bluuebunny/crossref_metadata_2025 huggingface dataset:
Selenium‐Promoted Oxidation of Organic Compounds: Reactions and Mechanisms
Authors: Młochowski Jacek , Brząszcz Monika , Giurg Mirosław , Palus Jerzy , Wójtowicz Halina
Published: November 2003

Oxidation reactions are fundamental processes widely applied in organic synthesis. Elemental selenium and more often its compounds have been successfully used as stoichiometric reagents and catalysts for oxidation of different organic substrates. Selenium(IV) oxide, areneseleninic acids and their anhydrides are widely used as stoichiometric oxidants or as oxygen‐transfer agents for oxygen donors, particularly hydrogen peroxide andtert‐butyl hydroperoxide. Organic diselenides (the precursors of seleninic acids) have been used as oxidation catalysts while dimethyl and diphenyl selenoxides are stoichiometric oxidants. Selenenamides, such as 2‐phenyl‐1,2‐benzisoselenazol‐3(2H)‐one (ebselen) and its analogues, known as glutathione peroxidase mimics acting via active hydroperoxide intermediates, are efficient and selective oxidation catalysts. Selenium(IV) oxide and some organoselenium compounds have been successfully applied for various oxidations useful in practical organic syntheses such as epoxidation, 1,2‐dihydroxylation, and α‐oxyfunctionalization of alkenes as well as for ring contraction of cycloalkanones, conversion of halomethyl, hydroxymethyl, or active methylene groups into formyl groups, oxidation of aldehydes into carboxylic acids, sulfides into sulfoxides, and secondary amines into nitrones, regeneration of parent carbonyl compounds from their azomethine derivatives and for other reactions. The oxidation mechanisms depend on the substrate and oxidant or catalyst used. The electrophilic center localized on the selenium atom or the nucleophilic center localized on the oxygen atom of the selenahydroperoxide group are involved in the reaction mechanism. In both cases the selenium‐containing moiety is a good leaving group. Exceptionally oxidation can proceed via free radical selenium species. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Potassium Trifluoro(organo)borates: New Perspectives in Organic Chemistry
Authors: Darses Sylvain , Genet Jean‐Pierre
Published: November 2003

Potassium trifluoro(organo)borates, highly stable organoboron derivatives, have recently emerged as promising alternatives to other organoboron reagents. These salts have shown interesting reactivity, not only through the intermediate formation of difluoroboranes, but also in transmetallation reactions with transition metals. In numerous reactions they have proven to be more reactive than boronic acids or esters. The preparation and reactivity of these ate complexes is discussed. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Synthesis of 1′‐Homo‐N‐nucleosides from Hexitols
Authors: Saladino Raffaele , Ciambecchini Umberto , Hanessian Stephen
Published: November 2003

This paper describes a new route for the synthesis of N‐(1′‐homo‐L‐gulitol)nucleosides and amino sugar analogues of N‐(1′‐homo‐L‐gulitol)nucleosides by nucleophilic epoxide ring‐opening followed by O‐heterocyclization of 1,2:5,6‐dianhydro‐3,4‐di‐O‐benzyl‐D‐mannitol and 1,2:5,6‐dianhydro‐3,4‐diazido‐D‐iditol, respectively. Magnesium perchlorate [Mg(ClO4)2] was found to be the best catalyst for the reaction of silylated bases, derived from uracil, thymine and adenine, with these bis(epoxides). (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Novel Biodegradable Pyridinium Amphiphiles for Gene Delivery
Authors: Pijper Dirk , Bulten Erna , Šmisterová Jarmila , Wagenaar Anno , Hoekstra Dick , Engberts Jan B. F. N. , Hulst Ron
Published: November 2003

Biodegradable synthetic cationic pyridinium‐based amphiphiles (SAINTs) prove to be promising non‐viral carrier systems for delivery of DNA into eukaryotic cells. Six novel SAINTs were synthesised from 3,5‐pyridinedicarboxylic acid as starting material, with two ester groups as linkers between the cationic headgroup and the hydrophobic tails. The vesicle‐forming properties of the amphiphiles were studied by differential scanning calorimetry and transmission electron microscopy, whereas the hydrolysis of the diesters in water was investigated by NMR spectroscopy. Finally, the transfection potential and cytotoxicity were determined on COS‐7 and HepG‐2 cells in culture. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
The Aldol Reaction under High‐Intensity Ultrasound: A Novel Approach to an Old Reaction
Authors: Cravotto Giancarlo , Demetri Alberto , Nano Gian Mario , Palmisano Giovanni , Penoni Andrea , Tagliapietra Silvia
Published: November 2003

We have employed high‐intensity ultrasound (HIU) to reinvestigate the aldol reaction (AR) in water. A number of aldols that under usual conditions would undergo elimination were isolated in acceptable to good yields. Within 15−30 min, acetophenone reacted with non‐enolizable aldehydes to afford the aldol exclusively, while under conventional conditions (stirring or heating under reflux) the same compounds either failed to react or gave, after several hours, the enone, often in complex product mixtures. A library of polyols was obtained starting from a series of acetophenones and excess formaldehyde. Benzaldehyde reacted with a series of 1,3‐dicarbonyl compounds to afford the corresponding bis(benzylidene) adducts. The results proved to be highly reproducible because the relevant sonochemical parameters were rigorously controlled. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Glycerol and Glycerol Glycol Glycodendrimers
Authors: Boysen Mike M. K. , Elsner Katharina , Sperling Oliver , Lindhorst Thisbe K.
Published: November 2003

