Construction of SnO2 buffer layer and analysis of its interface modification for Li and Li1.5Al0.5Ge1.5(PO4)3 in solid-state batteries

SnO2 layer between Li1.5Al0.5Ge1.5(PO4)3 (LAGP) and lithium anode was prepared through simple scratch-coating process to improve interface properties. The physical phase, morphology, and electrochemical properties of Li/SnO2/LAGP structure were characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, and electrochemical analytical methods. It was found that SnO2 layer effectively improved the interface stability of LAGP and lithium anode. The prepared Li/SnO2/LAGP/SnO2/Li symmetric cell exhibited a large critical current density of 1.8 mA cm-2 and demonstrated excellent cycling characteristics. The polarization voltages of symmetric cell were 0.1 V and 0.8 V after 1000 h of cycling at current densities of 0.04 mA cm-2 and 0.5 mA cm-2, respectively. Li/SnO2@LAGP/LiFePO4 solid-state full cells were also assembled, exhibiting a discharge specific capacity of 150 mAh g-1 after 200 cycles at 0.1C with capacity retention rate of 96 %. The good interface properties of Li/SnO2/LAGP structure are attributed to the transformation of SnO2 layer into a buffer layer containing Li2O, Sn0, and LixSny alloy during cycling process, which effectively inhibits the reduction reaction between LAGP and lithium anode.

[Effect of information-knowledge-attitude-practice theory-based health education on clonorchiasis control among community residents and primary school students in Zhongshan City]

OBJECTIVE

To evaluate the effect of information-knowledge-attitude-practice (IKAP) theory-based health education interventions on clonorchiasis control among community residents and primary school students in Torch High-tech Development Zone of Zhongshan City, so as to provide insights into formulation of clonorchiasis control strategies among different types of populations.

METHODS

Residents were randomly sampled from two communities and students from two primary schools using a random cluster sampling method in Torch High-tech Development Zone, Zhongshan City from 2019 to 2021, and health education pertaining to clonorchiasis control was performed based on the IKAP theory. The changes in the awareness of basic clonorchiasis control knowledge and belief, self-reported risk of Clonorchis sinensis infections and dietary behaviors were compared among community residents and primary school students before and after health education interventions.

RESULTS

The participants included 146 male and 151 female community residents and 158 male and 153 female primary school students, with no significant difference detected in gender distribution (χ2 = 0.16, P > 0.05). The mean awareness of basic clonorchiasis control knowledge increased by 44.71% and 43.28% among primary school students and community residents 6 months following health education, and there were significant differences in the awareness of each item of basic clonorchiasis control knowledge before and after health education (χ2 = 41.53 to 284.44, all P values < 0.05). The proportions of primary school students and community residents thinking very high and high risks of C. sinensis infections increased from 9.35% and 6.71% before health education to 22.15% and 37.75% after health education, but only the difference of the attitudes in community residents achieve statistical significance (χ2 = 92.18, P < 0.05). The frequency of separation of raw and cooked foods with chopping board and knife significantly increased among community residents and primary school students following health education (χ2 = 16.04 to 62.65, all P values < 0.05). The frequency of eating raw freshwater fish (χ2 = 32.85, P < 0.05), fish congee (χ2 = 7.02, P < 0.05) and fish fillet hot pot (χ2 = 4.88, P < 0.05) significantly reduced among primary school students following health education, while only the frequency and proportions of eating raw freshwater fish have significantly reduced in community residents (χ2 = 11.77, P < 0.05).

CONCLUSIONS

Health education interventions based on the IKAP theory are effective to increase the awareness of clonorchiasis control knowledge and improve dietary behaviors associated with C. sinensis infections among community residents and primary school students in Zhongshan City.

