bluuebunny/crossref_metadata_2025 huggingface dataset:
Analytical determination of antioxidants in tomato: Typical components of the Mediterranean diet
Authors: Gómez‐Romero María , Arráez‐Román David , Segura‐Carretero Antonio , Fernández‐Gutiérrez Alberto
Published: March 2007

Diets in the countries of the Mediterranean basin are characterised by abundant plant foods (fruits, vegetables, breads, nuts, seeds, wine, and olive oil) and include fish and low‐fat dairy products. Among the vegetables, tomatoes are a main component of the traditional Mediterranean diet, which has been associated with health protection and longevity. Eating tomatoes has been associated with reduced risks of some types of cancer and other diseases. These beneficial properties appear to be related to the antioxidant content of the fruit, particularly carotenoids (lycopene and β‐carotene), ascorbic acid, and phenols, which may play a role in inhibiting reactions mediated by reactive oxygen species. Due to the importance of antioxidant compounds in tomatoes and tomato products, we present here an overview of current analytical methods (from 2000 until the present date) for determining the different antioxidants. The analytical procedures used to determine individual compounds involve extraction from the sample, analytical separation, and quantification. The choice of analytical method depends on the particular focus of the analysis and the kind of product analysed. High‐performance liquid chromatography is the technique of choice for the analysis of tomato antioxidants.
Rapid analysis of food products by means of high speed gas chromatography
Authors: Donato Paola , Quinto Tranchida Peter , Dugo Paola , Dugo Giovanni , Mondello Luigi
Published: March 2007

Since the invention of GC, there has been an ever increasing interest within the chromatographic community for faster GC methods. This is obviously related to the fact that the number of samples subjected to GC analysis has risen greatly. Nowadays, in routine analytical applications, sample throughput is often the most important aspect considered when choosing an analytical method. Gas chromatographic instrumentation, especially in the last decade, has been subjected to continuous and considerable improvement. High‐speed injection systems, electronic gas pressure control, rapid oven heating/cooling and fast detection are currently available in a variety of commercial gas chromatographs. The main consequence of this favourable aspect is that high‐speed GC is being increasingly employed for routine analysis in different fields. Furthermore, the employment of dedicated software makes the passage from a conventional to a fast GC method a rather simple step. The present review provides an overview of the employment of fast GC techniques for the analysis of food constituents and contaminants. A brief historical and theoretical background is also provided for the approaches described.
Evaluation of the QuEChERS sample preparation approach for the analysis of pesticide residues in olives
Authors: Cunha Sara C. , Lehotay Steven J. , Mastovska Katerina , Fernandes José O. , Beatriz Maria , Oliveira P. P.
Published: March 2007

This paper describes the use of a quick, easy, cheap, effective, rugged, and safe (QuEChERS) method for extraction and cleanup of 16 pesticide residues of interest in olives and olive oil. These products contain a high lipid content, which can adversely affect pesticide recoveries and harm traditional chromatographic systems. For extraction, the main factors (oil and water content) were studied and optimized in experiments to maximize pesticide recoveries. Dispersive SPE with different sorbents was also investigated to minimize matrix coextractives and interferences. For analysis, a new automated DSI device was tested in GC‐MS to avoid nonvolatile coextractives from contaminating the instrument. LC‐MS/MS with positive ESI was used for those pesticides that were difficult to detect by GC‐MS. The final method was validated for olives in terms of recoveries, repeatabilities, and reproducibilities using both detection techniques. The results demonstrated that the method achieved acceptable quantitative recoveries of 70–109% with RSDs <20% for DSI‐GC‐MS and 88–130% with RSDs <10% for LC‐MS/MS, and LOQ at or below the regulatory maximum residue limits for the pesticides were achieved.
The economic return on education for hotel managers
Authors: Barros Carlos Pestana , Santos Carlos M.
Published: March 2007

This paper estimates econometrically the economic return on education among Portuguese hotels managers, based on a survey carried out in 2003. A Mincerian human capital model is estimated. The main findings indicate that the rate of return is in the range 12–15%, signifying that Portuguese hotel managers are better paid than the average population. The results also indicate that in this sector, the return on education does not depend on the number of employees in the hotels in which the individual works, nor on the region where the hotel is situated. Gender has an impact in this labour market. Being a foreign manager has a positive impact on earnings, as is also the case for partners in the hotel company. The research draws the attention of hotel managers to the need to acquire human capital to enable them to perform their tasks effectively in a globalised world. Copyright © 2007 John Wiley & Sons, Ltd.
Hierarchical Organization of Colloidal Particles: From Colloidal Crystallization to Supraparticle Chemistry
Authors: Edwards Erik W. , Wang Dayang , Möhwald Helmuth
Published: March 2007

Recent developments in the hierarchical organization of micro‐ and nanoparticles suggest a categorical shift in which the focus has changed from colloidal crystallization based on van der Waals forces to the assembly of clusters of a well‐controlled number of particles through various covalent and non‐covalent interactions, referred to here as supraparticle chemistry. This article highlights some of the advances that have been made during this transition and discusses some of the promising future directions that should be realized.

