The transport behavior of glucose through a cyclic peptide nanotube (CPN), composed of 8 × cyclo[-(Trp-d-Leu)-Gln-d-Leu-] rings embedded in DMPC lipid bilayers was examined using all-atom molecular dynamics (AAMD) simulations. Two conformational isomers of β-d-glucose, equatorial (C) and axial (C) chair conformers, were used to examine conformational effects on the hydrogen bond network, energetics, and diffusivity of glucose transport through the CPN. Calculations of the number of hydrogen bonds of the two glucose conformers with water molecules and with the CPN illustrate that the total number of hydrogen bonds of the conformers decreases inside the channel compared to bulk water due to the confinement characteristics of the interior of the CPNs although new hydrogen bonds between the hydroxyl and hydroxymethyl hydrogens of glucose and the carbonyl oxygens in the CPN backbone are formed. Despite the decrease of the number of hydrogen bonds inside the CPN, intramolecular hydrogen bonds of C are maintained during permeation of C through the CPN. The retention of intramolecular hydrogen bonds and the spherical shape of C give rise to considerably weaker orientational preferences and higher diffusion coefficients for C than those of C inside and outside the CPN. Due to larger dipole moments induced by the alignment of hydroxyl and hydroxymethyl groups, C has more favorable interactions with the CPN backbone at the channel entrances and inside the channel than C. In the middle of the CPN channel, entropic gains originating from higher orientational and translational degrees of freedom of C than those of C also contribute to lower free energy wells for C inside the CPN. This work reveals that the conformational variation and intramolecular hydrogen bond formation of β-d-glucose can have important effects on the energetics and dynamics of glucose transport through CPNs, providing insight into the translocation mechanism of d-glucose into the cell through glucose transporters (GLUTs) and the dynamics of glucose confined in silica nanochannels. It is also demonstrated that CPNs can indeed facilitate the permeation of small hydrophilic molecules such as glucose and can be utilized as a novel carrier system for hydrophilic drug compounds into the cell.
The effects of geometric restraints and frictional parameters on the energetics and dynamics of ion transport through a synthetic ion channel are investigated using molecular dynamics (MD) simulations for several different ions. To do so, potential of mean force profiles and position‐dependent diffusion coefficients for Na+, K+, Ca2+, and Cl− transport through a simple cyclic peptide nanotube, which is composed of 4× cyclo[−(D‐Ala‐Glu‐D‐Ala‐Gln)2−] rings, are calculated via an adaptive biasing force MD simulation method and a Baysian inference/Monte Carlo algorithm. Among the restraints and parameters examined in this work, the radius parameter used in the flat‐bottom half‐harmonic restraint at the entrance and exit to channel has a great effect on the energetics of ion transport through the variation of entropy in the outside of the channel. The diffusivity profiles for the ions show a strong dependence on the damping coefficient, but the dependence on the coefficient becomes minimal inside the channel, indicating that the most important factor which affects the diffusivity of ions inside the channel is local interactions of ions with the structured channel water molecules through confinement.
