bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cover Picture: Use of Rhodium N‐Heterocyclic Carbene Complexes in Catalytic Cyclization and Hydrosilylation of 1,6‐Enynes to 2‐Methyl‐1‐silylmethylidene‐2‐cyclopentane (Eur. J. Org. Chem. 22/2003)
Authors: Park Kang Hyun , Kim So Yeon , Son Seung Uk , Chung Young Keun 
Published: November 2003

AbstractThe cover picture shows a neutral rhodium complex [Rh(NHC)(cod)Cl] (NHC = N‐heterocyclic carbene) catalyzing the hydrosilylation/cyclization of 1,6‐enynes and HSiR3 (R3 = Et3 and PhMe2) to form 2‐methyl‐1‐silylmethylidene‐2‐cyclopentanes in high yields. Details are described in the Short Communication by Y. K. Chung et al. on p. 4341 ff.
Fabrication of porous polymer monoliths covalently attached to the walls of channels in plastic microdevices
Authors: Stachowiak Timothy B. , Rohr Thomas , Hilder Emily F. , Peterson Dominic S. , Yi Mingqiang , Svec Frantisek , Fréchet Jean M. J. 
Published: November 2003

AbstractUV‐initiated grafting of plastic tubes and microfluidic chips with ethylene diacrylate followed by the preparation of porous polymer monoliths has been studied. The first step affords a thin grafted layer of polymer with a multiplicity of pendent double bonds that are then used in the second step for covalent attachment of the monolith to the wall. As clearly seen on scanning electron micrographs, this procedure prevents the formation of voids at the monolith‐channel interface a problem that has always plagued approaches involving bulk polymerization in nontreated channels due to the shrinkage of the monolith during the polymerization process and its lack of compatibility with the material of the device. Irradiation with UV light through a photomask allows precise patterning specifying both the area subjected to surface modification and the location of the monolith within specific areas of the device.
Monolithic valves for microfluidic chips based on thermoresponsive polymer gels
Authors: Luo Quanzhou , Mutlu Senol , Gianchandani Yogesh B. , Svec Frantisek , Fréchet Jean M. J. 
Published: November 2003

AbstractThe direct preparation of thermoresponsive monolithic copolymers by photopatterning of a liquid phase consisting of an aqueous solution of N‐isopropylacrylamide, N‐ethylacrylamide, N,N'‐methylenebisacrylamide, and 4,4'‐azobis(4‐cyanovaleric acid) has been studied and the products used as valves within the channels of microfluidic devices. The volume change associated with the polymer phase transition at its lower critical solution temperature (LCST) leads to the rapid swelling and the deswelling of the 2.5% cross‐linked monolithic gel thus enabling the polymer to close or open the channel and to function as a nonmechanically actuated valve. The LCST at which the valve switches was easily adjusted within a range of 35°C–74°C by varying the proportions of the monovinyl monomers in the polymerization mixture. The closed valve holds pressures of up to 18 MPa without noticeable dislocation, structural damage, or leakage. In contrast, following deswelling by raising the temperature above LCST the valve offers no appreciable flow resistance since its large, micrometer‐size pores are open. Laser‐triggered photobleaching of a fluorescent dye contained in the liquid phase enabled monitoring of flow through the device and determination of the times required to open and close the valve. The valves are characterized by very fast actuation times in a range of 1–4 s depending on the type of device. No changes in performance were observed even after repeated open‐close cycling of the valves.
Automated chip‐based nanoelectrospray‐mass spectrometry for rapid identification of proteins separated by two‐dimensional gel electrophoresis
Authors: Zhang Sheng , Van Pelt Colleen K. , Henion Jack D. 
Published: November 2003

