Browsing by Author "Chen, Wei-Yu"

Now showing 1 - 20 of 25

A comparative study on the production yield of H atom in the thermal decomposition of i-C4H10 and n-C4H10: Examination of the contribution of the roaming radical channels
(2018-01-01)
Chen, Wei-Yu
;
Matsui, Hiroyuki
;
Wang, Niann-Shiah
;
應用化學系
;
Department of Applied Chemistry
The yields of H atoms in the thermal decomposition of i-C4H10 -> products (1) and n-C4H10 -> products (2) are measured at 1470-1800 K behind reflected shock waves. A comparative method is used to evaluate the branching fractions for i-C4H10 -> CH3 + i-C3H7 (1a) and n-C4H10 -> 2C(2)H(5) (2b), where, C3H6 is used as a reference. The branching fractions for (1a) and (2b) are expressed by k(1a)/ k(1) = (0.64 +/- 0.14) (10 T-3/ K) - (0.06 +/- 0.23) and, k(2b)/ k(2) = (0.050 +/- 0.059)(10 T-3/ K) + (0.49 +/- 0.10), respectively. Contributions of the roaming channels are less than 12 and 5% for i-C4H10 -> CH4 + C3H6 (1b) and n-C4H10 -> CH4 + C3H6 (2c), respectively. (C) 2017 Elsevier B. V. All rights reserved.
A physics-based transit time model for GaInP/GaAs HBT devices
(2005)
Tseng, Sheng-Che
;
Meng, Chinchun
;
Chen, Wei-Yu
;
Su, Jen-Yi
;
電信工程研究所
A compact physics-based transit time model has been established for the GaInP/GaAs HBT device. The VBIC model fails to describe the transit time frequency versus bias (I(C), V(CE)) especially at low and medium current regimes. Starting with the HICUM model, we introduce a new time constant to describe the transit time frequency versus bias (I(C), V(CE)) more precisely. This model has obvious advantage over the VBIC model to show the relation between the f(t) versus bias (I(C), V(CE)) in the low and medium current regimes for GaInP/GaAs HBT devices.
Acceleration of microwave-assisted enzymatic digestion reactions by magnetite beads
(2007-03-15)
Chen, Wei-Yu
;
Chen, Yu-Chie
;
應用化學系
;
應用化學系分子科學碩博班
;
Department of Applied Chemistry
In this study, we demonstrated that microwave-assisted enzymatic digestion could be greatly accelerated by multifunctional magnetite beads. The acceleration of microwave-assisted enzymatic digestion by the presence of the magnetite beads was attributable to several features of the beads. Their capacity to absorb microwave radiation leads to rapid heating of the beads. Furthermore, their negatively charged functionalities cause adsorption of proteins with opposite charges onto their surfaces by electrostatic interactions, leading to a concentration on the surfaces of the beads of proteins present in trace amounts in the solution. The adsorbed proteins are denatured and hence rendered vulnerable to enzymatic digestion and are digested on the beads. For microwave heating, 30 s was sufficient for carrying out the tryptic digestion of cytochrome c, in the presence of magnetite beads, while 1 min was adequate for tryptic digestion of myoglobin. The digestion products were characterized by MALDI-MS. This rapid enzymatic digestion allowed the entire time for identification of proteins to be greatly reduced. Furthermore, specific proteins present in trace quantities were enriched from the sample on the magnetite beads and could be rapidly isolated from the sample by employing an external magnetic field. These multiple roles of magnetite beads, as the absorber for microwave irradiation, the concentrating probe, and the agent for unfolding proteins, contributed to their capability of accelerating microwave-assisted enzymatic digestion. We also demonstrated that trypsin immobilized magnetite beads were suitable for use in microwave-assisted enzymatic digestion.
