A filter paper-based assay for laboratory evolution of hydrolases and dehydrogenases

Industrially important enzyme classes such as hydrolases and dehydrogenases are often not amenable to laboratory evolution methods due to a lack of sensitive and reliable high-throughput screening (HTS) systems. We developed a conceptually novel and technically simple high-throughput screening system based on detection of volatile aldehydes with the sensitive reagent Purpald (4-amino-3-hydrazino-5-mercapto-1,2,4-triazole). The aldehyde detection takes place on a filter-paper that is pre-soaked with Purpald and covers the microtiter plate. The filter paper-based Purpald assay separates aldehyde detection from biocatalytical conversion and thereby avoids interferences from biological materials with assay components. This screening principle allows, to our knowledge, for the first time to determine the synthetic activity of hydrolases such as lipases and esterases in organic solvents in a 96-well whole-cell format. Its simplicity and cost-effectiveness make the reported HTS system suitable as fast pre-screen in laboratory evolution experiments and for semi-quantitative assays of improved mutants.     

High-throughput selection system for assessing the activity of epoxide hydrolases

Crucial to the success of directed evolution of enantioselective enzymes for use as catalysts in synthetic organic chemistry is the availability of high-throughput assays for determining the enantiopurity of thousands of samples. Although several such ee-assays are available, they entail time and effort, which means that pre-tests for activity have been developed to eliminate non-active mutants prior to ee-screening. Pre-selection systems may be even more efficient and simple to perform. In the present paper an efficient pre-selection test for assessing the activity of epoxide hydrolases has been developed. The bacterial (E. coli) growth on agar plates is shown to be directly related to the presence of active epoxide hydrolases which catalyze the detoxicating hydrolysis of the epoxide substrates. Visual inspection of agar plates is all that is necessary to identify positive (active) hits in large libraries of mutant epoxide hydrolases.     

A mini review on synthesis,properties and applications of deep eutectic solvents

Organic solvents have been of great importance for many chemical synthesis, storage and separation processes. The industries and research laboratories are heavily dependent on organic solvents in bulk; are highly volatile, lipophilic, toxic and causes a number of issues to the human health and the environmental fitness. Neoteric solvents have been proposed as a better substitute to these harmful organic solvents, and scientists have come up with several neoteric solvents in the last three decades, to name a few: ionic liquids (ILs), switchable solvents, bio-based solvents and deep eutectic solvents (DESs). These neoteric solvents attract a great deal of interest from the scientific community due to plenty of possibilities, therefore, they have huge impact and novel studies are reported quite frequently on the same. In this review, we intend to focus to brief on deep eutectic solvents, about their properties, synthesis, promising applications, and how they gradually emerged from ILs and later stood out as a different class of neoteric solvent, which overcomes many shortcomings of ILs. DESs are possibly receptive synthetic compounds and their relationship based on the hydrogen bond donor or acceptor restricts their reactivity and allow to explore in different disciplines of science.     

钴萘酞菁的合成

采用Diels-Alder方法合成了2,3-萘二腈和6,7-二溴-2,3-萘二腈化合物,并以此为前体成功地合成了相应的钴萘酞菁系列化合物---一种新型的功能有机材料。另外还探讨了酞菁形成的机理,并讨论了若干影响因素。这些化合物具有较好的稳定性,在胺类或其它含氮的有机溶剂中有较好的溶解度,如苯胺、二甲基甲酰胺(DMF)或吡啶等。     

Supercritical fluid solvents in organic chemistry

The solubility of complex organic molecules in supercritical solvents is well-established. Under isothermal conditions, slightly above the critical temperature, this phenomenon, as well as most other physical properties of the solvent, exhibits a substantial pressure dependence. This behavior makes supercritical solvents attractive as media for organic reactions, both from a synthetic and a physical organic perspective.

An apparatus has been constructed and techniques have been developed to investigate the effects of supercritical solvent interactions on organic reaction rates and equilibria. The construction and operation of a supercritical reactor is described. Finally the reactor is used to investigate the photoisomerization of trans-stilbene in supercritical carbon dioxide.     

