3D‐printed Portable Platform for Mechanized Handling and Injection of Microvolumes Coupled to Electrochemical Detection

We present a low‐cost mechanized system fabricated using fused deposition modelling 3D‐printing technology to manipulate microvolumes and perform injections on an electrochemical cell in wall‐jet configuration. As a proof‐of‐concept, the amperometric detection of paracetamol (model analyte) on a screen‐printed electrode using 0.5 μL aliquots resulted in highly reproducible responses (RSD <3 %). Moreover, handling of microliter aliquots of butylhydroxytoluene (phenolic antioxidant) and 2,2‐diphenyl‐2‐picrylhydrazyl (DPPH) to promote the radical‐scavenging reaction to determine antioxidant capacity by electrochemical detection of residual DPPH was demonstrated (time‐controlled reaction). A final application of the system was devoted to the analysis of cocaine and a common adulterant found in seized samples. The mechanized 3D‐printed analytical platform is capable to execute diverse sample preparation steps on board by handling microliter aliquots and subsequent electrochemical detection. 3D‐printing technology enabled the fabrication of a versatile and low‐cost (<U$200) mechanized system accessible to general chemistry labs.     

Computer‐Assisted 3D Structure Elucidation (CASE‐3D): The Structural Value of 2JCH in Addition to 3JCH Coupling Constants

We present a method to use long‐range CH coupling constants to derive the correct diastereoisomer from the molecular constitution of small molecules. A set of 79 ²J_CH and ³J_CH values collected from a single HSQMBC experiment on a sample of strychnine were used in the CASE‐3D (computer‐assisted 3D structure elucidation) protocol. In addition to the most commonly used ³J_CH coupling constants, the subset of 32 ²J_CH values alone showed an excellent degree of configuration selection. The study is mainly based on comparison of DFT‐calculated ^2,3J_CH values with experimental ones, critical for the case of ²J_CH. But the configuration selection also works well using ³J_CH values predicted from a semi‐empirical Karplus‐based equation limited to H?C?C?C fragments. The robustness, shown using strychnine as a proof of concept, makes the J‐based CASE‐3D analysis a viable option for the application in fields such as peptide and carbohydrate research, organic synthesis, natural‐product identification and analysis, as well as medicinal chemistry.     

Pretreatment of alfalfa stems by wood decay fungus <Emphasis Type="Italic">Perenniporia meridionalis</Emphasis> improves cellulose degradation and minimizes the use of chemicals

Enzymes of wood decay fungi can be exploited to degrade lignocellulosic wastes for sustainable production of bioethanol. Perenniporia meridionalis was tested for growing at different temperatures on stems of alfalfa. The process aims to produce fermentable sugars and can be divided into the following steps: (1) fungal treatment to degrade lignin, (2) microwave pretreatment in water or in phosphoric acid, and (3) enzymatic hydrolysis of cell wall carbohydrates. Thermogravimetric analysis assessed the biomass content of cellulose and lignin after the fungal treatment. Throughout all steps HPLC analysis of sugars, oligomers and by-products (furfural, hydroxymethylfurfural and acids) was performed. Scanning electron microscopy was used for visual inspection and characterization of the experimental material during the treatments. The P. meridionalis pretreatment enhanced the yield of fermentable sugars obtainable by enzymatic hydrolysis in samples subjected to microwave-assisted pretreatment in water, but not in those in acid medium. This is probably related to the very selective removal of lignin by P. meridionalis, exposing cellulose fibers without depleting them. Furthermore, microwave treatment in water produced less byproducts than in acid medium. By exploiting the P. meridionalis lignin degradation is therefore possible to avoid H₃PO₄ use during the alfalfa stem pre-treatment, reducing economic and environmental impacts.     

A study of the relationships between unpaired electron density, spin-density and cumulant matrices

This work describes the derivation of simple relationships between the density matrix of effectively unpaired electrons and the spin-density matrix in N-electron systems. The link between both devices turns out to be the one-electron matrix arising from the diagonal contraction of the cumulant matrix corresponding to the second-order reduced density matrix. We study some features of this contracted matrix, showing its usefulness to describe the electronic correlation. Numerical determinations performed in selected systems with different spin symmetries confirm the theoretical predictions.     

