Synthesis,crystal structure,DNA/bovine serum albumin binding and antitumor activity of two transition metal complexes with 4‐acylpyrazolone derivative

Two new complexes, namely [Cu₆L₆] ( 1 ) and [Zn(HL)₂] ( 2 ) (H₂L = N‐(1‐phenyl‐3‐methyl‐4‐propenylidene‐5‐pyrazolone)‐2‐furancarboxylic acid hydrazide), have been synthesized and characterized. Single crystal X‐ray analysis indicates that complex 1 has a hexanuclear structure and complex 2 exhibits a mononuclear structure. The DNA/bovine serum albumin (BSA) binding properties of complexes 1 and 2 were investigated by absorption spectroscopy and fluorescence quenching. Both complexes could effectively intercalate to DNA with calculated quenching constants of 2.6 × 10⁵ and 1.25 × 10⁵ M^?1, respectively. The quenching mechanism of the intrinsic fluorescence of BSA by the complexes was found to be a static one. The cytotoxicities of 1 and 2 were investigated in two human tumor cell lines, human esophageal cancer cells (Eca‐109) and cervical cancer cells (HeLa). Complex 1 exhibits higher antitumor activity than 2 . Furthermore, 1 can inhibit HeLa cells by inducing apoptosis and G0/G1 phase cell cycle arrest. All results demonstrate that 1 and 2 both have DNA/BSA binding capacity and antitumor activity.     

Permanent antimicrobial silicone rubber based on bonding guanidine polymers

Recently, silicone rubber (VMQ) was extensively used in household articles and medical devices. To develop a kind of safe and long‐term antimicrobial VMQ was of great significance. In this work, a kind of vinyl‐contained polyhexamethylene guanidine hydrochloride (VPHMG) was synthesized and used as antimicrobial additive for VMQ. With the increasing of VPHMG addition, the mechanical properties and antimicrobial properties of VMQ‐VPHMG were significantly improved. In particular, the antimicrobial rates against Escherichia coli and Staphylococcus aureus were higher than 99.99% as for 4 wt% of VPHMG addition. Moreover, the surface concentration of VPHMG as well as the antimicrobial rates revealed almost unchanged after being extracted by water and methanol. All the results indicated the vinyl‐contained VPHMG vulcanization and therefore provided the permanent antimicrobial performance for VMQ.     

负反馈诱发神经电振荡的反常现象的复杂动力学

传统观念认为,负反馈容易使系统达到稳定平衡点而正反馈容易引起振荡.本研究基于神经元理论模型,提出了负反馈可以诱发稳定平衡点、也就是静息、变为振荡、也就是放电的新观点.在Hopf分岔点附近,作用在静息上的一次足够大的负向脉冲电流的抑制性刺激,能够引起一个动作电位及随后的衰减振荡的后电位;而能够在后电位上诱发出动作电位的负脉冲电流强度阈值也是衰减振荡的.在模型中,引入具有时滞($\tau$)的负反馈来模拟抑制性自突触,一个动作电位诱发的负反馈自突触电流会作用到比动作电位延迟$\tau$的后电位上.随时滞增加,能够诱发出放电的负反馈增益强度阈值呈现出具有衰减振荡特点的类似多重相干共振的特性,衰减振荡的周期与电流阈值曲线的周期以及分岔点附近的放电周期相关.另外,负反馈还能诱发出放电与静息共存的复杂行为.本研究的结果不仅揭示了负反馈的新的反常调控作用,还有助于理解在现实神经系统中存在的慢抑制性自突触的潜在功能.      

Fractional-order sliding mode control of uncertain QUAVs with time-varying state constraints

Nonlinear Dynamics - In this paper, a novel robust fractional-order sliding mode (FOSM)-based state constrained control scheme is designed for uncertain quadrotor UAVs (QUAVs). Model uncertainties...     

Self-Assembly Behavior and Application of Terphenyl-Cored Trimaltosides for Membrane-Protein Studies: Impact of Detergent Hydrophobic Group Geometry on Protein Stability

Amphipathic agents are widely used in various fields including biomedical sciences. Micelle-forming detergents are particularly useful for in vitro membrane-protein characterization. As many conventional detergents are limited in their ability to stabilize membrane proteins, it is necessary to develop novel detergents to facilitate membrane-protein research. In the current study, we developed novel trimaltoside detergents with an alkyl pendant-bearing terphenyl unit as a hydrophobic group, designated terphenyl-cored maltosides (TPMs). We found that the geometry of the detergent hydrophobic group substantially impacts detergent self-assembly behavior, as well as detergent efficacy for membrane-protein stabilization. TPM-Vs, with a bent terphenyl group, were superior to the linear counterparts (TPM-Ls) at stabilizing multiple membrane proteins. The favorable protein stabilization efficacy of these bent TPMs is likely associated with a binding mode with membrane proteins distinct from conventional detergents and facial amphiphiles. When compared to n-dodecyl-β-d -maltoside (DDM), most TPMs were superior or comparable to this gold standard detergent at stabilizing membrane proteins. Notably, TPM-L3 was particularly effective at stabilizing the human β₂ adrenergic receptor (β₂AR), a G-protein coupled receptor, and its complex with G_s protein. Thus, the current study not only provides novel detergent tools that are useful for membrane-protein study, but also suggests a critical role for detergent hydrophobic group geometry in governing detergent efficacy.     

Electrochemical Signal Enhancer Fabricated Using Lysine‐rich Peptide for Ultrasensitive Electrochemical DNA Biosensor Analysis

Here we present a novel design of electrochemical signal enhancer to increase the detection sensitivity of electrochemical DNA biosensors. The key element of this enhancer is a lysine‐rich peptide (LRP). Its C‐terminal is conjugated with a planer molecule, being able to intercalate into the base pairs of probe‐target duplexes. The lysine residues of LRP are covalently linked with electrochemical signal indicators, acting as an assembly of electrochemical signal indicators. Experimental results proved the feasibility of the novel design. We have examined the effects of the numbers of lysine residues and the hybridization conditions on the detection sensitivity. The optimization procedures have led to significant sensitivity enhancement, and the LOD (limit of detection) has been determined to be 1.4 amol. This enhancer demonstrates advantages of easy operation, simple instrumentation, and high exemption from environmental influence.     

Notable shift of ultraviolet intensity on Sn-doped ZnO nanostructure fabricated by sol–gel method

Sn-doped ZnO (SZO) thin films are deposited by sol–gel dip-coating method with Sn content at 0 at.% and 1–15 at.% with an increment of 2 at.%. The structure and luminescence of the films are investigated. X-ray diffraction results indicate that all the SZO samples show preferential orientation along the (002) direction, and the scanning electron microscope exhibits that the surface morphology of the films change from nanoparticles to nanorods with increasing Sn concentration. X-ray photoelectron spectroscopy reveals that Sn exists as valence of +4 in the matrix. The photoluminescence peaks at 381 and 398 nm are observed in all the samples. The ratio of intensity of peak at 381 nm to that of peak at 398 nm differed markedly. The intensity of peak at 398 nm might be due to the response for the Sn atoms, while the intensity of peak at 381 nm is probably related to the quantum size effect.     

Efficient One‐Pot Synthesis of Hydroxyflavanones by Cyclization and O‐Demethylation of Methoxychalcones

An efficient one‐pot method for the synthesis of hydroxyflavanones is described. Methoxychalcones are treated with 36% HBr to afford cyclization and regioselective O‐demethylation products (2a–i) while cyclization and complete O‐demethylation products (3a–e) are obtained in the presence of 45% HI.