Analysis of Redox Activity of Proteins on the Carbon Screen Printed Electrodes

Direct redox activity of different proteins was investigated on the surface of carbon screen printed electrodes (SPE). The signal attributed to the electrochemical oxidation of amino acid residues (cysteine (Cys), tryptophan (Trp) and tyrosine (Tyr)) was registered at E_max from 0.6 to 0.7 V (vs. Ag/AgCl). Based on the difference in the redox behavior of L ‐tyrosine and 3‐nitro‐L ‐tyrosine, the selective electrochemical detection of native and nitrated albumins was demonstrated. It was shown that the electrochemical signal correlated with the surface density of electroactive amino acid residues on the protein molecule. A simple electrochemical method for the total protein analysis was proposed.     

Gold microelectrode ensembles: cheap,reusable and stable electrodes for the determination of arsenic (V) under aerobic conditions

The determination of total arsenic through As(V) anodic stripping voltammetry (ASV) is, in some cases, preferable over As(III) ASV. The As(V) ASV procedure has no chemical reduction step from As(V) into As(III), which results in decreased analysis time and no contamination from reducting reagents. A simple and reliable procedure of As(V) determination is proposed. Anodic stripping determination of trace As(V) at gold microelectrode ensembles in diluted HCl solution in the presence of dissolved oxygen is shown. The electrode is based on a carbon black (30%)–polyethylene composite. The sensor was prepared by gold electrodeposition on the surface of the composite electrode. The given sensor is cheap, reliable and stable, especially when electrochemical activation is employed. The experimental parameters for the electrochemical determination were optimized, namely 0.005?M HCl as the background electrolyte, the deposition potential ?2.2?V (versus Ag/AgCl in 1?M KCl) and 180?mV?s^?1 linear scan rate. Calibration curves were obtained and were linear in [As(V)] over the 1.5–45?µg?L^?1 range, with a LOD of 0.5?µg?L^?1. The effect of common interfering species is studied. The electrochemical behaviour of As(III) form is studied in the same experimental conditions. It was found that As(III) is deposited at lower potentials (starting at ?0.6?V) and the sensitivity of As(III) detection is higher, but dependant on the presence of dissolved oxygen. The speciation of inorganic forms of arsenic is discussed.     

N,O-ditosylethanolamine as effective reagent for the synthesis of heterocyclic tertiary amine salts

During the synthesis of N-tosylaziridine, two unexpected products were isolated: 1-(2-(p-tolylsulfonamido)ethyl)pyridinium p-tolylsulfonate (3) and N,N,O-tri-(p-tolylsulfonyl)ethanolamine (3a). The structures of 3 and 3a were investigated in solid state by X-ray analysis. A new family of related salts was obtained using an efficient and facile one-pot synthesis consisting in the interaction between various nitrogen heterocycles and N,O-ditosylethanolamine.     

Novel approach to the design of potential bioactive alkaloid anabasine conjugates using click chemistry methodology

Anabasine‐containing azides and acetylenes were used as building blocks in copper(I)‐catalyzed 1,3‐dipolar cycloaddition reactions with a series of acetylenes and azides via click methodology to provide a range of anabasine conjugates being potential ligands for neuronal nicotinic acetylcholine receptors.     

Synthesis and crystal structures of the first germanium-containing alkylidene complexes of molybdenum R3Ge-CHMo(NAr)(OR′)2 (R = Me, Ph) with direct germanium-carbene carbon bond

The novel germanium-containing alkylidene complexes of molybdenum R₃Ge-CHMo(NAr)(OCMe₂CF₃)₂ (Ar = 2,6-i-Pr₂C₆H₃; R = Me, Ph) have been prepared by the reaction of organogermanium vinyl reagents R₃ GeCHCH₂ with known alkylidene compounds Alkyl-CHMo(NAr)(OCMe₂CF₃)₂ (Alkyl = Bu^t, PhMe₂C). The titled compounds were isolated as crystalline solids and characterized by elemental analysis, ¹H NMR, ¹³C NMR spectroscopy and X-ray diffraction studies. The geometry of the Mo atoms in the compounds can be described as a distorted tetrahedron.     