Non‐covalent interactions between structural parts of complex oligosaccharides and saccharide‐recognising proteins are of crucial importance for many cell communication phenomena. Specificity of such interactions and stability of these ligand‐receptor complexes are achieved through multivalent interactions between multiple copies of a saccharide ligand and a corresponding number of protein receptors. Substances presenting multiple copies of the saccharide ligand on easily accessible scaffold molecules therefore appear to be promising tools for study of multivalent interactions and their possible inhibition. Such multivalent glycomimetics can be prepared by attachment of saccharide residues to the surface functional groups of dendrimers. In the course of our work, we have prepared novel glycodendrimers with glycerol and glycerol glycol polyether scaffolds. Isopropylidene‐protected hydroxyethyl mannoside was chosen as the carbohydrate component, with the construction of the dendritic structures proceeding by a convergent approach featuring iterative Williamson etherification and ozonolysis/hydride reduction steps. Deprotected representatives of such structures are potential inhibitors of mannose‐binding lectins of E. coli. Three representative compounds were deprotected and their anti‐adhesive properties were examined. The route to these glycodendrimers was also evaluated in terms of synthetic chemistry. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)
Evaluation of RNA messengers involved in lipid trafficking of human intestinal cells by reverse‐transcription polymerase chain reaction with competimer technology and microchip electrophoresis
Authors: Cantàfora Alfredo , Blotta Ida , Rivabene Roberto , Pisciotta Livia , Bertolini Stefano
Published: November 2003

We developed a semiquantitative reverse‐transcription polymerase chain reaction (RT‐PCR) procedure based on the combination of competimer technology with microchip electrophoresis. The approach was applied to total RNA extracts from the human colon carcinoma cell line CaCo‐2 cultured for 22 days onto tissue plate inserts that allow the polarized cell growth. At time of experiment these cells were incubated for 2 h with lipid micelles containing either cholesterol or a mixture cholesterol/β‐sitosterol or serum‐free Dulbecco's modified Eagle medium (DMEM) alone. Total RNA was extracted from cell pellets by silica membrane spin columns and reverse‐transcribed by a genetically engineered M‐MuLV enzyme and an oligo (dT)15 primer. The cDNA underwent PCR amplification for the following genes: apolipoprotein A1 (ApoAI), apolipoprotein E (ApoE), ATP‐binding cassette A1 (ABCA1), liver X receptor α (LXRα) and farnesoid X receptor (FXR). The β‐actin gene, used as an endogenous reference, was coamplified with mixtures of primer and competimer at a ratio leading to a reference band of intensity comparable to that of the gene under analysis. Amplification products were separated and quantitated by microchip electrophoresis in order to determine, for each gene, the optimum cycle numbers and primer to competimer ratios for the β‐actin therefore used for evaluating the relative variations of gene expressions in the different experiments. The incubation with cholesterol micelles stimulated both LXR and FXR expression that was accompanied by an increased expression of ABCA1 and ApoAI genes (1.4‐ and 1.5‐fold, respectively) and halved the APOE expression. The effect on ABCA1 and ApoAI expression was even stronger (5.7‐ and 2.6‐fold, respectively) with β‐sitosterol‐containing micelles. Similar changes are in line with previous findings and suggest that the short incubation with β‐sitosterol‐enriched micelles stimulates a specific mechanism that, via ABCA1 activation, can increase the cholesterol and phytosterol basolateral efflux.
Microfluidic devices fabricated in Poly(dimethylsiloxane) for biological studies
Authors: Sia Samuel K. , Whitesides George M.
Published: November 2003

This review describes microfluidic systems in poly(dimethylsiloxane) (PDMS) for biological studies. Properties of PDMS that make it a suitable platform for miniaturized biological studies, techniques for fabricating PDMS microstructures, and methods for controlling fluid flow in microchannels are discussed. Biological procedures that have been miniaturized into PDMS‐based microdevices include immunoassays, separation of proteins and DNA, sorting and manipulation of cells, studies of cells in microchannels exposed to laminar flows of fluids, and large‐scale, combinatorial screening. The review emphasizes the advantages of miniaturization for biological analysis, such as efficiency of the device and special insights into cell biology.
Electrophoretic microchip with dual‐opposite injection for simultaneous measurements of anions and cations
Authors: Wang Joseph , Chen Gang , Muck Alexander , Collins Greg E.
Published: November 2003

A novel dual‐injection poly(methylmethacrylate) (PMMA) microchip electrophoretic system has been designed and fabricated for simultaneous measurements of anions and cations using a single channel and detection device. It consists of two sample reservoirs, on both sides of a common separation channel. Anions and cations can be simultaneously electrokinetically injected into both ends of the separation channel. Due to lower electroosmotic flow in polymer channels compared to glass ones, the cations and anions migrate in opposite directions and can be separated from each other and detected using a movable contactless conductivity detector (MCCD) positioned around the center of the separation channel. The effects of the detector position and of the separation voltage on the response and resolution have been studied and optimized for simultaneous determination of six low‐energy explosive‐related ions, including ammonium, methyl ammonium, sodium, chloride, nitrate, and perchlorate in a single analytical run (of ca. 3 min). Simultaneous detection of nerve‐agent degradation products along with explosive‐related anions and cations is also demonstrated. The versatile system can also be used for separately measuring anions or cations. The attractive behavior of the dual‐opposite injection microchip offers great promise for a wide range of applications, including “total ion analysis” of various samples.
Use of high‐molecular‐mass polyacrylamides as matrices for microchip electrophoresis of DNA fragments
Authors: Cretich Marina , Chiari Marcella , Rech Ivan , Cova Sergio
Published: November 2003