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Analysis of single rock blocks for general failure modes under conservative and non‐conservative forces
Authors: Tonon F.
Published: March 2007

After describing the kinematics of a generic rigid block subjected to large rotations and displacements, the Udwadia's General Principle of Mechanics is applied to the dynamics of a rigid block with frictional constraints to show that the reaction forces and moments are indeterminate. Thus, the paper presents an incremental‐iterative algorithm for analysing general failure modes of rock blocks subject to generic forces, including non‐conservative forces such as water forces. Consistent stiffness matrices have been developed that fully exploit the quadratic convergence of the adopted Newton–Raphson iterative scheme. The algorithm takes into account large block displacements and rotations, which together with non‐conservative forces make the stiffness matrix non‐symmetric. Also included in the algorithm are in situ stress and fracture dilatancy, which introduces non‐symmetric rank‐one modifications to the stiffness matrix. Progressive failure is captured by the algorithm, which has proven capable of detecting numerically challenging failure modes, such as rotations about only one point. Failure modes may originate from a limit point or from dynamic instability (divergence or flutter); equilibrium paths emanating from bifurcation points are followed by the algorithm. The algorithm identifies both static and dynamic failure modes. The calculation of the factor of safety comes with no overhead. Examples show the equilibrium path of a rock block that undergoes slumping failure must first pass through a bifurcation point, unless the block is laterally constrained. Rock blocks subjected to water forces (or other non‐conservative forces) may undergo flutter failure before reaching a limit point. Copyright © 2007 John Wiley & Sons, Ltd.
Pyrolysis mass spectrometry for the characterisation of straw and chemically treated straw
Authors: Morrison Ian M. , Mulder Marcel M.
Published: March 2007

Oat straw was treated with different chemical reagents to remove specific components from the cell walls. The effects of these treatments were investigated using traditional wet‐chemical analyses and pyrolysis mass spectrometry (Py‐MS) in both electron impact and chemical ionization modes. Separate treatments with permanganate and chlorite dissolved the major portion of the lignin, while alkaline peroxide treatment dissolved a proportion of the non‐cellulose polysaccharides (NCPs). Combined chlorite and sodium hydroxide treatments removed most of the lignin and NCPs whereas peracetic acid treatment showed a slight decrease in both NCPs and lignin contents. Py‐MS thus confirmed the wet chemistry results by showing reductions in the ion markers for both lignin and NCPs, where appropriate. In addition, Py‐MS showed other changes, such as the removal of phenolic acids, in a single analysis while differences between the residues from permanganate and chlorite treatment were also observed even though the chemical analyses gave virtually identical results.
Use of specific dyes in the detection of antimicrobial compounds from crude plant extracts using a thin layer chromatography agar overlay technique
Authors: Saxena Geeta , Farmer Susan , Towers G. H. N. , Hancock R. E. W.
Published: March 2007

An improved bioautographic agar overlay method was developed for the detection of antimicrobial compounds from crude plant extracts using phenol red and a tetrazolium compound as dyes to improve resolution. This method worked successfully with a wide variety of microorganisms including a number of Gram‐positive and Gram‐negative bacteria and fungi. Phenol red and the test organisms were incorporated directly into nutrient agar that was overlayed onto a thin layer chromatogram of plant extracts. In the case of bacteria, after spraying with thiazolyl blue (methylthiazolyltetrazolium chloride), dark red coloured inhibition zones appeared against blue background. Satisfactory results were obtained even with those compounds which were present in very small quantities. This method proved to be useful for activity‐guided fractionation or for target‐directed isolation of the active constituents of plants.
Chiral compounds of essential oils XIX. 4‐methyl‐5‐decanolide: Chirospecific analysis, structure and properties of the stereoisomers
Authors: Bartschat Dietmar , Lehmann Detmar , Dietrich Armin , Mosandl Armin , Kaiser Roman
Published: March 2007

Racemic mixtures of synthetic cis‐ or trans‐4‐methyl‐5‐decanolide were separated by enantioselective high performance liquid chromatography with Chiraspher‐RT to yield all four stereoisomers as enantiopure compounds of distinct odour activities. In order to elucidate stereochemical features the isolated stereoisomers were reduced to their corresponding 4‐methyl‐1,5‐decandiols by reductive ester cleavage with lithium aluminium hydride. Absolute configurations were derived from proton nuclear magnetic resonance studies of diastereomeric di‐(R)‐2′‐methoxy‐2′‐trifluoromethylphenylacetic acid esters of these 1,5‐diols. Using enantioselective multidimensional capillary gas chromatography (column combination SE 52/heptakis‐(2,3‐di‐O‐methyl‐6‐O‐tert butyldimethylsilyl)‐β‐cyclodextrin), the direct enantioselective analysis of all four lactone stereoisomers was achieved. The application of this method to the scent of living, white flowering orchids (Aerangis confusa) proves cis‐(4S)‐methyl‐(5S)‐decanolide as the unique and genuine stereoisomer of Aerangis lactone.
Fast ion bombardment mass spectrometry of sanguinarine and coptisine from Chelidonium majus L. callus cells
Authors: Rasetti Maria Francesca , Colombo Maria Laura , Bosisio Enrica , De Angelis Leonardo , Galli Giovanni , Tomè Franca
Published: March 2007

This paper reports the identification of sanguinarine and coptisine isolated from the crude extract of callus culture of Chelidonium majus by positive fast ion bombardment (FIB+) mass spectrometry (MS) and FIB+ tandem mass spectrometry (MS‐MS). Callus was cultivated on Gamborg B5 medium for three weeks at 25°C and extracted with 70% ethanol. The alkaloids were extracted into chloroform, following ion pair formation, and then separated on a silica gel column. The presence of sanguinarine and coptisine was initially determined from chromatographic analysis, and the structures of the compounds were confirmed by MS. MS‐MS analysis was not suitable for coptisine since this compound did not produce daughter ions.
Evaporative light scattering and thermospray mass spectrometry: Two alternative methods for detection and quantitative liquid chromatographic determination of ginkgolides and bilobalide in Ginkgo biloba leaf extracts and phytopharmaceuticals
Authors: Camponovo Fabrizio F. , Wolfender Jean‐Luc , Maillard Marc P. , Potterat Olivier , Hostettmann Kurt
Published: March 2007

