Functional regulation of an immobilized redox protein on an oriented metal coordinated peptide monolayer as an electron mediator

We fabricated a vertically and unidirectionally oriented metal coordinated α-helical peptide monolayer, Leu(2)Ala(Pyri)(Co(II))Leu(6)Ala(4-Pyri)(Co(II))Leu(6), by stepwise polymerization on a mixed self-assembled monolayer consisting of amino-alkanethiol, dialkyl disulfide, and ferrocenyl alkanethiol acted as a photoresponsive electron donor. Redox-active protein, nitrate reductase (NR), was fixed on the surface of the peptide monolayer. By contrast, we fixed NR on the mixed self-assembled monolayer directly. Upon photoirradiation, electron flow occurred from the excited ferrocenyl group on the substrate to the electron acceptor, NR, on the surface of the molecular layers. The activated NR on the molecular layers reduced the nitrate to nitrite. The amount of the bioelectrocatalytic product, nitrite, generated by the immobilized NR on the peptide monolayer was larger than that produced by the immobilized NR on the mixed self-assembled monolayer directly. That is to say, the NR on the peptide monolayer has been more activated rather than that on the peptide absent monolayer by photoirradiation. The effective activation of the NR on the peptide monolayer can be explained in terms of enhancement of the vectorial electron flow along the macro-dipole moment of the α-helical peptide that arranged unidirectionally. It suggested that the ordered metal coordinated α-helical peptide monolayer acted as an efficient electron mediator to achieve a communication between the electron donor and the redox-active moiety. Such a hybrid molecular system looks promising for novel nanodevices, such as nano-photoreactors.     

ESCA-Untersuchungen an Prussiaten

X-Ray Photoelectron Spectroscopic Studies of Prussiates The ionization energies of some prussiates are reported. The results are discussed in terms of the effects of σ-donor and π-acceptor bonds on ESCA data. Based on the foregoing discussion it is shown that charge equalization depends to a great extend on the number of possible π-bonds. Iron(II) and iron(III) salts of prussiates don't give any evidence for a ?valency exchange.”?     

Coupling of an atmospheric-samling ion source with an ion-trap mass spectrometer

An atomospheric-sampling glow-discharge ionization source has been interfaced with an ion-trap mass spectrometer. Under optimum conditions, the efficiency of ion injection is 1–5%. Several factors have a significant effect on the ion injection efficiency, including the voltages on the three-element lens system situated between the ion-source exit and the ion-trap entrance end-cap, the pressure of the bath gas present in the ion-trap vacuum housing, the nature of the bath gas and the amplitude of the radiofrequency voltage applied to the ring electrode during ion injection. Collision-induced dissociation (and electron detachment from anions) is also observed for some ions on injection, depending on the conditions. The most important experimental variables in determining the extent to which dissociation (or electron detachment) occurs are the nature of the bath gas, the bath gas presure and the radiofrequency voltage applied to the ring electrode during injection. These effects are illustrated with data obtained for polyatomic anions injected from the golw-discharge ion source.     

Electrostatic interaction between an ion-penetrable sphere and an ion-impenetrable sphere

The exact expression for the electrostatic interaction between an ionpenetrable sphere and an ion-impenetrable rigid sphere is derived on the basis of the linearized Poisson-Boltzmann equation without recourse to Derjaguin's approximation.     

Strukturuntersuchungen an Mannanderivaten

H-NMR investigations using a high resolution 220 MHz spectrometer were performed on methyl, acetyl and benzoyl derivatives of mannan from ivory nuts and Tubera salep, and on the corresponding d-mannopyranose derivatives. With the exception of the C(1) configuration the structure of these polysaccharides may be determined by comparing the coupling constants and chemical shifts of the substituted polysaccharides with those of the corresponding monosaccharide derivatives. The particularly broad signals in the spectra of low as well as high molecular weight acetyl and benzoyl mannans and furthermore, the differences between the chemical shifts of protons in 1,2,3,4,6-penta-O-acetyl-d-mannopyranose and those of the benzoylated mannans, are discussed in terms of relatively small flexibility of the polymer chains or chain segments in solution. In addition studies to determine the type of glycosidic bonds in polysaccharides from a comparison of the δ_H(1)-values of various polyglycan derivatives are reported.     

