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61.
Lee JH Kim Y Ha MY Lee EK Choo J 《Journal of the American Society for Mass Spectrometry》2005,16(9):1456-1460
Aminophenylboronic acid (APBA) has been immobilized on magnetic beads for the direct determination of glycoprotein by matrix assisted laser desorption/ionizaton time of flight mass spectrometry (MALDI-TOF-MS). An APBA layer was formed on the surface of carboxylic acid terminated magnetic beads by coupling with carbodiimide and subsequently reacted with an N-hydroxysuccinimide moiety. The immobilized APBA was identified by MALDI-TOF-MS without a matrix. Glycoproteins, such as HbA1c, fibrinogen, or RNase B were separated and desalted using APBA magnetic beads by simply washing the magnetic beads and then separating them by external magnet. Proteins can be identified by direct determination of proteins on beads on MALDI plate and confirmed again by peptide mass finger printing after digestion of proteins on magnetic beads by trypsin. Fluorescence image with a FITC tagging protein using confocal laser microscopy showed the difference of immobilization efficiency between glycoproteins and nonglycoproteins. The methods developed within this work allow the simple treatment and enrichment of glycoproteins as well as direct determination of proteins on beads by MALDI-TOF-MS. 相似文献
62.
Two new indole alkaloids, angustilodine ( 1 ), with an unprecedented pentacyclic carbon skeleton, and angustilocine ( 2 ), belonging to the seco‐angustilobine‐B group of alkaloids, were obtained from the leaf extract of the Malayan species Alstonia angustiloba, and their structures were established by spectroscopic analysis. 相似文献
63.
Choo Bong Hong Maria A. Häder Donat-P. Häder Kenneth L. Poff 《Photochemistry and photobiology》1981,33(3):373-377
Abstract— An apparatus has been developed to measure phototactic movement in a population of amoebae of Dictyostelium discoideum. Fluence–response curves in white light show a positive phototaxis to light below 100mW/m2 . Higher intensities cause a negative phototaxis. An action spectrum, based on the zero-crossing points in fluence–response curves for monochromatic light, shows a major peak at about 405nm and secondary maxima at about 450, 520, 580 and 640nm. This action spectrum resembles the action spectra for accumulations of amoebae in and dispersal from light traps and that of inhibition of aggregation by light, but is distinctly different from the action spectrum for phototaxis by D. discoideum pseudoplasmodia. 相似文献
64.
Based on theoretical calculations using the fragility concept and the nucleation theory for a model glass-forming system, we propose a dimensionless criterion, ?, expressed by Trg(ΔTx/Tg)a, with Trg, the reduced glass-transition temperature, ΔTx, the width of the supercooled liquid region when heating a glass, Tg, the glass transition temperature, and a, the exponent. The application of this simple criterion to various glasses, including network, metallic, and molecular glasses (except pure water), indicates an excellent correlation between the critical cooling rate Rc and ? in a Log Rc-? single master plot with a = 0.143. 相似文献
65.
We have studied the influence of the arc melting procedure of Nb-containing Zr-based bulk metallic glasses (BMGs) on their thermal and mechanical properties. We found that the strength and plastic strain to failure, determined at room temperature, increases by the addition of a few percentage of Nb into the Zr-based BMGs. High-resolution transmission-electron microscopy results show that the addition of 2 at.% Nb introduces the formation of as-cast nanocrystals. At the same time, thermal analyses indicate an increase in glass forming ability with the small addition of Nb. Contrary to the reported results in other amorphous alloys, we found that the plastic strain increases further after heat-induced structural relaxation in the Zr-based BMGs. 相似文献
66.
Fast and sensitive DNA analysis using changes in the FRET signals of molecular beacons in a PDMS microfluidic channel 总被引:3,自引:0,他引:3
Jung J Chen L Lee S Kim S Seong GH Choo J Lee EK Oh CH Lee S 《Analytical and bioanalytical chemistry》2007,387(8):2609-2615
A new DNA hybridization analytical method using a microfluidic channel and a molecular beacon-based probe (MB-probe) is described.
