Efficient Enzymatic Cyclization of Disulfide-Rich Peptides by Using Peptide Ligases

Disulfide-rich macrocyclic peptides—cyclotides, for example—represent a promising class of molecules with potential therapeutic use. Despite their potential their efficient synthesis at large scale still represents a major challenge. Here we report new chemoenzymatic strategies using peptide ligase variants—inter alia, omniligase-1—for the efficient and scalable one-pot cyclization and folding of the native cyclotides MCoTI-II, kalata B1 and variants thereof, as well as of the θ-defensin RTD-1. The synthesis of the kB1 variant T20K was successfully demonstrated at multi-gram scale. The existence of several ligation sites for each macrocycle makes this approach highly flexible and facilitates both the larger-scale manufacture and the engineering of bioactive, grafted cyclotide variants, therefore clearly offering a valuable and powerful extension of the existing toolbox of enzymes for peptide head-to-tail cyclization.     

Production of (S)-β-Nitro Alcohols by Enantioselective C−C Bond Cleavage with an R-Selective Hydroxynitrile Lyase

Hydroxynitrile lyase (HNL)-catalysed stereoselective synthesis of β-nitro alcohols from aldehydes and nitroalkanes is considered an efficient biocatalytic approach. However, only one S-selective HNL—Hevea brasiliensis (HbHNL)—exists that is appropriate for the synthesis of (S)-β-nitro alcohols from the corresponding aldehydes. Further, synthesis catalysed by HbHNL is limited by low specific activity and moderate yields. We have prepared a number of (S)-β-nitro alcohols, by kinetic resolution with the aid of an R-selective HNL from Arabidopsis thaliana (AtHNL). Optimization of the reaction conditions for AtHNL-catalysed stereoselective C−C bond cleavage of racemic 2-nitro-1-phenylethanol (NPE) produced (S)-NPE (together with benzaldehyde and nitromethane, largely from the R enantiomer) in up to 99 % ee and with 47 % conversion. This is the fastest HNL-catalysed route known so far for the synthesis of a series of (S)-β-nitro alcohols. This approach widens the application of AtHNL for the synthesis not only of (R)- but also of (S)-β-nitro alcohols from the appropriate substrates. Without the need for the discovery of a new enzyme, but rather by use of a retro-Henry approach, it was used to generate a number of (S)-β-nitro alcohols by taking advantage of the substrate selectivity of AtHNL.     

Synthesis conditions effect on the of photocatalytic properties of MnWO4 for hydrogen production by water splitting

This work aims to study the synthesis conditions effect on the photocatalytic properties of manganese tungstate (MnWO₄) for H₂ production by the water splitting reaction under visible light irradiation. This is achieved by relating the materials characterization and photocatalytic evaluation of MnWO₄ at different synthesis conditions. MnWO₄ was synthesized through a precipitation reaction between Mn²⁺ and (WO₄)^2- ionic species, while adding oleic acid (OA) as surfactant at two concentrations (0.1% and 1% V) and using three different stirring methods: magnetic stirring (AM), ultrasound (US) and high-shear stirring (UT). Characterization was carried out by TGA, XRD, BET surface area, UV–Vis spectroscopy and FESEM. XRD patterns confirm the wolframite structure of MnWO₄. BET surface area increased by using UT stirring. UV–Vis spectroscopy results revealed indirect transition Eg values of ≈2 eV, favorable for the MnWO₄ photoactivation under visible light irradiation. During the photocatalytic evaluation, sample 1%-UT produced the highest H₂ amount among all samples with a value of 72 μmolH₂g⁻¹, which was far higher compared to WO₃, which was taken as a reference photocatalyst.     

Super-oleophilicity Co-doping Co2+/F-/TiO2 one-dimensional nanotubes for photocatalytic denitrification of light oil

In this study, a simple hydrothermal synthesis method was adapted for the preparation of Co-doping Co²⁺/F^-/TiO₂ nanotubes photocatalyst, and the micro-nano structure of catalysts prepared by biomimetic technology which makes the catalyst have super-oleophilicity property. Co²⁺/F^-/TiO₂ revealed improved photocatalytic performance for denitrification of light oil compared to single TiO₂ photocatalysts. The enhance of photocatalytic activity can be attributed to narrowing the band gap, increasing the light response wavelength and exposing more highly active crystal surfaces due to synergistic effects of Co²⁺ and F^? in the photocatalyst.     

