IR-Spektren von deuteriertem Poly(methylmethacrylat), (-CD2C(CH3)COOCH3)n-

Ohne Zusammenfassung     

Polyhydroxy fullerenes

Characterization of C₆₀ polyhydroxyfullerenes (PHF) prepared in alkaline media, preparation facilitated by phase-transfer catalyst, presents challenges in determining the chemical structure resulting from the possibility of multiple isomers or analogs with greater or fewer hydroxyl groups from a single reaction mixture. This paper presents the utilization of analytical methods employed in tandem, especially X-ray photoelectron spectroscopy, nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy for semi-quantitative analysis on the number of hydroxyl groups present in PHF. Capillary Electrophoresis was used for purity estimation of the material. Multiple spectra and electropherograms were analyzed using a new simultaneous curve fitting method. The most accurate estimate of hydroxyl groups for C₆₀ polyhydroxy fullerenes obtained is between 16 and 18 allylic hydroxyl groups by combining analytical methods’ results with 5 % accuracy. High precision (reproducibility) of the experiments is observed. Purity of 98 % is estimated by capillary electrophoresis. The size of PHF nanoparticles or aggregates has been determined by atomic force microscopy to be 7.4–14.2 nm. According to the elemental analysis the average probable empirical formula for the most pure PHF at pH 7.1 is C₆₀O₁₇H₁₂Na₅(NaHCO₃)₃(H₂O)₁₃ and the average formula weight is 1,605.9 g/mol. This is the first thorough characterization of PHF in terms of purity.     

Analytical Scheme for the Direct Graphite-Atomizer/Flame Atomic Absorption Spectrometric Determination of Fifteen Trace Elements in Toenails for Biological Monitoring

An analytical scheme for the determination of up to fifteen trace elements in nails and hair has been proposed. Samples were solubilized by means of aqueous tetraalkylammonium hydroxide (alkyl = methyl or ethyl). Cadmium, Cr, Cu, Fe, Mn, Pb and Zn were determined by pulse-nebulization flame AAS, employing the Slotted Tube Atom Trap (STAT) for Cd and Pb. Suitable chemical modifiers have been applied in electrothermal AAS (ETAAS) determinations of Cd and Pb (ammonium hydrogen phosphate), As, Sb, Se and Sn (palladium), while no modifier was needed in determinations of Al, Co, Cr, Mn, Mo and Ni. Calibration was performed by means of matrix-matched standards and the technique was verified by standard additions, comparison with neutron activation and analysis of hair reference material. The usefulness of this technique for occupational exposure monitoring is briefly discussed.     

The thermodynamic properties of 4-pentenoic acid

The enthalpy of formation of liquid 4-pentenoic acid was determined by combustion calorimetry. The vapor pressure and enthalpy of vaporization of the compound were measured by the transfer method over the temperature range 289–324 K. Conformational analysis was performed. The equilibrium structure, fundamental vibrations, moments of inertia, and total energy of the stablest acid conformers were calculated by the B3LYP/6-311G(d, p) and G3MP2 quantum-chemical methods. The experimental IR spectrum and calculated vibrational frequencies were used to assign IR bands. The thermodynamic properties of monomeric 4-pentenoic acid in the ideal gas state were calculated over the temperature range 0–1500 K. Additive and quantum-chemical methods were used to estimate the Δ_f H°(g) and Δ_vap H° values. Close agreement between the calculation results and experimental data was obtained. It was shown that additive and quantum-chemical methods could be used for estimating the enthalpies of formation and vaporization of nonconjugated alkenoic acids.     

Do bacteria have an electric permanent dipole moment?