DNA fragment analysis requires the use of polymer solutions as sieving matrices. Generally, such matrices are constituted of high‐molar‐weight polymers employed at a concentration higher than their entanglement threshold concentration. These polymer solutions are highly viscous and difficult to use in the narrow channels of a microchip. Ultralarge polyacrylamides synthesized via a nonconventional method, being the low‐temperature plasma‐induced polymerization (PIP), were used as DNA sieving matrices for microchip electrophoresis. The distinctive features of these polymers (ultralarge molecular mass and linearity) allow their use at a dilute concentration. Dilute PIP polyacrylamides revealed a constant value of resolution in a broad range of DNA fragment sizes (123 bp–1353 bp), thus proving to be effective in common genotyping applications. Moreover, the low viscosity of the dilute solutions enable it to be easier and faster in filling the channel between runs, thus enhancing the throughput of the microchip devices.
Microfluidic device for capillary electrochromatography‐mass spectrometry
Authors: Lazar Iulia M. , Li Lijuan , Yang Yu , Karger Barry L.
Published: November 2003

A novel microfabricated device that integrates a monolithic polymeric separation channel, an injector, and an interface for electrospray ionization‐mass spectrometry detection (ESI‐MS) was devised. Microfluidic propulsion was accomplished using electrically driven fluid flows. The methacrylate‐based monolithic separation medium was prepared by photopolymerization and had a positively derivatized surface to ensure electroosmotic flow (EOF) generation for separation of analytes in a capillary electrochromatography (CEC) format. The injector operation was optimized to perform under conditions of nonuniform EOF within the microfluidic channels. The ESI interface allowed hours of stable operation at the flow rates generated by the monolithic column. The dimensions of one processing line were sufficiently small to enable the integration of 4–8 channel multiplexed structures on a single substrate. Standard protein digests were utilized to evaluate the performance of this microfluidic chip. Low‐ or sub‐fmol amounts were injected and detected with this arrangement.
A microfabricated hybrid device for DNA sequencing
Authors: Liu Shaorong
Published: November 2003

We have created a hybrid device of a microfabricated round‐channel twin‐T injector incorporated with a separation capillary in order to extend the straight separation distance for high speed and long readlength DNA sequencing. Semicircular grooves on glass wafers are obtained using a photomask with a narrow line‐width and a standard isotropic photolithographic etching process. Round channels are made when two etched wafers are face‐to‐face aligned and bonded. A two‐mask fabrication process has been developed to make channels of two different diameters. The twin‐T injector is formed by the smaller channels whose diameter matches the bore of the separation capillary, and the “usual” separation channel, now called the connection channel, is formed by the larger ones whose diameter matches the outer diameter of the separation capillary. The separation capillary is inserted through the connection channel all the way to the twin‐T injector to allow the capillary bore flush with the twin‐T injector channels. The total dead‐volume of the connection is estimated to be ∼ 5 pL. To demonstrate the efficiency of this hybrid device, we have performed four‐color DNA sequencing on it. Using a 200 μm twin‐T injector coupled with a separation capillary of 20 cm effective separation distance, we have obtained readlengths of 800 plus bases at an accuracy of 98.5% in 56 min, compared to about 650 bases in 100 min on a conventional 40 cm long capillary sequencing machine under similar conditions. At an increased separation field strength and using a diluted sieving matrix, the separation time has been reduced to 20 min with a readlength of 700 bases at 98.5% base‐calling accuracy.
Nanocapillary liquid chromatography interfaced to tandem matrix‐assisted laser desorption/ionization and electrospray ionization‐mass spectrometry: Mapping the nuclear proteome of human fibroblasts
Authors: Malmström Johan , Larsen Kristoffer , Malmström Lars , Tufvesson Ellen , Parker Ken , Marchese Jason , Williamson Brian , Patterson Dale , Martin Steve , Juhasz Peter , Westergren‐Thorsson Gunilla , Marko‐Varga György
Published: November 2003

