Multi-element speciation of metalloproteins in fish tissue using size-exclusion chromatography coupled "on-line" with ICP-isotope dilution-time-of-flight-mass spectrometry

An on-line isotope dilution (ID) method in combination with the coupling of size-exclusion high-performance liquid chromatography (SE-HPLC) to an axial inductively coupled plasma time-of-flight mass spectrometer (ICP-TOFMS) was applied to the quantitative speciation of Cu, Zn and Cd in carp and eel cytosols. Quantitative information on the distribution of essential and toxic metals between the different molecular weight fractions in kidney cytosols of control and Cd exposed carp was obtained with species-unspecific spiking by post-column addition of the enriched isotopes 65Cu, 67Zn and 106Cd. The isotope ratios 63Cu/65Cu, 64Zn/67Zn and 114Cd/106Cd, were monitored by ICP-TOFMS in transient signal mode. The determination of the total cytosolic element concentration was performed by flow injection conventional nebulization ICP-TOFMS. Speciation differences were encountered between control and Cd-stressed carp, indicating that quantitative speciation studies might be useful for ecotoxicological and biomonitoring purposes. Application of this methodology to quantitation of metals associated with metallothioneins (MT) in European eel, sampled at three different sites in Flanders, Belgium was also addressed. A significant increase of the amount of Cd, Cu and Zn bound to hepatic MT was observed with the increase of the total metal and MT concentrations of hepatic eel tissue.     

SCF Xα SW calculations of chemical shifts of X-ray and electron emission lines and relaxation properties of SiX4 molecules

SCF Xα SW calculations of the 1s and 2p binding energies, KLL Auger energies and Kα transition energies for the molecules SiH₄, SiCl₄ and SiF₄ and the corresponding atomic Xα calculations for charged free silicon ions have been carried out. The results provide information about relaxation properties and anomalous chemical Kα shifts in hydrides.     

A Tetrameric Neodymium Silanolate: [Nd(OSiMe3)3]4

The title compound [Nd(OSiMe₃)₃]₄ ( 1 ) was prepared by reaction of [Nd{N(SiMe₃)₂}₃] with Me₃SiOH in toluene at room temperature. Compound 1 crystallized from a concentrated toluene solution in the monoclinic space group P2₁/n with the lattice constants a = 15.144(1) Å, b = 25.142(1) Å, c = 20.391(1) Å and β = 103.755(2)°. In the solid state a tetramer is observed which shows Nd‐O bond distances in the range 2.129(2)‐2.675(2) Å.     

Rapid screening for ethyl carbamate in stone-fruit spirits using FTIR spectroscopy and chemometrics

Ethyl carbamate (EC, urethane, C₂H₅OCONH₂) is a known genotoxic carcinogen of widespread occurrence in fermented food and beverages with the highest concentrations being found in stone-fruit spirits. Time-consuming procedures requiring extraction and gas chromatographic–mass spectrometric determination are regarded as reference procedures for the analysis of EC in alcoholic beverages. In this study, the rapid method of Fourier transform infrared (FTIR) spectroscopy in combination with partial least-squares (PLS) regression using selected wavelength bands is applied for the first time to the screening analysis of EC in stone fruit spirits (analysis time only 2 min). Apart from the actual content of EC in the sample, additional information was available from the FTIR spectra. This included data concerning the EC precursor hydrocyanic acid (HCN) and the maximum EC concentration which could be formed during storage. The PLS procedure was validated using an independent set of samples (Q² = 0.71–0.76, SEP = 0.42–0.67). The method was found to lack the accuracy required for a quantitative determination; it could only be used semi-quantitatively in the context of a screening analysis. If a rejection level of 0.8 mg L^–1 is applied as cut-off, overall correct classification rates of 85–91% for the calibration set and 77–85% for the validation set were achieved. False negative results can be avoided by lowering the cut-off to 0.6 mg L^–1. Through use of FTIR screening, 60–70% of all samples can be classified as negative and removed, leaving only conspicuous analysis results exceeding cut-off to be confirmed by complex and labour-intensive reference analyses.     