Evaporative light scattering and thermospray mass spectrometry have been investigated as two alternative methods for the liquid chromatographic detection of ginkgolides and bilobalide. Both techniques were used to quantify these metabolites in leaf extracts and in some phytopharmaceuticals. Only a minimum of sample pre‐purification was required. Results were compared with those obtained by gas chromatography (flame ionization detection), which is one of the most suitable methods for routine determinations of such compounds. The isolation of ginkgolides A, B, C, and J and bilobalide from leaves of Ginkgo biloba is also described.
Concentrations of taxol and related taxanes in the needles of different Taxus cultivars
Authors: Elsohly Hala N. , Croom Edward M. , Kopycki Wlodzimierz J. , Joshi Alpana S. , Elsohly Mahmoud A. , McChesney James D.
Published: March 2007

The taxane content of the needles of 57 cultivars obtained from five major nurseries in the United States is presented. The analysis of taxol (1), and five other related taxanes, 10‐desacetyl‐7‐epi‐taxol (2), cephalomannine (3), 10‐desacetyl taxol (4), baccatin III (5) and 10‐desacetyl baccatin III (6) was carried out using a high performance liquid chromatographic method developed in our laboratory. The results of these analyses showed that the total “useful” taxanes varied between 0.0232%‐0.113%, with 1 and 6 being the most abundant taxanes. The survey identified 11 cultivars with a content of 1 ranging from 0.028% to 0.062%, and ten cultivars with a content of 6 ranging from 0.028% to 0.066%; 3 and 4 each represented approximately 30%‐50% of the concentration of taxol in most cultivars. Therefore, the needles of ornamental Taxus represent a significant, rich and renewable source for taxol and other related taxanes.
Gas liquid chromatographic determination of canthinone alkaloids in Hannoa chlorantha root bark and tissue cultures
Authors: Diakanamwa Carlos , Diallo Billo , Vanhaelen‐Fastré Renée , Vanhaelen Maurice , Jaziri Mondher , Homès Jacques
Published: March 2007

A capillary gas chromatographic method has been developed for the determination of canthinone alkaloids. The method was applied to the semi‐quantitative determination of canthin‐6‐one, 1‐methoxycanthin‐6‐one, 1‐hydroxycanthin‐6‐one, 8‐hydroxycanthin‐6‐one, 10‐hydroxycanthin‐6‐one, and canthin‐6‐one‐3‐N‐oxide in callus and shoot cultures, and in root barks of Hannoa chlorantha. The results showed that their concentrations were highly dependent on the sample origin and on the culture conditions.
Direct isolation of olefinic and acetylenic 3‐alkyl‐4‐hydroxy‐butenolides occurring within the apiaceae
Authors: Werner Andreas , Hadaček Franz
Published: March 2007

Underivatized alkylbutenolides from several Peucedanum species including P. alsaticum L., P. austriacum (Jacq.) Koch, P. arenarium Waldst. & Kit., P. venetum (Sprengel) Koch and P. rablense (Wulfen) Koch (Apiaceae‐Apioideae) were separated by high performance liquid chromatography and preparative chromatography on a reversed phase system at a pH of 2.5. The chromatographic separation on RP‐18 with methanol: water as eluent is strongly affected by the enol‐enolate equilibrium of these compounds. In protic solutions these compounds exist as enolate anions. The dissociation constant of alkylbutenolides in methanol‐:water mixtures was determined. The alkylbutenolides show rather good solubility in polar solvents and high acidity compared to the corresponding fatty acids.
Solubilization and extraction of allantoinase and allantoicase from the green alga Chlamydomonas reinhardtii
Authors: Piedras Pedro , Cárdenas Jacobo , Pineda Manuel
Published: March 2007

Several physical and chemical methods for the solubilization and extraction of allantoinase and allantoicase from the unicellular green alga Chlamydomonas reinhardtii have been tested and compared. Of all the methods employed (i.e. freezing‐thawing, extraction at high ionic strength, disruption with the French press, sonication, and detergent solubilization) sonication gave the best results for extraction of both substances, while sodium deoxycholate extracted allantoinase optimally but not allantoicase. Allantoinase and allantoicase were characterized as two separate enzyme proteins differently associated with membranes or located in different cellular compartments. It is also demonstrated that allantoate is enzymatically degraded in vitro by a cell‐free algal extract and that allantoicase is the enzyme responsible for this catabolism.
Agmatine determination in plant material: Aspects of the benzoylation and high performance liquid chromatographic analysis
Authors: Wehr J. Bernhard
Published: March 2007

