Pectin production has recently attracted considerable research interest due to its various applications arising from its unique characteristics. Lime peel, as a by-product of juice factories, has a promising potential for pectin extraction. Methods:: Lime peel pectin samples were extracted by three extraction processes: a) 90°C of heating for 120 min, b) 90°C of heating for 90 min and then 32 min of sonication, and c) 80°C of heating for 60 min and then 22 min of sonication. Then, they were purified either by ethanol or sodium caseinate (SC) and characterized. Results:: SC purification did not enhance the pectin yield; rather, it diminished the level of nonpectin components and resulted in purer pectin (i.e., lower sugar content). The samples purified with SC showed much lower viscosity in solution and storage modulus than the samples purified with ethanol, which could be attributed to their lower sugar content and higher pH (~ 4.6 vs. 2). However, pectin samples purified with SC had a relatively high sugar gel consistency, maybe due to protein retention in their structure as well as the preferential hydration effect of added sucrose. Conclusion:: The compact and extended conformations of the pectin sample, which was extracted by “(c) extraction method” and purified with ethanol, resulted in its high viscosity and storage modulus in solution and the highest gel consistency (16.91 Kg.s) compared to the other samples. Regardless of the conditions of extraction procedures, the purification method had a considerable impact on the pectin samples’ characteristics and potential applications.

Preparation of Controlled Multicompartmental Gel Microcarriers Based on Aqueous Two-Phase Emulsions for 3D Partitioned Cell Coculture In Vitro.

A facile method was proposed for preparing controllable multicompartment gel microcarriers using an aqueous two-phase emulsion system. By leveraging the density difference between the upper polyethylene glycol solution and the lower dextran-calcium chloride (CaCl2) solution in the collection solution and the high viscosity of the lower solution, controllable fusion of core-shell droplets made by coextrusion devices was achieved at the water/water (w/w) interface to fabricate microcarriers with separated core compartments. By adjusting the sodium alginate concentration, collected solution composition, and number of fused liquid droplets, the pore size, shape, and number of compartments could be controlled. Caco-2 and HepG2 cells were encapsulated in different compartments to establish gut-liver coculture models, exhibiting higher viability and proliferation compared to monoculture models. Notably, significant differences in cytokine expression and functional proteins were observed between the coculture and monoculture models. This method provides new possibilities for preparing complex and functional three-dimensional coculture materials.

Response of sand added with various biopolymer contents under repetitive loading and freeze–thaw cycles

Biopolymers have recently been used as ecofriendly materials for soil improvement in terms of stabilization, compressibility, and engineering parameters. The objective of this study is to assess the effect of biopolymer content in sand mixtures during freeze–thaw repetitive loading cycles. The biopolymers were mixed at weight ratios of 0.0, 0.5, 1.0, 2.0, 5.0, and 10 % (BPC 0.0—BPC 10), and the relative density and degree of saturation were fixed at 60 % and 20 %, respectively. The measurement system was located in an ice chamber for freeze–thaw, and 100 cycles of repetitive loads were applied. The test results showed that the deformation decreased from BPC 0.0, to BPC 1.0 owing to the cementation effect produced by the biopolymer chain and coating. However, the deformation increased from BPC 1.0 to BPC 5.0 because high-viscosity solutions might separate the sand particles, causing a density reduction and generating more deformation by compaction. The relative permittivity varied with respect to BPC and freeze–thaw repetitive loading stages that were affected by unfrozen water content, volume contraction, and water consumption during dehydration. The shear wave velocity gradually increased from BPC 2.0 to BPC 10 because the effect of fines in coarse–fine mixtures, rather than the cementation effect. Therefore, the module containing the sensors used in this study can be used to understand the role of biopolymers as reinforcing materials in railway subgrades.

