Improvements of Tolerance to Stress Conditions by Genetic Engineering in Saccharomyces Cerevisiae during Ethanol Production

Saccharomyces cerevisiae, industrial yeast isolate, has been of great interest in recent years for fuel ethanol production. The ethanol yield and productivity depend on many inhibitory factors during the fermentation process such as temperature, ethanol, compounds released as the result of pretreatment procedures, and osmotic stress. An ideal strain should be able to grow under different stress conditions occurred at different fermentation steps. Development of tolerant yeast strains can be achieved by reprogramming pathways supporting the ethanol metabolism by regulating the energy balance and detoxicification processes. Complex gene interactions should be solved for an in-depth comprehension of the yeast stress tolerance mechanism. Genetic engineering as a powerful biotechnological tool is required to design new strategies for increasing the ethanol fermentation performance. Upregulation of stress tolerance genes by recombinant DNA technology can be a useful approach to overcome inhibitory situations. This review presents the application of several genetic engineering strategies to increase ethanol yield under different stress conditions including inhibitor tolerance, ethanol tolerance, thermotolerance, and osmotolerance.     

Three-dimensional Octameric Assembly of Icosahedral M13 Units in [Au8Ag57(Dppp)4(C6H11S)32Cl2]Cl and its [Au8Ag55(Dppp)4(C6H11S)34][BPh4]2 Derivative

The high-dimensional (that is, three-dimensional (3D)) assembly of nanomaterials is an effective means of improving their properties; however, achieving this assembly at the atomic level remains challenging. Herein, we obtained a novel nanocluster, [Au₈Ag₅₇(Dppp)₄(C₆H₁₁S)₃₂C_l2]Cl (Dppp=1,3-bis(diphenylphosphino)propane) showing a 3D octameric assembly mode involving the kernel penetration of eight complete icosahedral Au@Ag₁₀Au₂ units for the first time. The atomically precise structure was determined by single-crystal X-ray diffraction, and further confirmed by thermogravimetric analysis, X-ray photoelectron spectroscopy, and electrospray ionization mass spectrometry measurements. Furthermore, ligand-induced transformation prompted the conversion of [Au₈Ag₅₇(Dppp)₄(C₆H₁₁S)₃₂Cl₂]Cl, with complete octameric fusion into [Au₈Ag₅₅(Dppp)₄(C₆H₁₁S)₃₄][BPh₄]₂, with incomplete octameric fusion. These observations will hopefully facilitate further research on the assembly of M₁₃ nanobuilding blocks.     

面向脑机接口的犹他神经电极技术

A human brain is composed of a large number of interconnected neurons forming a neural network. To study the functional mechanism of the neural network, it is necessary to record the activity of individual neurons over a large area simultaneously. Brain-computer interface (BCI) refers to the connection established between the human/animal brain and computers/other electronic devices, which enables direct interaction between the brain and external devices. It plays an important role in understanding, protecting, and simulating the brain, especially in helping patients with neurological disorders to restore their impaired motor and sensory functions. Neural electrodes are electrophysiological devices that form the core of BCI, which convert neuronal electrical signals (carried by ions) into general electrical signals (carried by electrons). They can record or interfere with the state of neural activity. The Utah Electrode Array (UEA) designed by the University of Utah is a mainstream neural electrode fabricated by bulk micromachining. Its unique three-dimensional needle-like structure enables each electrode to obtain high spatiotemporal resolution and good insulation between each other. After implantation, the tip of each electrode affects only a small group of neurons around it even allowing to record the action potential of a single neuron. The availability of a large number of electrodes, high quality of signals, and long service life has made UEA the first choice for collecting neuronal signals. Moreover, UEA is the only implantable neural electrode that can record signals in the human cerebral cortex. This article mainly serves as an introduction to the construction, manufacturing process, and functioning of UEA, with a focus on the research progress in fabricating high-density electrode arrays, wireless neural interfaces, and optrode arrays using silicon, glass, and metal as that material of construction. We also discuss the surface modification techniques that can be used to reduce the electrode impedance, minimize the rejection by brain tissue, and improve the corrosion resistance of the electrode. In addition, we summarize the clinical applications where patients can control external devices and get sensory feedback by implanting UEA. Furthermore, we discuss the challenges faced by existing electrodes such as the difficulty in increasing electrode density, poor response of integrated wireless neural interface, and the problems of biocompatibility. To achieve stability and durability of the electrode, advancements in both material science and manufacturing technology are required. We hope that this review can broaden the scope of ideas for the development of UEA. The realization of a fully implantable neural microsystem can contribute to an improved understanding of the functional mechanisms of the neural network and treatment of neurological diseases.     