Affinity-based mass spectrometry using magnetic iron oxide particles as the matrix and concentrating probes for SALDI MS analysis of peptides and proteins
(2006-10-01)
Chen, Wei-Yu
;
Chen, Yu-Chie
;
應用化學系
;
應用化學系分子科學碩博班
;
Department of Applied Chemistry
Silane-immobilized magnetic iron oxide particles were used as the assisting material in surface-assisted laser desorption/ionization (SALDI) mass spectrometric analysis. This approach can be used to analyze small proteins and peptides. The upper detectable mass range is approximately 16 kDa. The detection limit for peptides is about 20 fmol. Silanized iron oxide particles with negatively charged functionalities can also be used as the affinity probes to selectively trap oppositely charged species from sample solutions by adjusting the pH of the solution. A tryptic digest product of cytochrome C at a concentration as low as 10 nM can be enriched by the particles and directly analyzed by iron oxide SALDI MS without the need for elution steps. Affinity-based mass spectrometry using the bifunctional silanized magnetic iron oxide particles as the SALDI matrix and concentrating probe is demonstrated in this study.
Convergent Solution Phase Synthesis of Chimeric Oligonucleotides by a 2+2 and 3+3 Phosphoramidite Strategy
(2010)
Chen, Chih-Hau
;
Chen, Wei-Yu
;
Chen, Yu-Chie
;
Lee, Ming-Juan
;
Huang, Chyuan-Der
A chimeric oligonucleotide tetramer and hexamer were synthesized by the phosphoramidite approach using a 2+2 and 3+3 strategy, respectively. The concept of convergent synthesis provides an efficient route toward the synthesis of longer chimeric oligonucleotides, such as small interfering RNA oligonucleotides without the pollution of n - 1 or shorter failures. This methodology offers an efficient and economical way to scale-up the synthesis of high purity oligonucleotides for clinical trials and commercial uses.
Crystal Quality of 3C-SiC Influenced by the Diffusion Step in the Modified Four-Step Method
(2010)
Chen, Wei-Yu
;
Wang, Wei-Lin
;
Liu, Jui-Min
;
Chen, Chien-Cheng
;
Hwang, Jenn-Chang
The atomic arrangement and bonding characteristics of void-free 3C-SiC/Si(100) grown by the modified four-step method are presented. Without the diffusion step, Si-C bonds are partially formed in the as-carburized layer on Si(100). The ratio of C-C bonds to Si-C bonds is about 7:3, which can be lowered to about 1:9 after the diffusion step at 1350 degrees C for 5 min or at 1300 degrees C for 7 min according to C 1s core level spectra. The residual C-C bonds cannot be removed, which is associated with an irregular atomic arrangement (amorphous) located either at the 3C-SiC/Si(100) interface or at the intersection of twin boundaries in the 3C-SiC buffer layer based on the lattice image taken by transmission electron microscope. The diffusion step helps the formation of Si-C bonds more completely and results in a SiC buffer layer of high quality formed on Si(100) before the growth step. However, twins and stacking faults still appear in the 3C-SiC buffer layer after the diffusion step. The formation mechanism of the 3C-SiC buffer layer is proposed and discussed.
Dextran-encapsulated photoluminescent gold nanoclusters: synthesis and application
(2014-06-17)
Chiu, Wei-Ju
;
Chen, Wei-Yu
;
Lai, Hong-Zheng
;
Wu, Ching-Yi
;
Chiang, Hsiang-Lin
Dextrans are widely used as additives in food, pharmaceutical, and cosmetics because of their hydrophilicity, biocompatibility, and low toxicity. These features allow the use of dextrans to modify the surface of nanoparticles to improve cell compatibility for biomedical applications. Additionally, dextran molecules covalently bound with fluorescent dyes are frequently used as tracers in animal studies. These facts show that dextrans are useful compounds for biomedicine-related applications and research. Our aim was to explore a facile way to generate dextran-derived nanoparticles with photoluminescent property for the use in fluorescence imaging of bacteria and cancer cells. Dextran-encapsulated gold nanoclusters (AuNCs@ dextran) were generated through a one-pot reaction by stirring dextrans and aqueous tetrachloroauric acid overnight. The generated AuNCs exhibit bright and green photoluminescence under the illumination of an ultraviolet lamp (lambda(max) = 365 nm), and high cell biocompatibility was found as well. Therefore, the generated AuNCs can be used as fluorescence tracers and nanoprobes. We explored the suitability of AuNCs@ dextran as labeling agents for bacteria, such as Staphylococcus aureus and Escherichia coli. After the bacteria were labeled by AuNCs@ dextran, they became quite visible under a fluorescence microscope. Additionally, we demonstrated that nanocomposites composed of AuNCs@ dextran and silica beads can be readily internalized by cancer cells. The nanocomposites can be readily detected in the cells through their photoluminescence, suggesting possible applications in drug delivery and fluorescence imaging.