Near-infrared fluorescent probe for the imaging of viscosity in fatty liver mice and valuation of drug efficacy

Fatty liver disease affects at least 25 percent of the population worldwide and is a severe metabolic syndrome. Viscosity is closely related to fatty liver disease, so it is urgent to develop an effective tool for monitoring viscosity. Herein, a NIR fluorescent probe called MBC-V is developed for imaging viscosity, consisting of dimethylaniline and malonitrile-benzopyran. MBC-V is non-fluorescent in low viscosity solutions due to intramolecular rotation. In high viscosity solution, the intramolecular rotation of MBC-V is suppressed and the fluorescence is triggered. MBC-V has long emission wavelength at 720 nm and large Stokes shift about 160 nm. Moreover, MBC-V can detect changes in cell viscosity in fatty liver cells, and can image the therapeutic effects of drug in fatty liver cells. By taking advantage of NIR emission, MBC-V can be used as an imaging tool for fatty liver disease and a way to evaluate the therapeutic effect of drug for fatty liver disease.

Porous pectin particle formation utilizing spray drying with a three-fluid nozzle

The development of advanced porous particles with a high surface area and interconnected porosity is pivotal in material science for various applications. Pectin, a biocompatible and biodegradable polysaccharide, has shown promise for the synthesis of porous particles, especially in the biomedical and food industries. The high viscosity of pectin and CaCO3 nanoparticle (NP) solutions has been a significant challenge for producing these particles. This study introduces a novel spray drying technique with a three-fluid nozzle, designed to handle high-viscosity solutions and to increase production rates by 30-fold over the conventional two-fluid nozzle. Using the proposed technique, notable improvements are achieved in particle surface areas and pore volumes by controlling the distribution of CaCO3 NPs within the pectin particles, especially at a CaCO3 NPs to pectin ratio of 15. This resulted in porous pectin particles with sizes of 3.4 to 6.2 μm, surface areas of up to 261 m2/g, and enhanced lysozyme adsorption capacities are obtained by varying types of precursor solutions. Thus, this approach facilitates the synthesis of multifunctional composites and porous particles.

Concentration-Dependent Diffusion of Monoclonal Antibodies: Underlying Mechanisms of Anomalous Diffusion.

The development, storage, transport, and subcutaneous delivery of highly concentrated monoclonal antibody formulations pose significant challenges due to the high solution viscosity and low diffusion of the antibody molecules in crowded environments. These issues often stem from the self-associating behavior of the antibody molecules, potentially leading to aggregation. In this work, we used a dissipative particle dynamics-based coarse-grained model to investigate the diffusion behavior of IgG1 antibody molecules in aqueous solutions with 15 and 32 mM NaCl and antibody concentrations ranging from 10 to 400 mg/mL. We determined the coarse-grained interaction parameters by matching the calculated structure factor with the computational and experimental data from the literature. Our results indicate Fickian diffusion for antibody concentrations of 10 and 25 mg/mL and anomalous diffusion for concentrations exceeding 50 mg/mL. The anomalous diffusion was observed for ∼0.33 to 0.4 μs, followed by Fickian diffusion for all antibody concentrations. We observed a strong linear correlation between the diffusion behavior of the antibody molecules (diffusion coefficient D and anomalous diffusion exponent α) and the amount of aggregates present in the solution and between the amount of aggregates and the Coulomb interaction energy. The investigation of underlying mechanisms for anomalous diffusion revealed that in crowded environments at high antibody concentrations, the attractive interaction between electrostatically complementary regions of the antibody molecules could further bring the neighboring molecules closer to one another, ultimately resulting in aggregate formation. Further, the Coulomb attraction can continue to draw more molecules together, forming larger aggregates.