Untersuchungen an Lahnsedimenten

Zusammenfassung Die aus Untersuchungen an 40 Sedimentproben der Lahn gewonnenen Analysenergebnisse (insgesamt 18 Variablen) wurden mit Hilfe von Verfahren der multivariaten Statistik ausgewertet. Zum Einsatz kamen die multiple Korrelationsrechnung, die Faktorenanalyse, die Clusteranalyse und die multiple Regressionsanalyse. Diese chemometrische Auswertung lieferte unter anderem Hypothesen über die relative Bedeutung verschiedener Bindungsarten (Bindung durch Kationenaustausch und Adsorption, organische, hydroxidische und carbonatische Bindung) der vier toxischen Schwermetalle Kupfer, Quecksilber, Cadmium und Blei in den Lahnsedimenten.

---

Studies on sediments of the river Lahn2. Chemometric evaluation

Summary The analytical results of investigations on 40 samples of sediments of the river Lahn were evaluated by multivariate statistical methods. We accomplished multiple correlation analysis, factor analysis, cluster analysis and multiple regression analysis. Using this chemometric approach we obtained information about the relative importance of the different types of bonding (bonding by organic substances, hydroxides and carbonates and by cation-exchange and adsorption) for the toxic heavy metals copper, mercury, cadmium and lead in the sediments of the river Lahn.

     

Ringschlussreaktionen an Pleiocarpa-Alkaloiden

Alkaloids with the pleiocarpin skeleton have been found to undergo ring closure on pyrolysis to give heptacyclic compounds with the kopsan (XI) carbon skeleton. Kopsinic acid (V), the main example, gave kopsanone (XIII). The structure XIII for kopsanone has been established by physical and chemical methods, degradation to the methine base XVII and reduction to kopsan (XI). A mechanism to explain these cyclizations is discussed.     

Reaktionen an Allencarotinoiden 2

The conversion of the allenic end group 1 on HCl/CHCl₃ treatment to the acetylenic 2 resp. to the chlorinated end group 3 previously reported has been confirmed using neoxanthin ( 4a ) and its diacetate ( 4b ). Analogous HBr treatment provided the corresponding brominated end group. Chemical and spectroscopical evidence for the position of the halogen atom at C(7) is given. Transformation to allenic anhydro products and acetylenic products on treatment of neoxanthin diacetate ( 4b ) with phosphorous oxychloride in pyridine, as well as dehydration and chlorine substitution of neoxanthin ( 4a ) are reported. These results are consistent with previous observations on related carotenoids.     

Interaction of an infrared surface plasmon with an excited molecular vibration

The interaction of an infrared surface plasmon and an excited molecular vibration was investigated by using a square array of subwavelength holes in a Ni film which supports propagating, surface-plasmon-mediated, transmission resonances. The largest transmission resonance [the (1,0)(-)] was tuned through the rocking vibration of the hexadecane molecule (at 721 cm(-1)) in a hexadecane film on the mesh by varying the thickness of the film. The interaction of the rocking vibration and surface plasmon is characterized spectroscopically by an increase in the intensity of the vibrational band by more than a factor of 2, variation of the vibrational line shape relative to the spectrum on a nonmetallic surface, and shifts in vibrational peak position by as much as 3.0 cm(-1). Relationships are developed between the transmission resonance position and the thickness and dielectric properties of the coating.     

Activating an enzyme by an engineered coiled coil switch

We designed a de novo protein based on a circular permutant of RNaseT1, in which the enzymatic activity can be manipulated by engineered peptide binding. The circular permutant of RNaseT1 was obtained by tethering the original C- and N-termini with a GPAG linker and cleaving the molecule between Glu82 and Asn83. This mutant lacked enzymatic activity, due to the destabilization of entire protein structure. We previously reported the construction of ABC-type heterotrimeric coiled coil peptides, in which the A- and B-type peptides cannot form the folded trimeric structure without the C-type peptide. The introduction of the A- and B-type coiled coil peptides to the C- and N-termini of the circular permutant of RNaseT1, respectively, and the subsequent addition of the C-type coiled coil peptide enabled the RNaseT1 domain to refold properly, thus, restoring the enzymatic activity. The formation of the trimeric coiled coil structure should bring the cleaved sites of RNaseT1 close enough to refold the RNaseT1 domain spontaneously.     

EPR-Untersuchungen an Vanadylkomplexen

EPR Examination of Vanadyl Complexes For a series of bidentate ligands the reaction with VOSO₄ · 3 H₂O was studied in homogeneous solution. The resulting complexes were examined by EPR spectroscopy in chloroform at T = 295 and 133 K to receive evidence of the redox behavior of the compounds and of bonding relations in the first coordination sphere in dependence on the equatorial donor atoms.     