Direct measurement of site-specific rates of reactions of H with C3H8, i-C4H10, and n-C4H10
(2017-08-14)
Lin, Chia-Chieh
;
Chen, Wei-Yu
;
Matsui, Hiroyuki
;
Wang, Niann-Shiah
;
應用化學系
We measured the rates of abstraction of a hydrogen atom from specific sites in propane C3H8, 2-methyl propane (i-C4H10), and butane (n-C4H10); the sites are a primary hydrogen of C3H8 and i-C4H10 and a secondary hydrogen of n-C4H10. The excellent reproducibility of conditions of a diaphragm-less shock tube enabled us to conduct comparative measurements of the evolution of H atoms in three mixtures-(i) 0.5 ppm C2H5I + Ar, (ii) 0.5 ppm C2H5I + 50-100 ppm alkane as C3H8 or i-C4H10 or n-C4H10 + Ar, and (iii) the same concentrations of alkane + Ar without C2H5I-in the temperature range 1000-1200 K and at a pressure of 2.0 bars. The net profile of rise and decay of H atoms in the C2H5I + alkane mixture was derived on subtracting the absorbance of (iii) from that of (ii). Measurements of the mixture (iii) are important because the absorption of alkanes at 121.6 nm is not negligible. In the temperature range 1000-1100 K, the rate of decomposition of C2H5I was evaluated directly on analyzing the exponential growth of H atoms in the mixture (i). The rate of decomposition of C2H5I is summarized as ln(k/s(-1)) = (33.12 +/- 1.4) - (25.23 +/- 1.5) 10(3)/T (T = 1000-1100 K, P = 2.0 bars); the broadening factor F(T) in the Lindemann-Hinshelwood formula was evaluated in the fall-off region. The site-specific rates of H + (C-3-C-4) alkanes are summarized as follows: H + C3H8 -> H-2 + 1-C3H7, ln(k(1a)) = -(21.34 +/- 0.86) - (5.39 +/- 0.93) 10(3)/T, H + i-C4H10 -> H-2 + i-C4H9, ln(k(2a)) = -(20.50 +/- 1.36) - (6.14 +/- 0.13) 10(3)/T, H + n-C4H10 -> H-2 + 2-C4H9, ln(k(3b)) = - (21.37 +/- 1.15) - (4.83 +/- 1.26) 10(3)/T. The present experimental results are compared with published results from quantum-chemical calculations of potential-energy surfaces and transition-state theory. The present experiments are consistent with those calculations for the reaction rates for the attack at the primary site for H + C3H8 and H + i-C4H10, but for the attack at the secondary site of n-C4H10, our results are substantially smaller than the computational prediction, which might indicate a hindrance by the C-H bonds of the primary sites that serves to decrease the rate of abstraction from the secondary site of n-C4H10. The influence on the total rates of reactions H + alkane and the group additivity rule are discussed. Published by AIP Publishing.
Functional Fe(3)O(4)@ZnO magnetic nanoparticle-assisted enrichment and enzymatic digestion of phosphoproteins from saliva
(2010-11-01)
Chen, Wei-Yu
;
Chen, Yu-Chie
;
應用化學系
;
Department of Applied Chemistry
Saliva contains various proteins, particularly abundant are phosphoproteins, that may be related to disease occurrences and that play significant roles in a biological system. Thus, medical diagnostics will benefit tremendously if disease-related protein biomarkers are discovered from saliva. In this paper, we propose and demonstrate an approach using functional zinc oxide coated iron oxide magnetic nanoparticles (Fe(3)O(4)@ZnO MNPs) as affinity probes to selectively enrich phosphoproteins from complex saliva samples and as microwave absorbers to assist the enrichment and subsequent tryptic digestion of trapped proteins under microwave heating. The target species trapped by MNPs were characterized by matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) combined with protein database search. Entire analysis time was shortened to less than 20 min. The detection limit of this approach for a monophosphopeptide was as low as 250 pM (10 mu L).
