Π11‐Martin‐Löf randomness and Π11‐Solovay completeness

Developing an analogue of Solovay reducibility in the higher recursion setting, we show that results from the classical computably enumerable case can be extended to the new context.     

Voltammetric Sensing of Mercury and Copper Cations at Poly(EDTA‐like) Film Modified Electrode

Complexing polymer‐coated electrodes have been synthesized by oxidative electropolymerization of ethylenediamine tetra‐N‐(3‐pyrrole‐1‐yl)propylacetamide (monomer L ). The presence of four polymerizable pyrrole fragments on the same EDTA skeleton was thought to confer enhanced rigidity and controlled dimensionality to the resulting complexing materials, which were used for the electrochemical detection of Hg(II), Cu(II), Pb(II) and Cd(II) ions by means of the chemical preconcentration‐anodic stripping technique. The polyamide electrode material showed particularly a significant selectivity towards mercury ions, even in the presence of a large excess of other metal cations. Moreover, the use of imprinted polymer‐coated electrodes prepared by electropolymerization of L in the presence of metal cations turned out to significantly improve the detection limits, down to 5×10^?10 mol L^?1 for Hg(II) and Cu(II) species.     

Immobilization of anionic iron(III) porphyrins into ordered macroporous layered double hydroxides and investigation of catalytic activity in oxidation reactions

The first generation anionic iron(III) porphyrin [Fe(TSPP)] and the second generation anionic complexes [Fe(TDFSPP)], [Fe(TCFSPP)], and [Fe(TDCSPP)] were immobilized into three-dimensionally macroporous layered double hydroxide (3DM-LDH), using the direct reconstruction of 3DM-LDH from macroporous mixed oxides MOX or the anionic exchange on DDS intercalated 3DM-LDH. The macroporous layered double hydroxides were obtained at the surface of nanometric polystyrene spheres, which were synthesized by an inverse opal method. Polystyrene was removed after calcination in oxidizing atmosphere, nanostructured mixed oxides (3DM-MOX) were obtained, which after reconstruction give origin to macroporous layered double hydroxide (3DM-LDH). Following metalloporphyrin immobilization, the resulting materials were characterized by powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), UV–vis (glycerin mull) spectroscopy, attenuated total reflectance Fourier transform infrared spectroscopy (ATR/FTIR), and electron paramagnetic resonance (EPR). Results revealed that the complexes are either immobilized at the surface of the macroporous layered double hydroxide or intercalated between the layers, displacing some dodecylsufate anions. The obtained materials were investigated as catalysts for oxidation reactions, to find out whether they function as cytochrome P-450 models.     

Enantioseparation of chiral benzimidazole derivatives by electrokinetic chromatography using sulfated cyclodextrins

Baseline separation of 18 new substituted benzimidazole derivatives, potent AMP‐activated protein kinase (AMPK) activators, with one chiral center, was achieved by CD‐EKC using sulfated and highly sulfated CDs (SCDs and HS‐CDs) as chiral selectors. The influence of the type and concentration of the chiral selectors on the enantioseparations was investigated. The SCDs exhibit a very high enantioselectivity power since they allow excellent enantiomeric resolutions compared to those obtained with the neutral CDs. The enantiomers were resolved with analysis times around 6 min using 25 mM phosphate buffer at pH 2.5 containing either β‐S‐CD, HS‐β‐CD, HS‐γ‐CD (3 or 4% w/v) at 25°C, with a voltage of 20 kV. The apparent association constants of the inclusion complexes were calculated. The study of the solute structure‐enantioseparation relationships seems to show the high contribution of the interactions between the solutes phenyl ring and the CDs to the enantiorecognition process. The optimized method was briefly validated (LOD less than 1%) and the purity of enantiomers of compound 3 was determined. The enantiomer migration shows reversal order depending on the kind of CD.     