NMR-untersuchungen an cyclohexanen: 220 MHz-messungen an di- und trisubstituierten cyclohexanen

In the course of configurational and conformational investigations on substituted cyclohexanes, 220 MHz spectra of di- and tri- substituted derivatives were obtained. In many cases the higher frequency permits detailed assignments of all ring protons. Special features of the spectra are discussed.     

Untersuchungen an festem Dichlorhexoxid: Erste Kristallstrukturbestimmung an einem Chloroxid

Investigations on Solid Dichlorinehexaoxide: The First Crystal Structure Determination of a Chlorine Oxide Cl₂O₆ was synthesized by reaction of ClO₂ with O₂/O₃ mixtures and purified by trap-to-trap condensation. Crystal growth was achieved by sublimation (?5°C→ ?20°C) at p = 10^?4 bar on a cold finger. The crystal structure was solved using diffractometer data (Cc; a = 556.3(2), b = 861.3(3), c = 978.5(3) pm, β = 100.56(5)°; Z = 4; MoKα; ?70°C; 666 independent reflections; 71 variable parameters; R_w = 2,46%). In the solid state Cl₂O₆ is ionically mixed-valent which can be expressed by the formula ClO₂⁺ClO₄^?. The arrangement of the compound anions and cations derives from the CsCl type of structure. Raman and infrared spectra of solid Cl₂O₆ have been recorded and an assignement of the observed spectra is proposed.     

Reaction fronts in an ionic autocatalytic system with an applied electric field

The effects of applying an electric field to an ionic autocatalytic reaction with a cubic rate law are discussed. The constant field strength approximation is made and the resulting equations for the model examined by first considering the corresponding travelling wave equations. These show ranges of field strength over which travelling waves do not exist, these ranges being dependent on whether D< 1 or D< 1, where D is the ratio of diffusion coefficients of autocatalyst and substrate. Numerical simulations of the full system are obtained and these show that, when travelling waves exist, these are formed as the long time behaviour of the system. When travelling waves do not exist, complete electrophoretic separation of the reacting ionic species results, forming separate fronts in autocatalyst and substrate, their direction of propagation depending on D. Comparisons with a related problem with a quadratic rate law are made and the implications for experiments based on the iodate–arsenous acid reaction assessed.     

Adsorption study of an industrial dye by an organic clay

In this study, the adsorption of an industrial dye Supranol Yellow 4GL onto Cetyltrimethylammonium-bentonite (CTAB-bentonite) is investigated. The organobentonite is synthesised by exchanging cetyltrimethylammonium cations (CTAB) with inorganic ions on the surface of bentonite. The adsorption of Supranol Yellow 4GL onto organobentonite is found to be maximum when the concentration of CTAB exchanged is 100% according to the cation exchange capacity of the clay (CEC). The modification of organobentonite is examined using XRD and FTIR techniques. The effect of the process parameters such as: contact time, adsorbate concentration, adsorbent dose, pH and temperature are reported. Nearly 1200 seconds of contact time are found to be sufficient for the adsorption to reach equilibrium. The pseudo second order model is used to describe the kinetic data, and the rate constant is therefore evaluated. The dye adsorption to organobentonite is characterized by monolayer isotherm and caused by adsorption with relatively strong uptake. The Langmuir and Freundlich models adsorption are applied to describe the isotherm equilibrium and to determine its constants. The Langmuir and Freundlich models agree well with the experimental data with a adsorption capacity of 0.5 g of dye per g of organobentonite. A better fixation was obtained at acidic pH. The effect of temperature on the adsorption of dye has been also studied and the thermodynamic parameters ΔH, ΔS, ΔG, were determined. Organobentonite is found to be effective for removing Supranol Yellow 4GL dye from wastewater.     