Determination of carbapenems in water samples by UHPLC–MS/MS

A rapid and reliable method for the detection of five carbapenems (biapenem, imipenem, doripenem, meropenem, and faropenem) in water was developed and validated. After acidification of water samples with acetic acid, carbapenems were isolated using a Bond Elut PPL cartridge. The target compounds were separated using ultra high performance liquid chromatography with a chromatographic run time of 5 min and detected on a triple quadrupole mass spectrometer operated in positive electrospray ionization and multiple reaction monitoring mode. Mean recoveries were in the range of 76.6–106.5%, with satisfactory intraday and interday relative standard deviations lower than 10.0 and 10.8%, respectively. The limits of detection and quantification were in the ranges of 0.05–0.2 µg/L and 0.1–0.5 µg/L, respectively, depending on the analyte. The proposed method was applied to the analysis of river samples and wastewater samples from swine farms, and no carbapenems were detected in the collected samples.     

碳化硅量子点荧光标记技术及其生物学应用

通过一步法完成SiC量子点的合成和表面改性,并对其微观结构、光学性质和理化性质进行了表征,结果表明该量子点半径小于激子波尔半径,导致了量子限制效应现象而产生光致发光,通过对其红外光谱的分析发现碳化硅量子点表面既已耦合了巯基,因此该量子点可以作为量子点标记技术中又一种新型的标记材料,然后用SiC量子水相溶液对有、无根皮苷环境下的串珠镰刀菌进行标记并长时程荧光成像,同时让已成功标记的该菌侵染苹果植株幼苗,试验表明,根皮苷能够促进串珠镰刀菌的生长,主要表现在菌落成长的速度和数量上,进一步研究发现,串珠镰刀菌生长态势随周围环境中根皮苷含量的增加而更趋旺盛,此外串珠镰刀菌对苹果幼苗侵染的动态示踪过程表明幼苗的第一感染部位为根毛区.     

聚吡咯/氧化钒@硫正极材料制备及其在锂硫电池中的应用

采用聚吡咯/中空氧化钒@硫(PPy/H-V2O5@S)作为锂硫电池正极,其中间层极性V2O5中空球壳为硫的体积膨胀提供足够的空间并通过化学键固定多硫化物,外层聚吡咯对多硫化物的扩散起双重固定作用,并作为导电骨架提高正极导电性,共同提高正极对硫化物的固定作用,提高电池循环稳定性.PPy/H-V2 O5@S正极在0.5C、1C、2C、4C电流密度300次循环后,放电容量分别保持在825.6 mA·h·g-1、673.6 mA·h·g-1、625.1mA·h·g-1、583.3 mA·h·g-1,库伦效率保持在98;以上,展现出极好的循环稳定性.     

Crystal structure and computational studies of (E)-1-(benzo[b]thiophen-3-yl)-N-(4-ethoxyphenyl)methanimine

Crystallography Reports - The title compound, C17H15NOS, crystallizes in the orthorhombic sp. gr. Pca21. Two molecules in the asymmetric unit have similar structure. Crystal structure contains weak...     

Viscoelastic materials with a double porosity structure

This paper in concerned with the linear theory of materials with memory that possess a double porosity structure. First, the formulation of the initial-boundary-value problem is presented. Then, a uniqueness result is established. The semigroup theory of linear operators is used to prove existence and continuous dependence of solutions. A minimum principle for the dynamical theory is also derived.     

New 19F NMR methodology reveals structures of molecules in complex mixtures of fluorinated compounds

Although the number of natural fluorinated compounds is very small, fluorinated pharmaceuticals and agrochemicals are numerous. ¹⁹F NMR spectroscopy has a great potential for the structure elucidation of fluorinated organic molecules, starting with their production by chemical or chemoenzymatic reactions, through monitoring their structural integrity, to their biotic and abiotic transformation and ultimate degradation in the environment. Additionally, choosing to incorporate ¹⁹F into any organic molecule opens a convenient route to study reaction mechanisms and kinetics. Addressing limitations of the existing ¹⁹F NMR techniques, we have developed methodology that uses ¹⁹F as a powerful spectroscopic spy to study mixtures of fluorinated molecules. The proposed ¹⁹F-centred NMR analysis utilises the substantial resolution and sensitivity of ¹⁹F to obtain a large number of NMR parameters, which enable structure determination of fluorinated compounds without the need for their separation or the use of standards. Here we illustrate the ¹⁹F-centred structure determination process and demonstrate its power by successfully elucidating the structures of chloramination disinfectant by-products of a single mono-fluorinated phenolic compound, which would have been impossible otherwise. This novel NMR approach for the structure elucidation of molecules in complex mixtures represents a major contribution towards the analysis of chemical and biological processes involving fluorinated compounds.

¹⁹F-centred NMR structure determination protocol alleviates the need for compound separation. Disinfection byproducts of chloramination were unraveled by analyzing the reaction pathways of a single fluorinated molecule.