Biosynthesis of silver nanoparticles in collagen gel improves their medical use in periodontitis treatment

Silver nanoparticles (AgNP) suspensions were biosynthesized by silver ions reduction in the presence of collagen, a nontoxic, organic polymer, intending to improve their medical use in periodontitis treatment. Spectrophotometric measurements showed a time- and concentration-dependent increase of AgNP formation in each suspension variant. Transmission electron microscopy revealed spherical morphology of AgNP in collagen and their mean diameter size was around 30?nm. The particle size distribution and zeta potential values of AgNP in collagen were determined by dynamic light scattering measurements. The surface charge of AgNP in collagen was positive, while commercial AgNP stabilized in citrate had negative surface charge. In vitro cytotoxicity testing of AgNP in collagen showed that they were biocompatible with human gingival fibroblasts in a wider range of concentrations than commercial nanoparticles. The antibacterial activity of AgNP in collagen against two pathogenic strains present in the periodontal pocket was dose-dependent and higher than that of AgNP in citrate. All these results demonstrated that AgNP prepared in collagen gel had improved properties, like small diameter, positive surface charge, high biocompatibility in human gingival fibroblasts, efficiency against bacterial growth and, thus, better therapeutic potential in periodontal disease treatment.     

可见光催化需氧氧化在有机合成中的应用

可见光催化具有无污染、节能、优秀的官能团兼容性及良好的化学选择性,目前已经作为重要的有机合成手段之一,绿色化学在氧气与可见光的结合下得到了极大的发展,本文从白藜芦醇及其类似物的合成、芳构化反应和α位醛酮羰基的取代反应催化几个方面简略阐述了可见光催化需氧氧化在有机合成中的应用方式。     

Predictive association of metal–organic systems in the solid-state: the molecular electrostatic potential based approach

Designing crystalline solids with improved properties or performances remains a challenging task, despite great strides that have been made within the field of crystal engineering since its birth several decades ago. Herein, we are bringing examples that illustrate recent successes in taking supramolecular synthetic guidelines from the organic crystal engineering and adjusting those to metal-containing systems, particularly to the lower-dimensional ones. The versatility of calculated molecular electrostatic potential (MEP) as a new crystal engineering tool is demonstrated.     

碳化二亚胺类抗水解稳定剂Bio-SW100的合成与应用

以硫脲法工艺路线合成了单体型碳化二亚胺抗水解稳定剂SW-100,通过红外光谱、元素分析以及液相色谱考察了产物的结构、纯度。红外光谱和元素分析确定了合成产物结构正确,液相色谱确定产物纯度达到99%以上。在结构和纯度确定的基础上,将合成产物添加到聚乳酸中进行水解性能测试。结果表明,在1%添加量下聚乳酸拉伸强度保持率较纯树脂提高了80%。     

Room temperature response and enhanced hydrogen sensing in size selected Pd-C core-shell nanoparticles: Role of carbon shell and Pd-C interface

In the present work, the effect of carbon shell around size selected palladium (Pd) nanoparticles on hydrogen (H₂) sensing has been studied by investigating the sensing response of Pd-C core-shell nanoparticles having a fixed core size and different shell thickness. The H₂ sensing response of sensors based on Pd and Pd-C nanoparticles deposited on SiO₂ and graphene substrate has been measured over a temperature range of 25 °C–150 °C. It is observed that Pd-C nanoparticle sensor shows higher sensitivity with increase in shell thickness and faster response/recovery in comparison to that of Pd nanoparticle samples. Pd-C nanoparticles show room temperature H₂ sensitivity in contrast to Pd nanoparticles which respond only at higher temperatures. Role of carbon shell is also understood by investigating H₂ sensing properties of Pd and Pd-C nanoparticles on graphene substrates. These results show that higher catalytic activity and electronic interaction at Pd-C interface, a complete coverage and protection of Pd surface by carbon and presence of structural defects in nanoparticle core are important for room temperature and higher sensing response.     

Catalytic hydrogenation of CO2 from 600 MW supercritical coal power plant to produce methanol: A techno-economic analysis

Electricity and water from renewable hydropower plant are used as input for electrolysis unit to generate hydrogen, while CO₂ is captured from 600 MW supercritical coal power plant using post-combustion chemical solvent based technology. The captured CO₂ and H₂ generated through electrolysis are used to synthesize methanol through catalytic thermo-chemical reaction. The methanol synthesis plant is designed, modeled and simulated using commercial software Aspen Plus^®. The reactor is analyzed for two widely adopted kinetic models known as Graaf model and Vanden-Bossche (VB) model to predict the methanol yield and CO₂ conversion. The results show that the methanol reactor based on Graaf kinetic model produced 0.66 tonne of methanol per tonne of CO₂ utilized which is higher than that of the VB kinetic model where 0.6 tonne of methanol is produced per tonne of CO₂ utilized. The economic analysis reveals that 1.2 billion USD annually is required at the present cost of both H₂ production and CO₂ abatement to utilize continuous emission of 3.2 million tonne of CO₂ annually from 600 MW supercritical coal power unit to synthesize methanol. However, sensitivity analysis indicates that methanol production becomes feasible by adopting anyone of the route such as by increasing methanol production rate, by reducing levelised cost of hydrogen production, by reducing CO₂ mitigation cost or by increasing the current market selling price of methanol and oxygen.