A polymer–solvent system with two homogeneous double critical points: Polystyrene (PS)/(n-heptane + methylcyclohexane)

Liquid–liquid (LL) critical demixing loci have been experimentally determined in the (T,P) projection for some polystyrene/solvent systems with nonspecific interaction for (∼ 270 K < T < ∼ 500 K) and (0 MPa < P < 200 MPa). A lower homogeneous double critical pressure and lower homogeneous double critical temperature have been located for a solution of PS (M_w = 2.0 × 10⁶) dissolved in an n-heptane/methylcyclohexane mixture [PS/n-C₇H₁₆/CH₃C₆H₁₁//0.029/0.194/0.777 (wt. fractions)]. That solution forms the first example of a polymer/solvent with nonspecific interaction that exhibits two double critical points. A symmetrical representation of the LL critical loci in the (P,T) plane is developed. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 2747–2753, 1999     

Synthesis and Characterisation of 1‐[9‐(H,Me3Si,Me3Ge,Me3Sn)9‐Fluorenyl]‐3,7,10‐trimethylgermatranes. The Crystal Structure Analysis of 1‐(9‐Fluorenyl)‐3,7,10‐trimethylgermatrane

The title compounds, viz. C₁₃H₈(R)Ge · (OCHMeCH₂)₃N ( 1 : R = H, 2 : R = Me₃Si; 3 : R = Me₃Ge) were prepared as mixtures of diastereomers by the reaction of N(CH₂CHMeOSnAlk₃)₃ ( 7 : Alk = Et; 8 : Alk = Bu) with C₁₃H₈(R)GeBr₃ ( 4 : R = H, 5 : R = Me₃Si; 6 : R = Me₃Ge), respectively. The synthesis of C₁₃H₈(Me₃Sn)Ge · (OCHMeCH₂)₃N ( 13 ) by the reaction of germatrane ( 1 ) with Me₃SnNMe₂ is reported. Identity and structures were established by elemental analyses, ¹H and ¹³C NMR spectroscopy and mass spectrometry. The crystal structure of 1 was determined by X‐ray diffraction methods.     

Diarylheptanoid-rich extract of grey and black alder barks: an effective dietary antioxidant in mayonnaise

Diarylheptanoid-rich extracts (DAHEs) isolated from grey and black alder bark with pressurized ethyl acetate were tested in mayonnaise as a dietary antioxidant using the Oxipres method. DAHE contains >700 mg g^?1 of oregonin possessing quite similar structure to the well-known dietary antioxidant curcumin, which is widely used as a bioactive constituent of food supplements. Strong radical scavenging capacity of oregonin was clearly demonstrated by the online HPLC–DPPH^? scavenging assay. The antioxidative effect of DAHEs in mayonnaise was dose dependent; however, even the lowest concentration (0.5 mg g^?1) of DAHE additive increased the induction period of oxidation more than two times. Consequently, DAHE may be considered as a promising natural antioxidant for commercial applications.     

Synthesis,characterization, and structures of 1-(9-Fluorenyl)-germatrane and 1-(Phenylacetylenyl)germatrane

Syntheses of the title compounds, viz. N(CH₂CH₂O)₃GeY ( 2 Y?Fluorenyl; 4 Y?PhC?C) by the reaction of X₃GeY ( 1 Y?Fluorenyl, X?Br; 5 Y?PhC?C, X?Cl) with N(CH₂CH₂OSnR₃)₃ ( 3 R?Et; 6 R?Bu) are reported including the preparation of the new compound 1 . Identity and structures were established by elemental analyses, ¹H and ¹³C NMR spectroscopy. 2 and 4 were characterized by mass spectrometry. Single crystal structures of 1 , 2 and 4 were determined by X-ray diffraction methods.     

Solid-like states of a dendrimer liquid displayed by scanning force microscopy

Adsorption and aggregation of carbosiloxane dendrimers on mica and pyrolytic graphite were investigated by scanning force microscopy (SFM). The aggregation process started from (i) single molecules which coagulated to (ii) clusters and (iii) fluid droplets followed by formation of (iv) a complete layer on the solid substrate. The molecules were displayed as a globular particle with a diameter of about 2.5 nm. Tapping SFM of the liquid was possible due to the fact that the dendrimer undergoes a transition to a viscoelastic state below the tapping frequency of about 360 kHz. Dynamic shear compliance experiments have shown a plateau of 5 · 10⁻⁷ Pa⁻¹ around this frequency. Dendrimer droplets slowly spread into polygonal lamellae with a thickness of two molecular layers. The structures indicate a rather regular dense packing of the globular molecules.