Miniaturized liquid chromatography nanoseparation in combination with minigel fractionation of human primary cell nuclei is presented. We obtained high‐sensitivity and high‐throughput identification of expressed proteins by subcellular fractionation and nanocapillary liquid chromatography interfaced to both electrospray ionization (ESI)‐ and matrix‐assisted laser desorption/ionisation (MALDI) tandem mass spectrometry. The reversed‐phase nanocapillary eluents were applied directly onto the MALDI target plate as discrete crystal spots using in‐line matrix infusion. When working with primary cells, only a limited amount of sample is available. To maximize the number of identified proteins from a restricted amount of sample, miniaturized sample preparation protocols and nanoflow separation is a necessity, especially when working with low‐abundant proteins. From the same isolated nuclear sample, complementary separation of intact proteins by two‐dimensional (2‐D) gel electrophoresis was made. In total 594 gene products from the nuclear preparations were identified out of which 261 were unique. Several proteins involved in transcriptional events were identified such as TATA‐binding protein, EBNA‐co‐activator, and interleukin enhancer binding proteins, indicating that sufficient proteomic depth is obtained to study transcriptional controlling events. Our results suggest that by sample prefractionation and downscaled nanoflow separation along with a combined mass spectrometry strategy, it is possible to identify a large number of nuclear proteins from human primary cells. These findings are of particular importance due to the disease link of these targets cells.
Poly(dimethylsiloxane)‐based microfluidic device with electrospray ionization‐mass spectrometry interface for protein identification
Authors: Sung Wang‐Chou , Huang Sheng‐Yu , Liao Pao‐Chi , Lee Gwo‐Bin , Li Chun‐Wei , Chen Shu‐Hui
Published: November 2003

An easy method to fabricate poly(dimethylsiloxane) (PDMS)‐based microfluidic chips for protein identification by tandem mass spectrometry is presented. This microchip has typical electrophoretic microchannels, a flow‐through sampling inlet, and a sheathless nanoelectrospray ionization (ESI) interface. The surface of the microchannel was modified with 2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid (AMPS) and the generated electroosmotic flow under acidic buffer condition used for the separation was found to be more stable compared to that generated by the microchannel without modification. The feasibility of the device for flow‐through sampling, separation, and ESI‐MS/MS analysis was demonstrated by the analysis of a standard mixture composed of three tryptic peptides. Results show that four peaks corresponding to three peptide standards and acetylated products of the standard peptide were well resolved and the deduced sequences were consistent with those expected. Furthermore, the compatibility of this device with other miniaturized devices to integrate the whole process was also explored by connecting a miniaturized enzymatic digestion cartridge and a desalting cartridge in series to the sampling inlet of the microchip for the identification of a model protein, β‐casein.
Electrokinetic characterization of poly(dimethylsiloxane) microchannels
Authors: Spehar Anna‐Maria , Koster Sander , Linder Vincent , Kulmala Sakari , de Rooij Nico F. , Verpoorte Elisabeth , Sigrist Hans , Thormann Wolfgang
Published: November 2003

This paper characterizes the basic electrokinetic phenomena occurring within native poly(dimethylsiloxane) (PDMS) microchannels. Using simple buffers and current measurements, current density and electroosmosis data were determined in trapezoidal, reversibly sealed PDMS/PDMS and hybrid PDMS/glass channels with a cross‐sectional area of 1035.5 μm2 and about 6 cm length. This data was then compared to that obtained in an air‐thermostated 50 μm inner diameter (1963.5 μm2 cross‐sectional area) fused‐silica (FS) capillary of 70 cm length. Having a pH 7.8 buffer with an ionic strength (I) of 90 mM, Ohms's law was observed in the microchannels with electric field strengths of up to about 420 V/cm, which is about twice as high as for the FS capillary. The electroosmotic mobility (μEO) in PDMS and FS is shown to exhibit the same general dependences on I and pH. For all configurations tested, the experimentally determined μEO values were found to correlate well with the relationship μEO = a + b log(I), where a and b are coefficients that are determined via nonlinear regression analysis. Electroosmotic fluid pumping in native PDMS also follows a pH dependence that can be estimated with a model based upon the ionization of silanol. Compared to FS, however, the magnitude of the electroosmotic flow in native PDMS is 50–70% smaller over the entire pH range and is difficult to maintain at acidic pH values. Thus, the origin of the negative charge at the inner wall of PDMS, glass, and FS appears to be similar but the density is lower for PDMS than for glass and FS.
High‐speed electrophoretic analysis of 1‐phenyl‐3‐methyl‐5‐pyrazolone derivatives of monosaccharides on a quartz microchip with whole‐channel UV detection
Authors: Suzuki Shigeo , Ishida Yoshiro , Arai Akihiro , Nakanishi Hiroaki , Honda Susumu
Published: November 2003

1‐Phenyl‐3‐methyl‐5‐pyrazolone (PMP) derivatives of monosaccharides were analyzed by electrophoresis on a quartz microchip with whole‐channel UV detection. Rapid separation of PMP derivatives of aldopentoses was achieved by plain‐zone electrophoresis in a neutral phosphate buffer with the height equivalent to a theoretical plate at the micrometer level. Zone electrophoresis as borate complexes was also successful for the separation of PMP derivatives of a few aldoses, which were separated within 1 min. Separation by microchip electrophoresis was compared to that by capillary electrophoresis, and the difference was discussed in terms of column efficiency and sample column capacity.
Microdevice for separation and quantitative fraction collection
Authors: Spěšný Michal , Foret František
Published: November 2003

A new microfluidic concept for quantitative whole‐column fraction collection of electrophoretically separated zones was developed. The prototype device, fabricated on a polycarbonate disk by injection molding, integrated electrophoretic separation channels with fraction collection reservoirs distributed along the separation channel. The microdevice was designed in a CD‐like format to use the centrifugal force for moving the liquid in the microchannels. A serpentine shape of the separation channel was selected to create segments for quantitative whole‐column fraction collection. The operation was tested with visual monitoring of isotachophoretic separation and collection of cationic dyes.
Manipulation and characterization of red blood cells with alternating current fields in microdevices
Authors: Minerick Adrienne R. , Zhou Ronghui , Takhistov Pavlo , Chang Hsueh‐Chia
Published: November 2003

