Towards a quantitative description of excitonic couplings in photosynthetic pigment-protein complexes: quantum chemistry driven multiscale approaches

A structure-based quantitative calculation of excitonic couplings between photosynthetic pigments has to describe the dynamical polarization of the protein/solvent environment of the pigments, giving rise to reaction field and screening...

Mild Reaction of Highly-Oriented Collagen Fibril Arrays with Simulated Body Fluid

The highly-oriented collagen fibrils that paralleled to one (rubbing) direction were fabricated by which the collagen molecular solution was spin-coated and self-assembled on the rubbed polyimide film. Subsequently, the hydroxyapatite crystals were precipitated on the collagen fibrils by immersing into simulated body fluid. In details, the carboxyl groups on the collagen fibrils were used as a reaction field for adsorption of Ca2+ ions and promoted the formation of hydroxyapatite crystals. As a result, the hydroxyapatite crystals grew along the a-axis leading to the formation of stable interfaces between hydroxyapatite crystals and collagen fibrils. Moreover, the oriented collagen fibril arrays were more useful for the nucleation and growth of hydroxyapatite. Therefore, we successfully fabricated the highly-oriented collagen fibril arrays which were useful for the precipitation of hydroxyapatite crystals.

Metal-Free Fabrication of Fused Silica Extended Nanofluidic Channel to Remove Artifacts in Chemical Analysis

In microfluidics, especially in nanofluidics, nanochannels with functionalized surfaces have recently attracted attention for use as a new tool for the investigation of chemical reaction fields. Molecules handled in the reaction field can reach the single–molecule level due to the small size of the nanochannel. In such surroundings, contamination of the channel surface should be removed at the single–molecule level. In this study, it was assumed that metal materials could contaminate the nanochannels during the fabrication processes; therefore, we aimed to develop metal-free fabrication processes. Fused silica channels 1000 nm-deep were conventionally fabricated using a chromium mask. Instead of chromium, electron beam resists more than 1000 nm thick were used and the lithography conditions were optimized. From the results of optimization, channels with 1000 nm scale width and depth were fabricated on fused silica substrates without the use of a chromium mask. In nanofluidic experiments, an oxidation reaction was observed in a device fabricated by conventional fabrication processes using a chromium mask. It was found that Cr6+ remained on the channel surfaces and reacted with chemicals in the liquid phase in the extended nanochannels; this effect occurred at least to the micromolar level. In contrast, the device fabricated with metal-free processes was free of artifacts induced by the presence of chromium. The developed fabrication processes and results of this study will be a significant contribution to the fundamental technologies employed in the fields of microfluidics and nanofluidics.

Membrane Reactor for Methanol Synthesis Using Si-Rich LTA Zeolite Membrane

We successfully demonstrated the effect of a membrane reactor for methanol synthesis to improve one-pass CO2 conversion. An Si-rich LTA membrane for dehydration from a methanol synthesis reaction field was synthesized by the seed-assisted hydrothermal synthesis method. The H2O permselective performance of the membrane showed 1.5 × 10−6 mol m−2 s−1 Pa−1 as H2O permeance and around 2,000 as selectivity of H2O/MeOH at 473 K. From the results of membrane reactor tests, the CO2 conversion of the membrane reactor was higher than that of the conventional packed-bed reactor under the all of experimental conditions. Especially, at 4 MPa of reaction pressure, the conversion using the membrane reactor was around 60%. In the case of using a packed-bed reactor, the conversion was 20% under the same conditions. In addition, the calculated and experimental conversion were in good agreement in both the case of the membrane reactor and packed-bed reactor.

Local Anesthetics Transfer Across the Membrane: Reproducing Octanol-Water Partition Coefficients by Solvent Reaction Field Methods

Local anesthetics are one of the most widely used drug classes in clinical practice. Like many other biological molecules, their properties are altered depending on their protonation status, which is dependent on the pH of the environment. We studied the transport energetics of seven local anesthetics from the extracellular fluid across the biological membrane to the axoplasm in order to understand the effect of pH value on their efficacy and other pharmaco-dynamic roperties. In this we applied three different methods of solvent reaction field in conjunction with quantum chemical calculations to reproduce experimental values of n-octanol/water partition coefficients for both neutral and protonated forms. Only the SMD method of Cramer and Truhlar was able to reproduce experimental partition coefficient values. The results are discussed in terms of the function of local anesthetics under physiological conditions and in the case of local acidosis.

Solvation-Induced Onsager Reaction Field Rather than Double Layer Field Controls CO2 Reduction on Gold

<div><p>The selectivity and activity of the carbon dioxide reduction reaction (CO2R) are sensitive functions of the electrolyte cation. By measuring the vibrational Stark shift of in-situ generated CO on Au in the presence of alkali cations, we quantify the total electric field present during turnover and deconvolute this field into contributions from 1) the electrochemical Stern layer and 2) the Onsager, or solvation-induced, reaction field. The magnitude of the Onsager field is shown to be on the same order as the Stern layer field (∼10 MV/cm) but follows an opposite trend with cation, increasing from Li⁺< Na⁺< K⁺< Rb⁺≈Cs⁺. Contrary to theoretical reports,CO₂R kinetics are not correlated with the Stern field but instead are controlled by the strength of the Onsager reaction field with Cs⁺ as an exception. Spectra of interfacial water as a function of cation show that Cs⁺ induces a change in the interfacial water structure correlated with a dramatic drop in CO₂R activity, highlighting the importance of cation-dependent interfacial water structure on reaction kinetics. These findings show that both the Onsager reaction field and interfacial solvation structure must be explicitly considered for accurate modeling of CO₂R reaction kinetics.</p><br></div>