Functional Fe3O4@ZnO magnetic nanoparticle-assisted enrichment and enzymatic digestion of phosphoproteins from saliva
(2010-11-01)
Chen, Wei-Yu
;
Chen, Yu-Chie
;
應用化學系
;
Department of Applied Chemistry
Saliva contains various proteins, particularly abundant are phosphoproteins, that may be related to disease occurrences and that play significant roles in a biological system. Thus, medical diagnostics will benefit tremendously if disease-related protein biomarkers are discovered from saliva. In this paper, we propose and demonstrate an approach using functional zinc oxide coated iron oxide magnetic nanoparticles (Fe3O4@ZnO MNPs) as affinity probes to selectively enrich phosphoproteins from complex saliva samples and as microwave absorbers to assist the enrichment and subsequent tryptic digestion of trapped proteins under microwave heating. The target species trapped by MNPs were characterized by matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS) combined with protein database search. Entire analysis time was shortened to less than 20 min. The detection limit of this approach for a monophosphopeptide was as low as 250 pM (10 mu L).
Functional gold nanoclusters as antimicrobial agents, for antibiotic-resistant bacteria
(2010-07-01)
Chen, Wei-Yu
;
Lin, Ju-Yu
;
Chen, Wei-Jen
;
Luo, Liyang
;
Diau, Eirc Wei-Guang
Aims: Our aim was to demonstrate that lysozyme-directed generation of gold nanoclusters (Au NCs) are potential antimicrobial agents for antibiotic-resistant bacteria and broad labeling agents for pathogenic bacteria. Materials & methods: Lysozyme is an enzyme that is capable of hydrolyzing the cell walls of bacteria. In this study, we demonstrated the generation of functional Au NCs by using lysozyme as the sequester and the reducing agent for Au precursors at 40 degrees C. In addition, to shorten the reaction time, the reaction was conducted under microwave irradiation within a short period of time for the first time. Results: The bioactivity of the lysozyme on the Au NCs was retained. Therefore, the as-prepared lysozyme Au NCs with desirable fluorescence feature were successfully employed to be broad-band labeling agents for pathogenic bacteria. Furthermore, we also demonstrated that the lysozyme Au NCs can be used to effectively inhibit the cell growth of notorious antibiotic-resistant bacteria, including pan-drug-resistant Acinetobacter baumannii and vancomycin-resistant Enterococcus faecalis. Conclusion: The potential of employing the lysozyme Au NCs for bacterial labeling and as antimicrobial agents is expected.
Growth of 3C-SiC on Si(111) using the four-step non-cooling process
(2010-08-02)
Liu, Jui-Min
;
Chen, Wei-Yu
;
Hwang, J.
;
Huang, C-F.
;
Wang, Wei-Lin
A modified four-step method was applied to grow a 3C-SiC thin film of high quality on the off-axis 1.5 degrees Si(111) substrate in a mixed gas of C(3)H(8), SiH(4) and H(2) using low pressure chemical vapor deposition. The modified four-step method adds a diffusion step after the carburization step and removes the cooling from the traditional threestep method (clean, carburization, and growth). The X-ray intensity of the 3C-SiC(111) peak is enhanced from 5 x 10(4) counts/s (the modified three steps) to 1.1 x 10(5) counts/s (the modified four steps). The better crystal quality of 3C-SiC is confirmed by the X-ray rocking curves of 3C-SiC(111). 3C-SiC is epitaxially grown on Si( 111) supported by the selected area electron diffraction patterns taken at the 3C-SiC/Si(111) interface. Some (111) stacking faults and twins appear inside the 3C-SiC, which may result from the stress induced in the 3C-SiC thin film due to lattice mismatch. The diffusion step plays roles in enhancing the formation of Si-C bonds and in reducing the void density at the 3C-SiC/Si(111) interface. (C) 2010 Elsevier B.V. All rights reserved.