Various steps in the existing procedure (Slocum, R. D., Flores, H. E., Galston, A. W. and Weinstein, L. H., Plant Physiol. (1989) 89, 512) for the analysis of agmatine as its benzoyl derivative were found to impair the quantification of agmatine, leading to irreproducible results. Degradation of benzoylated agmatine is a major factor contributing to erratic results, and two mechanisms of degradation have been observed. Firstly, benzoylagmatine undergoes a temperature‐dependent hydrolysis in alkaline solution and this reaction has a half‐life of 168 min at 22°C. Therefore, the benzoylation reaction time and temperature have to be controlled in order to ensure reliable results; a maximum yield of benzoylagmatine may be obtained after incubation for 30 min. Secondly, benzoylagmatine can undergo rapid alkali‐catalysed methanolysis with a half‐life of 12 min at 22°C. Methanolysis produces a degradation product that was originally considered to be agmatine or benzoylurea, but is probably N‐benzoylmethoxybenzamidomethylene imine. The formation of benzoylagmatine depends on the amount of benzoylchloride added since small volumes of the reagent do not exhaustively derivatize agmatine, hence leading to unreliable results. Mass spectrometry of benzoylagmatine showed that tribenzoylagmatine is the main derivative formed. The suggested modifications to the existing procedure enable the rapid and reliable determination of agmatine in various plant materials.
Indirect spectrophotometric determination of phytic acid with zinc chloranilate
Authors: Kamaya Minori , Furuki Tomohiro , Nagashima Kunio , Ishii Eizen , Saito Hirotsuga
Published: March 2007

The indirect spectrophotometric determination of phytic acid with zinc chloranilate has been studied. The method, based on the measurement of chloranilate released by the replacement reaction of phytic acid and zinc chloranilate, could be used to determine phytic acid in the range of 0.3 to 3.0 × 10−5 M. The method showed high reproducibility for measuring phytate in foods, and was more rapid than conventional methods.
Sample preparation for gas chromatography‐isotope ratio mass spectrometry: An investigation with volatile components from strawberries
Authors: Schumacher Katja , Turgeon Heidi , Mosandl Armin
Published: March 2007

The influence of sample preparation on the accuracy of 13C/12C‐ratios is investigated. Dynamic headspace, simultaneous distillation‐extraction and solvent extraction are used as methods of sample preparation in order to gain access to the volatiles of strawberries.
Survey of solvents for the extraction of grape seed phenolics
Authors: Kallithraka Stamatina , Garcia‐Viguera Cristina , Bridle Peter , Bakker Johanna
Published: March 2007

The effect of different solvents on the extraction of some phenolic compounds from grape seeds was investigated. The main compounds identified by high performance liquid chromatography were gallic acid, (+)‐catechin, (‐)‐epicatechin, the dimeric procyanidins B1 and B2, the trimeric procyanidin C1 and epicatechin gallate. The solvents tested were water, absolute ethanol, 75% ethanol, acetone, 70% acetone, methanol, n‐butanol, diethyl ether, ethyl acetate and a combination of diethyl ether followed by ethyl acetate. Results showed that methanol was the best solvent for the extraction of (+)‐catechin, (‐)‐epicatechin and epigallocatechin, whereas 70% acetone yielded the largest amounts of procyanidins and 75% ethanol yielded the largest amount of gallic acid. The greatest amount of total phenols was extracted by 70% acetone.
Phycobiliproteins: Determination of chromophore composition and content
Authors: Stadnichuk I. N.
Published: March 2007

Phycobiliproteins are homologous, intensively coloured protein pigments functioning as photosynthetic light‐harvesting complexes. Their ability to absorb light in the visible spectrum is due to various chromophore prosthetic groups, which are linear tetrapyrroles covalently attached to apoprotein. The chromophore composition influences spectral properties and serves as one of the main characteristics of these pigments. The procedures for determining phycobiliprotein chromophore composition and content are described.
Application of off‐line supercritical fluid extraction—gas chromatography for the investigation of chemical constituents in Curcuma zedoaria
Authors: Ma Xizhong , Yu Xiaobing , Han Jun
Published: March 2007

Analytical supercritical fluid extraction (SFE) was used to investigate the chemical constituents of Curcuma zedoaria, a very useful Chinese herbal medicine. The qualitative and quantitative analysis of extracts was performed by gas chromatography with mass spectrometry. The effects of pressure, temperature and flow rate of the extracting fluid on the extraction efficiency of SFE were investigated quantitatively. It was found that at a fixed density, changing temperature in a given experimental range had no great influence on the distribution of SFE products, but that an appropriate increase of flow rate and fluid volume improves the extraction efficiency. SFE using supercritical carbon dioxide was a more efficient extraction technique than steam distillation.
Palladium‐mediated copolymerization of diazocarbonyl compounds with phenyldiazomethane
Authors: Ihara Eiji , Kida Masami , Fujioka Masayasu , Haida Nobuyuki , Itoh Tomomichi , Inoue Kenzo
Published: March 2007

Phenyldiazomethane was found to be polymerized by the reaction with palladium‐based initiating systems. Homopolymerization of phenyldiazomethane afforded a polymer, whose main chain consists of phenylmethylene framework (–CHPh–) and azo groups (–NN–). The incorporation of the azo group was suggested from the results of elemental analyses, and confirmed by Raman spectroscopy. Palladium‐mediated copolymerization of phenyldiazomethane with (E)‐1‐diazo‐3‐nonen‐2‐one or ethyl diazoacetate proceeded to give copolymers having phenylmethylene framework, azo group, and acylmethylene or ethoxycarbonylmethylene framework in the main chain, with a variety of their compositions. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1536–1545, 2007
Amine‐blocked polyisocyanates. I. Synthesis of novel N‐methylaniline‐blocked polyisocyanates and deblocking studies using hot‐stage fourier transform infrared spectroscopy
Authors: Sankar Govindarajan , Nasar A. Sultan
Published: March 2007

