A convenient route to 1,3-diynes using ligand-free Cadiot–Chodkiewicz coupling reaction at room temperature under aerobic conditions

In this study, we report a copper-catalyzed ligand-free Cadiot–Chodkiewicz coupling reaction. No additives or ligands are required for this Cu-catalyzed C(sp)–C(sp) coupling reaction of terminal alkynes with alkynyl halides. The low cost of copper catalyst, excellent yield of the products, suppression of side-products and mild reaction conditions are the major advantages of this protocol.     

Molecular volume calculation using AM1 semi-empirical method toward diffusion coefficients and electrophoretic mobility estimates in aqueous solution

Diffusion coefficients and electrophoretic mobility are two important physicochemical parameters used in mass transport phenomenon studies. The volume of the solute is required to determine or estimate these parameters. Classical methods, such as the LeBas method are commonly used. However, although valid, this method may represent a boring and time-consuming task, depending on the nature and number of compounds to be calculated. In this study, the volumes of a series of neutral and charged substances of the main functional groups present in organic molecules, amino acids, drugs and diverse compounds, such as cytosine and glucose, were calculated according to the LeBas method (V_M) and the AM1 semi-empirical method, V_W(AM1). The latter showed to be statistically coincident with the former. Employed as a pure value or corrected by the LeBas molar volume, the AM1 molecular volume was also demonstrated to estimate the diffusion coefficients in infinite aqueous dilution within an acceptable average error, according to the Othmer–Thakar, Wilke–Chang and Hayduk–Laudie methods, as well as the electrophoretic mobility of charged substances, such as carboxylates and protonated amines. According to these results, the AM1 method was seen to be statistically valid to calculate molecular volume. Many advantages in the construction of most diverse structures were noted, as well as a reduction in time and an increase in the quality of the information, when run on molecular modeling software.     

Adhesive transfer of thin viscoelastic films

Micellar suspensions of acrylic diblock copolymers are excellent model materials for studying the adhesive transfer of viscoelastic solids. The micellar structure is maintained in films with a variety of thicknesses, giving films with a well-defined structure and viscoelastic character. Thin films were cast onto elastomeric silicone substrates from micellar suspensions in butanol, and the adhesive interactions between these coated elastomeric substrates and a rigid indenter were quantified. By controlling the adhesive properties of the film/indenter and film/substrate interfaces we were able to obtain very clean transfer of the film from the substrate to the portion of the glass indenter with which the film was in contact. Adhesive failure at the film/substrate interface occurs when the film/indenter interface is able to support an applied energy release rate that is sufficient to result in cavity nucleation at the film/substrate interface. Cavity formation is rapidly followed by delamination of the entire region under the indenter. The final stage in the transfer process involves the failure of the film that bridges the indenter and the elastomeric substrate. This film is remarkably robust and is extended to three times its original width prior to failure. Failure of this film occurs at the periphery of the indenter, giving a transferred film that conforms to the original contact area between the indenter and the coated substrate.     

Morphological characterization of elastin-mimetic block copolymers utilizing cryo- and cryoetch-HRSEM.

Elastin-mimetic block copolymers were produced by genetic engineering. Genetically driven synthesis permitted control of the final physiochemical characteristics of the block copolymers. We designed BB and BAB block copolymers in which the A-block was hydrophilic and the B-block was hydrophobic. By designing the copolymers in this manner, it was proposed that they would self-assemble into micellar aggregates that, at high concentration, would form thermoreversible hydrogels. To analyze the three-dimensional fine surface morphology of the copolymers, to the resolution level of a few nanometers, we employed cryo-HRSEM. This method provided vast expanses of the specimen in its frozen hydrated state for survey. In our initial cryo-HRSEM studies, we observed the protein filaments and micelles surrounded by lakes of vitreous ice. Upon examination at low and intermediate magnifications, there was an extensive honeycomb-like filamentous network. To delineate the fine morphology of the hydrogel network at high magnification and to greater depths, we cryoetched away unbound water from the sample surface, in high vacuum, prior to chromium deposition. By using this technique, we were able to visualize for characterization purposes the fine fibril networks formed from the micellar aggregates over the surface of the hydrogel.     

