Degradative analysis of aquatic fulvic acid: CuO oxidation versus pyrolysis after tetramethylammonium hydroxide treatments in air and helium atmospheres

The structural composition of Nordic aquatic reference fulvic acid was investigated using chemical and thermal degradation methods: alkaline CuO oxidation and analytical pyrolysis after tetramethylammonium hydroxide (TMAH) pretreatment. Off-line procedures of the TMAH treatments were carried out under both air and helium atmospheres, with the aim of clarifying the effect of oxygen. Irrespective of the fact that the chemical and thermal degradation methods gave qualitatively quite similar basic products (mainly phenols and phenolic acids together with aromatic and aliphatic carboxylic acids), they also revealed their unique selectivity and efficiency for releasing different kinds of structural constituents. The results verify the formation of additional carboxyl functionality in the CuO oxidation. However, some similar oxidative reactions also appeared to take place during the pretreatment procedures of strongly basic TMAH, especially under an air atmosphere. The use of inert and protective atmosphere during the TMAH pretreatment is therefore recommended for producing more relevant structural information about the complex composition of humic substances.     

The preparation of a cabbage reference material for environmental monitoring and food analysis

 Cabbage is frequently used in environmental monitoring and food control, and, hence, cabbage reference materials (RMs) are required for ensuring quality assurance. A cabbage RM was prepared in view of certification of specific elements from the "black list" of high toxicological interest and nutritive importance. All tasks of the RM production (production of the plant material, cutting and freeze-drying, determination of the residual water content, preparation of the RM, homogeneity testing, stability testing, certification measurements) are described in detail. Received: 12 November 1999 / Accepted: 29 January 2000     

HER-2/neu and topoisomerase IIalpha--simultaneous drug targets in cancer

In solid tumors the predominant genetic mechanism for oncogene activation is through amplification of genes. The HER-2 (also known as ErbB2/c-erbB2/HER-2/neu) oncogene is the most frequently amplified oncogene in breast cancer and is also commonly amplified in other forms of cancer. Alongside its important role in tumor induction, growth and progression, HER-2 is also a target for a new form of chemotherapy. Since 1998, breast cancer patients have been treated with considerable success with Herceptin (trastuzumab), a recombinant antibody designed to block signaling through the HER-2 receptor. In addition to Herceptin, a large number of various HER-2 directed immunological and genetic approaches, either targeting the HER-2 receptor, its signaling pathways or both HER-2 and epidermal growth factor receptor (EGFR) together, have demonstrated promising pre-clinical potential towards HER-2 amplified carcinomas. Moreover, the HER-2 amplicon contains other genes with altered copy numbers that could be used as targets for chemotherapy. The topoisomerase IIalpha (topoIIalpha) gene (TOP2A) is located adjacent to the HER-2 oncogene at the chromosome location 17q12-q21 and is either amplified or deleted, with equal frequency, in almost 90% of HER-2 amplified primary breast tumors. Recent data suggest that amplification or deletion of TOP2A may account for both sensitivity or resistance to topoII-inhibitor-chemotherapy, depending on the specific genetic defect at the TOP2A locus. The understanding of HER-2 amplification and its role in the pathogenesis of cancer is expanding. The number of therapeutic strategies targeting HER-2 signaling pathways will most probably be introduced in the treatment of HER-2 amplified tumors within the next few years. Combining HER-2 targeting therapies with conventional forms of cytotoxic chemotherapy, where additional diagnostics tests such as those ascertaining topoIIalpha status, may be helpful for the ideal selection of patients for the combination therapy of a HER-2 targeting drug together with a cytotoxic drug. The clinical and therapeutic importance of the HER-2 and TOPO2A status of tumor cells in cancer management will only increase within the next few years.     

Effects of various washing procedures on the chromium content of human scalp hair

The effects of four wash procedures on the concentration of chromium in a pooled sample of human scalp hair are compared. The wash solutions examined are Triton X-100, sodium lauryl sulphate, acetone, and a mixture (1 + 1) of hexane and ethanol. The plateaux reached for hair chromium concentration are functions of the number of washings, and are characteristic for each wash solution. The wash procedure recommended involves two 20-min washes with aqueous 1% sodium lauryl sulphate solution after a hexane rinse.     