Roles of soybean β-conglycinin subunit fractions in fibril formation and the effects of glycinin on them

This research is aimed at exploring the fibrillation of soybean β-conglycinin (7S) subunits (αα′ and β) at 90 °C and pH 2.0, as well as the effects of glycinin (11S) on them. Fibril formation kinetics was monitored by measuring changes in thioflavin T (Th T) fluorescence intensity of the proteins. This analysis showed that αα′ subunits had a higher fibrillation capacity but slower fibril formation rate than the β subunit. Glycinin accelerated the rate of fibrillation of the αα′ and β subunits but weakened the fibril structure. The size of the fibrils first decreased and then increased with increasing heating time. Circular dichroism and intrinsic fluorescence spectroscopy analysis indicated that the β-sheet structure and hydrophobic interactions were important for the generation of ordered fibrils. Shear viscosity and transmission electron microscopy analysis suggested that the αα′ subunits formed relatively rigid fibrils that led to a high solution viscosity. In contrast, β subunit fibrils became unstable after prolonged heating, forming shorter fibrils (fragments) that tended to aggregate, which led to a lower solution viscosity. This research also suggested that the extension region of αα′ subunits played an important role in fibrillation, and the presence of the highly hydrophobic basic polypeptides of glycinin might be the main reason for the inhibition of soy protein fibrillation. Our analysis of soy protein fibrillization at the subunit level provides insights that might enhance the future application of soy protein fibrils as functional ingredients in foods.

Innovative submucosal injection solution for endoscopic resection with phosphorylated pullulan: a preclinical study

A submucosal injection solution is used to assist in endoscopic surgery. The high viscosity of current solutions makes them difficult to inject. In the present study, we developed an extremely low-viscosity, easy-to-use submucosal injection solution using phosphorylated pullulan (PPL). The PPL solutions were prepared at different concentrations, and their viscosities were measured. The mucosal elevation capacity was evaluated using excised porcine stomachs. Controls included 0.4% sodium hyaluronate (SH), 0.6% sodium alginate (SA), and saline. To evaluate the practicality, the catheter injectability of 0.7% PPL was measured, and EMR and endoscopic submucosal dissection (ESD) were performed using the stomach and colorectum of live pigs. As controls, 0.4% SH and saline were used. The PPL solutions were of extremely low viscosity compared to the solutions of 0.4% SH and 0.6% SA. Nevertheless, the mucosal elevation capacity of PPL solutions for up to 0.7% concentration was similar to that of 0.4% SH, and 0.7% PPL was less resistant to catheter infusion than 0.4% SH and 0.6% SA. In live pig experiments with endoscopic mucosal resection and ESD, snaring after submucosal injection of 0.7% PPL was easier than with 0.4% SH, ESD with 0.7% PPL produced less bubble formation than with 0.4% SH, and the procedure time tended to be shorter with 0.7% PPL than with 0.4% SH because of the shorter injection time. The PPL solution is an innovative and easy-to-use submucosal injection solution.

Foam and emulsion properties of crude saponin extract from saffron (Crocus sativus L.) corm

The emulsion and foam stability of the crude saponin extract from the saffron corm (SS) were compared with commercially available saponin (CS) and Tween 60 (T60). The purity of the SS sample was calculated relative to CS and showed a value of 84.43%. Most stable emulsions with the smallest oil droplet size were acquired with T60. Also, T60 showed the lowest surface tension, interfacial tension, and the lowest contact angle. However, a reduction of interfacial tension and surface tension up to 77% and 32% was recorded for SS, respectively. Commercially available saponin indicated the best foam stability regarding film drainage, coalescence, and bubble disproportionation due to its highest solution viscosity. The antioxidant activity of samples was evaluated regarding the FRAP assay and the DPPH free radical scavenging activity. The results showed FRAP values of 2.41 and 1.20 mmol L−1 Fe (II)/100 g sample, and DPPH IC50 values of 2103 and 2326 mg kg−1 for CS and SS, respectively. The investigation showed that SS can form stable emulsions and abundant and persistent foams. Our results provide valuable insights for using saffron corm saponin extract as a new potential natural surfactant for selected applications of the food and pharmaceutical industries.

3D printing in microfluidics: experimental optimization of droplet size and generation time through flow focusing, phase, and geometry variation.