The influence of drug solubility and sampling frequency on metformin and glibenclamide release from double-layered particles: experimental analysis and mathematical modelling

Co-axial electrohydrodynamic atomization was used to prepare core/shell polymethylsilsesquioxane particles for co-delivery of metformin and glibenclamide in a sustained release manner. The drug-loaded microparticles were mostly spherical and uniformly distributed in size, with average diameters between 3 and 5 µm across various batches. FTIR was used to confirm the presence of drugs within the particles while X-ray diffraction studies revealed drugs encapsulated existed predominantly in the amorphous state. Intended as systems that potentially can act as depot formulations for long-term release of antidiabetics, a detailed analysis of drug release from these particles was necessary. Drugs of different solubilities were selected in order to study the effects of drug solubility from a core/shell particle system. Further analyses to determine how conditions such as release into a limited volume of media, sampling rate and partitioning of drug between the core and shell layers influenced drug release were conducted by comparing experimental and mathematically modelled outcomes. It was found that while the solubility of drug may affect release from such systems, rate of removal of drug (sampling frequency) which upsets local equilibrium at the particle/solution interface prompting a rapid release to redress the equilibrium influenced release more.

Reflectance difference microscopy for nanometre thickness microstructure measurements

The discontinuity of medium at the boundary produces optically anisotropic response which makes reflectance difference microscopy (RDM) a potential method for nanometre-thickness microstructure measurements. Here, we present the methodology of RDM for the edge measurement of ultrathin microstructure. The RD signal of microstructure's boundary is mathematically deduced according to boundary condition and polarization optics theory. A normal-incidence RDM setup was built simply with one linear polarizer, one liquid crystal variable retarder and one 5 × objective. Then, the performance of the developed setup was identified using homogenous reflection mirror and high quality linear polarizer. For demonstration, microstructures array with 100 nm step height was measured. The results show that the RD signal is sensitive to the edge and its sign reflects the change direction of the edge. Furthermore, a height sensitivity of better than 10 nm and a spatial resolution of ∼3 μm offer this technique a good candidate for characterizing ultrathin microstructures.

Pharmacokinetics, Biodistribution, Excretion and Plasma Protein Binding Studies of Acteoside in Rats

Acteoside is a representative phenylethanoid glycoside, exhibiting great potency in neurodegenerative diseases treatment, such as Alzheimer's disease. This study was aimed to explore the pharmacokinetic characteristics, tissue distribution, excretion and plasma protein binding of acteoside in Sprague-Dawley rats after oral administration at 20, 40 and 80 mg/kg by a validated LC-MS/MS method. Acteoside was absorbed quickly after oral administration at 3 dose levels. Acteoside reached the peak concentration at 0.29±0.17 h, exhibiting a maximum concentration (Cmax) of 312.54±44.43 ng/mL after oral administration at 40 mg/kg, and the elimination half-life was 1.05±0.23 h. Both the Cmax and AUC showed a linear increase with the oral doses administered. The absolute bioavailability of acteoside was only around 1%. After oral administration, acteoside was extensively and rapidly distributed in most tissues including brain, but little amount of acteoside was excreted in urine, bile or feces. And the rat plasma protein binding ratio with equilibrium dialysis was about 60%. The pharmacokinetic characteristics of the fast gastro-intestinal absorption, the noteworthy distribution in most tissues including brain, the absence of acteoside in urine, bile and feces and valuable plasma protein binding ratio in rats will provide important reference for further research.

A convenient and asymmetric protocol for the synthesis of natural products containing chiral alkyl chains via Zr-catalyzed asymmetric carboalumination of alkenes. Synthesis of phytol and vitamins E and K

[reaction: see text]. A convenient and asymmetric protocol for the synthesis of chiral oligoisoprenoids is described. Typically, a C14 vitamin E side chain 5 was synthesized in 47% yield over four steps. Isomeric purity of 5 was upgraded to >99% R at C-2 and 97% R at C-6 by the statistical formation of stereoisomeric p-phenylenebisurethanes and their diastereomeric separation. In addition, phytol and vitamin K were synthesized in 21% and 28% overall yields, respectively, over five steps from 1.

Anomalous scaling of the surface width during Cu electrodeposition

Kinetic roughening during thin film growth is a widely studied phenomenon, with many systems found to follow simple scaling laws. We show that for Cu electrodeposition from additive-free acid sulphate electrolyte, an extra scaling exponent is required to characterize the time evolution of the local roughness. The surface width w(l,t) scales as t(beta(loc))lH, when the deposition time t is large or the size l of the region over which w is measured is small, and as t(beta+beta(loc)) when l is large or t is small. This is the first report of such anomalous scaling for an experimental ( 2+1)-dimensional system. When the deposition current density or Cu concentration is varied, only beta(loc) changes, while the other power law exponents H and beta remain constant.