A series of substituted N‐methylaniline‐blocked polyisocyanates based on 4,4′‐methylenebis(phenyl isocyanate) and poly(tetrahydrofuran) were prepared and characterized thoroughly with FTIR, 1H NMR, and 13C NMR spectroscopy methods. Compared with unsubstituted N‐methylaniline, a blocking agent with an electron‐releasing substituent at the para position took a shorter time, whereas those with an electron‐releasing substituent at the ortho position or an electron‐withdrawing substituent at the ortho and para positions took longer times for the blocking reaction. The thermal dissociation reactions of blocked polyisocyanates were carried out with an FTIR spectrophotometer attached to hot‐stage accessories under dynamic and isothermal conditions. The dynamic method was used to determine the deblocking temperature, and the isothermal method was used to calculate the deblocking kinetics and activation parameters. The cure times of blocked polyisocyanates with hydroxyl‐terminated polybutadiene were also determined. The deblocking temperatures, the results of cure‐time studies, and the kinetic parameters revealed that the thermal dissociation of the N‐methylaniline‐blocked polyisocyanates was retarded by electron‐donating substituents and facilitated by electron‐withdrawing substituents. The action of N‐methylanilines as blocking agents for isocyanate was explained by the formation of a four‐center, intramolecularly hydrogen‐bonded ring structure during the thermal dissociation of the blocked polyisocyanates. The formation of such a hydrogen‐bonded ring structure was confirmed and supported by variable‐temperature 1H NMR studies and entropy parameters, respectively. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1557–1570, 2007
Evolution of prokaryotic subtilases: Genome‐wide analysis reveals novel subfamilies with different catalytic residues
Authors: Siezen Roland J. , Renckens Bernadet , Boekhorst Jos
Published: March 2007

Subtilisin‐like serine proteases (subtilases) are a very diverse family of serine proteases with low sequence homology, often limited to regions surrounding the three catalytic residues. Starting with different Hidden Markov Models (HMM), based on sequence alignments around the catalytic residues of the S8 family (subtilisins) and S53 family (sedolisins), we iteratively searched all ORFs in the complete genomes of 313 eubacteria and archaea. In 164 genomes we identified a total of 567 ORFs with one or more of the conserved regions with a catalytic residue. The large majority of these contained all three regions around the “classical” catalytic residues of the S8 family (Asp‐His‐Ser), while 63 proteins were identified as S53 (sedolisin) family members (Glu‐Asp‐Ser). More than 30 proteins were found to belong to two novel subsets with other evolutionary variations in catalytic residues, and new HMMs were generated to search for them. In one subset the catalytic Asp is replaced by an equivalent Glu (i.e. Glu‐His‐Ser family). The other subset resembles sedolisins, but the conserved catalytic Asp is not located on the same helix as the nucleophile Glu, but rather on a β‐sheet strand in a topologically similar position, as suggested by homology modeling. The Prokaryotic Subtilase Database (www.cmbi.ru.nl/subtilases) provides access to all information on the identified subtilases, the conserved sequence regions, the proposed family subdivision, and the appropriate HMMs to search for them. Over 100 proteins were predicted to be subtilases for the first time by our improved searching methods, thereby improving genome annotation. Proteins 2007. © 2007 Wiley‐Liss, Inc.
Detection of structural changes in a cofactor binding protein by using a wheat germ cell‐free protein synthesis system coupled with unnatural amino acid probing
Authors: Abe Masato , Ohno Satoshi , Yokogawa Takashi , Nakanishi Takeshi , Arisaka Fumio , Hosoya Takamitsu , Hiramatsu Toshiyuki , Suzuki Masaaki , Ogasawara Tomio , Sawasaki Tatsuya , Nishikawa Kazuya , Kitamura Masaya , Hori Hiroyuki , Endo Yaeta
Published: March 2007

A cell‐free protein synthesis system is a powerful tool with which unnatural amino acids can be introduced into polypeptide chains. Here, the authors describe unnatural amino acid probing in a wheat germ cell‐free translation system as a method for detecting the structural changes that occur in a cofactor binding protein on a conversion of the protein from an apo‐form to a holo‐form. The authors selected the FMN‐binding protein from Desulfovibrio vulgaris as a model protein. The apo‐form of the protein was synthesized efficiently in the absence of FMN. The purified apo‐form could be correctly converted to the holo‐form. Thus, the system could synthesize the active apo‐form. Gel filtration chromatography, analytical ultracentrifugation, and circular dichroism‐spectra studies suggested that the FMN‐binding site of the apo‐form is open as compared with the holo‐form. To confirm this idea, the unnatural amino acid probing was performed by incorporating 3‐azido‐L‐tyrosine at the Tyr35 residue in the FMN‐binding site. The authors optimized three steps in their system. The introduced 3‐azido‐L‐tyrosine residue was subjected to specific chemical modification by a fluorescein‐triarylphosphine derivative. The initial velocity of the apo‐form reaction was 20 fold faster than that of the holo‐form, demonstrating that the Tyr35 residue in the apo‐form is open to solvent. Proteins 2007. © 2007 Wiley‐Liss, Inc.
New possibilities for determination of solids surface parameters by X‐ray reflectivity
Authors: Fodchuk I. , Balovsyak S.
Published: March 2007