Droplet-based microfluidics systems have become widely used in recent years thanks to their advantages, varying from the possibility of handling small fluid volumes to directly synthesizing and encapsulating various living forms for biological-related applications. The effectiveness of such systems mainly depends on the ability to control some of these systems' parameters, such as produced droplet size and formation time, which represents a challenging task. This work reports an experimental study on tuning droplet size and generation time in a flow-focusing geometry fabricated with stereolithography 3D printing by exploring the interplay of phase and geometrical parameters. We produced droplets at different low flow rates of continuous and dispersed phases to assess the effect of each of these phases on the droplets' size and formation time. We observed that smaller droplets were produced for high viscosity oil and water phase, along with high flow rates. In addition, changing the microfluidics channels' width, and morphology of the orifice has shown a similar effect on droplet size, as shown in the case of high-viscosity solutions. The variation of the bifurcation angle shows a noticeable variation in terms of the achieved droplet size and formation time. We further investigated the impact of modifying the width ratio of the continuous and dispersed phases on droplet formation.

Nanorobots simulation by using an amplified cell model with motor

Nanotechnology is the future research area that could benefit human beings in many different directions. In order to build that technology for the human beings, it is necessary to do some research on the simulators to find out some important mechanical properties of these robots in the environment they are in, in other word, low Reynolds environments. To check the availability of the cell model, it is necessary to construct it by using MATLAB and SOLIDWORKS. After construction, the testing process would show that behavior difference of the model in relative high Reynolds environments and low Reynolds environments. The cell simulator would provide a faster swirling speed but a slower velocity in high viscosity solutions than in low viscosity solutions. That would be contradictory to the theory of the Reynolds number which potentially indicate a failure in the experiment. Thus, the macroscopic simulation model might not provide an accurate result for future nanorobotics.

Research of novel polyamine-based biphasic absorbents for CO2 capture using alkanolamine to regulate the viscosity and mechanism analysis

Biphasic solvent has attracted widespread attention in CO2 chemical absorption technology due to its significant potential for reducing capture energy consumption. However, the high viscosity of CO2-rich phase after phase split could lead to issues such as high flow resistance, low heat transfer efficiency, and phase separation instability in application. To address these limitations, a strategy of using alkanolamine as a viscosity regulator for biphasic solvents was proposed. Diethanolamine(DEA), an alkanolamine regulator, was introduced to a system of polyamine/amide absorbent, and then a novel biphasic solvent of diethylenetriamine (DETA)/diethanolamine(DEA)/N, N-Dimethylacetamide(DMAC)/water(H2O) was developed. The viscosity of the CO2-rich phase solvent was reduced to 19.02 mPa⋅s, a significant decrease compared to the solution without DEA regulation. The novel solvent exhibited a high cyclic capacity of 2.08 mol/kg, which was 43.4 % higher than that of the solution without DEA, and a desorption rate twice as high as 30 wt% monoethanolamine(MEA). Quantitative 13C Nuclear Magnetic Resonance (NMR) and Molecular Dynamics (MD) simulations revealed the phase split and viscosity regulation mechanisms. It was proved that DETA species, especially carbamates, tend to self-aggregate with each other due to intermolecular hydrogen bonding with the CO2 loading increases, which leads to phase split and high viscosity of the saturated solution. Through DEA regulation, the protonation of carbamates and the generation of HCO3–/CO32– were promoted, which weakened the self-aggregation of carbamates species, decreasing the viscosity and the regeneration energy of saturated CO2-rich phase solution. The regeneration energy reached 2.19 GJ/ton CO2, which exhibited a 42.4 % reduction compared with that of 30 wt% MEA.

