Detecting Single‐Molecule Dynamics on Lipid Membranes with Quenchers‐in‐a‐Liposome FRET

Tracking membrane‐interacting molecules and visualizing their conformational dynamics are key to understanding their functions. It is, however, challenging to accurately probe the positions of a molecule relative to a membrane. Herein, a single‐molecule method, termed LipoFRET, is reported to assess interplay between molecules and liposomes. It takes advantage of FRET between a single fluorophore attached to a biomolecule and many quenchers in a liposome. This method was used to characterize interactions between α‐synuclein (α‐syn) and membranes. These results revealed that the N‐terminus of α‐syn inserts into the membrane and spontaneously transitions between different depths. In contrast, the C‐terminal tail of α‐syn is regulated by calcium ions and floats in solution in two conformations. LipoFRET is a powerful tool to investigate membrane‐interacting biomolecules with sub‐nanometer precision at the single‐molecule level.     

Characterization and on‐line adjustment of the sagittal‐bent Laue crystal profile

The sagittal‐bent Laue monochromator can provide an ideal way to focus high‐energy X‐ray beams. However, the anticlastic curvature induced by sagittal bending has a great influence on the crystal performance. Thus, characterizing the bent‐crystal shape is very important for predicting the performance of the bent‐crystal monochromator. In this paper the crystal profile is measured by off‐line optical metrology and on‐line X‐ray experiments. The off‐line results showed that the bent‐crystal surface could be well fitted to a saddle surface apart from a redundant cubic term which was related to the different couples applied on the crystal. On‐line characterization of the meridional and the sagittal radius of the bent crystal includes double‐crystal topography and ray‐tracing measurement. In addition, the double‐crystal topography experiment could be used as a quick diagnostic method for the bending condition adjustment. The sagittal radius of the bent crystal was characterized through a ray‐tracing experiment by using a particularly designed tungsten mask. Moreover, rocking curves under different bending conditions were measured as well. The results were highly consistent with analytical results derived from the elastic theory. Furthermore, radii along different vertical positions under various bending conditions were measured and showed a quadratic relationship between the vertical positions and the meridional radii.     

Heterogeneous oxidization of graphene nanosheets damages membrane

Graphene-based materials exhibit unique properties that have been sought to utilize for various potential applications. Many studies suggest that graphene-based materials can be cytotoxic, which may be attributed to destructive effects on cell membranes.However, there still are conflicting results regarding interactions between graphene-based materials and lipid membranes. Here,through cryo-electron microscopy(Cryo-EM) and dye-leakage experiments along with in silico methods, we found that graphene oxide nanosheets induce significant membrane damage, while the effect of pristine graphene is negligible. We revealed the importance of heterogeneous oxidization of graphene-based nanosheets in damaging vesicle membranes. Moreover, that not only the oxidization degree but also the oxidization loci and membrane tension play important roles in the cytotoxicity of the graphene-based nanosheets.     

Synthesis of C-acyl furanosides via the cross-coupling of glycosyl esters with carboxylic acids

C-Acyl furanosides are versatile synthetic precursors to a variety of natural products, nucleoside analogues, and pharmaceutical molecules. This report addresses the unmet challenge in preparing C-acyl furanosides by developing a cross-coupling reaction between glycosyl esters and carboxylic acids. A key step is the photoredox activation of the glycosyl ester, which promotes the homolysis of the strong anomeric C–O bond through CO₂ evolution to afford glycosyl radicals. This method embraces a large scope of furanoses, pyranoses, and carboxylic acids, and is readily applicable to the synthesis of a thymidine analogue and diplobifuranylone B, as well as the late-stage modification of (+)-sclareolide. The convenient preparation of the redox active glycosyl ester from native sugars and the compatibility with common furanoses exemplifies the potential of this method in medicinal chemistry.

A cross-coupling of glycosyl esters with carboxylic acids to prepare C-acyl furanosides and pyranosides. The reaction proceeds through photoredox activation of the glycosyl ester to afford glycosyl radicals.     

轨道车辆轮对的关键力学问题及研究进展

从服役失效模式、原因与后果入手,研究了轨道车辆轮对可靠性与安全性相关的关键力学问题与进展.首先总结了5种车轮踏面失效与4种非踏面失效、5种车轴失效和6种轴承失效模式.阐述了与失效模式相关的成因和后果.讨论了可能的解决方法.然后介绍了超长疲劳寿命可靠性分析、光滑表面疲劳短裂纹理论与结构安全评价方法和轮轨接触材料与形貌匹配3个关键力学问题与研究进展.进一步展望了轮轨接触多学科优化、考虑几何与载荷约束及环境影响的轴承接触疲劳理论和轮对集成可靠性与安全性分析评价方法是未来3个值得研究的关键力学问题.     

