On-line bioaffinity-electrospray mass spectrometry for simultaneous detection,identification, and quantification of protein-ligand interactions

We describe here an on-line combination of a surface acoustic wave (SAW) biosensor with electrospray ionization mass spectrometry (SAW-ESI-MS) that enables the direct detection, identification, and quantification of affinity-bound ligands from a protein-ligand complex on a biosensor chip. A trapping column was used between the SAW-biosensor and the electrospray mass spectrometer equipped with a micro-guard column, which provides simultaneous sample concentration and desalting for the mass spectrometric analysis of the dissociated ligand. First applications of the on-line SAW-ESI-MS combination include (1), differentiation of β-amyloid (Aβ) epitope peptides bound to anti-Aβ antibodies; (2), the identification of immobilized Substance P peptide-calmodulin complex; (3), identification and quantification of the interaction of 3-nitrotyrosine-modified peptides with nitrotyrosine-specific antibodies; and (4), identification of immobilized anti-α-synuclein-human α-synuclein complex. Quantitative determinations of protein-ligand complexes by SAW yielded dissociation constants (K_D) from micro-to low nanomolar sample concentrations. The on-line bioaffinity-ESI-MS combination presented here is expected to enable broad bioanalytical application to the simultaneous, label-free determination and quantification of biopolymer-ligand interactions, as diverse as antigen-antibody and lectin-carbohydrate complexes.     

Core–Shell PbI2@WS2 Inorganic Nanotubes from Capillary Wetting

Multiwall WS ₂ nanotube templates were used as hosts to prepare core–shell PbI₂@WS₂ nanotubes by a capillary‐wetting method. Conformal growth of PbI₂ layers on the inner wall of the relatively wide WS₂ nanotubes (i.d. ca. 10 nm) leads to nanotubular structures which were not previously observed in narrow carbon nanotube templates. Image simulation after structural modeling (see picture) showed good agreement with the experimental HRTEM image.

     

Non-extractive procedure followed by LC/APCI MS/MS analysis of trimetazidine in plasma samples for assessing bioequivalence of immediate/modified release formulations

Trimetazidine and internal standard [1-(2,4,5-trimethoxybenzyl)piperazine] were isolated from plasma by protein precipitation with trifluoroacetic acid. The neutralized supernatant was separated on a C(8) column with methanol-aqueous 0.11% triethylamine adjusted to pH 3.3 with formic acid (1:4, v/v) at a flow rate of 0.85 mL/min. The separation was achieved within 8 min and the column ef fluent was transferred into an ion trap analyzer via an atmospheric pressure chemical ionization interface. The mass analyzer was used in the selected reaction monitoring mode, to enhance detection selectivity. The method was fully validated with a quantitation limit for trimetazidine of 1.5 ng/mL. The method was successfully applied to assess bioequivalence of two immediate and two modified commercially available pharmaceutical formulations containing 20 and 35 mg of trimetazidine, respectively.     

α-(3,7-Dioxa-r-1-azabicyclo[3.3.0]oct-c-5-ylmethoxy)-diazines. Part 2: Functionalisation via directed ortho-metallation and cross-coupling reactions

The functionalisation of the title compounds via regioselective Directed ortho-Metallation (DoM) and cross-coupling reactions is studied. The compatibility of the 3,7-DiOxa-r-1-AzaBicyclo[3.3.0]Oct-c-5-ylmethoxy system (DOABO-CH₂O) to typical reaction conditions is established. Its role as Directed ortho-Metallation Group (DoMG) is examined, including competition with classical DoMGs, chlorine and methoxy. The chelating ability of some functionalised terms such as DOABO-CH₂O substituting chiral diarylmethanols and polyaza analogues of 2,6-terpyridine is discussed as intramolecular steric relationships determining configuration and aptitude to bind selectively transition metals, respectively.     

