Racemic and Quasi‐Racemic X‐ray Structures of Cyclic Disulfide‐Rich Peptide Drug Scaffolds

Cyclic disulfide‐rich peptides have exceptional stability and are promising frameworks for drug design. We were interested in obtaining X‐ray structures of these peptides to assist in drug design applications, but disulfide‐rich peptides can be notoriously difficult to crystallize. To overcome this limitation, we chemically synthesized the L ‐ and D ‐forms of three prototypic cyclic disulfide‐rich peptides: SFTI‐1 (14‐mer with one disulfide bond), cVc1.1 (22‐mer with two disulfide bonds), and kB1 (29‐mer with three disulfide bonds) for racemic crystallization studies. Facile crystal formation occurred from a racemic mixture of each peptide, giving structures solved at resolutions from 1.25 Å to 1.9 Å. Additionally, we obtained the quasi‐racemic structures of two mutants of kB1, [G6A]kB1, and [V25A]kB1, which were solved at a resolution of 1.25 Å and 2.3 Å, respectively. The racemic crystallography approach appears to have broad utility in the structural biology of cyclic peptides.     

Antibacterial Activity of Synthetic Curcumin Derivatives: 3,5-Bis(benzylidene)-4-Piperidone (EF24) and EF24-Dimer Linked via Diethylenetriaminepentacetic Acid (EF2DTPA)

Curcumin is well known for its antimicrobial and anti-inflammatory properties. However, since systemic absorption and bioavailability of curcumin from gastrointestinal tract is considerably poor, synthetic curcuminoids are being developed as better alternatives. Two curcumin derivatives: 3,5-bis(benzylidene)-4-piperidone (EF24) and EF24-dimer linked via diethylenetriaminepentacetic acid (EF₂DTPA), were included in this study. We investigated the antibacterial activity of EF24 and EF₂DTPA against Gram-negative (Escherichia coli) and Gram-positive (Enterococcus faecalis, Staphylococcus aureus) bacteria. We also studied the effects of EF24 and EF₂DTPA on uptake and localization of pHrodo-labeled E. coli in the acidic compartments (phagolysosomes) of dendritic cells (DCs) under in vitro conditions. Our results demonstrate that treatment with EF24 and EF₂DTPA directly suppresses the bacterial growth. However, these compounds do not affect the bacterial uptake or localization in the DCs.     

Surface Design for Immobilization of an Antimicrobial Peptide Mimic for Efficient Anti-Biofouling

Microbial surface attachment negatively impacts a wide range of devices from water purification membranes to biomedical implants. Mimics of antimicrobial peptides (AMPs) constituted from poly(N-substituted glycine) „peptoids“ are of great interest as they resist proteolysis and can inhibit a wide spectrum of microbes. We investigate how terminal modification of a peptoid AMP-mimic and its surface immobilization affect antimicrobial activity. We also demonstrate a convenient surface modification strategy for enabling alkyne–azide „click“ coupling on amino-functionalized surfaces. Our results verified that the N- and C-terminal peptoid structures are not required for antimicrobial activity. Moreover, our peptoid immobilization density and choice of PEG tether resulted in a „volumetric“ spatial separation between AMPs that, compared to past studies, enabled the highest AMP surface activity relative to bacterial attachment. Our analysis suggests the importance of spatial flexibility for membrane activity and that AMP separation may be a controlling parameter for optimizing surface anti-biofouling.     

Passive ranging of a moving sound source using three-dimensional measured information

To solve the problem of passive ranging of a moving sound source,a method of estimating the initial distance of target is presented by using the measured inform...     

Herbarumin Ⅲ的立体选择性全合成

以正丁醛和1,5-戊二醇为起始原料, 以不对称烯丙基化、改良的Julia成烯反应和Yamaguchi内酯化为关键步骤, 通过13步反应, 立体选择性地合成了具有植物毒性的天然十元内酯化合物Herbarumin Ⅲ(3)及其差向异构体22.     

邻硝基乙酰苯胺衍生物的XPS振起伴峰及其价带谱的研究

研究了一组邻硝基乙酰苯胺衍生物的X射线光电子能谱(XPS).观察到硝基的N1s光电子谱有明显分裂,可认为是N1s振起伴峰的反映,而且苯环上的取代基对该振起伴峰强度有影响,按照Pignataro等关于振起伴峰与主峰的能量分离以及分子内电荷转移有关的观点,计算了振起伴峰与主峰的面积比.结果表明,峰间距与面积比的趋势一致.因此二者都可作为分子内电荷转移的粗略估计.     

and Au6 clusters: Superatomic molecules bearing an SP3‐hybrid Au6 core

The octahedral Au₆ core is explored for the formation of novel SP³‐hybrid superatomic molecules by considering and Au₆ clusters (X= F, Cl, Br, I). The bonding between the four capping atoms and the Au₆ core requires a combination of 1S and 1P shells of the core leading to a set of four equivalent hybrid orbitals. Thus, combining the superatom concept with both the Lewis structure model and VSEPR theory contributes to the rationalization of structure and bonding in metal clusters. For example, our results consider the Au₆ clusters as analogues of the simplest perhalogenated hydrocarbon, CX₄.     

Bi4V2O11/石墨烯异质结光催化剂的制备及其在降解抗体污染物中应用

发展和设计高效、廉价和稳定的光催化剂用于抗生素污染物降解仍然存在巨大的挑战。 本文通过一种便捷的水热方法制备了Bi₄V₂O₁₁/石墨烯复合材料并用于可见光下抗生素污染物光催化降解。 通过自由基追踪实验,确认了光催化降解过程中活性物质为h⁺和·OH基团。 根据实验结果,提出了相应的反应机理。 石墨烯的引入可以有效地促进光生电子-空穴对的分离,从而增强光催化活性。 该复合催化剂展现出良好的活性和稳定性。 该方法以石墨烯为载体制备了光催化降解材料,为高性能光催化剂的制备提供了参考。