AbstractWe report a method using a fully automated chip‐based nanoelectrospray system for two‐dimensional (2‐D) gel sample analyses with mass spectrometric detection. The automated nanoelectrospray system, consisting of the NanoMate and electrospray ionization (ESI) chip, serves as both an autosampler and nanoESI source. This infusion system aspirates samples from a 96‐well plate using disposable pipette tips and then delivers these samples sequentially to an ESI chip. This chip is a fully integrated monolithic device consisting of a 10×10 array of nozzles. The automated nanoelectrospray system is easily controlled through software, permitting the user to select the number of samples to be analyzed, the volume of sample to aspirate, the spray voltage, and analysis time. The system offers all the advantages of conventional nanoelectrospray plus automated, high‐throughput analyses without analyte carryover. The system was used for a protein identification study of 2‐D gel spots of both Escherichia coli and yeast crude cell extracts. The identification of 50 spots from E. coli crude cell extract and 27 spots from yeast extract is presented, demonstrating the powerful combination of the automated nanoESI system, the Thermo Finnigan LCQ Deca ion‐trap mass spectrometer, and SEQUEST search software. In addition, the effects of silver staining and colloidal Coomassie blue staining of 2‐D gel spots on the detection sensitivity and protein sequence coverage are compared and discussed. Furthermore, the comparison results using the multiwell microscale preparation kit versus manual extraction for in‐gel samples are presented.
Cross‐linked coatings for electrophoretic separations in poly(dimethylsiloxane) microchannels
Authors: Hu Shuwen , Ren Xueqin , Bachman Mark , Sims Christopher E. , Li G. P. , Allbritton Nancy 
Published: November 2003

AbstractWe have developed a strategy using ultraviolet light to polymerize mixed monomer solutions onto the surface of a poly(dimethylsiloxane) (PDMS) microdevice. By including monomers with different chemical properties, electrophoretic separations were optimized for a test set of analytes. The properties of surfaces grafted with a single neutral monomer, a neutral and a negative monomer, or a neutral, negative, and cross‐linking monomer were assessed. The highest quality separations were achieved in channels with cross‐linked coatings. The separation efficiency for biologically relevant peptides (kinase substrates) on these surfaces was as high as 18 600 theoretical plates in a 2.5 cm channel. The test peptides were fluorescein‐AEEEIYGEFEAKKKK, fluorescein‐GRPRAATFAEG, fluorescein‐GRPRAA(T‐PO3)FAEG, fluorescein‐DLDVPIP GRFDRRVSVAAE, and fluorescein‐DLDVPIPGRFDRRV(S‐PO3)VAAE. Separations between two different peptides occurred in as little as 400 ms after injection into the separation channel. The simultaneous separation of five kinase and phosphatase substrates was also demonstrated. By carefully selecting mixtures of monomers with the appropriate properties, it may be possible to tailor the surface of PDMS for a large number of different electrophoretic separations.
Preconcentration and separation of double‐stranded DNA fragments by electrophoresis in plastic microfluidic devices
Authors: Wainright Ann , Nguyen Uyen T. , Bjornson TorLeif , Boone Travis D. 
Published: November 2003

AbstractWe have evaluated double‐stranded DNA separations in microfluidic devices which were designed to couple a sample preconcentration step based on isotachophoresis (ITP) with a zone electrophoretic (ZE) separation step as a method to increase the concentration limit of detection in microfluidic devices. Developed at ACLARA BioSciences, these LabCard™ devices are plastic 32 channel chips, designed with a long sample injection channel segment to increase the sample loading. These chips were designed to allow stacking of the sample into a narrow band using discontinuous ITP buffers, and subsequent separation in the ZE mode in sieving polymer solutions. Compared to chip ZE, the sensitivity was increased by 40‐fold and we showed baseline resolution of all fragments in the ΦX174/HaeIII DNA digest. The total analysis time was 3 min/sample, or less than 100 min per LabCard device. The resolution for multiplexed PCR samples was the same as obtained in chip ZE. The limit of detection was 9 fg/μL of DNA in 0.1×polymerase chain reaction (PCR) buffers using confocal fluorescence detection following 488 nm laser excitation with thiazole orange as the fluorescent intercalating dye.
Sequencing of real‐world samples using a microfabricated hybrid device having unconstrained straight separation channels
Authors: Liu Shaorong , Elkin Christopher , Kapur Hitesh 
Published: November 2003