Analysis of trace levels of domoic acid in seawater and plankton by liquid chromatography without derivatization,using UV or mass spectrometry detection

Quantitation of trace levels of domoic acid (DA) in seawater samples usually requires labour-intensive protocols involving chemical derivatization with 9-fluorenylmethylchloroformate and liquid chromatography with fluorescence detection (FMOC–LC–FLD). Procedures based on LC–MS have been published, but time-consuming and costly solid-phase extraction pre-concentration steps are required to achieve suitable detection limits. This paper describes an alternative, simple and inexpensive LC method with ultraviolet detection (LC–UVD) for the routine analysis of trace levels of DA in seawater without the use of sample pre-concentration or derivatization steps. Qualitative confirmation of DA identity in dubious samples can be achieved by mass spectrometry (LC–MS) using the same chromatographic conditions. Addition of an ion-pairing/acidifying agent (0.15% trifluoroacetic acid) to sample extracts and the use of a gradient elution permitted the direct analysis of large sample volumes (100 μl), resulting in both high selectivity and sensitivity (limit of detection = 42 pg ml⁻¹ by LC–UVD and 15 pg ml⁻¹ by LC–MS). Same-day precision varied between 0.4 and 5%, depending on the detection method and DA concentration. Mean recoveries of spiked DA in seawater by LC–UVD were 98.8% at 0.1–10 ng ml⁻¹ and 99.8% at 50–1000 ng ml⁻¹. LC–UVD exhibited strong correlation with FMOC–LC–FLD during inter-laboratory analysis of Pseudo-nitzschia multiseries cultures containing 60–2000 ng DA ml⁻¹ (r² > 0.99), but more variable results were obtained by LC–MS (r² = 0.85). This new technique was used to confirm the presence of trace DA levels in low-toxicity Pseudo-nitzschia spp. isolates (0.2–1.6 ng ml⁻¹) and in whole-water field samples (0.3–5.8 ng ml⁻¹), even in the absence of detectable Pseudo-nitzschia spp. cells in the water column.     

2,2′‐Bipyrimidine as Efficient Sensitizer of the Solid‐State Luminescence of Lanthanide and Uranyl Ions from Visible to Near‐Infrared

Treatment of Ln(NO₃)₃?nH₂O with 1 or 2 equiv 2,2′‐bipyrimidine (BPM) in dry THF readily afforded the monometallic complexes [Ln(NO₃)₃(bpm)₂] (Ln=Eu, Gd, Dy, Tm) or [Ln(NO₃)₃(bpm)₂]?THF (Ln=Eu, Tb, Er, Yb) after recrystallization from MeOH or THF, respectively. Reactions with nitrate salts of the larger lanthanide ions (Ln=Ce, Nd, Sm) yielded one of two distinct monometallic complexes, depending on the recrystallization solvent: [Ln(NO₃)₃(bpm)₂]?THF (Ln=Nd, Sm) from THF, or [Ln(NO₃)₃(bpm)(MeOH)₂]?MeOH (Ln=Ce, Nd, Sm) from MeOH. Treatment of UO₂(NO₃)₂?6H₂O with 1 equiv BPM in THF afforded the monoadduct [UO₂(NO₃)₂(bpm)] after recrystallization from MeOH. The complexes were characterized by their crystal structure. Solid‐state luminescence measurements on these monometallic complexes showed that BPM is an efficient sensitizer of the luminescence of both the lanthanide and the uranyl ions emitting visible light, as well as of the Yb^III ion emitting in the near‐IR. For Tb, Dy, Eu, and Yb complexes, energy transfer was quite efficient, resulting in quantum yields of 80.0, 5.1, 70.0, and 0.8 %, respectively. All these complexes in the solid state were stable in air.     