High-Efficiency Current Control Methods Based on Multidimensional Feedback Quantization and Its Application to Three-Phase PMSM
(2014-11-01)
Chen, Hung-Chi
;
Chen, Keng-Yuan
;
Chen, Wei-Yu
;
電機資訊學士班
;
Undergraduate Honors Program of Electrical Engineering and Computer Science
In a six-switch three-phase inverter, the conventional pulsewidth modulation (PWM) has six switching times in every switching period based on the average concept. The used multidimensional feedback quantized modulation (MDFQM) strategy selects one switching state and keeps it in every sampling period based on the minimization of filtered voltage errors between the desired voltage commands and the output voltages. The widths of the output voltage pulse are integer times the fixed sampling time in MDFQM. In this paper, two high-efficiency current control methods based on MDFQM are proposed. They integrate the MDFQM strategy and the current control function to minimize the filtered current errors between the desired current commands and the inverter current. Due to the main advantages of less switching numbers and more closed fundamental current, a high-efficiency performance is achieved. The proposed methods are applied to the current control of a three-phase permanent-magnet synchronous motor. The simulation results and experimental results verify the effectiveness of the proposed methods.
Iron Oxide/Niobium Oxide Core-Shell Magnetic Nanoparticle-Based Phosphopeptide Enrichment from Biological Samples for MALDI MS Analysis
(2009-04-01)
Lin, Hong-Yi
;
Chen, Wei-Yu
;
Chen, Yu-Chie
;
應用化學系
;
Department of Applied Chemistry
The feasibility of using niobium oxide-coated magnetic nanoparticles (NPs) as affinity probes for selectively trapping phosphopeptides from peptide mixtures including tryptic digest of caseins, serum, and cell lysate was demonstrated in this study. Phosphopeptide enrichment was rapid when subjecting these systems to microwave heating for 1 min; the probe-target species, which were readily isolated through magnetic separation, were then analyzed using matrix-assisted laser desorption/ionization mass spectrometry (MALDI MS). Only signals for phosphopeptides were present in the resulting mass spectra. The detection limit for monophosphopeptide was as low as 5 fmol.
Iron oxide/tantalum oxide core-shell magnetic nanoparticle-based microwave-assisted extraction for phosphopeptide enrichment from complex samples for MALDI MS analysis
(2009-08-01)
Lin, Hong-Yi
;
Chen, Wei-Yu
;
Chen, Yu-Chie
;
應用化學系
;
Department of Applied Chemistry
A new type of metal-oxide-coated magnetic nanoparticles (NPs)-tantalum-oxide-coated magnetic iron oxide (Fe(3)O(4)@Ta(2)O(5)) NPs-which are used as affinity probes for selectively trapping phosphopeptides from complex samples, is demonstrated in this study. In this approach, phosphopeptide enrichment was achieved by incubating the NPs with sample solutions under microwave heating within 1 min. The NP-target species conjugates were readily isolated from samples by magnetic separation followed by matrix-assisted laser desorption/ionization (MALDI) mass spectrometric analysis. When using human serum as the sample, phosphorylated fibrinopeptide-A-derived ions are the only ions observed in the MALDI mass spectra after enrichment by the Fe(3)O(4)@Ta(2)O(5) NPs. Furthermore, only phosphopeptides appear in the MALDI mass spectra after using the affinity probes to selectively trap target species from the tryptic digest of a cell lysate and milk sample. The results demonstrated that the Fe(3)O(4)@Ta(2)O(5) NPs have the capability of selectively trapping phosphorylated peptides from complex samples. The detection limit of this approach for a phosphopeptide (FQpSEEQQQTEDELQDK) was similar to 10 fmol.
Multi-Dimensional Feedback Quantized Modulation used in Three-Phase PMSM Motor Current Control
(2013)
Chen, Hung-Chi
;
Chen, Keng-Yuan
;
Chen, Wei-Yu
;
Hu, Jwu-Sheng
;
電控工程研究所
A current controlled switching strategy using multi-dimensional feedback quantized modulation is proposed in this work. The proposed strategy finds an optimal state that minimizes the power of current error, in contrast to conventional space vector pulse width modulation (SVPWM), which switches states in an equivalent mean phase voltage manner. The main advantage is that the output power factor is increased, i.e., an improved power efficiency. The proposed scheme is applied to the control of 3-phase permanent-magnet synchronous motor (PMSM). The simulations confirm the proposed control strategy.