Pyrrole macrocyclic ligands for Cu-catalyzed asymmetric Henry reactions

New chiral perazamacrocycles containing four pyrrole rings have been synthesized by the [2+2] condensation of (R,R)-diaminocyclohexane and 5,5'-(alkane-2,2-diyl)bis(1H-pyrrole-2-carbaldehydes). These macrocycles, differing for the alkyl/aryl meso-substituents, were used as ligands in the copper-catalyzed Henry reactions of aromatic and aliphatic aldehydes with nitroalkanes. In the optimized experimental conditions, the condensations of nitromethane and aromatic and aliphatic aldehydes in the presence of catalytic amounts of copper diacetate and methyl-substituted macrocyclic ligand (2:1 ratio) in ethanol at room temperature provided products often with high enantiomeric excesses (up to 95% ee). The positive influence of the macrocyclic structure on the efficiency/enantioselectivity of the catalytic system was demonstrated by comparison with the outcomes of Henry reactions performed using analogous macrocyclic ligands (trianglamines) and open-chain ligands derived from (R,R)-diaminocyclohexane.     

A fast and reliable method for the quantitative determination of benzimidazoles and metabolites in milk by LC-MS/MS with on-line sample treatment

A method to detect the presence of common wheat in durum wheat flour samples was developed and tested. Flour samples, or ground wheat samples, were digested by pepsin and chymotrypsin, and the peptide mixture obtained was analyzed by LC/ESI-MS and LC/ESI-MS/MS, which led to the identification of two marker peptides. One peptide was coded only in the DD genome, and thus present only in common wheat; the second was present in all wheat samples (both common and durum), so it was used as marker of the total wheat content. The ratio of the chromatographic areas of these two peptides, as determined by LC/ESI-MS, was related to the proportion of common wheat in the sample using a calibration curve that was constructed with standards of known composition. The proportions of common wheat in samples obtained by mixing different common and durum wheat varieties were accurately determined by this method. Finally, the method was applied in a survey of several durum wheat flour brands present on the Italian market. The results of the survey revealed that contamination of durum wheat flour with common wheat is commonplace.     

2-Acetylpyridine- and 2-benzoylpyridine-derived thiosemicarbazones and their antimony(III) complexes exhibit high anti-trypanosomal activity

Complexes [Sb(2Ac4oClPh)Cl₂] (1), [Sb(2Ac4oFPh)Cl₂] (2), [Sb(2Ac4oNO₂Ph)Cl₂] (3), [Sb(2Bz4oClPh)Cl₂] (4), [Sb(2Bz4oFPh)Cl₂] (5) and [Sb(2Bz4oNO₂Ph)Cl₂] (6) were obtained with 2-acetylpyridine-N(4)-ortho-chlorophenyl thiosemicarbazone (H2Ac4oClPh) and its N(4)-ortho-fluor (H2Ac4oFPh) and N(4)-ortho-nitro (H2Ac4oNO₂Ph) analogues, and with the corresponding 2-benzoylpyridine-derived thiosemicarbazones (H2Bz4oClPh, H2Bz4oFPh, H2Bz4oNO₂Ph). The studied compounds are excellent inhibitors of Trypanosoma cruzi growth. H2Bz4oClPh and complexes (4) and (1) were the most trypanosomicidal.Upon coordination of H2Ac4oClPh to antimony(III) in 1, the therapeutic index (TI) goes from 10.58 to 14.35. However, the best values of TI were found for H2Bz4oClPh (TI = 1240) and H2Ac4oNO₂Ph (TI = 773). Structure-activity relationship (SAR) studies did not allow the establishment of correlations between the anti-trypanosomal activity and physico-chemical parameters, but correlations were found between the cytotoxicities and physico-chemical properties.