The NADH Electrochemical Detection Performed at Carbon Nanofibers Modified Glassy Carbon Electrode

In this work, the capability of carbon nanofibers to be used for the design of catalytic electrochemical biosensors is demonstrated. The direct electrochemistry of NADH was studied at a glassy carbon electrode modified using carbon nanofibers. A decrease of the oxidation potential of NADH by more than 300 mV is observed in the case of the assembled carbon nanofiber‐glassy carbon electrode comparing with a bare glassy carbon electrode. The carbon nanofiber‐modified electrode exhibited a wide linear response range of 3×10^?5 to 2.1×10^?3 mol L^?1 with a correlation coefficient of 0.997 for the detection of NADH, a high specific sensitivity of 3637.65 (μA/M cm²), a low detection of limit (LOD=3σ) of 11 μM, and a fast response time (3 s). These results have confirmed the fact that the carbon nanofibers represent a promising material to assemble electrochemical sensors and biosensors.     

Study of some properties of poly(N-vinyl imidazole) partially quaternized with n-butyl bromide aqueous solutions

This paper presents a study of the properties of aqueous solutions of poly(N-vinyl imidazole) quaternized with n-butyl bromide (PVIQ3). The influence of the temperature and polymer concentration on refractive index, electrical conductivity and surface tension was studied. The critical micelar concentration of PVIQ3 in aqueous solution was determined and correlated with the polymer solubility in water.All the PVIQ3 aqueous solutions properties were compared with those of poly(N-vinyl imidazole) (PNVI) and the influence of the quaternization process on the polymer properties was evidenced.     

Kinetic model for methanol conversion over Mg-ZSM-5 zeolite

The catalytic conversion of methanol to olefins over ZSM-5 zeolite modified by ion exchange with Mg exhibits an autocatalytic character. On this basis an overall kinetic model of the reaction was proposed which allowed the determination of rate constants and apparent activation energy.

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ZSM-5, Mg, . , .

     

Entropy-Based Behavioural Efficiency of the Financial Market

The most known and used abstract model of the financial market is based on the concept of the informational efficiency (EMH) of that market. The paper proposes an alternative which could be named the behavioural efficiency of the financial market, which is based on the behavioural entropy instead of the informational entropy. More specifically, the paper supports the idea that, in the financial market, the only measure (if any) of the entropy is the available behaviours indicated by the implicit information. Therefore, the behavioural entropy is linked to the concept of behavioural efficiency. The paper argues that, in fact, in the financial markets, there is not a (real) informational efficiency, but there exists a behavioural efficiency instead. The proposal is based both on a new typology of information in the financial market (which provides the concept of implicit information—that is, that information ”translated” by the economic agents from observing the actual behaviours) and on a non-linear (more exactly, a logistic) curve linking the behavioural entropy to the behavioural efficiency of the financial markets. Finally, the paper proposes a synergic overcoming of both EMH and AMH based on the new concept of behavioural entropy in the financial market.     

α-(3,7-Dioxa-r-1-azabicyclo[3.3.0]oct-c-5-ylmethoxy)-diazines. Part 1: Synthesis and stereochemistry. Extension to s-triazine series

The general and efficient synthesis of the title compounds, consisting of the (selective) replacement of chlorine in commercial α-chlorodiazines and cyanuryl chloride by the 3,7-dioxa-r-1-azabicyclo[3.3.0]oct-c-5-ylmethoxy group (Williamson method) is described. The stereochemistry of this new series of derivatives is analysed in terms of different conformational chirality exhibited in solution (¹H NMR) versus solid state (X-ray diffractometry), meso against chiral forms, respectively. In solid state, the inclusion capacity of some chiral networks as well as their supramolecular aggregation is pointed out. A good correlation between rotameric behaviour of the c-5-di(s-tri)diazinyloxymethyl group in the two states is found.     

Environmentally friendly approach for nonlithographic nanostructuring of materials

Self‐organized quasi‐ordered two‐dimensional hexagonal arrays of pores with diameters as low as 70 nm in n‐InP substrates subjected to anodic etching in aqueous solution of NaCl are reported. We show that proper periodic modulation of the applied potential with time allows one to reach 3D nanostructuring of the material. Anodization in salty water proves to be a cost‐effective and environmentally‐friendly tool for spatial nanostructuring of materials and nonlithographic manufacturing of semiconductor nanotemplates for nanofabrication. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)