Polyborane reactions in ionic liquids: new efficient routes to functionalized decaborane and o-carborane clusters

In contrast to reactions that have been observed in traditional organic solvents, decaborane olefin-hydroboration and alkyne-insertion reactions have been found to proceed in ionic liquid solvents without the need of a catalyst. These reactions now provide important new, high-yield synthetic pathways to functionalized decaborane and o-carborane clusters.     

Low operational stability of enzymes in dry organic solvents: changes in the active site might affect catalysis

The potential of enzyme catalysis in organic solvents for synthetic applications has been overshadowed by the fact that their catalytic properties are affected by organic solvents. In addition, it has recently been shown that an enzyme's initial activity diminishes considerably after prolonged exposure to organic media. Studies geared towards understanding this last drawback have yielded unclear results. In the present work we decided to use electron paramagnetic resonance spectroscopy (EPR) to study the motion of an active site spin label (a nitroxide free radical) during 96 h of exposure of the serine protease subtilisin Carlsberg to four different organic solvents. Our EPR data shows a typical two component spectra that was quantified by the ratio of the anisotropic and isotropic signals. The isotropic component, associated with a mobile nitroxide free radical, increases during prolonged exposure to all solvents used in the study. The maximum increase (of 43%) was observed in 1,4-dioxane. Based on these and previous studies we suggest that prolonged exposure of the enzyme to these solvents provokes a cascade of events that could induce substrates to adopt different binding conformations. This is the first EPR study of the motion of an active-site spin label during prolonged exposure of an enzyme to organic solvents ever reported.     

Properties and Synthetic Applications of Enzymes in Organic Solvents

Biotransformations already represent an effective and sometimes preferable alternative to chemical synthesis for the production of fine chemicals and optically active compounds. To further widen the versatility of the biological approach, the so-called "nonaqueous enzymology", which now represents an important area of research and biotechnological development, has emerged in the last ten years or so. This new methodology is especially suitable for the modification of precursors of pharmaceutical compounds and fine chemicals, which, in most cases, are insoluble or poorly soluble in water. Even though the idea of carrying out an enzymatic process in organic solvent was initially considered with scepticism, biocatalysis in such media is now investigated and exploited in numerous academic and industrial laboratories. One of the reasons that makes enzymatic catalysis in nonaqueous media so appealing, is the important new properties that enzymes exhibit in organic solvents. For example, they are often more stable and can catalyze reactions that are impossible or difficult in water. Furthermore, enzyme selectivity can also differ from that in water and can change, or even reverse, from one solvent to another. This phenomenon, which can be called "medium engineering", can be exploited as a valid alternative to protein engineering. The first part of this review examines the thermodynamic, kinetic, spectroscopic, and physical approaches that have been adopted to investigate the factors that affect activity, stability, structure, and selectivity of enzymes in organic solvents. These combined studies have brought the understanding of enzyme catalysis in organic solvents to a level almost comparable to that reached for biocatalysis in aqueous media. The second part surveys a number of the synthetic applications of enzymes in organic media, which span from the preparation of milligrams of specifically labeled compounds to the modification of fats on multiton scale and from the preparation of complex key intermediates for the pharmaceutical industry to the synthesis of polymers.     

Green synthesis of three- to five-membered O-heterocycles using ionic liquids

The investigation for replacement of organic solvents in organic synthesis is a growing area of interest due to increasing environmental issues. The use of ionic liquid salts as solvents and catalysts in organic reactions has gained extensive interest. Ionic liquids provided a new environmentally benign and improved alternative to traditional methods in modern synthetic chemistry. The aim of present review is to focus on the applications of ionic liquids for the synthesis of O-heterocycles.     