The motion of a suspension of erythrocytes (red blood cells, RBCs) in response to a high‐frequency alternating current (AC) field in a microfluidic device is examined with parallel and orthogonal electrode configurations to delineate the various fundamental driving forces. Cell repulsion from the platinum electrodes due to electrode polarization interacting with cell membrane polarizations is observed to be the strongest force acting on the particles in the first few seconds of field application. We exploit this strong repulsion to concentrate the bioparticles between the microelectrodes to amplify multiparticle aggregation phenomenon and dielectrophoretic (DEP) manipulation in a small and well‐characterized region within the microfluidic device. Secondary motions include RBC pearl chain formation along field lines due to particle polarization followed by classical dielectrophoretic motion of the chains across field lines to regions of weaker field. These are driven by far weaker dipole‐dipole and field‐dipole interactions than the preliminary electrode repulsions. RBC chain length and total aggregated cells are presented for a variety of AC frequencies and are significantly amplified by the electrode repulsion. Motion of particles away from the polarized electrode is found to be species‐ and age‐sensitive and can stand by itself as a promising identification and separation mechanism. In a 0.1 S/m isotonic phosphate buffer saline medium, we observe the largest cell mobilities at an optimal frequency of approximately 1 MHz, corresponding to the inverse diffusion time across the double layer of the cell and across the electrode's polarized layer. This suggests that the dielectric responses of both particles and electrodes in the low MHz frequency range are mostly determined by normal electromigration of ions from the bulk to their interfaces. Sensitivity to RBC age and species suggests that the surface proteins and membrane ion channels can affect the capacitance of the interface to accommodate the ions from the bulk. Such surface ion accumulation and polarization mechanisms are different from the classical dielectric theories. The resonant frequency of electrode polarization at around 1 MHz falls between positive and negative dielectrophoretic resonant frequency peaks – suggesting that the double‐layer polarization mechanism is a distinct and potentially important bioparticle manipulation tool.
Surface modification in microchip electrophoresis
Authors: Belder Detlev , Ludwig Martin
Published: November 2003

Different approaches and techniques for surface modification of microfluidic devices applied for microchip electrophoresis are reviewed. The main focus is on the improved electrophoretic separation by reducing analyte‐wall interactions and manipulation of electroosmosis. Approaches and methods for permanent and dynamic surface modification of microfluidic devices, manufactured from glass, quartz and also different polymeric substrates, are described.
Chemical processing on microchips for analysis, synthesis, and bioassay
Authors: Tokeshi Manabu , Kikutani Yoshikuni , Hibara Akihide , Sato Kiichi , Hisamoto Hideaki , Kitamori Takehiko
Published: November 2003

This review describes our recent research on miniaturization of chemical systems. We have developed a miniaturization methodology based on pressure‐driven multiphase laminar flow and a highly sensitive detection tool, the thermal lens microscope. Some representative applications of the methodology in the fields of analysis, synthesis, and bioassay are described.
Miniaturization in carbohydrate analysis
Authors: Suzuki Shigeo , Honda Susumu
Published: November 2003

Recent progress of microchip electrophoresis (ME) of carbohydrates is overviewed. Carbohydrate analysis by ME encounters difficulties such as lack of electric charge and deficiency of a chromophore/fluorophore in analyte molecules, however, it benefits from the accumulated knowledge of capillary electrophoresis (CE) and rapid separation of simple sugars also by ME, with high column efficiency comparable to CE, has become possible. Analysis at high pH, with electrochemical detection, is a promising approach because carbohydrates can be ionized by weak dissociation of the hydroxyl groups and the in situ formed ionic species can be effectively separated by the zone electrophoresis mode. The separated species can be sensitively monitored by electrochemical detection on a gold or copper electrode. Ionization as borate complexes and refractometric detection is also possible, though sensitivity is lower. Introduction of UV‐absorbing or fluorescent tags is potentially useful but the time‐consuming derivatization processes sacrifice the rapidity of ME. Examples of ME of carbohydrates as 1‐phenyl‐3‐methyl‐5‐pyrazolone (PMP; for simple mono‐ and oligosaccharides with UV detection), 8‐aminopyrene‐1,3,6‐trisulfonate (APTS; for oligosaccharides ladders with LIF detection), and 4‐nitro‐2,1,3‐benzoxadiazole (NBD‐F; for amino sugars and aminoalditols with LIF detection) derivatives are presented, with details of the analytical conditions. Since ME in a short separation channel enables rapid analysis within 1 min, it presents an ideal tool for clinical analysis, as shown in a few papers reporting protocols for specific blood glucose assay. Finally, the usefulness of microfluidic reactors and microarrays for enzyme‐assisted carbohydrate analysis as well as glycan profiling is pointed out.
New directions of miniaturization within the proteomics research area
Authors: Marko‐Varga György , Nilsson Johan , Laurell Thomas
Published: November 2003

