bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractDNA 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

AbstractA 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

AbstractWe 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

AbstractMiniaturized 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

AbstractAn 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

AbstractThis 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

Abstract1‐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

AbstractA 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

AbstractThe 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

AbstractDifferent 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

AbstractThis 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

AbstractRecent 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

AbstractAn 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

AbstractThe 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

AbstractThe 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

AbstractAn 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

AbstractThe 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.