Ionic liquid: An efficient and recyclable medium for the synthesis of fused six-membered oxygen heterocycles

The investigation for replacement of organic solvents in chemical synthesis is a growing area of interest due to increasing environmental issues. The use of ionic liquid salts as solvents and catalysts in organic reactions has gained extensive interest. Ionic liquids provided a new environmentally benign and improved alternative to traditional methods in modern synthetic chemistry. The aim of present review is to focus on the applications of ionic liquids for the synthesis of fused six-membered oxygen heterocycles.     

Impact of organic solvents on the resolution of synthetic peptides by capillary electrophoresis

The effect of variations in the concentrations of different organic solvents, including acetonitrile, methanol, ethanol, propanol and isopropanol, with aqueous buffer electrolytes of defined composition and pH on the electroosmotic flow velocity, v(EOF), of uncoated fused silica capillaries and on the electrophoretic mobility, mu(e), of synthetic peptides in high-performance capillary electrophoresis (HPCE) has been systematically investigated. In these experiments, the volume fractions of the organic solvent in the aqueous buffer electrolyte were changed from psi = 0.0 to 0.80. The addition of these organic solvents to the aqueous buffer electrolyte reduced the electroosmotic flow (EOF) of the system, but to significantly different extents. For the protic solvents as the alkyl chain of the alcohol increased, at the same volume fraction the greater was the influence on the electroosmotic flow. However, for the aprotic solvent, acetonitrile, the EOF did not change substantially as the volume fraction was varied. The electrophoretic mobility of synthetic peptides under the different buffer electrolyte conditions showed similar trends, confirming that the content and type of the organic modifier can be rationally employed to subtly manipulate the separation selectivity of synthetic peptides. These results, therefore, provide fundamental insight into the experimental options that can be used to maximise resolution of synthetic peptides in HPCE with aqueous buffer-organic solvent mixtures as well as a basis to select optimal binary or ternary buffer electrolyte compositions for the analysis of peptides when hyphenated techniques, such as HPCE-electrospray ionisation mass spectrometry (ESI-MS), are contemplated for the analysis of peptide samples of low abundance as can often be experienced in proteomic investigations.     

Versatile electrochemiluminescent organic emitters

Organic luminophores for electrochemiluminescence (ECL), namely polycyclic aromatic hydrocarbons, have been the first molecules investigated since the beginning of ECL studies. Moving from organic solvents to water-based solutions in view of analytical applications, the attention on ECL emitters shifted to soluble inorganic complexes, which prevailed in both fundamental and applied research. However, the investigation of organic molecules has recently revived owing to new synthetic procedures and concepts. Polymeric nanoparticles, surface functionalisation, aggregation-induced emission (AIE), and thermally activated delayed fluorescence (TADF) sparked the research with renovated interest for organic molecules. Here, we introduce and summarise these new concepts behind organic emitters for ECL.     

Alkylation of Anions on Solid Inorganic Supports: Synthesis of Nitriles,Esters, Phenolic Ethers and Mono-C-Substituted Acetoacetic Esters

The use of inorganic supports as alternatives to organic solvents is becoming increasingly widespread in synthetic organic chemistry^1,2. Such media involve milder reactions conditions, simpler work-up and often higher selectivity. We have undertaken a systematic study of anionic condensations on solid inorganic supports, and we have recently reported that malonic ester anions may be generated on “basic” inorganic supports (silica and alumina gels) where they undergo either intra- or intermolecular alkylation reactions selectively and in high yield³.     

THE SYNTHESIS OF URUSHIOL TITANIUM CHELATE POLYMERS AND THEIR STRUCTURAL CHARACTERISTICS

The synthetic method and structural characteristics of urushiol-titanium chelates (UT) and urushiol-titanium chelate polymer for anticorrosive coatings have been studied.Two kinds of coating films made from UT polymer show excellent physico-mechanical properties and possess good chemical resistance to strong acids and alkalis, many kinds of salt solutions and organic solvents, stable at high temperature.     

