Molecularly imprinted polymer grafted to porous polyethylene frits: a new selective solid-phase extraction format

In this paper, a novel format for selective solid-phase extraction based on a molecularly imprinted polymer (MIP) is described. A small amount of MIP has been synthesized within the pores of commercial polyethylene (PE) frits and attached to its surface using benzophenone (BP), a photo-initiator capable to start the polymerisation from the surface of the support material. Key properties affecting the obtainment of a proper polymeric layer, such as polymerisation time and kind of cross-linker were optimised. The developed imprinted material has been applied as a selective sorbent for cleaning extracts of thiabendazole (TBZ), as model compound, from citrus samples. The use of different solvents for loading the analyte in the imprinted frits was investigated, as well as the binding capacity of the imprinted polymer. Imprinted frits showed good selectivity when loads were performed using toluene and a linear relationship was obtained for the target analyte up to 1000 ng of loaded analyte. Prepared composite material was applied to the SPE of TBZ in real samples extracts, showing an impressive clean-up ability. Calibrations showed good linearity in the concentration range of 0.05-5.00 μg g(-1), referred to the original solid sample, and the regression coefficients obtained were greater than 0.996. The calculated detection limit was 0.016 μg g(-1), low enough to satisfactory analysis of TBZ in real samples. RSDs at different spiking levels ranged below 15% in all the cases and imprinted frits were reusable without loss in their performance.     

Application of Modified Tafel Analysis to the Identification of Corrosion Products on Archaeological Metals Using Voltammetry of Microparticles

An operational modification of Tafel analysis, applied to the intermediate region of square wave voltammetric curves, devoted to the identification of corrosion products on archaeological metal, is described. This is based on the voltammetry of microparticles methodology using conventional abrasive conditioning of the electrode, as well as ‘one‐touch’ and layer‐by‐layer techniques. The proposed methodology is applied to the identification of copper and silver corrosion products in mediaeval silver‐copper coins from the Libertad street hoard in Valencia (Spain).     

Simultaneous Differential Pulse Adsorptive Stripping Determination of Imipramine and Its Metabolite Desipramine by the PLS‐1 Multivariate Method

A method, using stripping differential pulse voltammetry, for the simultaneous determination of Imipramine and its metabolite Desipramine is reported. Both compounds produce, at glassy carbon electrode, an electrochemical signal due to an adsorptive‐oxidative process. The voltammograms show a very high overlap degree between IM and DE peaks. The multivariate calibration method PLS‐1 was employed for the simultaneous determination of both compounds. An experimental design together with the response surface methodology has been used to find the optimum experimental conditions. The developed procedure has been utilized in the analysis of fortified human serum samples with good recovery values for each analyte.     

Synthesis,characterization, crystal structure and cytotoxicity of 2,4-bis(selenomethyl)quinazoline

Organoselenium compounds have already been reported to be good anticarcinogenic candidates. A new selenoquinazoline derivative, 2,4-bis(selenomethyl)quinazoline (compound 1), has been synthesized, spectroscopically characterized and its crystal structure has been studied. An intermolecular coupling between C₂ and \( {\text{H}}_{5}^{\prime } \) in the Heteronuclear Multiple Bond Correlation (HMBC) experiment has been observed. Assuming that the head-to-tail overlap of parallel molecules (as identified by X-ray diffraction) remains in solution to give bimolecular entities, the π–π interaction enables heteronuclear coupling between the former atoms with a three-bond distance [C₂···(π–π)···\( {\text{C}}_{5}^{\prime } \)–\( {\text{H}}_{5}^{\prime } \)]. The crystal structure of compound 1 has been solved by X-ray diffraction. It crystallizes in triclinic system, space group P?1. Unit cell parameters are a = 7.4969(7) Å, b = 8.7008(8) Å, c = 10.1666(9) Å, α = 110.215(2)°, β = 90.354(2)°, γ = 115.017(1)°. Linear chains in crystals of compound 1 are generated by C–H···Se and Se···Se bonds between molecules. Furthermore, head-to-tail overlap of parallel molecules, in which π–π interactions can occur, is observed. Compound 1 exhibited a cytotoxic effect in all of the evaluated tumoral cell lines and showed a higher cytotoxic effect in colon and breast cancer cell lines than etoposide, which was used as a reference compound.     

In-source fragmentation and accurate mass analysis of multiclass flavonoid conjugates by electrospray ionization time-of-flight mass spectrometry