EPR spectroscopy of Cu(I)-NO adsorption complexes formed over Cu-ZSM-5 and Cu-MCM-22 zeolites

The Cu(I)-NO adsorption complexes were formed over copper exchanged and autoreduced high siliceous Cu-ZSM-5 and Cu-MCM-22 zeolites and studied by EPR spectroscopy at X-, Q-, and W-band frequencies. The spin Hamiltonian parameters of the Cu(I)-NO species are indicative of a nitrogen-centered radical complex with a bent geometry and a significant contribution of the Cu(I) 4s atomic orbital to the wave function of the unpaired electron. Two different Cu(I)-NO species were found in both zeolites. It has been confirmed by comparing the experimental data with the results of previous theoretical studies that the presence of two different species is due to the formation of Cu(I)-NO adsorption complexes from two different Cu(I) sites in the zeolite matrix with different numbers of oxygen coligands. The structure of the two sites in the Cu-ZSM-5 and Cu-MCM-22 zeolites must be similar as the spin Hamiltonian parameters are found to be almost independent of the zeolite matrix, where the Cu(I)-NO complex is formed. The EPR signal intensity of the Cu(I)-NO species was studied as a function of the NO loading, and the formation of diamagnetic Cu(I)-(NO)(2) species with rising NO pressure at the expense of paramagnetic Cu(I)-NO monomers could be demonstrated for both systems at low temperatures.     

Fullerene-porphyrin architectures; photosynthetic antenna and reaction center models

Fullerenes and porphyrins are molecular architectures ideally suited for devising integrated, multicomponent model systems to transmit and process solar energy. Implementation of C60 as a 3-dimensional electron acceptor holds great expectations on account of their small reorganization energy in electron transfer reactions and has exerted a noteworthy impact on the improvement of light-induced charge-separation. This article describes how the specific compositions of porphyrin chromophores linked to C60--yielding artificial light harvesting antenna and reaction center mimics--have been elegantly utilized to tune the electronic couplings between donor and acceptor sites and the total reorganization energy. Specifically, the effects that these parameters have on the rate, yield and lifetime of the energetic charge-separated states are considered.     

Total synthesis of human insulin under directed formation of the disulfide bonds

A preliminary account is given of a total synthesis of human insulin involving directed formation of the three disulfide bonds at different stages of the fragment-condensation approach. The synthesis was facilitated by the application of two new methods for the selective removal of protecting groups. In the first, two S-Trt-protected cysteine residues are converted to the disulfide without affecting S-Acm-protected cysteine residues. The second new method consists in a very mild, pH-controlled, acidolysis of N(α)-Trt, leaving intact N(α)-Bpoc and other acid-labile protecting groups. The last step of the synthesis was the formation of the disulfide bridge between the Acm-protected cysteine residues A7 and B7 by iodine. Extensive counter-current distribution yielded the synthetic hormone in pure form. It was compared and found to be identical with natural human insulin. Identification was achieved by means of thinlayer chromatography and electrophoretic procedures, as well as by comparing the pattern of break-down by enzymes (finger-printing). The natural and synthetic hormones were crystallized under identical conditions. The synthetic human insulin was found to possess full biological activity in an in vitro system.     

Über die Projektivitätengruppen von Semikörperebenen gerader Ordnung

Let S be a finite proper semifield of even order and II the group of projectivities of the projective plane over S.We prove that if S is commutative or of Knuth-type II, III or IV and ¦S¦>16 then consists of even permutations only. On the other hand we give examples of semifields of order 16, 32 and 64 whose corresponding groups contain odd permutations.

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Dieser Artikel entstand als Kurzfassung einer von Hr. Prof. Dr. J. Joussen vergebenen Diplomarbeit.

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Nicht nur für die Betreuung während der Diplomarbeit, sondern auch für die Hilfe bei der Erstellung dieser Kurzfassung, bin ich Hr. Prof. Dr. J. Joussen sehr dankbar.     

Electroaddressable Selective Functionalization of Electrode Arrays: Catalytic NADH Detection Using Aryl Diazonium Modified Gold Electrodes

We report the application of 4‐nitrophenyl diazonium modified electrodes towards the electrochemical detection of NADH. Selective activation of individual electrodes on a 5 element array by electro‐addressable conversion of nitro groups to amines and subsequent EDC/NHS crosslinking to the NADH oxidant, pyrroloquinoline quinone (PQQ), is demonstrated. Inactivated electrodes retained nitro functionality and were protected against non‐specific adsorption and mild chemical reactions. Electrodeposition conditions were used to control nitrophenyl film thickness and showed that while increased film thickness leads to greater functionalization density of PQQ, it also results in decreased electron transfer kinetics. The electrodeposition protocol can therefore serve as a method to control electrode functionalization density and film electron transfer kinetics. We believe this simple technique for selective electrode functionalization may facilitate the development of next generation multianalyte electrochemical sensors.