An overview of the current trends within protein expression profiling is given where multidimensional separation of both gel‐ and liquid‐phase techniques linked to mass spectrometry is viewed as a major route in the global proteome mapping. A clear trend in these biochemical developments is the effort to sequence and identify low‐abundant protein expressions where assay miniaturization and integrated sample processing plays a central role. Two areas of miniaturization within the proteomics field are addressed: (i) sample cleanup and enrichment, and (ii) silicon microstructure developments for protein chip microarrays.
Detection of DNA fragmentation in a single apoptotic cardiomyocyte by electrophoresis on a microfluidic device
Authors: Klepárník Karel , Horký Marcel
Published: November 2003

The detection of doxorubicin‐induced apoptosis in individual cardiomyocytes was performed on a microfluidic device. Microstructures integrated on a CD‐like plastic disk were adapted for the selection of individual cells their lysis in an alkaline environment and the separation of released apoptotic DNA fragments. The fragments with typical 180 base pairs ladder pattern were electrophoretically resolved in a 2% solution of linear polyacrylamide with 0.1 M NaOH on a migration distance of 6 mm. The laser‐induced fluorescence of fragments labeled by ethidium bromide was monitored by a photomultiplier tube mounted on a confocal microscope. The causal relation between the enhanced doxorubicin concentration and the extent of DNA fragmentation in a single cell was confirmed. The results show that the extent of DNA fragmentation is proportional to the time of a cell treatment. Onset of necrosis was evident in cardiomyocytes treated by doxorubicin for more than 24 h. The adverse effect of doxorubicin, an important cytostatics used for the treatment of many solid tumors, leads to the destruction of cardiomyocytes and, consequently, may result in the heart failure of treated individuals. Therefore, the monitoring of the extent of apoptotic DNA damage of cardiac myocytes represents critical step toward understanding of the development of chronic doxorubicin‐induced cardiomyopathy.
Zooplankton Distribution in Tropical Reservoirs, South China
Authors: Lin Qiu‐Qi , Duan Shun‐Shan , Hu Ren , Han Bo‐Ping
Published: November 2003

The zooplankton of 18 reservoirs of South China was investigated in 2000. 61 Rotifera species, 23 Cladoceras and 14 Copepodas were identified. The most frequent Rotifera genera were Keratella, Brachionus, Trichocerca, Diurella, Ascomorpha, Polyarthra, Ploesoma, Asplanchna, Pompholyx and Conochilus. Bosmina longirostris, Bosminopsis deitersi, Diaphanosoma birgei, D. brachyurum and Moina micrura were typical of Cladocera in the reservoirs. Phyllodiaptomus tunguidus, Neodiaptomus schmackeri and Mesocyclops leuckarti were the most frequent Copepoda and M. leuckarti dominated Copepoda in most reservoirs. High zooplankton species richness with low abundance was characteristic of the throughflowing reservoir, whereas low species richness with low abundance was found in the reservoir with the longest retention time. Relative high abundance and medium species diversity were the distinction of intermediate retention time reservoirs.
Ecological Integrity Assessment of Lakes Using Fish Communities – Suggestions of New Metrics Developed in Two Austrian Prealpine Lakes
Authors: Gassner Hubert , Tischler Gerhard , Wanzenböck Josef
Published: November 2003

An ecological assessment method for lakes based on fish communities similar to the IBI‐system was developed and further tested on two Austrian prealpine lakes. Important quality criteria used were species composition, reproductive success, size structure and total fish biomass. The reference status of each lake was established by the reconstruction of the native fish community and the native total fish biomass.

In Hallstättersee only minor deviations from the reference status could be observed. Additionally to the 12 native (reconstructed) fish species two exotic species were found inhabiting this lake. There was no change in the number of intolerant fish species and for 10 native fish species reproduction success was confirmed.

The fish community of Irrsee differed to a higher extent from the reference status. Three native fish species were missing. Seven exotic species were confirmed by catches and four of these are reproducing in Irrsee. No reproductive success could be verified for five native species. The sum of scores in our proposed scoring system revealed a value of 92 points for Hallstättersee, which corresponds to a “high ecological status” and of 60 points for Irrsee, which corresponds to a “moderate ecological status” of the fish community.
Effects of Adult Dreissena polymorpha on Settling Juveniles and Associated Macroinvertebrates
Authors: Mörtl Martin , Rothhaupt Karl‐Otto
Published: November 2003

The impact of Dreissena polymorpha settlement on recruitment of juvenile mussels and density of other macroinvertebrates was studied in field experiments using blank concrete blocks and tiles (control), blocks and tiles with attached empty zebra mussel shells, and blocks and tiles with attached living mussels. On blocks, dominant invertebrate taxa showed colonization patterns coinciding with increased habitat complexity owing to zebra mussel settlement or the biodeposition of faeces and pseudofaeces. Adult and especially juvenile zebra mussels preferred blocks with empty shells to blank blocks and blocks with living mussels; this might possibly be caused by a chemical cue that induces gregarious settlement. Lower recruitment on blocks with attached living mussels compared to blocks with only shells could be the consequence of ingestion of larvae by adult mussels and of competition for food. On tiles, the sediments deposited and the organic content of the sediment were investigated. Sedimentation was significantly higher on shell‐only and live‐mussel tiles compared to blank tiles. Organic matter differed significantly between blank and live‐mussel tiles.
Dry mechanochemical synthesis of hydroxyapatites from dicalcium phosphate dihydrate and calcium oxide: A kinetic study
Authors: Briak‐BenAbdeslam Hassane El , Mochales Carolina , Ginebra Maria Pau , Nurit Josiane , Planell Josep A. , Boudeville Philippe
Published: November 2003