In the scientific literature in the last 40 years, some data for the permanent dipole moment and the electric polarizability of Escherichia coli can be found [S.P. Stoylov, Colloid Electro-Optics - Theory, Techniques and Application, Academic Press, London, 1991]. In this paper the data based mainly on electro-optic investigation is considered as much as some dipolophoretic (most often called dielectrophoretic) studies. Serious grounds are found to doubt the conclusions made for the electric dipole moments of bacteria by one of the authors of this paper (SPS) and by some other researchers. This concerns both the permanent dipole moment and the electric charge dependent polarizabilities of E. coli. Here, along with the discussion of the old experimental data, new experimental data are shown for a strain of E. coli HB101. The conclusions from the analysis of the old and the new experimental data is that they do not provide correct evidence for the presence of a permanent dipole moment. It seems that all statements for the existence of electric permanent dipole moment in bacteria [S.P. Stoylov, Colloid Electro-Optics - Theory, Techniques and Application, Academic Press, London, 1991; S.P. Stoylov, S. Sokerov, I. Petkanchin, N. Ibroshev, Dokl. AN URSS 180 (1968) 1165; N.A. Tolstoy, A.A. Spartakov, A.A. Trusov, S.A. Schelkunova, Biofizika 11 (1966) 453; V. Morris, B. Jennings, J. Chem. Soc. Faraday Trans. II 71 (1975) 1948; V. Morris, B. Jennings, J. Colloid Interface Sci. 55 (1978) 313; S.P. Stoylov, V.N. Shilov, S.S. Dukhin, S. Sokerov, I. Petkanchin, in: S.S. Dukhin (Ed.), Electro-optics of Colloids, Naukova Dumka, Kiev, 1977 (in Russian).] based on electro-optic studies are result of incorrect interpretation. Therefore, they should be further ignored.     

Membrane-bound alpha-synuclein forms an extended helix: long-distance pulsed ESR measurements using vesicles, bicelles, and rodlike micelles

We apply pulsed dipolar ESR spectroscopy (Ku-band DEER) to elucidate the global conformation of the Parkinson's disease-associated protein, alpha-synuclein (alphaS) bound to small unilamellar phospholipid vesicles, rodlike SDS micelles, or lipid bicelles. By measuring distances as long as approximately 7 nm between introduced pairs of nitroxide spin labels, we show that distances are close to the expectations for a single continuous helix in all cases studied. In particular, we find distances of 7.5 nm between sites 24 and 72; 5.5 nm between sites 24 and 61; and 2 nm between sites 35 and 50. We conclude that alphaS does not retain a "hairpin" structure with two antiparallel helices, as is known to occur with spheroidal micelles, in agreement with our earlier finding that the protein's geometry is determined by the surface topology rather than being constrained by the interhelix linker. While the possibility of local helix discontinuities in the structure of membrane-bound alphaS remains, our data are more consistent with one intact helix. Importantly, we demonstrate that bicelles produce very similar results to liposomes, while offering a major improvement in experimentally accessible distance range and resolution, and thus are an excellent lipid membrane mimetic for the purpose of pulse dipolar ESR spectroscopy.     

Activity of immobilized trypsin in the layer structure of polyelectrolyte microcapsules (PEMC)

Polyelectrolyte microcapsules composed by using the LbL technique on stabilized RBC as templates were coated with up to ten layer pairs of trypsin/PSS or trypsin/alginate. The trypsin layer growth was confirmed by particle electrophoresis, confocal laser scanning microscopy, flow cytometry, and protein determination according to Lowry. In the coating series with trypsin/PSS, the amount of immobilized enzyme was larger than that with trypsin/alginate. The enzyme immobilization led to activity reduction of up to 90% compared to that of the same enzyme amount in the solution. No significant differences between the activities of trypsin immobilized in combination with PSS and with alginate were found.     

Complex Activity and Sensor Potential toward Metal Ions in Environmental Water Samples of N-Phthalimide Azo-Azomethine Dyes

Herein, the spectral and electrochemical characterizations of three different substituted N-phthalimide azo-azomethine (NAA) dyes (L) containing an o-hydroxy group and their NAA-M(II) chelates [M(II): Cu, Ni, Co, Pb] were reported by using UV–Vis and fluorescence spectroscopy and potentiometric and voltamperometric techniques. The pK value of the dyes as well as the stoichiometry and stability of the NAA-metal chelates were studied, and the stoichiometry was found to be mostly 1:2 (ML₂) with high complex stability constant values. The sensor activity of N-phthalimide azo-azomethine derivatives toward pH and metal ions has been also investigated and tested for indicator application in acid–base analysis and detection of Cu(II) ions in real samples of surface river water using voltamperometric detection. The results showed that one of the ligands possesses the highest electrochemical response upon binding to copper ions and could be successfully used in the analysis of copper in water at a concentration range of the analyte from 3.7 × 10⁻⁷ to 5.0 × 10⁻⁶ mol L⁻¹, with analytical characteristics of the method being Sr = 1.5%, LOD = 3.58 µg L⁻¹ and LOQ =11.9 µg L⁻¹