Growth of spinel crystals in vanadium slag and their characterization

Morphology of vanadium slags were investigated by scanning electron microscopy (SEM). The mineralogical phases were characterized by energy disperse X‐ray spectrometry (EDS) and powder X‐ray diffraction (XRD). The obtained results show that spinels and silicates are the major phases in the vanadium slag, and V is concentrated in Fe_xV_3‐xO₄ and Mg_x(V, Ti)_3‐xO₄. Both the spinel grain size and volume fraction in the slag with higher V₂O₃ content are much larger than that with lower V₂O₃ content. (Fe, Mn)₂SiO₄ and (Fe, Mn)SiO₃ have a higher proportion in the slag with lower V₂O₃ and higher SiO₂ content. The relation among cooling conditions and grain size and volume fraction of spinels is also discussed. It is found that low cooling rate and long holding time benefit spinel crystal growth, especially for the interval of 1200‐1250 °C. Both mean diameter and volume fraction of spinels could achieve or exceed the industry vanadium slag when holding more than 45 min. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

a-Si(n)/c-Si(p)异质结太阳电池薄膜硅背场的模拟优化

采用AFORS-HET数值模拟软件,对不同带隙的薄膜硅材料在a-Si(n)/c-Si(p)异质结太阳电池上的背场效果进行了模拟,分析了影响背场效果的原因,得到了薄膜硅背场在a-Si(n)/c-Si(p)异质结太阳电池上的适用条件为薄膜硅材料是带隙16 eV,硼掺杂浓度在10¹⁸cm^-3以上的微晶硅材料,其最佳厚度在5nm左右. 这种背场从工艺上易于实现,并且,与常用的Al扩散背场相比,在相同的掺杂浓度下,电池效率可以大大提高. 关键词： 薄膜硅 背场 硅异质结太阳电池     

DFT study on addition reaction mechanism of guanine‐cytosine base pair with OH radical

The addition reaction mechanism of OH radical with guanine‐cytosine (G^.C) base pair has been explored at the B3LYP/DZP++ level of density functional theory (DFT). Structures perturbations along the hydroxylation of G^.C base pair cause strain in the pairing and double‐strand breaks in DNA. Seven possible hydroxylation reactions are exothermic, and the reaction energy decreases in the order of G^.C^C4 > G^C5.C > G^C2.C > G^C4.C > G^.C^C5 > G^.C^C6 > G^C8.C. The hydroxylation reactions at G^.C^C5 and G^C8.C sites appear to be barrierless, and the sequence of the barrier energy is G^.C^C4 > G^C4.C > G^C2.C > G^C5.C > G^.C^C6 > G^.C^C5 ~ G^C8.C. The results indicate that hydroxylation at G^C8.C, G^.C^C5 and G^.C^C6 are more thermodynamically and kinetically favorable than other sites in G^.C base pair. Considering the solvent effects by using the polarizable continuum model, the stabilities of all the compounds are increased significantly. Little change is taken place on the data of the reaction energies and barrier energies. Their sequences and the stability order follow the same trends like them in gas phase. The fluctuation of natural bond orbital charge further confirms that the hydroxylation reactions are exothermic. And transient spectra computed with the time‐dependent density functional theory (TD‐DFT) match well with the previous experimental and theoretical reports. Our deduced mechanism is in good agreement with the experimentally observed hydroxylated adducts. Copyright © 2015 John Wiley & Sons, Ltd.     

储存环光学速调管自发辐射模拟研究

用蒙特卡洛方法模拟了合肥储存环上ＴＯＫ的自发辐射，通过模拟结果分析和讨论了电子束团能散和发射度对自发辐射谱的作用，并和实验结果进行了比较，分析了实验测出的自发辐射谱调制因子很低的原因。     

Stereospecific polymerization of butene-1 with supported titanium catalyst

Butene-1 was polymerized with a highly-active supported titanium catalyst which was developed in this laboratory. The influences of various conditions (e.g., catalyst composition, temperature, external ester, H₂, triethylaluminum, and catalyst concentration) on the catalytic activity, decay of polymerization rate, molecular weight, and isotacticity of the products were studied in detail. The structural properties of the PB-1 were characterized by WAXD, DSC, and ¹³C-NMR. It was found that the catalyst TiCl₄, Ti(OBu)₄/MgCl₂/ethyl benzoate (EB)/Ph₂SiCl₂–AlEt₃ shows high activity, i.e., 3.2 × 10⁴ g PB/g Ti h. Isotacticity of the product was increased by adding p-CH₃C₆H₄COOEt into the catalytic system. Molecular weight of the product can be easily controlled by H₂. The decay of polymerization rate with time fulfills the equation: R_t ? R_s = (R_o ? R_s)e^?βt. © 1993 John Wiley & Sons, Inc.