Ultrasound-assisted immersion freezing reduces the structure and gel property deterioration of myofibrillar protein from chicken breast

The effects of air freezing (AF), immersion freezing (IF) and ultrasound-assisted immersion freezing (UF) at different power levels (125, 165, 205 and 245 W) on the structure and gel properties of the myofibrillar protein (MP) of chicken breast were investigated. UF at 165 W (UF-165) had no obvious negative impact on the primary structure of the MP and effectively reduced the change in the secondary and tertiary structure. In addition, UF-165 significantly reduced the losses in the elastic modulus (G′), gel strength, and gel water holding capacity (P < 0.05). According to low field nuclear magnetic resonance analysis, the T₂₁ and T₂₂ of the UF-165 MP gels were shorter than those of the AF and IF samples, which meant that the UF-165 reduced the mobility of the immobilized water and free water in MP gel. A scanning electron microscopy analysis showed that the appropriate ultrasonic power promoted the formation of a compact and homogeneous protein gel network. These results suggested that the appropriate ultrasonic power maintained the MP structure and reduced the loss of gel quality.     

Application of ultrasound-assisted physical mixing treatment improves in vitro protein digestibility of rapeseed napin

The in vitro protein digestibility (IVPD) of napin was studied using different pretreatment methods, including ultrasound, mixing napin with lactalbumin, and ultrasound-assisted protein mixing. The relationships between IVPD, molecular structure, and disulfide bonds were explored, showing that the IVPD of napin was the highest compared with the control when treated with 40% ultrasound power. When the proportion of napin to lactalbumin was 5:5, a synergistic influence between the two proteins was observed. Further investigation showed that the IVPD of napin was clearly improved by treatment with ultrasound-assisted protein mixing. Compared with the single protein in the control, the β-sheet content in the secondary structure of the mixed protein after sonication was reduced from 45.02% to 37.16%. The ordered protein structure was also disrupted by ultrasound, as supported by fluorescence intensity and surface hydrophobicity analyses. The decreased number of disulfide bonds and conformational changes indicated that the IVPD of rapeseed napin was closely related to the disulfide bond content. This study provides a theoretical basis for improving protein digestibility by combining ultrasound with physical mixing.     

Identifying aspirin polymorphs from combined DFT-based crystal structure prediction and solid-state NMR

A combined experimental and computational approach was used to distinguish between different polymorphs of the pharmaceutical drug aspirin. This method involves the use of ab initio random structure searching (AIRSS), a density functional theory (DFT)-based crystal structure prediction method for the high-accuracy prediction of polymorphic structures, with DFT calculations of nuclear magnetic resonance (NMR) parameters and solid-state NMR experiments at natural abundance. AIRSS was used to predict the crystal structures of form-I and form-II of aspirin. The root-mean-square deviation between experimental and calculated ¹H chemical shifts was used to identify form-I as the polymorph present in the experimental sample, the selection being successful despite the large similarities between the molecular environments in the crystals of the two polymorphs.     

Nonmetal Doping as a Robust Route for Boosting the Hydrogen Evolution of Metal-Based Electrocatalysts

Recently, nonmetal doping has exhibited its great potential for boosting the hydrogen evolution reaction (HER) of transition-metal (TM)-based electrocatalysts. To this end, this work overviews the recent achievements made on the design and development of the nonmetal-doped TM-based electrocatalysts and their performance for the HER. It is also shown that by rationally doping nonmetal elements, the electronic structures of TM-based electrocatalysts can be effectively tuned and in turn the Gibbs free energy of the TM for adsorption of H* intermediates (ΔG_H*) optimized, consequently enhancing the intrinsic activity of TM-based electrocatalysts. Notably, we highlight that concurrently doping two nonmetal elements can continuously and precisely regulate the electronic structures of the TM, thereby maximizing the activity for HER. Moreover, nonmetal doping also accounts for enhancing the physical properties of the TM (i.e. surface area). Therefore, nonmetal doping is a robust strategy for simultaneous regulation of the chemical and physical features of the TM.     

Canonical Lorentzian spin structure and twistor spinors on the Fefferman space of a contact Riemannian manifold

The Fefferman space of a contact Riemannian manifold carries a Lorentzian spin structure canonically. On the Lorentzian spin manifold, we investigate the Dirac operator and the twistor operator closely. In particular, we show that, if the contact Riemannian manifold is integrable, then there exist non-zero global solutions of the twistor equation.     

A benchmark of optimally folded protein structures using integer programming and the 3D-HP-SC model

The Protein Structure Prediction (PSP) problem comprises, among other issues, forecasting the three-dimensional native structure of proteins using only their primary structure information. Most computational studies in this area use synthetic data instead of real biological data. However, the closer to the real-world, the more the impact of results and their applicability. This work presents 17 real protein sequences extracted from the Protein Data Bank for a benchmark to the PSP problem using the tri-dimensional Hydrophobic-Polar with Side-Chains model (3D-HP-SC). The native structure of these proteins was found by maximizing the number of hydrophobic contacts between the side-chains of amino acids. The problem was treated as an optimization problem and solved by means of an Integer Programming approach. Although the method optimally solves the problem, the processing time has an exponential trend. Therefore, due to computational limitations, the method is a proof-of-concept and it is not applicable to large sequences. For unknown sequences, an upper bound of the number of hydrophobic contacts (using this model) can be found, due to a linear relationship with the number of hydrophobic residues. The comparison between the predicted and the biological structures showed that the highest similarity between them was found with distance thresholds around 5.2–8.2 Å. Both the dataset and the programs developed will be freely available to foster further research in the area.     

无机钙钛矿太阳能电池Cs2SnI6的电子结构和光学性质的第一性原理研究

近年来,Cs2SnI6作为一种无毒性、稳定性好的新型钙钛矿材料应用于太阳能电池中,其电池的光电转换效率由最初不到1%增长到现在的8.5%,使之成为有可能替代铅基钙钛矿太阳能电池的新型太阳能电池。本文采用基于广义密度泛函和杂化密度泛函的第一性原理方法研究了Cs2SnI6的电子结构、光学特性和钙钛矿太阳能电池的光电性能参数。研究结果表明,导带底和价带顶位于同一高对称点Γ而属于直接跃迁型半导体,且电子态主要来自于I-5p轨道和Sn-5s轨道。在近红外和可见光波长范围内有较高的吸收系数,当Cs2SnI6钙钛矿厚度达到10μm时,吸收率在311~989 nm之间接近100%,不考虑潜在损失的情况下,理论上太阳能电池可获得短路电流为32.86 mA/cm2、开路电压0.91 V、填充因子87.4%、光电转换效率26.1%。为实验上制备高效Cs2SnI6钙钛矿太阳能电池提供了参考。     

硫钒铜矿化合物电子结构和电致变色特性的第一原理研究

基于密度泛函的第一原理赝势平面波方法，计算晶体结构、电子结构和光学性质，研究硫钒铜矿化合物Cu₃VS₄、Cu₃NbS₄和Cu₃TaS₄的电子输运及电致变色特性，探讨作为透明半导体材料应用于太阳能电池和电致变色器件的可能性.电子结构的计算表明这类化合物是间接带隙半导体，其电子能带的导带底和价带顶分别位于布里渊区的X点和R点.价带顶的电子本征态主要来自于Cu原子的d电子轨道，而导带底电子态主要来源于VB族元素原子的d电子轨道.能带结构、电荷布居分析、电子局域化函数和光吸收及反射谱的计算表明这些硫钒铜矿化合物属于极性共价半导体，具有较高的电荷迁移率和优良的电致变色特性，可应用于高效电致变色器件.