Calcium phosphate ceramics have been used successfully as synthetic bone substitutes in orthopedics, dentistry, and maxillofacial surgery. One way of preparing these ceramics is the sintering of a calcium‐deficient hydroxyapatite (CDHA), which can be obtained in different ways. Mechanochemistry is one possible means of synthesizing CDHA, with an expected molar calcium‐to‐phosphate (Ca/P) ratio ± 0.005. The grinding can be carried out under dry or wet conditions. To optimize the experimental conditions of CDHA preparation by dry mechanosynthesis and for a better understanding of the DCPD/CaO mechanochemical reaction, we performed a kinetic study in which some of the experimental parameters were varied. Carried out with two different vertical rotating ball mills, this kinetic study showed that (1) experiments are reproducible and give as a final product a hydroxyapatite powder, formed of nano‐sized crystals of around 20 nm, with a controlled Ca/P ratio; (2) the time for complete disappearance of DCPD and the time for complete reaction are in direct proportion to the mass of the ground powder; but (3) the time for complete disappearance of DCPD is independent of the Ca/P ratio while the time for complete reaction increases exponentially with the Ca/P ratio; and (4) the time for complete disappearance of DCPD corresponds to the time for complete reaction solely for Ca/P = 1.5. These observations suggest a reaction mechanism in two well differentiated stages: (First stage) CaO reacts with DCPD to give first an amorphous calcium phosphate (ACP) with a low Ca/P ratio that transforms into CDHA when its Ca/P ratio reaches 1.5. At the same time, CaO is hydrated into Ca(OH)2 by the water produced by the reaction. (Second stage) If the Ca/P > 1.5 in the initial mixture, the excess Ca(OH)2 is added to CDHA 1.5 by reacting with the HPO4 group of CDHA until its Ca/P ratio reaches the expected value. The slower the reaction, the higher the Ca/P in the initial mixture. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 927–937, 2003
Adhesion and growth of human Schwann cells on trimethylene carbonate (co)polymers
Authors: Pêgo Ana Paula , Vleggeert‐Lankamp Carmen L. A. M. , Deenen Marga , Lakke Egbert A. J. F. , Grijpma Dirk W. , Poot André A. , Marani Enrico , Feijen Jan
Published: November 2003

Seeding of artificial nerve grafts with Schwann cells is a promising strategy for bridging large nerve defects. The aim of the present study was to evaluate the adhesion and growth of human Schwann cells (HSCs) on 1,3‐trimethylene carbonate (TMC) and ϵ‐caprolactone copolymers, with the final goal of using these materials in the development of an artificial nerve graft. The adhesion, proliferation, and morphology of HSCs on copolymers containing 10 and 82 mol % of TMC and on the parent homopolymers were investigated. HSCs adhered faster and in greater numbers on the copolymer with 82 mol % of TMC and on the TMC homopolymer compared with the other (co)polymers. On all polymer films, cell adhesion was lower than on gelatin (positive control). Despite differences in cell adhesion, cells displayed exponential growth on all tested surfaces, with similar growth rates. Cell numbers doubled approximately every 3 days on all substrates. When the polymer films were coated with fibronectin, no significant differences in cell adhesion and proliferation were observed between coated polymer surfaces and gelatin. The results indicate that all tested materials support the adhesion and proliferation of HSCs and can in principle be used for the preparation of flexible and slowly degrading nerve guides. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 876–885, 2003
In vivo mechanisms of hydroxyapatite ceramic degradation by osteoclasts: Fine structural microscopy
Authors: Wenisch S. , Stahl J.‐P. , Horas U. , Heiss C. , Kilian O. , Trinkaus K. , Hild A. , Schnettler R.
Published: November 2003

In the present study the in vivo mechanism of calcium‐phosphate (CaP) ceramic degradation has been investigated by means of transmission electron microscopy. The results revealed osteoclast‐mediated degradation of hydroxyapatite ceramic implanted into sheep bone by simultaneous resorption and phagocytosis. After 6 weeks of implantation, osteoclasts were localized immediately beneath the ceramic surface. They had formed resorption lacunae and exhibited typical ultrastructural features, such as the ruffled border, the clear zone, and the dorsal microvilli. Their resorption capacity also had become evident by alterations of the electron density and the shape of the CaP crystals localized within the acidic microenvironment of the ruffled border. Moreover, the osteoclasts simultaneously were capable of phagocytosing the resorbed CaP crystals. The formation of endophagosomes was performed (1) by the uptake of particles into large intracellular vacuoles, which were generated by deep invagination of the membranes of the osteoclastic ruffled border, and (2) by the encircling of particles due to the development of pseudopodia‐like plasmaprotrusions of the ruffled border. The formation of endophagosomes was followed by the in situ fragmentation of the inclusion material, which subsequently was released into the extracellular space and phagocytosed by macrophages. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 713–718, 2003
Effect of silicon rubber crosslink density on fibroblast cell behavior in vitro
Authors: Mirzadeh Hamid , Shokrolahi Fateme , Daliri Morteza
Published: November 2003