New possibilities for research on solids surface morphology by X‐ray reflectivity (XRR) methods are presented. The method for reconstruction of surface geometry fragments is suggested. A series of GaAs crystals with a periodic surface relief and SiO2 plates with a random surface relief are investigated as test samples. Correlation of parameters of the XRR curves and surface relief with the results of atomic‐force microscopy is refined. The algorithms of the XRR curves calculation and surface‐profile reconstruction are complemented. The fractal approach to describing the shape of the XRR curves and surface profiles is used. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photoluminescence properties of GaSb epitaxial layers passivated in hydrogen plasma
Authors: Gladkov P.
Published: March 2007

Undoped and Si‐doped GaSb layers grown by low pressure MOVPE have been treated in hydrogen plasma and the effect of this treatment on photoluminescent (PL) and electrical properties is presented. Hall‐effect and PL measurements reveal that hydrogenation leads to reduction in the concentration of electrically active native acceptors, while the concentration of shallow acceptor SiSb remain practically unaffected. The hydrogenation of layers grown at Sb rich conditions results in nearly complete quenching of the PL line peaking at 896.5 meV, denoted in the literature as BE4. The origin of the BE4 line is ascribed to radiative recombination of excitons bound to a “bare” gallium vacancy. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Thermal and non‐thermal saturation effects in the output characteristic of UV‐to‐violet emitting (AlGaIn)N LEDs
Authors: Baeumler M. , Kunzer M. , Schmidt R. , Liu S. , Pletschen W. , Schlotter P. , Köhler K. , Kaufmann U. , Wagner J.
Published: March 2007

UV‐to‐violet emitting (AlGaIn)N LEDs have been investigated with respect to the temperature‐dependence of the output power characteristics and non‐thermal rollover of the quantum efficiency at higher current densities. Analyzing MOVPE grown LED chips emitting in the 377 to 428 nm wavelength interval, the temperature sensitivity was found to increase and the output power to decrease with decreasing wavelength λ for λ < 400 nm. A sub‐linear increase of the output power with increasing injection current even in the absence of any thermal effects, i.e. a non‐thermal rollover of the quantum efficiency, was observed to be most pronounced for longer wavelength LEDs (λ > 400 nm). Furthermore, the transient temperature rise after turn‐on has been studied for differently packaged 377 nm LEDs, for which the temperature coefficient of the output power has been found to be particularly large. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Local control of SiC polytypes
Authors: Pezoldt J. , Morales F. M. , Kalnin A. A.
Published: March 2007

In the case of SiC different methods for the formation of laterally and vertically stacked desired polytype inclusions are presented. The methods are based on a combination of ion implantation and annealing combined with epitaxial growth by sublimation technique. Nanoheteropolytype structures were formed using CVD. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Application of non‐linear theory to analysis of Benedicks effect in semiconductors
Authors: Piotrowski T. , Jung W. , Sikorski S.
Published: March 2007

Benedicks thermovoltage resulting from non‐symmetric distribution of temperature gradients for different surface recombinations on sample surfaces has been determined in this paper using non‐linear system of transport equations. Density distributions of generalised Price internal current Jp, taking into account the excess carrier generation and Γ potential being the measure of charge carrier injection have also been determined. Minority carrier distributions and quasi‐fermi levels variations for electron and holes resulting from Fermi level splitting due to thermoinjection have been calculated. Quasi‐fermi level variations were used for determination thermo emf values. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Strain and wafer curvature of 3C‐SiC films on silicon: influence of the growth conditions
Authors: Zielinski M. , Ndiaye S. , Chassagne T. , Juillaguet S. , Lewandowska R. , Portail M. , Leycuras A. , Camassel J.
Published: March 2007

We study the influence of the growth conditions on the residual strain and related optical and structural properties in the case of 3C‐SiC films grown on (001) silicon substrates. We show that two possible mechanisms compete to manage the final sample bow: one is by controlling the composition of the gaseous phase (C/Si ratio) the other one by adjusting the growth temperature and duration (creep effect). In both cases, we compare the low temperature photoluminescence spectra of samples grown under tensile or compressive final stress. We show that better results can be obtained when using the creep effect. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Transparent ohmic contacts to GaSb/In(Al)GaAsSb photovoltaic cells
Authors: Golaszewska K. , Kamińska E. , Piotrowska A. , Rutkowski J. , Kruszka R. , Kowalczyk E. , Papis E. , Wawro A. , Piotrowski T. T.
Published: March 2007

In this paper we present the results of study of thin oxide films: CdO, ZnO and RuSiO4 used as transparent ohmic contacts to GaSb/InGaAsSb/AlGaAsSb photodiodes. Thin oxide films with thickness of 50 nm were deposited by magnetron sputtering. CdO and RuSiO4 were formed in a reactive process in Ar–O2 atmosphere, from Cd and Ru1Si1 targets, respectively. ZnO films were deposited directly from ZnO target by rf sputtering. We have shown that application of CdO, ZnO and RuSiO4 transparent films instead of conventional metal‐based contacts enables to improve of photodiode properties. As a result, GaSb/InGaAsSb/AlGaAsSb photodiodes with detectivity D * increased by factor of 2 and reduced by factor of 3 the series resistance were obtained. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Islet Vasculature as a Regulator of Endocrine Pancreas Function
Authors: Ballian Nikiforos , Brunicardi F. Charles
Published: March 2007