Studies on the reactivity of phenyliodonium ylide of 2-hydroxy-1,4-naphthoquinone: reactions with indole derivatives and other C-nucleophiles

[reaction: see text] Thermal decomposition of phenyliodonium ylide of 2-hydroxy-1,4-naphthoquinone (lawsone) in the presence of indole derivatives affords 3-acylated indoles existing in their enol forms, through a ring contraction and alpha,alpha'-dioxoketene formation reaction. The same reactants afford 3-(3-indolyl)-2-hydroxy-1,4-naphthoquinones in a copper-catalyzed reaction. Enamines, among other C-nucleophiles tested, give analogous results.     

Stir bar sorptive extraction based on restricted access material for the direct extraction of caffeine and metabolites in biological fluids

A biocompatible stir bar sorptive extraction (SBSE) device was prepared using an alkyl-diol-silica (ADS) restricted access material (RAM) as the SBSE coating. The RAM-SBSE bar was able to simultaneously fractionate the protein component from a biological sample, while directly extracting caffeine and its metabolites, overcoming the present disadvantages of direct sampling in biological matrices by SBSE, such as fouling of the extraction coating by proteins. Desorption of the analytes was performed by stirring the bar in a water/ACN mixture (3/1, v/v) and subsequently reconcentrating the sample solution in water to enable HPLC-UV analysis to be performed. The limit of detection, based on a signal to noise ratio of 3, for caffeine was 25 ng/mL in plasma. The method was confirmed to be linear over the range of 0.5-100 microg/mL of caffeine with an average linear coefficient (R2) value of 0.9981. The injection repeatability and intra-assay precision of the method were evaluated over ten injections, resulting in a %RSD of approximately 8%. The RAM-SBSE device was robust (>50 extraction in plasma without significant signal loss) and simple to use, providing many direct extractions and subsequent determination of caffeine and its metabolites in biological fluids. In contrast to existing sample preparation methods for the analysis of caffeine and selected metabolites in biological fluids, this feasibility study using a biocompatible SBSE approach was advantageous in terms of simplifying the sample preparation procedures.     

Liquid chromatography–mass spectrometry based global metabolite profiling: A review

Untargeted, global metabolite profiling (often described as metabonomics or metabolomics) represents an expanding research topic and is, potentially, a major pillar for systems biology studies. To obtain holistic metabolic profiles from complex samples, such as biological fluids or tissue extracts, requires powerful, high resolution and information-rich analytical methods and for this spectroscopic technologies are generally used. Mass spectrometry, coupled to liquid chromatography (LC–MS), is increasingly being used for such investigations as a result of the significant advances in both technologies over the past decade. Here we try to critically review the topic of LC–MS-based global metabolic profiling and describe and compare the results offered by different analytical strategies and technologies. This review highlights the current challenges, limitations and opportunities of the current methodology.     

A canted antiferromagnetic ordered phase of cyanido-bridged Mn(III)(2)Re(IV) single-chain magnets

A new cyanido-bridged Re(IV)-Mn(III) heterometallic 1D system, [Mn(III)(5-Me-saltmen)](2)[Re(IV)Cl(4)(CN)(2)]·3CH(3)CN (), was designed and structurally characterized. Interchain interactions stabilize a canted antiferromagnetic ordered state below 6.2 K that does not prevent slow relaxation of the magnetization reminiscent of the single-chain magnet properties of the individual chains.     

Fourier transformed infrared spectral investigations of molecular interactions in propionic acid–2-propanol binary system

FTIR spectra of propionic acid (PA), 2-propanol (PROH) and its binary mixtures with varying molefraction of the PA were recorded in the region 500–3500 cm^?1, to investigate the formation of hydrogen bonded complexes in a mixed system. The observed features in ν(CO), ν(CO) and δ(COH) of PA, ν(CO) of PROH and δ(COH) of PA + PROH have been explained in terms of the hydrogen bonding interactions between PROH and PA and dipole–dipole interaction. The dipole moment derivative for the above mentioned vibrational modes have also been predicted from the integrated absorbance. The intrinsic linewidth for the vibrational modes ν(CO) and δ(COH) of PA has been elucidated using Bondarev and Mardaeva model.