AbstractWe describe a microfabricated hybrid device that consists of a microfabricated chip containing multiple twin‐T injectors attached to an array of capillaries that serve as the separation channels. A new fabrication process was employed to create two differently sized round channels in a chip. Twin‐T injectors were formed by the smaller round channels that match the bore of the separation capillaries and separation capillaries were incorporated to the injectors through the larger round channels that match the outer diameter of the capillaries. This allows for a minimum dead volume and provides a robust chip/capillary interface. This hybrid design takes full advantage, such as sample stacking and purification and uniform signal intensity profile, of the unique chip injection scheme for DNA sequencing while employing long straight capillaries for the separations. In essence, the separation channel length is optimized for both speed and resolution since it is unconstrained by chip size. To demonstrate the reliability and practicality of this hybrid device, we sequenced over 1000 real‐world samples from Human Chromosome 5 and Ciona intestinalis, prepared at Joint Genome Institute. We achieved average Phred20 read of 675 bases in about 70 min with a success rate of 91%. For the similar type of samples on MegaBACE 1000, the average Phred20 read is about 550–600 bases in 120 min separation time with a success rate of about 80–90%.
High‐efficiency peptide analysis on monolithic multimode capillary columns: Pressure‐assisted capillary electrochromatography/capillary electrophoresis coupled to UV and electrospray ionization‐mass spectrometry
Authors: Ivanov Alexander R. , Horváth Csaba , Karger Barry L. 
Published: November 2003

AbstractHigh‐efficiency peptide analysis using multimode pressure‐assisted capillary electrochromatography/capillary electrophoresis (pCEC/pCE) monolithic polymeric columns and the separation of model peptide mixtures and protein digests by isocratic and gradient elution under an applied electric field with UV and electrospray ionization‐mass spectrometry (ESI‐MS) detection is demonstrated. Capillary multipurpose columns were prepared in silanized fused‐silica capillaries of 50, 75, and 100 μm inner diameters by thermally induced in situ copolymerization of methacrylic monomers in the presence of n‐propanol and formamide as porogens and azobisisobutyronitrile as initiator. N‐Ethylbutylamine was used to modify the chromatographic surface of the monolith from neutral to cationic. Monolithic columns were termed as multipurpose or multimode columns because they showed mixed modes of separation mechanisms under different conditions. Anion‐exchange separation ability in the liquid chromatography (LC) mode can be determined by the cationic chromatographic surface of the monolith. At acidic pH and high voltage across the column, the monolithic stationary phase provided conditions for predominantly capillary electrophoretic migration of peptides. At basic pH and electric field across the column, enhanced chromatographic retention of peptides on monolithic capillary column made CEC mechanisms of migration responsible for separation. The role of pressure, ionic strength, pH, and organic content of the mobile phase on chromatographic performance was investigated. High efficiencies (exceeding 300 000 plates/m) of the monolithic columns for peptide separations are shown using volatile and nonvolatile, acidic and basic buffers. Good reproducibility and robustness of isocratic and gradient elution pressure‐assisted CEC/CE separations were achieved for both UV and ESI‐MS detection. Manipulation of the electric field and gradient conditions allowed high‐throughput analysis of complex peptide mixtures. A simple design of sheathless electrospray emitter provided effective and robust low dead volume interfacing of monolithic multimode columns with ESI‐MS. Gradient elution pressure‐assisted mixed‐mode separation CE/CEC‐ESI‐MS mass fingerprinting and data‐dependent pCE/pCEC‐ESI‐MS/MS analysis of a bovine serum albumin (BSA) tryptic digest in less than 5 min yielding high sequence coverage (73%) demonstrated the potential of the method.
Immobilized metal‐ion chelating capillary microreactor for peptide mapping analysis of proteins by matrix assisted laser desorption/ ionization‐time of flight‐mass spectrometry
Authors: Guo Zhong , Xu Songyun , Lei Zhengdeng , Zou Hanfa , Guo Baochuan 
Published: November 2003

AbstractPeptide mass mapping analysis, utilizing a regenerable enzyme microreactor with metal‐ion chelated adsorption of enzyme, combined with matrix assisted laser desorption/ionization‐time of flight‐mass spectrometry (MALDI‐TOF‐MS) was developed. Different procedures from the conventional approaches were adopted to immobilize the chelator onto the silica supports, that is, the metal chelating agent of iminodiacetic acid (IDA) was reacted with glycidoxypropyltrimethoxysilane (GLYMO) before its immobilization onto the inner wall of the fused‐silica capillary pretreated with NH4HF2. The metal ion of copper and subsequently enzyme was specifically adsorbed onto the surface to form the immobilized enzyme capillary microreactor, which was combined with MALDI‐TOF‐MS to apply for the mass mapping analysis of nL amounts of protein samples. The results revealed that the peptide mapping could routinely be generated from 0.5 pmol protein sample in 15 min at 50°C, even 20 fmol cytochrome c could be well digested and detected.
Hybrid microdevice electrophoresis of peptides, proteins, DNA, viruses, and bacteria in various separation media, using UV‐detection
Authors: Végvári Ákos , Hjertén Stellan 
Published: November 2003