In-source collision-induced dissociation (CID) fragmentation features of multiclass flavonoid glycoconjugates were examined using liquid chromatography electrospray time-of-flight mass spectrometry. Systematic experiments were performed to search for optimal conditions for in-source fragmentation in both positive and negative ion modes. The objective of the study was to attain uniformly appropriate conditions for a wide range of analytes independently of the aglycone, the attached sugar part and the type of bond between the aglycone and the glycan moieties (O- or C-glycosides). Studied substances included representatives of flavonols, flavones, flavanones and anthocyanins and, regarding their glycan parts, mono-, di- and triglycosides with varying distribution of carbohydrate moieties (di-O-glycosides, O-diglycosides, O,C-diglycosides). The breakdown properties of the analytes along with the abundances of the characteristic diagnostic ions required for structural elucidation of complex flavonoid derivatives were evaluated. An optimized value was found for the instrument parameter (fragmentor voltage) affecting the in-source CID fragmentation of the analytes [230 V (ESI+) and 330 V (ESI-)]. Thus, appropriate performance in terms of both highly sensitive full-scan acquisition and fragmentation information was obtained for all the investigated flavonoids. In addition, singularities in the abundance of selected diagnostic ions (e.g. Y(0), Y(1) and Y*) due to variations in the interglycosidic linkage (rutinoside-neohesperidoside) in the glycan part were found and are also evaluated and discussed in detail. The combination of in-source CID fragmentation with high mass accuracy MS detection establishes a working basis for the development of versatile and useful LC-MS methods for wide-scope screening, non-targeted detection and tentative identification of flavonoid derivatives.     

Quantum chemical study of carbohydrate-phospholipid interactions

Carbohydrates on host membranes are fundamental to many important biological processes. Here, we seek a basic understanding of the nature of the interactions between carbohydrates and phospholipids to dissect their roles in molecular recognition. A hybrid quantum mechanics/quantum mechanics (QM/QM) scheme with two different levels of treatment was used to explore the conformations and energetics of carbohydrate-phospholipid complexes. We investigate the interactions of two phospholipids (POPC and DOPC) with mannose using density functional theory. Carbohydrate-phospholipid interactions are probed with respect to competing interactions with water. Our hybrid QM/QM approach demonstrates that mannose interactions with phospholipids can result in alterations in charge distributions and conformations of phospholipids. The results clearly reveal the interplay between conventional and nonconventional hydrogen bonding; moreover, nonpolar interactions are shown to be crucial in the recognition and further stabilization of carbohydrate-phospholipid complexes. The influence of the acyl chain on phospholipid headgroup orientation is clearly evident in our investigation. The significance of the conventional OH···O and nonconventional CH···O and CH···C interactions in the stabilization of the intermolecular complexes is deduced from the molecular electron density topology using Bader's atoms-in-molecules theory. Finally, we have compared the QM energies with molecular mechanics energies for the same interactions to aid in the refinement of the all-atom lipid-carbohydrate force fields.     

Radical-based grafting of GMA on sutures of different nature

Irradiation of a number of different sutures largely employed in the clinical practice with either high energy electrons or with γ-rays followed by quenching with glycidyl methacrylate (GMA) conveniently led to derivatization through a radical-based process. The radicals involved were detected by means of ESR spectroscopy and were characterized on the basis of their ESR spectral parameters which were also found to be consistent with the hfs constants predicted by DFT calculations. Evidence of the GMA derivatization of the sutures was obtained via(13)C CP-MAS NMR spectroscopy, while its extent was evaluated gravimetrically.     

Synthesis, structural characterization, photophysical properties and theoretical analysis of gold(I) thiolate-phosphine complexes

A series of luminescent dinuclear neutral complexes of stoichiometry [(AuSPh)(2)(PPh(2)-(C(6)H(4))(n)-PPh(2))] (n = 1, 2, 3) as well as their tetranuclear cationic derivatives [(Au(2)SPh)(2)(PPh(2)-(C(6)H(4))(n)-PPh(2))(2)](PF(6))(2) are reported. Their crystal structures have been elucidated by X-ray studies. These studies indicate that, for the dinuclear species, only when n = 1 the molecules exhibit intermolecular aurophilic interactions. None of the tetranuclear species crystallizes in their molecular form, due to the formation of aggregates through Au···Au interactions. The origin of the luminescence has been analyzed by computational studies indicating that the presence or absence of aurophilic interactions does not affect the luminescent behavior and that intraligand charge transfer processes which involve the thiolate and the diphosphine are responsible for the emissions. The result is in contrast with the thiolate-gold charge transfer processes which dominate the photophysics of gold-thiolate compounds and reveals the influence of the phenylene spacers in the emissive behavior of these compounds.     

Potent "clicked" MMP2 inhibitors: synthesis, molecular modeling and biological exploration

A new series of MMP2 inhibitors is described, following a fragment-based drug design approach. One fragment containing an azide group and a well known hydroxamate Zinc Binding Group in a α-sulfone, α-tetrahydropyrane scaffold, has been synthesized. Water-LOGSY, STD and competition-STD experiments indicate that this fragment binds to the active site of the enzyme. A click chemistry reaction was used to connect the azide to lipophilic alkynes selected to interact selectively with the S1' subunit of MMP2, as shown by docking and molecular dynamic experiments of the designed compounds. The most potent compounds 18 and 19 displayed an IC(50) of 1.4 and 0.3 nM against MMP2 respectively, and showed negligible activity towards MMP1 and MMP7, two metalloproteinases which have a shallow S1' subsite. Compound 18 also showed a promising selectivity profile against some antitarget metalloproteinases, such as MMP8, and considerably less activity against MMP14 (IC(50) = 65 nM), and MMP9 (IC(50) = 98 nM), other MMPs characterized by having a deep S1' pocket and, therefore, more similar to MMP2.