Spatiotemporally controlled emergence of nanoparticle microvortices under electric field

AbstractControlled assembly of nanoparticles (NPs) has garnered much interest over the past two decades. Beyond established techniques, new methods utilizing local short‐range or large‐scale long‐range interactions remain to be explored to achieve diverse micro‐ and nanoscale structures. Here, we report the controlled emergence of vortex‐pair arrays within monodispersed gold nanorods by applying a direct current electric field across a pair of sawtooth electrodes. By employing in situ darkfield microscopy and particle collective analysis, we elucidate the mechanism behind the formation and stabilization of the NP vortices, attributing it to the combined effects of the electrode shape, high NP density, and high solution viscosity. We further explore the controllability of the vortex‐pair arrays and obtain multiple complex vortice patterns. Our findings will facilitate the investigation of efficient and controlled dynamic assembly of NPs under external fields and help manufacture next‐generation optoelectronic functional materials.

Stimuli-Responsive Properties on a Bisbenzofuropyrazine Core: Mechanochromism and Concentration-Controlled Vapochromism.

Stimulus-responsive organic materials with luminescence switching properties have attracted considerable attention for their practical applications in sensing, security, and display devices. In this paper, bent-type bisbenzofuropyrazine derivatives, Bent-H and Bent-sBu, with good solubilities were synthesized, and their physical and optical properties were investigated in detail. Bent-H gave three crystalline polymorphs, and they showed different luminescence properties depending on their crystal packing structures. In addition, Bent-H exhibited mechanochromic luminescence in spite of its rigid skeleton. Bent-sBu exhibited unique concentration-dependent vapochromic luminescence. Ground Bent-sBu was converted to blue-emissive, green-emissive, and green-emissive high-viscosity solution states at low, moderate, and high concentrations of CHCl3 vapor, respectively. This finding represents a concentration-dependent multi-phase transition with an organic solvent, which is of potent interest for application in sensing systems.

COMPARATIVE STUDY OF THE RHEOLOGICAL BEHAVIOR OF SOLUTIONS OF THE CHITIN-GLUCAN COM-PLEX FROM THE FRUIT BODIES OF ARMILLARIA MELLEA IN ACETIC AND HYDROGENIC ACID

The article is devoted to the study of the rheological properties of the chitin-glucan complex (CGC) in aqueous solutions of hydrochloric and acetic acids. The CGC sample was isolated from the fruiting bodies of the Armillaria mellea, biotechnologically obtained from an easily renewable plant material. The flow of solutions of chitin-glucan complex with a concentration of 1, 5, 10% (wt.) in hydrochloric acid and 1, 3, 5% (wt.) in acetic acid was studied by the method of rotational viscometry in the range from 10 s-1 to 1000 s-1 at temperatures from 20°C to 50°C. The values of the rheological coefficients of the Ostwald equation are determined. The phenomena of non-Newtonian viscosity anomalies are established. The high viscosity of solutions may be due to the presence of an internal supramolecular structure in solutions of the chitin-glucan complex. The predominantly pseudoplastic nature of the rheological behavior of the studied solutions is shown. The flow index in this case varies from 0,18 to 0,79 for solutions of the chitin-glucan complex in hydrochloric acid and from 0,01 to 0,47 in solutions of acetic acid with a concentration of 3 to 5% (wt.). The pseudoplastic flow mechanism of such solutions can be explained by the destruction of the internal structure of the solution with an increase in shear loads. The dilatant nature of the flow of CGC solutions in acetic acid at a concentration of 1% (wt.) at a shear rate of 10 to 100 s-1 was also revealed. The flow index in this case ranges from 1,28 to 1,57. The dilatant nature of the flow may be due to the predominance of the processes of formation of a new internal structure in solution over the destruction of the existing structure in solution at a low concentration of the chitin-glucan complex. The influence of temperature on the rheological behavior of solutions is strongly distorted by the influence of other factors.

Deposition of Uniform Nanoscale Patterns on Silicon Dioxide Based on Coaxial Jet Direct Writing.