AbstractRecently we described the design of a hybrid microdevice for micro(nano)electrophoresis and electrochromatography, discussed its advantages and disadvantages compared to conventional microdevices and presented a few applications with low‐molecular‐weight samples. In this paper, we demonstrate the broad application range of this device using UV‐based analyses of (i) peptides by free‐zone electrophoresis and electrophoresis in a recently introduced gel (polyacrylamide cross‐linked with allyl‐β‐cyclodextrin), (ii) proteins by electrophoretic molecular‐sieving in a polymer solution supplemented with SDS, (iii) DNA fragments by electrophoresis in the above gel, (iv) virus particles in this gel, as well as in free buffer and (v) bacteria in free buffer. To illustrate the advantages of the hybrid microdevice we can mention that electrophoresis of proteins in a polymer‐containing buffer, supplemented with sodium dodecyl sulfate (SDS), in a 4.30 (2.75) cm long channel gave a resolution similar to that in conventional capillary electrophoresis in a 23.5 (18.6) cm long capillary and analysis times which were 15‐fold shorter.
Electrokinetic supercharging preconcentration and microchip gel electrophoretic separation of sodium dodecyl sulfate‐protein complexes
Authors: Xu Zhongqi , Ando Tomomi , Nishine Tsutomu , Arai Akihiro , Hirokawa Takeshi 
Published: November 2003

AbstractA microchip gel electrophoresis (MCGE) method with electrokinetic supercharging (EKS, electrokinetic injection with transient isotachophoresis) on a single channel chip was developed for high‐sensitive detection of a standard mixture of six proteins (phosphorylase b, albumin, ovalbumin, carbonic anhydrase, trypsin inhibitor, and α‐lactalbumin) in the form of sodium dodecyl sulfate (SDS) complexes. An average lower limit of detectable concentration (LLDC) achieved using UV detection at 214 nm was 0.27 μg/mL that is 30 times lower than that of conventional MCGE on a cross geometry chip. The calibration curves for molecular weight and concentration of SDS‐protein complexes suggested that the present EKS‐MCGE method had a better linear dynamic range and benefited future applications for qualitative and quantitative analysis of unknown protein samples. It was found that an excessive amount of unbound SDS in the sample deteriorated the preconcentration effect and resolution. The developed method appears greatly promising for high‐speed and high sensitive analysis of SDS‐proteins by MCGE.
Surface modification of poly(dimethylsiloxane) microchannels
Authors: Makamba Honest , Kim Jin Ho , Lim Kwanseop , Park Nokyoung , Hahn Jong Hoon 
Published: November 2003

AbstractThis review looks at the efforts that are being made to modify the surface of poly(dimethylsiloxane) (PDMS) microchannels, in order to enhance applicability in the field of microfluidics. Many surface modifications of PDMS have been performed for electrophoretic separations, but new modifications are being done for emerging applications such as heterogeneous immunoassays and cell‐based bioassays. These new modification techniques are powerful because they impart biospecificity to the microchannel surfaces and reduce protein adsorption. Most of these applications require the use of aqueous or polar solvents, which makes surface modification a very important topic.
Microfluidic systems in proteomics
Authors: Lion Niels , Rohner Tatiana C. , Dayon Loïc , Arnaud Isabelle L. , Damoc Eugen , Youhnovski Nikolay , Wu Zhi‐Yong , Roussel Christophe , Josserand Jacques , Jensen Henrik , Rossier Joël S. , Przybylski Michael , Girault Hubert H. 
Published: November 2003

AbstractWe present the state‐of‐the‐art in miniaturized sample preparation, immunoassays, one‐dimensional and multidimensional analyte separations, and coupling of microdevices with electrospray ionization‐mass spectrometry. Hyphenation of these different techniques and their relevance to proteomics will be discussed. In particular, we will show that analytical performances of microfluidic analytical systems are already close to fulfill the requirements for proteomics, and that miniaturization results at the same time in a dramatic increase in analysis throughput. Throughout this review, some examples of analytical operations that cannot be achieved without microfluidics will be emphasized. Finally, conditions for the spreading of microanalytical systems in routine proteomic labs will be discussed.
Targeting hepatocytes from liver tissue by laser capture microdissection and proteomics expression profiling
Authors: Marko‐Varga György , Berglund Magnus , Malmström Johan , Lindberg Henrik , Fehniger Thomas E. 
Published: November 2003