Calculating structures and free energies of complex molecules: combining molecular mechanics and continuum models

A historical perspective on the application of molecular dynamics (MD) to biological macromolecules is presented. Recent developments combining state-of-the-art force fields with continuum solvation calculations have allowed us to reach the fourth era of MD applications in which one can often derive both accurate structure and accurate relative free energies from molecular dynamics trajectories. We illustrate such applications on nucleic acid duplexes, RNA hairpins, protein folding trajectories, and protein-ligand, protein-protein, and protein-nucleic acid interactions.

Direct computation of long time processes in peptides and proteins: reaction path study of the coil-to-helix transition in polyalanine

The MaxFlux reaction path algorithm was used to isolate optimal transition pathways for the coil-to-helix transition in polyalanine. Eighteen transition pathways, each connecting one random coil configuration with an ideal alpha-helical configuration, were computed and analyzed. The transition pathway energetics and mechanism were analyzed in terms of the progression of the peptide nonbonded contact formation, helicity, end-to-end distance and energetics. It was found that (1) localized turns characterized by i, i + 3 hydrogen bonds form in the early stages of the coil-to-helix transition, (2) the peptide first collapses and then becomes somewhat more extended in the final stage of helix formation, and (3) 310-helix formation does not appear to be a necessary step in the transition from coil to helix. These conclusions are in agreement with the results of more computationally intensive direct molecular dynamics simulations. Proteins 1999;36:249-261.

Contribution of increased length and intact capping sequences to the conformational preference for helix in a 31-residue peptide from the C terminus of myohemerythrin

In order to examine the effects of chain length on the propensity of short peptides to form helix-like structures in aqueous solution, we have studied a peptide of 31 residues consisting of the C-terminal sequence (residues 88-118) of the four-helix bundle protein myohemerythrin from Themiste zostericola. This peptide, termed MDC, represents the final two elements of secondary structure in the protein, the D-helix and the C-terminal loop sequence, together with a five-residue sequence at the N terminus corresponding to the linker between the C- and D-helices. An N-capping sequence, VDAKNV, immediately precedes the D-helix sequence, and a C-capping sequence, VNHIKGT, corresponding to the alphaL termination motif, occurs at the C-terminal end. The effect of replacement of a cysteine residue in the middle of the sequence with an alanine was explored by the comparison of the MDC peptide and a 16-residue peptide representing the sequence of the D-helix alone, both containing the change Cys99Ala. Significant changes in the NMR and CD spectra were seen for both peptides compared to the wild-type sequence. A comparison of the fluorescence spectra of the wild-type and Cys99Ala peptides indicated that a specific interaction between the side chains of Cys 99 and Trp 102 acts to quench the fluorescence of the tryptophan ring and probably contributes a component that distorts the CD spectrum of the wild-type peptide at approximately 220-235 nm. The effect of an increase in the length of the peptide, with the incorporation of capping sequences derived from the native sequence, was explored by NMR and CD spectroscopy of the 31-residue and 16-residue peptides in aqueous solution and in TFE/water mixtures. Evidence for the formation of a significant population of helical conformers in the region of the MDC peptide corresponding to the D-helix was observed in aqueous solution using CD and NMR spectroscopy. The C-terminal 10 residues of the MDC peptide behave in solution in a manner identical to that of a 10-residue peptide with the same sequence; a highly specific local interaction between an aromatic ring and a glycine amide proton appears to be retained in the longer peptide. Upon addition of trifluoroethanol (TFE), significant shifts are observed in a number of resonances in the NMR spectrum, and both chemical shifts and NOEs provide evidence for a higher population of helix in the D-helix region of the peptide in TFE. However, TFE is unable to promote the propagation of helix beyond the N-cap or alphaL termination motifs, and the specific local interaction observed in the C-terminal sequence is retained in TFE. The CD spectrum in TFE shows an increase in the proportion of helix, to an overall maximum of approximately 55% helix at 50% v/v TFE, corresponding to approximately 100% helix in the D-helix sequence of the peptide, since the N and C termini of the MDC peptide are not helical according to the NMR spectra. The high proportion of helix observed in the D-helix sequence of the longer MDC peptide demonstrates that the presence of intact capping sequences can constrain the peptide conformational ensemble to resemble that seen in the native protein. A compendium of results from this and previous peptide studies has also led to a novel observation, the existence of a correlation between the amide proton chemical shift and temperature coefficient.