Nitrilotriacetic acid-coated magnetic nanoparticles as affinity probes for enrichment of histidine-tagged proteins and phosphorylated peptides
(2007-10-01)
Li, Yi-Cheng
;
Lin, Ya-Shiuan
;
Tsai, Pei-Jane
;
Chen, Cheng-Tai
;
Chen, Wei-Yu
We herein demonstrate superparamagnetic Fe3O4 nanoparticles coated with nitrilotriacetic acid derivative (NTA) that can bind with different immobilized metal ions are capable of probing diverse target species. Immobilized Ni(II) on the surfaces of the NTA-magnetic nanoparticles have the capability of selectively trapping histidine (His)tagged proteins such as a mutated streptopain tagged with 6x His, i.e., C192S (MW similar to 42 kDa), from cell lysates. Enrichment was achieved by vigorously mixing the sample solution and the nanoparticles by pipetting in and out of a sample vial for only 30 s. After enrichment, the probe-target species could be readily isolated by magnetic separation. We also characterized the proteins enriched on the affinity probes using on-probe tryptic digestion under microwave irradiation for only 2 min, followed by matrix-assisted laser desorption/ionization mass spectrometry analysis. Using this enrichment and tryptic digestion, the target species can be rapidly enriched and characterized, reducing the time required for carrying out the complete analysis to less than 10 min. Furthermore, when either Zr(IV) or Ga (III) ions are immobilized on the surfaces of the NTA-magnetic nanoparticles, the nanoparticles have the capability of selectively enriching phosphorylated peptides from tryptic digests of alpha-, beta-caseins, and diluted milk. The detection limit for the tryptic digests of alpha- and,beta-caseins is similar to 50 finol.
Potent Antibacterial Nanoparticles for Pathogenic Bacteria
(2015-01-28)
Lai, Hong-Zheng
;
Chen, Wei-Yu
;
Wu, Ching-Yi
;
Chen, Yu-Chie
;
應用化學系
Antibiotic-resistant bacteria have emerged because of the prevalent use of antibacterial agents. Thus, new antibacterial agents and therapeutics that can treat bacterial infections are necessary. Vancomycin is a potent antibiotic. Unfortunately, some bacterial strains have developed their resistance toward vancomycin. Nevertheless, it has been demonstrated that vancomycin-immobilized nanoparticles (NPs) are capable to be used in inhibition of the cell growth of vancomycin-resistant bacterial strains through multivalent interactions. However, multistep syntheses are usually necessary to generate vancomycin-immobilized NPs. Thus, maintaining the antibiotic activity of vancomycin when the drug is immobilized on the surface of NPs is challenging. In this study, a facile approach to generate vancomycin immobilized gold (Van-Au) NPs through one-pot stirring of vancomycin with aqueous tetrachloroauric acid at pH 12 and 25 degrees C for 24 h was demonstrated. Van-Au NPs (8.4 +/- 1.3 nm in size) were readily generated. The generated Van-Au NPs maintained their antibiotic activities and inhibited the cell growth of pathogens, which included Gram-positive and Gram-negative bacteria as well as antibiotic-resistant bacterial strains. Furthermore, the minimum inhibitory concentration of the Van-Au NPs against bacteria was lower than that of free-form vancomycin. Staphylococcus aureus-infected macrophages were used as the model samples to examine the antibacterial activity of the Van-Au NPs. Macrophages have the tendency to engulf Van-Au NPs through endocytosis. The results showed that the cell growth of S. aureus in the macrophages was effectively inhibited, suggesting the potential of using the generated Van-Au NPs as antibacterial agents for bacterial infectious diseases.