Development of an improved synthetic route to an AB phenylquinoxaline monomer

The primary objective of this research was the development of an efficient synthetic route for a previously prepared self‐polymerizable PPQ monomer mixture, 2‐(4‐hydroxyphenyl)‐3‐phenyl‐6‐fluoroquinoxaline and 3‐(4‐hydroxyphenyl)‐2‐phenyl‐6‐fluoroquinoxaline. Thus, the intermediate, 4‐hydroxybenzil, was synthesized in good yield, starting from phenol with phenylacetyl chloride, followed by oxidation. The other intermediate, 4‐fluoro‐1,2‐phenylenediamine, was also less costly synthesized, starting from 2,4‐difluoronitrobenzene with ammonium hydroxide, followed by reduction, giving excellent yield. The overall monomer yield was superior to previous reports. Another research objective involved preparation of various monomer mixtures that could be synthesized even less costly, and attempts on polymerization could generate the same structure of PPQ from an original monomer mixture. Thus, the monomer mixture that had switched functional groups from the original one, 2‐(4‐fluorophenyl)‐3‐phenyl‐6‐hydroxyquinoxaline and 3‐(4‐fluorophenyl)‐2‐phenyl‐6‐hydroxyquinoxaline, was prepared. Various monomers with different functional groups attached on the 6‐position of the quinoxaline ring, such as chloro‐ and nitro‐substituted monomers instead of fluoro‐substituted ones, were also prepared. Several attempts to build up high molecular weights were not successful. In the case of the switched monomer mixture, weaker nucleophility and less activation on the fluorine atom were to be the reason in the switched monomer. In the cases of chloro‐ and nitro‐substituted monomers, poorer leaving power and side reactions were to be the reasons. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 801–814, 2005     

NMR-untersuchungen an piperidinen—III. 1H-messungen an alkylpiperidinen

The ¹H-220 MHz spectra of several alkylpiperidines are reported. Almost complete assignments for all ring protons are possible. The effects of N-methyl and C-methyl groups on adjacent ring protons are discussed in detail.     

Assay of cholinesterase in an electrode system with an immobilized substrate

A rapid, simple method for the measurement of cholinesterase based on an immobilized acetylcholine substrate is described. Each assay requires only 3 min and the immobilized substrate can be used for 10 assays with excellent results; the substrate can then be renewed easily and quickly. The precision obtained (2.5 %) is the same as that possible with the soluble substrate system.     

Electrophoresis of an arbitrarily oriented toroid in an unbounded electrolyte solution

The electrophoresis of a non-conducting rigid toroid in an unbounded Newtonian electrolyte solution having an arbitrary orientation is modeled theoretically under the condition of low surface potential. In particular, the influence of the orientation angle, defined as the angle between the applied electric field and the center line of the toroid, on its electrophoretic behavior as the thickness of double layer varies is investigated. The results of numerical simulation reveal that both the thickness of double layer and the orientation angle can influence appreciably the mobility of the toroid. In general, for a fixed orientation, the mobility of the toroid increases with decreasing double layer thickness, and for a fixed double layer thickness, the scaled electrophoresis mobility increases with increasing orientation angle. If the double layer is infinitely thin, then the present result reduces to that predicted by Smoluchowski, that is, the scaled electrophoretic mobility of the toroid is unity, and is not influenced by its shape. On the other hand, if it is infinitely thick, then the present result follows the same trend as that predicted by Henry, that is, the electrophoretic mobility of the toroid depends highly on its form effect, and the thicker the double layer the smaller that mobility. If the thickness of double layer is comparable to the radius of a toroid, the variation in the orientation angle can lead to as much as 40% difference in the mobility.     

Transport phenomena in an agitated vessel with an eccentrically located impeller

The paper presents results of an experimental analysis of the transport phenomena at the vicinity of the wall of an unbaffled agitated vessel with an eccentrically located impeller. Distributions of the transport coefficients were experimentally studied using an electrochemical method within the turbulent regime of the Newtonian liquid flow. Measurements were carried out in an agitated vessel with the inner diameter T = 0.3 m. Liquid height in the vessel was equal to the inner diameter, H = T. The agitated vessel was equipped with a Rushton or a Smith turbine or an A 315 impeller. Eccentricity of the impeller shaft was varied from 0 to 0.53. Local values of the dimensionless shear rate, shear stress, dynamic velocity and friction coefficient were integrated numerically for the whole surface area of the cylindrical wall of the vessel. Averaged values of these quantities were correlated with the impeller eccentricity and modified Reynolds number. The proposed Eqs. (5)–(8), with the coefficients given in Table 2, have no equivalent in open literature concerning this subject. Distributions of the shear rate, γ/n, and friction coefficient, f, at the vicinity of the cylindrical wall of the unbaffled vessel equipped with eccentric Rushton or Smith turbine or A 315 impeller are very uneven and they depend significantly on the impeller eccentricity, e/R. Maximum local values of these variables are located on the wall section closest to the impeller blades. From among the tested impellers, the greatest effects of the impeller eccentricity, e/R, and the liquid turbulence (described by the modified Reynolds number Re _P,M) on the averaged dimensionless shear rate (γ/n)_m and friction coefficient, f _m, are found for the radial-flow Rushton turbine located eccentrically in an unbaffled agitated vessel.