Hydrogen exchange in the lipid bilayer-bound gramicidin channel

Hydrogen exchange experiments for a membrane-bound polypeptide could lead to interesting functional and structural insights. Here, hydrogen/deuterium exchange, saturation transfer and differential relaxation experiments have been performed on oriented lipid bilayer-bound polypeptide samples to measure the exchange lifetimes. The polypeptide, gramicidin A, forms a monovalent cation selective channel across membranes. The pH dependent results suggest that the indole N epsilon 1-H groups show base catalyzed hydrogen exchange, but that the backbone amide sites are not base catalyzed, consistent with the exclusion of anions from this channel. Furthermore, the recently described [1] orientational distribution of the individual peptide carbonyls (i.e. carbonyls either tipped slightly in toward or away from the channel axis) is consistent with the observed difference in odd- and even-numbered amide residue exchange lifetimes.

Macromolecular structural elucidation with solid-state NMR-derived orientational constraints

The complete structure determination of a polypeptide in a lipid bilayer environment is demonstrated built solely upon orientational constraints derived from solid-state NMR observations. Such constraints are obtained from isotopically labeled samples uniformly aligned with respect to the B(0) field. Each observation constrains the molecular frame with respect to B(0) and the bilayer normal, which are arranged to be parallel. These constraints are not only very precise ( a few tenths of a degree), but also very accurate. This is clearly demonstrated as the backbone structure is assembled sequentially and the i to i + 6 hydrogen bonds in this structure of the gramicidin channel are shown on average to be within 0.5 A of ideal geometry. Similarly, the side chains are assembled independently and in a radial direction from the backbone. The lack of considerable atomic overlap between side chains also demonstrates the accuracy of the constraints. Through this complete structure, solid-state NMR is demonstrated as an approach for determining three-dimensional macromolecular structure.

Conformational trapping in a membrane environment: a regulatory mechanism for protein activity?

Functional regulation of proteins is central to living organisms. Here it is shown that a nonfunctional conformational state of a polypeptide can be kinetically trapped in a lipid bilayer environment. This state is a metastable structure that is stable for weeks just above the phase transition temperature of the lipid. When the samples are incubated for several days at 68 degrees C, 50% of the trapped conformation converts to the minimum-energy functional state. This result suggests the possibility that another mechanism for functional regulation of protein activity may be available for membrane proteins: that cells may insert proteins into membranes in inactive states pending the biological demand for protein function.

Lipid-peptide interface: valine conformation and dynamics in the gramicidin channel

High-resolution dynamic and structural characterizations have been achieved for each of the valine side chains of the gramicidin channel while solubilized in hydrated lipid bilayers. The characterizations have been achieved by 2H NMR spectra of both oriented and unoriented samples obtained at 36 and 5 degrees C, respectively. Powder patterns displaying intermediate time frame averaging provide dynamic information, and quadrupole splittings from aligned samples provide orientational constraints for the side chain structure. Librational amplitudes for each site throughout the side chain have also been characterized. Val6 and Val8 are shown to be fixed in rotameric states, potentially constraining two of the indole rings and the functionally important indole dipole moment orientations. Val1 and Val7 undergo three-state jump motions. The jump frequencies increase from the microsecond to nanosecond time frame upon increasing the temperature through the lipid phase transition. For the same temperature range, there is no evidence for changes in conformational state populations. Despite small differences in the substate populations for the two residues, the motions may be loosely coupled as indicated by the high-resolution structure.