The islets of Langerhans consist of endocrine cells embedded in a network of specialized capillaries that regulate islet blood flow. Despite evidence for a critical role of islet perfusion in endocrine pancreas function, there is information to support no fewer than three models of endocrine cell perfusion, emphasizing the lack of a universally accepted physiological theory. Islet blood flow is regulated by signals, such as hormones and nutrients that reach the islet vasculature from distant tissues via the bloodstream. In addition, islet perfusion determines communication between endocrine and exocrine cells and between different types of endocrine cells within islets. Interest in islet microcirculation has increased after improvements in islet transplantation, a therapy for diabetes mellitus that requires revascularization of grafted islets in a new host organ. Abnormal revascularization is thought to be partly responsible for differences in graft and native islet function. Similarly, angiogenesis has been shown to be a critical step in the transformation of islet hyperplasia to neoplasia.
Central Lymph Node Dissection in Differentiated Thyroid Cancer
Authors: White Matthew L. , Gauger Paul G. , Doherty Gerard M.
Published: March 2007

Background

There has been renewed interest in extensive lymph node dissection for papillary thyroid cancer (PTC), and a number of reports have been published concerning compartment‐oriented dissection of regional lymph nodes in PTC. A comprehensive review of this body of literature using evidence‐based methodology is pending.

Methods

Systematic review of the literature using evidence‐based criteria.

Results

Issue 1: Systematic compartment‐oriented central lymph node dissection (CLND) may decrease recurrence of PTC (Levels IV and V data, no recommendation) and likely improves disease‐specific survival (grade C recommendation). Limited level III data suggest survival benefit with the addition of prophylactic dissection to thyroidectomy (grade C recommendation). The addition of CLND to total thyroidectomy can significantly reduce levels of serum thyroglobulin and increase rates of athyroglobulinemia (level IV data, no recommendation). Issue 2: There may be a higher rate of permanent hypoparathyroidism and unintentional permanent nerve injury when CLND is performed with total thyroidectomy than for total thyroidectomy alone (grade C recommendation). Issue 3: Reoperation in the central neck compartment for recurrent PTC may increase the risk of hypoparathyroidism and unintentional nerve injury when compared with total thyroidectomy with or without CLND (grade C recommendation), supporting a more aggressive initial operation.

Conclusion

Evidence‐based recommendations support CLND for PTC in patients under the care of experienced endocrine surgeons.
Genetics of focal segmental glomerulosclerosis
Authors: Woroniecki Robert P. , Kopp Jeffrey B.
Published: March 2007

The recent advances in understanding the pathophysiology of focal segmental glomerulosclerosis (FSGS) and molecular function of glomerular filtration barrier come directly from genetic linkage and positional cloning studies. The exact role and function of the newly discovered genes and proteins are being investigated by in vitro and in vivo mechanistic studies. Those genes and proteins interactions seem to change susceptibility to kidney disease progression. Better understanding of their exact role in the development of FSGS may influence future therapies and outcomes in this complex disease.
International Morquio A Registry: Clinical manifestation and natural course of Morquio A disease
Authors: Montaño A. M. , Tomatsu S. , Gottesman G. S. , Smith M. , Orii T.
Published: March 2007

Mucopolysaccharidosis IVA (MPS IVA; Morquio A disease) is a lysosomal storage disorder caused by deficiency of N‐acetylgalactosamine‐6‐sulfate sulfatase. The natural history of this disease is incompletely understood. To study which variables influence the clinical outcome, we conducted a study in which MPS IVA patients were asked to fill out a questionnaire with inquiries regarding family history, diagnosis, signs and symptoms, height, weight, surgical history, physical activity, and general complaints. A total of 326 patients (172 male, 154 female) from 42 countries enrolled in the Morquio A Registry programme. The mean age of patients enrolled was 14.9 years for males and 19.1 years for females, with a wide range of 1–73 years. Sixty‐four per cent of the patients were under 18 years. Initial symptoms were recognized between 1 and 3 years of age (mean age 2.1 years) and mean age at diagnosis for the patients was 4.7 years. A progressive skeletal dysplasia was commonly observed among the MPS IVA patients. Fifty per cent of patients underwent surgical operations to improve their quality of life. The most frequent surgical sites include neck (51%), ear (33%), leg (26%) and hip (25%). The birth length for affected males and females was 52.2 ± 4.7 cm and 52.2 ± 4.5 cm, respectively. The final adult height for affected males and females was 122.5 ± 22.5 cm and 116.5 ± 20.5 cm, respectively. The results of this study provide a reference for assessment of efficacy for studies of novel therapies.
Enzyme, cell and gene‐based therapies for metachromatic leukodystrophy
Authors: Sevin C. , Aubourg P. , Cartier N.
Published: March 2007

Metachromatic leukodystrophy (MLD) is a demyelinating storage disease caused by deficiency of the lysosomal enzyme arylsulfatase A (ARSA). Lack of ARSA activity leads to the accumulation of galactosylceramide‐3‐O‐sulfate (sulfatide) in the central and peripheral nervous systems. Based on the age at onset, the disease is usually classified into three forms: the late‐infantile form, which manifests in the second year of life; the juvenile variants (onset between 4 and 12 years), which are subdivided into early‐juvenile (EJ, onset before 6 years) and late‐juvenile (LJ, onset after 6 years); and the adult form (onset after 12 years of age). Currently, there is no efficient therapy for the late‐infantile form of MLD (50% of the patients), death occurring within a few years after onset of neurological symptoms. Allogeneic haematopoietic cell transplantation (HCT), when performed at a very early stage of the disease, may improve selected patients with juvenile or adult forms of MLD. As with other lysosomal storage diseases, the physiopathology of MLD is poorly understood. Demyelination is the main pathological finding, but substantial storage of sulfatides in neurons also occurs, and may contribute to the clinical phenotype. The physiopathological process leading to neuronal and glial cell degeneration and apoptosis involves accumulation of undegraded sulfatides but also secondary abnormalities (storage/mislocalization of unrelated lipids, inflammatory processes). This review summarizes the recent advances in the understanding of the physiopathology of MLD and the new therapeutic perspectives currently under preclinical investigation, including enzyme replacement therapy, gene therapy and cell therapy.
Phenylketonuria: Dietary and therapeutic challenges
Authors: Giovannini M. , Verduci E. , Salvatici E. , Fiori L. , Riva E.
Published: March 2007