The first suberate lanthanum(III) complex without uncoordinated water

catena‐Poly­[[aqua­lanthanum(III)]‐μ‐(8‐carboxy­octanoato)‐μ‐octanedioato], [La(C₈H₁₂O₄)(C₈H₁₃O₄)(H₂O)]_n, is, to our knowledge, the first reported rare‐earth complex containing a flexible long‐chain ligand that crystallizes without water of crystallization. The layered polymeric structure is built from infinite chains of one‐edge‐sharing LaO₈(H₂O) polyhedra, connected through the carbon backbone chains of the ligands. The two chemically different ligands act in the same coordination modes, exhibiting chelating bonds and μ‐1,1‐bridging monodentate linkage, and adopting the same extended conformation. In the relatively limited hydrogen‐bonding network, a very strong hydrogen bond between the deprotonated and protonated ligand ends stabilizes the framework.     

Evidence for ion–ion interactions between peptides and anions (HSO4− or ClO4−) derived from high‐acidity acids

The existence of gas‐phase electrostatic ion–ion interactions between protonated sites on peptides ([Glu] Fibrinopeptide B, Angiotensin I and [Asn¹, Val⁵]‐Angiotensin II) and attaching anions (ClO₄^? and HSO₄^?) derived from strong inorganic acids has been confirmed by CID MS/MS. Evidence for ion–ion interactions comes especially from the product ions formed during the first dissociation step, where, in addition to the expected loss of the anion or neutral acid, other product ions are also observed that require covalent bond cleavage (i.e. H₂O loss when several carboxylate groups are present, or NH₃ loss when only one carboxylate group is present). For [[Glu] Fibrinopeptide B + HSO₄]^?, under CID, H₂O water loss was found to require less energy than H₂SO₄ departure. This indicates that the interaction between HSO₄^? and the peptide is stronger than the covalent bond holding the hydroxyl group, and must be an ion–ion interaction. The strength and stability of this type of ion‐pairing interaction are highly dependent on the accessibility of additional mobile charges to the site. Positive mobile charges such as protons from the peptide can be transferred to the attaching anion to possibly form a neutral that may depart from the complex. Alternatively, an ion–ion interaction can be disrupted by a competing proximal additional negatively charged site of the peptide that can potentially form a salt bridge with the positively charged site and thereby facilitate the attaching anion's departure. Copyright © 2014 John Wiley & Sons, Ltd.     

Comparison of the activation time effects and the internal energy distributions for the CID,PQD and HCD excitation modes

Reproducibility among different types of excitation modes is a major bottleneck in the field of tandem mass spectrometry library development in metabolomics. In this study, we specifically evaluated the influence of collision voltage and activation time parameters on tandem mass spectrometry spectra for various excitation modes [collision‐induced dissociation (CID), pulsed Q dissociation (PQD) and higher‐energy collision dissociation (HCD)] of Orbitrap‐based instruments. For this purpose, internal energy deposition was probed using an approach based on Rice–Rampserger–Kassel–Marcus modeling with three thermometer compounds of different degree of freedom (69, 228 and 420) and a thermal model. This model treats consecutively the activation and decomposition steps, and the survival precursor ion populations are characterized by truncated Maxwell–Boltzmann internal energy distributions. This study demonstrates that the activation time has a significant impact on MS/MS spectra using the CID and PQD modes. The proposed model seems suitable to describe the multiple collision regime in the PQD and HCD modes. Linear relationships between mean internal energy and collision voltage are shown for the latter modes and the three thermometer molecules. These results suggest that a calibration based on the collision voltage should provide reproducible for PQD, HCD to be compared with CID in tandem in space instruments. However, an important signal loss is observed in PQD excitation mode whatever the mass of the studied compounds, which may affect not only parent ions but also fragment ions depending on the fragmentation parameters. A calibration approach for the CID mode based on the variation of activation time parameter is more appropriate than one based on collision voltage. In fact, the activation time parameter in CID induces a modification of the collisional regime and thus helps control the orientation of the fragmentation pathways (competitive or consecutive dissociations). Copyright © 2014 John Wiley & Sons, Ltd.