In this study, samples of poly(dimethylsiloxane) (PDMS) with different crosslink densities were prepared in order to produce samples with different crosslink density and, subsequently, different molecular mobilities. Crosslink density and chain mobility changes in PDMS networks were determined using differential scanning calorimetery and dynamic mechanical thermal analysis, respectively. Surface roughness was studied by scanning electron microscopy (SEM). To evaluate biocompatibility, mouse fibroblast L‐929 cells were cultured onto different samples, and their numbers and growth behaviors were investigated by optical microscopy. The results showed that crosslink density and, consequently, molecular mobility cause changes in cell behavior. Moreover, we found that there is an optimum molecular mobility for PDMS at which the number and the surface areas of cells show the best cell attachment and proliferation. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 727–732, 2003
Atomic force microscopy and nanoindentation characterization of human lamellar bone prepared by microtome sectioning and mechanical polishing technique
Authors: Xu J. , Rho J. Y. , Mishra S. R. , Fan Z.
Published: November 2003

Surface topography, microstructure, and micromechanical properties of human lamellar bone were characterized by atomic force microscopy and nanoindentation. The lamellar bone surfaces were prepared by two different methods: microtome sectioning and mechanical polishing. The lamellar bone surfaces prepared by mechanical polishing revealed that thin lamellae formed depressions approximately 200 nm deep, whereas the surfaces prepared by microtome sectioning were flat. Atomic force microscopy surface topographic images at higher magnification showed differences between thick and thin lamellae in polished samples, but these differences were less pronounced in microtomed samples. Roughness measurements confirmed that there was a significant difference between thick (21.0 nm) and thin lamellae (8.3 nm) in polished samples (p < 0.001). The difference in surface roughness between thick (13.9 nm) and thin lamellae (12.7 nm) in microtomed sample was statistically insignificant (p = 0.74). Higher elastic modulus values were observed for thick lamella in microtomed samples compared with that of thin lamellae, whereas measured elastic modulus differences between thick and thin lamellae in polished samples were found to be statistically insignificant. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 719–726, 2003
Characterization of the mechanical properties of demineralized bone
Authors: Summitt Matthew C. , Reisinger Kim D.
Published: November 2003

Demineralized bone has had limited use as a medical implant, although, recently Jackson et al. (Am J Sports Med 1996;24(4):405–414) examined using demineralized bone as an anterior cruciate ligament (ACL) replacement and found that within 1 year the demineralized bone had remodeled from a haversian system (bone‐like) into a ligament‐like structure. Little research has been done to characterize the mechanical properties of demineralized bone and examine its potential as a ligament replacement. This research examined the mechanical properties of demineralized bone as a function of acid saturation time and methods of processing and sterilization using specimens from various anatomic locations. Bone specimens were manufactured from the tibia, metatarsus, femur, radius, and humerus of bovine bone. Tensile strength, strain, and modulus of elasticity were examined for various acid saturation times and sterilization treatments. Additionally, viscoelastic properties, creep and stress relaxation, and fatigue properties were examined. The findings indicate that completely demineralized bone has mechanical properties similar to the ACL and, therefore, has increased likelihood for success in ACL reconstruction surgery. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 742–750, 2003
Influence of the in vitro culture period on the in vivo performance of cell/titanium bone tissue‐engineered constructs using a rat cranial critical size defect model
Authors: Sikavitsas Vassilios I. , Dolder Juliette van den , Bancroft Gregory N. , Jansen John A. , Mikos Antonios G.
Published: November 2003

The aim of this study was to investigate the in vivo performance in bone‐regenerating capability of cell/scaffold constructs implanted into an orthotopic site. Bone marrow stromal osteoblasts were seeded on titanium fiber mesh scaffolds using a cell suspension (5 × 105 cells per scaffold) and cultured for 1, 4, and 8 days under either static or flow perfusion conditions forming six different treatment groups. A total of 16 constructs from each one of the six treatment groups were then implanted into an 8‐mm critical size calvarial defect created in the cranium of adult syngeneic male Fisher rats. Half of the constructs from each group were retrieved 7 days postimplantation, and the other half of the constructs were retrieved 30 days postimplantation and examined for new bone formation and tissue response. Constructs retrieved 7 days postimplantation were filled with fibrous tissue and capillaries, but no bone formation was observed in any of the six treatment groups. Constructs retrieved 30 days postimplantation showed bone formation (at least 7 out of 8 constructs in all treatment groups). Titanium fiber meshes seeded with bone marrow stromal osteoblasts and cultured for 1 day under flow perfusion conditions before implantation appeared to give the highest percentage of bone formation per implant (64 ± 17%). They also showed the highest ratio of critical size cranial defects that resulted in union of the defect 30 days postimplantation (7 out of 8) together with the constructs cultured for 1 day under static conditions before implantation. There were no significant differences between the different treatment groups; this finding is most likely due to the large variability of the results and the small number of animals per group. However, these results show that titanium fiber mesh scaffolds loaded with bone marrow stromal osteoblasts can have osteoinductive properties when implanted in an orthotopic site. They also indicate the importance of the stage of the osteoblastic differentiation and the quality of the in vitro generated extracellular matrix in the observed osteoinductive potential. © 2003 Wiley Periodicals, Inc. J Biomed Mater Res 67A: 944–951, 2003