PKU subjects need special attention in the definition of optimal supplementation of nutrients, which may be insufficient in relation to the type of diet and may otherwise manifest symptoms of deficit. In particular, it is necessary to pay great attention to the long‐chain polyunsaturated fatty acid (LC‐PUFA) levels in relation to correct development of the central nervous system. On the basis of numerous beneficial effects currently known, a permanent supplementation with LC‐PUFAs, in particular with docosahexaenoic acid, should be considered. Moreover, new formulas, Phe‐free peptides, and ‘modulated’ amino acid preparations might help in preventing nutritional deficiencies and imbalances, with the ultimate aim of improving growth. New strategies—such as supply of tetrahydrobiopterin—need to be optimized in terms of targets, patients and expected outcomes.
Diagnosis of families with familial hypercholesterolaemia and/or Apo B‐100 defect by means of DNA analysis of LDL‐receptor gene mutations
Authors: Widhalm K. , Dirisamer A. , Lindemayr A. , Kostner G.
Published: March 2007

Background:One major problem of using hypercholesterolaemia alone as a primary criterion for diagnosing familial hypercholesterolaemia (FH) is that 15–40% of relatives may be misdiagnosed because plasma lipid levels in FH heterozygotes overlap with those in the general population.Setting:General Hospital/University of Vienna, Department of Pediatrics, Outpatient lipid clinic.Methods:As a part of the MED‐PED (make early diagnosis – prevent early death) project we are currently investigating children, adolescents and their relatives who are suspected to be affected with FH in our out‐patient clinic for metabolic diseases using MED‐PED inclusion criteria and confirming the diagnosis by means of DNA analysis.Patients:263 patients with premature atherosclerosis and/or hypercholesterolaemia: 116 children (mean age 11.6 ± 4.1 years; 57 girls and 59 boys) and 147 adults (64 women, mean age 41.5 ± 13.7 years; 83 men, mean age 42.8 ± 10.8 years).Results:119 patients with mutations have been detected; 56 children with either low density lipoprotein receptor (LDLR) and/or ApoB mutations (27 girls and 29 boys; mean total cholesterol (TC) 275 ± 71 mg/dl, triglycerides (TG) 101 ± 57 mg/dl, high‐density lipoprotein cholesterol (HDL‐C) 49 ± 12 mg/dl, low‐density lipoprotein cholesterol (LDL‐C) 198 ± 67 mg/dl) and one boy with a homozygous. LDLR mutation. A further 62 adults with LDLR and/or ApoB mutations were documented; 33 women (mean age 36.9 ± 11.1 years; mean TC 283 ± 76 mg/dl, TG 137 ± 78 mg/dl, HDL‐C 55 ± 17 mg/dl, LDL‐C 210 ± 67 mg/dl) and 29 men (mean age 45.0 ± 10.6 years; mean TC 301 ± 87 mg/dl, TG 163 ± 112 mg/dl, HDL‐C 42 ± 12 mg/dl, LDL‐C 233 ± 83 mg/dl). In 32 of these subjects (11 children (21%), 21 adults (42%)), serum lipid levels were lower than the diagnostic MED‐PED limits adopted, so that they might have been misclassified without an additional DNA analysis.Conclusion:In our study, diagnosis of FH and related disorders (ApoB‐100 defect) by means of conventional laboratory methods missed at least 21% in children and 42% in adults affected with LDLR and/or ApoB gene mutations. Genetic FH diagnosis provides a tool for specific diagnosis of mutation carrier status.
Risk factors for postoperative pulmonary complications in coronary artery bypass graft surgery patients
Authors: Jensen Louise , Yang Liyan
Published: March 2007

Background

Despite numerous advances in anesthesia, surgical techniques, and postoperative care for coronary artery bypass graft (CABG) surgery, postoperative pulmonary complications (PPCs) still account for postoperative morbidity.

Objective

To determine current risk factors for PPCs in CABG surgery patients.

Methods

A retrospective cohort design was used. Health records were reviewed for patients ( n=315) who had CABG surgery at a large quaternary healthcare center over a 4 month period. Pre-, peri-, and postoperative risk factors for PPCs were recorded as binary variables. Data were further assessed according to PPCs and non-PPCs using logistic regression models.

Results

PPCs occurred in 99.4% of this CABG surgical cohort. Atelectasis, pleural effusion, atelectasis with pleural effusion, and pneumonia were the most frequent PPCs post CABG surgery. Age >65 years, diabetes, and ASA classification N3 were found to be related to the presence of atelectasis. No significant risk factors were related to the development of pleural effusion or atelectasis with pleural effusion. Postoperative pneumonia was associated with previous myocardial infarction, ventilation >10 h, and hospital stay >5 days. History of bronchitis and COPD were related to postoperative pneumothorax; history of heart failure, COPD, and other lung diseases were related to postoperative pulmonary edema.

Conclusion

These findings contribute to the understanding of PPCs in post-CABG surgery patients and assist in identification of patients at risk for developing PPCs.