Production of H and O(P-3) Atoms in the Reaction of CH2 with O-2
(2012-09-20)
Lee, Pei-Fang
;
Matsui, Hiroyuki
;
Chen, Wei-Yu
;
Wang, Niann-Shiah
;
應用化學系
The reaction CH2 + O-2 -> 4 products has been studied by using atomic resonance absorption spectrometry (ARAS) of H and O(P-3) atoms behind reflected shock waves over 1850-2050 K and 2.1-1.7 atm. Measurements of [H] and [O] are conducted using mixtures of highly diluted CH2I2 (0.2 and 0.4 ppm) with excess O-2 (100 and 262 ppm) in Ar; comparative measurement of [H] in the 0.2 and 0.4 ppm CH2I2 + 300 ppm H-2 mixture has been conducted simultaneously to confirm the initial concentration of CH2. The apparent reaction rate of CH2 + O-2 (k(2)'), including the contributions of (CH2)-C-3 + O-2 -> products (2) and (CH2)-C-1 + O-2 -> products (3), has been measured from the evolutions of [H] and [O] and summarized as k(2)'/cm(3) molecule(-1) s(-1) = (1.90 +/- 0.31) x 10(-11). The contribution of (CH2)-C-1 + O-2 reaction on the measured k(2)' has been evaluated as 0.15 +/- 0.04, with an assumption that k(3) is independent of temperature and given by the result measured at room temperature [Langford, A. O.; Petek, H.; Moore, C. B. J. Chem. Phys. 1983, 78, 6650-6659]. The net rate for the (CH2)-C-3 + O-2 reaction is given as k(2)/cm(3) molecule(-1) s(-1) = (1.69 +/- 0.31) x 10(-11). The result on k(2) in this study is found to be consistent with the extrapolation of the previous work at lower temperature range of 295-600 K. [Vinckler, C.; Debruyn, W. J. Phys. Chem. 1979, 83, 2057-2062]; these results can be summarized as k(2)/cm(3) molecule(-1) s(-1) = 2.74 x 10(-11) exp(-874/T), (T = 295-2050 K). The apparent production yields of H and O atoms for the reaction channels (CH2)-C-1,3 + O-2 -> H + products (2a, 3a) and (1)'(CH2)-C-3 + O-2 -> O(P-3) + products (2h, 3b) have been evaluated as phi(2a)' = 0.59 +/- 0.06 and phi(2b)' = 0.23 +/- 0.06, respectively. The contributions of (CH2)-C-1 + O-2 reaction on measured phi(2a)' and phi(2b)' are indicated to be minor; the net branching fractions for the (CH2)-C-3+O-2 reaction are estimated as phi(2a) = 0.58 +/- 0.06 and phi(2b) = 0.25 +/- 0.06. No obvious temperature dependence is indicated in the measured rate constant nor in the branching fractions of H and 0 atoms. The mechanism of the reaction of CH2 with O-2 is discussed based on the result of the present study together with those of the previous theoretical/experimental studies.
Rapid enrichment of phosphopeptides and phosphoproteins from complex samples using magnetic particles coated with alumina as the concentrating probes for MALDI MS analysis
(2007-01-05)
Chen, Cheng-Tai
;
Chen, Wei-Yu
;
Tsai, Pei-Jane
;
Chien, Kun-Yi
;
Yu, Jau-Song
In this study, we used nanocomposite magnetic particles coated with alumina as the affinity probes to selectively concentrate phosphorylated peptides and proteins from a low volume of sample solution. Tryptic digest products of phosphoproteins including alpha- and beta-caseins, human protein phosphatase inhibitor 1, nonfat milk, egg white, and a cell lysate were used as the samples to demonstrate the feasibility of this approach. In only 30 and 90 s, phosphopeptides and phosphoproteins sufficient for characterization by MALDI-MS were enriched by the particles, respectively. Proteins trapped on the particles could be directly digested on the particles. The same particles in the digest solution were employed for enrichment of phosphopeptides. We estimated the required time for performing the enrichment of phosphopeptides from complex samples and characterization by MALDI MS was within 5 min. A small volume (50 mu L) and a low concentration (5 x 10(-10) M) of tryptic digest product of a phosphoprotein sample could be dramatically enriched and characterized using this approach.