AbstractA tissue proteomics process is presented where hepatocyte cell isolation in combination with two‐dimensional (2‐D) gel electrophoresis and mass spectrometric identification were used to annotate the liver proteome. Laser microdissection of 8 μm liver tissue sections was performed and protein expression profiling was compared using a variety of quantities of input cells, and gel separation conditions. The 30 μm diameter laser generated the highest protein yields from the polymer coated caps following microsolubilization. We found that 6000 laser pulses (approximately 7200 hepatocytes) were required in order to generate high‐resolution gel maps. Within homogeneous tissue samples, this could be accomplished in a total cycle time of 20 min using an automated dissection procedure. Close to 1000 high‐quality gel annotations were generated from the corresponding 2‐D gel expression profiles which matched closely the corresponding patterns of analytical‐scale liver preparations detected by silver staining.
A massively parallel PicoTiterPlate™ based platform for discrete picoliter‐scale polymerase chain reactions
Authors: Leamon John H. , Lee William L. , Tartaro Karrie R. , Lanza Janna R. , Sarkis Gary J. , deWinter Alex D. , Berka Jan , Lohman Kenton L. 
Published: November 2003

AbstractWe demonstrate successful, simultaneous polymerase chain reaction (PCR) amplification of up to 300 000 discrete reactions in a novel platform, the PicoTiterPlate™. In addition to elevated throughput, the PicoTiterPlate™ based amplifications (PTPCR) can be performed in extremely small volumes: individual reactions volumes are as low as 39.5 pL, with a total 15.3 μL reaction volume for the entire PicoTiterPlate™. The bulk PTPCR product can be recovered and assayed with real‐time PCR, or discrete PTPCR products can be driven to solid supports, enabling downstream applications such as translation/transcription or sequencing.
Improved solid‐phase microextraction device for use in on‐line immunoaffinity capillary electrophoresis
Authors: Guzman Norberto A. 
Published: November 2003

AbstractA simple solid‐phase microextraction device was fabricated for use in on‐line immunoaffinity capillary electrophoresis (CE). The device, designed in the form of a four‐part cross‐shaped or cruciform configuration, includes a large‐bore tube to transport samples and washing buffers and a small‐bore fused‐silica capillary for separation of analytes. At the intersection of the transport and separation tubes, a small cavity was fabricated, termed the analyte concentrator‐microreactor, which contains four porous walls or semipermeable membranes (one for each inlet and outlet of the tubes) permitting the confinement of beads or suitable microstructures. The surface of the beads in the analyte concentrator carried a molecular recognition adsorbing chemical or affinity ligand material. The improved cruciform configuration of the analyte concentrator‐microreactor device, designed for use in on‐line immunoaffinity CE, enables it to specifically trap, enrich, and elute an analyte from any biological fluid or tissue sample extract without any sample pretreatment except filtration, centrifugation, and/or dilution allowing the separation and characterization of target analyte(s) with improved speed, sensitivity, and lower cost than existing techniques. As a model system, Fab' fragments derived from a purified immunoglobulin G (IgG) antibody were covalently bound to controlled‐porosity glass and used as constituents of the analyte‐microreactor device. The high‐specificity polyclonal antibodies employed in these experiments were individually raised against the acidic nonsteroidal anti‐inflammatory drugs ibuprofen and naproxen, and the neuropeptides angiotensin II, and neurotensin. These compounds, which were present in simple and complex matrices were captured by and eluted from the analyte concentrator‐microreactor using a 50 mM sodium tetraborate buffer solution, pH 9.0, followed by a 100 nL plug of 300 mM glycine buffer, pH 3.4. Two analyte concentrators were tested independently: one containing Fab' fragments derived from antibodies raised against ibuprofen and naproxen; the other containing Fab' fragments derived from antibodies raised against angiotensin II and neurotensin. Each resulting electropherogram demonstrated the presence of two eluted materials in less than 20 min. Immunoaffinity CE performed in a cruciform structure was simpler and faster than previously reported in the literature using on‐line microextraction devices designed in a linear format. The new concentration‐separation system operated consistently for many runs, maintaining reproducible migration times and peak areas for every analyte studied.