A stem-loop DNA oligonucleotide labeled with two fluorophores at the 5′ and 3′ termini (a donor dye, TET, and an acceptor
dye, TAMRA, respectively) was used to carry out a fast and sensitive DNA analysis. The MB-probe utilized the specificity and
selectivity of the DNA hairpin-type probe DNA to detect a specific target DNA of interest. The quenching of the fluorescence
resonance energy transfer (FRET) signal between the two fluorophores, caused by the sequence-specific hybridization of the
MB-probe and the target DNA, was used to detect a DNA hybridization reaction in a poly(dimethylsiloxane) (PDMS) microfluidic
channel. The azoospermia gene, DYS 209, was used as the target DNA to demonstrate the applicability of the method. A simple
syringe pumping system was used for quick and accurate analysis. The laminar flow along the channel could be easily controlled
by the 3-D channel structure and flow speed. By injecting the MB-probe and target DNA solutions into a zigzag-shaped PDMS
microfluidic channel, it was possible to detect their sequence-specific hybridization. Surface-enhanced Raman spectroscopy
(SERS) was also used to provide complementary evidence of the DNA hybridization. Our data show that this technique is a promising
real-time detection method for label-free DNA targets in the solution phase.
Figure FRET-based DNA hybridization detection using a molecular beacon in a zigzag-shaped PDMS microfluidic channel 相似文献
67.
68.
Wan-Keun Kim Kyung A Sung Keun-Hwan Oh Min-Ju Choo Kuk Young Cho Ki-Yun Cho Jung-Ki Park 《Electrochemistry communications》2009,11(8):1714-1716
A new concept of in situ pore generation to reduce water flooding in cathode catalyst layer (CCL) of polymer electrolyte membrane fuel cell (PEMFC) is proposed with the introduction of water soluble poly(ethylene glycol) (PEG) as a porogen to CCL based on sulfonated poly(ether ether ketone) (sPEEK). In this new type of CCL, PEG is directly removed by water produced during the cathode reaction. The new CCL exhibited much higher cell performance especially in mass transport limitation region compared to the pristine sPEEK-CCL. In addition, the presence of PEG in the new CCL lowered the glass transition temperature of the sPEEK binder, and it could improve the transference of catalyst layer onto the polymer electrolyte membrane. 相似文献
69.
Singlet molecular oxygen, O2(1Σ), is one of the important intermediate species in the atmospheres of Earth, Mars, and Venus. To elucidate the chemistry of this excited molecular oxygen, a series of kinetic measurements have been undertaken using the flow-discharge/optical-emission technique. By monitoring the characteristic emission (762 nm for 1Σ), the quenching rates for several important molecules have been obtained at room temperature. The following table summarizes measurements.
The error limits represent one standard deviation. The systematic error is estimated to be about 15%. For CO2 and O3 molecules, the quenching rate constants were also measured in the temperature range of 245–362 K. In both reactions, negligible temperature dependences (with the activation energy less than 0.6 kcal/mole) were observed. 相似文献
Quencher | Rate Constants (cm3/s) |
---|---|
CH2 | (4.6 ± 0.5) × 10?13 |
H2 | (7.0 ± 0.3) × 10?13 |
N2 | (1.7 ± 0.1) × 10?15 |
Cl2 | (4.5 ± 0.8) × 10?16 |
CO | (4.5 ± 0.5) × 10?15 |
O3 | (2.2 ± 0.3) × 10?11 |
2,3 DBM-2 | (6.0 ± 0.1) × 10?13 |
70.
A discharge-flow apparatus with resonance fluorescence and chemiluminescence detection has been used to monitor O2(b 1σ) production from several reactions of the HO2 radical at 300 K and 1-torr total pressure. O2(b), HO2, and OH were observed when F atoms were added to H2O2 in the gas phase. Signal strengths of O2(b) were proportional to initial concentrations of H2O2 and HO2. These observations were analyzed by using a simple three step mechanism and a more complete computer simulation with 22 reaction steps. The results indicate that the F + HO2 reaction yields O2(b) with an efficiency of (3.6 ± 1.4) × 10?3. By monitoring [O2(b)] and [HO2] upon addition of an excess second reactant to HO2, O2(b) yields from the reactions of HO2 with O, Cl, D, H, and OH were found to be <1 × 10?2, <5 × 10?4, <2 × 10?3, <8 × 10?3, and <1 × 10?3, respectively. Yields of O2(b) from the HO2 ± HO2 reaction were found to be less than 3 × 10?2. 相似文献