To increase the printing stability of low-viscosity solutions, an auxiliary method was proposed using a coaxial electrohydrodynamic jet. A high-viscosity solution was employed as the outer layer in the printing process, and it could be removed (dissolved away) after printing the structures. A combination of mechanical and electrical forces was proposed to enhance the consistency, durability, and alignment of the printed versatile structures. The instability of the jet trajectory (which arose from the repulsion between the jet and the base with a residual charge, in addition to the winding effect of the solution) was also reduced using the drag force along the direction of movement. Moreover, the jet velocity, the surface charge, and the influence of various working voltages on the jet speed were simulated. An array of IDT-BT nanostructures measuring about 100 nm was prepared on silicon dioxide (using an inner needle with a diameter of 130 µm) by equating the moving speed (350 mm/s) of the substrate to the speed of the jet. Moreover, the moving speed (350 mm/s) of the substrate was compared exclusively to the speed of the jet. The method proposed throughout this study can provide a reference for enhancing the stability of low-viscosity solutions on substrates for high-efficiency fabrication devices (NEMS/MEMS).

Regulation Mechanism of Electron Transfer Reaction from Cytochrome C to Cytochrome C Oxidase

The respiratory chain in mitochondria is quite essential for the energy generation in cells, effectively producing “the energy currency in living organisms”, ATP. The driving force for this system is a series of electron transfers form Complex I (NADH:quinone oxidoreductase) to Complex IV (Cytochrome c Oxidase; CcO) in inner mitochondria membrane, and these electron transfer reactions promote the proton pumping from the matrix to the intermembrane space in mitochondria, and, by use of the resulting proton concentration gradient across the membrane, Complex V (ATP synthase) produces ATP. These series of electron transfer reactions terminate at CcO to reduce molecular oxygen to water molecules. The electrons required for this four-electron reduction of molecular oxygen in CcO are donated from a small soluble electron transfer hemoprotein, Cytochrome c (Cyt c), and this electron transfer is also associated with the proton pumping for the ATP generation in the respiratory chain. To examine the molecular regulation mechanism of the electron transfer reaction to terminate the electron transport chain for four-electron reduction of molecular oxygen and proton pumping for the ATP generation, we kinetically followed the electron transfer reaction and analyzed the electron transfer reaction by the Michaelis-Menten equation. By utilizing the Cyt c mutants, we identified the amino acid residues to regulate the electron transfer reactions (Biochem. J., 2020, 477,1565). The kinetic analysis of the electron transfer reaction also revealed that the apparent rate for the electron transfer reaction determined by the steady-state kinetics is much slower than the intramolecular electron transfer rate in the Cyt c – CcO complex. On the other hand, we successfully determined the interaction site between Cyt c and CcO by using NMR (Proc. Natl. Acad. Sci., 2011, 108, 12271) and protein-protein docking simulation (J. Biol. Chem., 2016, 291, 15320). The Cyt c – CcO complex structure estimated from the NMR and protein-protein docking simulation clearly showed that the two redox centers, heme iron in Cyt c and CuA in subunit II of CcO, were located more than 20 Å apart, and the complexes exhibiting shorter redox center distances were energetically unstable. Combined with the results from kinetic and structural studies, we proposed a “conformationally gated electron transfer mechanism”, where the thermal fluctuation of the protein structure controls the electron transfer rate. However, direct experimental evidence that protein conformational fluctuations regulate electron transfer reactions has not been obtained. In this study, we focused on the viscosity of the protein solution as a factor to regulate the conformational fluctuation of the proteins, based on the assumption that high viscosity of the solution suppresses the conformational fluctuation. The electron transfer reaction from Cyt c to CcO was examined in the high viscosity solution and NMR relaxation measurements under high viscosity were also performed to identify the local structural fluctuation responsible for the regulation of the electron transfer rate. Together with the transient complex structures between Cyt c and CcO estimated by the MD simulation, the regulation mechanism of the electron transfer from Cyt c to CcO based on the “conformational gating” will be discussed.