Ruthenium dye-based dye-sensitized solar cells (DSSCs) have received great deal of attraction from chemists and material scientists because of their over 10% of photon to current conversion efficiency.1 The high cost and much synthetic efforts of ruthenium dyes, nevertheless, has often been reported as problematic. 2Recently, organic dye-based DSSCs whose photon to current conversion efficiency approximates near 9% are suggested as an alternative.3 Organic dyes have several advantages compared to Ru dyes for DSSCs.4 For instance, organic dyes have larger absorption coefficients than Ru-based dyes which is attributed to an intramolecular π-π transition, that leads to an effective light harvesting properties. Organic dyes vary in structure and can be easily modified for molecular design, essential features for tuning the absorption characteristics of DSSCs. In addition, the use of organic dyes as DSSCs eliminates the requirement of large quantities of heavy metals which is an advantage considering escalating costs for metals and their limited availability.Generally, organic dyes consist of three parts: electrondonor, electron-acceptor, and spacer as a linker between the two. A variety of organic dyes with high efficiency have been synthesized to date, 2 particularly, when electron donor material contributed to high efficiencies.2,5 Arylamine derivatives are reported as the electron donors mainly because these compounds make it easy to produce holes and to stabilize the complex through modification of the geometric structure in excited state.6 However, the synthesis of organic dyes with carbazole substituted electron donors and the performance of DSSC has been rarely done in spite of the similar properties of carbazole derivatives to those of arylamine in organic electronics.7 In addition, studies on increasing the efficiency of DSSC by controlling the spacer has been rarely explored, contrasting to the number of studies regarding increased efficiency of DSSC by varying the electron donors and/or acceptors. 8The previous studies suggest that including a thiophenesubstituted spacer shows a comparatively large value of molar extinction coefficient in the absorption spectra. Moreover, additional studies on spacer control of organic dyes are related to the effect of introduction of steric bulky groups. A bulky group introduced into the molecular framework does not only increase the electron life time (τ e ) of the dyes in the conduction band of TiO 2 but also inhibit dyeaggregation. This results in an increase of open-circuit voltage (V oc ). Such an approach was introduced by the Hara group, in which a bulky spacer, such as a hexylthiophene, was incorporated into the organic structure.7 We have previously synthesized a system containing thiophene analogs as a spacer, 8 coupled with a phenyl-carbazole segment as an electron donor. Systematic investigation into the effect of bulky substituent in the spacers on efficiency of the DSSCs was carried out by molecular engineering. In this study, we report the synthesis of fou...
Because peanut is a legume of nutrient abundance and contains a wide variety of chemical constituents such as proteins, carbohydrates, fibers, fats, niacin, folate, thiamine, resveratrol, flavonoids, magnesium, and phosphorus, a lot of researcher focus the study on the peanut. Especially the peanut has high content of resveratrol, so the health benefits including anti-aging, anticancer, anti-inflammatory and the prevention of cardiovascular disease, therefore the study that the peanut is used to process food and treat disease carried out widely. In this study, the condition to optimize the process programmes of fermentative germinated peanut drink by response surface experiment and to increase resveratrol contents by lactic acid bacteria is determined. In order to improve the resvertrol contents of fermentative germinated peanut drink, was prepared by using four-day germinated peanut as raw materials?adding Lactobacillus and xylitol before pasteurized, fermentation and cold storge. By single factor analysis and response surface experiments, the optimum conditions for fermentative germinated peanut drink were the amount of inoculum 3.26%, the amount of xylitol 6.2%, the fermentation time 15h and the ratio of material to water 1:5(g/mL). Product quality was evaluated through sensory evaluation. Investigate the change in resveratrol content of fermentative germinated peanut drink by HPLC. Resveratrol contents were increased from 674.22 ±2.47 μg/L to 815.82±4.53 μg/L in germination peanut drink after fermentation.
In this study, the thermal denaturation mechanism and secondary structures of two types of human insulin nanoparticles produced by a process of solution-enhanced dispersion by supercritical fluids using dimethyl sulfoxide (DMSO) and ethanol (EtOH) solutions of insulin are investigated using spectroscopic approaches and molecular dynamics calculations. First, the temperature-dependent IR spectra of spherical and rod-shaped insulin nanoparticles prepared from DMSO and EtOH solution, respectively, are analyzed using principal component analysis (PCA) and 2D correlation spectroscopy to obtain a deeper understanding of the molecular structures and thermal behavior of the two insulin particle shapes. All-atom molecular dynamics (AAMD) calculations are performed to investigate the influence of the solvent molecules on the production of the insulin nanoparticles and to elucidate the geometric differences between the two types of nanoparticles. The results of the PCA, the 2D correlation spectroscopic analysis, and the AAMD calculations clearly reveal that the thermal denaturation mechanisms and the degrees of hydrogen bonding in the spherical and rod-shaped insulin nanoparticles are different. The polarity of the solvent might not alter the structure or function of the insulin produced, but the solvent polarity does influence the synthesis of different shapes of insulin nanoparticles.
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