Hydration state of nonionic surfactant monolayers at the liquid/vapor interface: structure determination by vibrational sum frequency spectroscopy

The OH stretching region of water molecules in the vicinity of nonionic surfactant monolayers has been investigated using vibrational sum frequency spectroscopy (VSFS) under the polarization combinations ssp, ppp, and sps. The surface sensitivity of the VSFS technique has allowed targeting the few water molecules present at the surface with a net orientation and, in particular, the hydration shell around alcohol, sugar, and poly(ethylene oxide) headgroups. Dramatic differences in the hydration shell of the uncharged headgroups were observed, both in comparison to each another and in comparison to the pure water surface. The water molecules around the rigid glucoside and maltoside sugar rings were found to form strong hydrogen bonds, similar to those observed in tetrahedrally coordinated water in ice. In the case of the poly(ethylene oxide) surfactant monolayer a significant ordering of both strongly and weakly hydrogen bonded water was observed. Moreover, a band common to all the surfactants studied, clearly detected at relatively high frequencies in the polarization combinations ppp and sps, was assigned to water species located in proximity to the surfactant hydrocarbon tail phase, with both hydrogen atoms free from hydrogen bonds. An orientational analysis provided additional information on the water species responsible for this band.     

The analysis of chromium, cobalt, iron, nickel, niobium, tantalum, titanium and zinc in cemented tungsten carbides with cobalt as a binder by inductively coupled plasma atomic emission spectrometry

 Inductively coupled plasma atomic emission spectrometry (ICP-AES) was applied as a rapid routine method for the analysis of cemented tungsten carbides. Chromium, cobalt, iron, nickel, niobium, tantalum, titanium and zinc were selected as major, minor and trace constituents in the material investigated. In the first step, the sample was treated with hydrochloric and orthophosphoric acid. The second step consisted of the simultaneous addition of hydrofluoric and nitric acids. Cemented tungsten carbides dissolved completely, leaving only minor quantities of carbon in the solution. Multiple linear regression proved to be very effective in the search for interfering elements. Using simple acid based standards, all the elements investigated could be determined individually from the complicated matrix using an appropriate method of calculation. The method described was successfully applied to real type commercial samples. The advantages of the ICP-AES method in comparison with the XRF-method are discussed. Received: 15 February 1996/Revised: 22 April 1996/Accepted: 2 May 1996     

Isolation and Characterization of Cellulosic Pulp Fines and Their Interactions with Cationic Polyacrylamides

Four different types of cellulosic fines were isolated from refiner mechanical and kraft pulp samples to characterize their chemical and physical properties. The pulp fines were flocculated using four different types of cationically modified polyacrylamides. The extent of flocculation was observed with multiple light scattering apparatus. The maximum adsorption of the polyelectrolytes on the pulp fines was determined by polyelectrolyte titration. It was concluded that it is the combination of the molar mass and the charge density of a polyelectrolyte, as well as the origins and characteristics of the fines which define the adsorption and flocculation behavior. None of these properties alone could fully describe these phenomena, but the molar mass of the polyelectrolyte was the predominant factor. The most important fines characteristics were the charge properties and the microstructure.     

The Structural Diversity of Benzofuran Resorcinarene Leads to Enhanced Fluorescence

An unexpected and previously unknown resorcinarene mono‐crown with a fused benzofuran moiety in its macrocyclic core was obtained as a byproduct from a bridging reaction of tetramethoxy resorcinarene with tetraethylene glycol ditosylate. The formation of the fused benzofuran moiety in the resorcinarene macrocycle resulted in a unique rigid and puckered boat conformation, as shown by XRD studies in the solid state. Modification of the macrocycle was also observed to affect the photophysical properties in solution by enhancing the fluorescence brightness compared with a conventional resorcinarene macrocycle. The fluorescent properties enabled unique detection of structural features, that is, the rigid boat conformation with the conjugated benzofuran system and the more flexible crown bridge part, in solution.