Self-Assembling Synthetic Oligopeptide-Based Gelators

Synthetic self-assembling oligopeptide gelators are an important class of compounds which form thermoreversible gels in various organic solvents as well as in aqueous medium. These gels are soft, viscoelastic materials which are envisaged for useful applications in biological and material sciences. The terminally protected self-assembling synthetic tripeptide Boc-Ala-Aib-β-Ala-OMe 1 (Aib: α-aminoisobutyric acid i.e. dimethyl glycine and β-Ala: β-Alanine) forms gels in various organic solvents, whereas its structural analog i.e. the peptide Boc-Ala-Gly-β-Ala-OMe 2 (another self-assembling synthetic tripeptide) fails to form gels under similar conditions and this issue has been addressed. The terminally protected tripeptide Boc-Ala-Val-Ala-OMe 3 has been found to form gels in different aromatic organic solvents. Several structural analogs of peptide 3 [using small structural changes either in protecting groups (at the N or C-terminal position) or in amino acid side chains] have been synthesized, characterized and studied for gelation to address the question how structural changes can regulate the gelation property. Results of the gelation studies indicate that some structural changes are useful to make new peptide gelators with some variations in gelation property and efficiency, while a few structural changes in the protecting groups are really detrimental, leading to abolition the gelation property. These gels are studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-Transform Infrared (FT-IR) spectroscopy and ¹H NMR studies.     

Synthesis and photophysical properties of tetraphenylethylene-based conjugated dendrimers with triphenylamine core

Two new conjugated dendrimers bearing a tetraphenylethylene moiety as dendrons and triphenylamine as a core have been synthesized through a convergent synthetic strategy using threefold Heck/threefold Sonogashira coupling reaction. These dendrimers showed excellent solubility in common organic solvents and emit light in the blue and violet regions.     

含偶氮类非线性光学活性侧基的聚酰亚胺的合成及表征

报道八种含偶氮类非线性光学活性侧基的聚酰亚胺材料的合成及表征．由于采用了新的合成路线，聚合物中的发色团含量最高接近１００％（ｍｏｌ）．预聚体聚酰胺酸易溶于二甲基亚砜、Ｎ，Ｎ 二甲基甲酰胺、Ｎ 甲基 ２ 吡咯烷酮等有机溶剂，成膜性好，亚胺化后得到较高软化点的聚酰亚胺．     

New Generation of Biocatalysts for Organic Synthesis

The use of enzymes as catalysts for the preparation of novel compounds has received steadily increasing attention over the past few years. High demands are placed on the identification of new biocatalysts for organic synthesis. The catalysis of more ambitious reactions reflects the high expectations of this field of research. Enzymes play an increasingly important role as biocatalysts in the synthesis of key intermediates for the pharmaceutical and chemical industry, and new enzymatic technologies and processes have been established. Enzymes are an important part of the spectrum of catalysts available for synthetic chemistry. The advantages and applications of the most recent and attractive biocatalysts—reductases, transaminases, ammonia lyases, epoxide hydrolases, and dehalogenases—will be discussed herein and exemplified by the syntheses of interesting compounds.     

Ion-exchange resins in non-aqueous solvents-III Solvent-uptake properties of ion-exchange resins and related adsorbents

Solvent-uptake properties for several synthetic resins and common adsorbents were determined by the centrifugation method. Data are reported for eighteen different solvents, which include water and the common polar and non-polar organic solvents. The cation-exchange resins are of two varieties: the microreticular or gel type and the macroreticular or porous type. The latter resin being rigid and porous takes up all types of solvents, whereas the former resin, which relies on swelling of the resin matrix, does not take up the nonpolar solvents. Data for the H(+) form and Na(+) form macroreticular resin are compared. Unsulphonated polystyrene-divinylbenzene polymers which possess similar micro- and macroreticular properties to the cation-exchange resins were also studied in the same solvents. The swelling properties of these non-polar resins are compared with each other and with the polar cation resins. Other adsorbents, which are frequently used as supports in chromatography were also examined in the same solvents. Several of these have large average pore diameters and surface areas like the macroreticular resin.