31 results on '"Lin He"'
Search Results
2. Point Discharge Microplasma Optical Emission Spectrometer: Hollow Electrode for Efficient Volatile Hydride/Mercury Sample Introduction and 3D-Printing for Compact Instrumentation
- Author
-
Lin He, Xi Wu, Mengtian Li, Kai Li, Xiaoliang Zeng, Xiandeng Hou, and Xiaoming Jiang
- Subjects
Detection limit ,Fabrication ,Chemical substance ,Spectrometer ,Microplasma ,Chemistry ,business.industry ,010401 analytical chemistry ,010402 general chemistry ,01 natural sciences ,0104 chemical sciences ,Analytical Chemistry ,Optical Emission Spectrometer ,Electrode ,Optoelectronics ,business ,Excitation - Abstract
A miniaturized optical emission spectrometer was constructed with improved point discharge microplasma as an excitation source to enhance sample introduction efficiency and excitation efficiency. By using a hollow electrode as one of the discharge electrodes, analyte-containing chemical vapor yielded via hydride generation was transported and confined into the hollow electrode and subsequently guided into the microplasma with high sample introduction efficiency. Moreover, gaseous analyte species were directly diffused from inside the electrode into the center of the microplasma, instead of traditional external diffusion into the microplasma, resulting in sufficient participation in interactions and excitation in the plasma; thus, high excitation efficiency and stability can be achieved. A 3D-printing technique was used to fabricate some components for compact integration of this spectrometer. Physical characteristics of the microplasma, 3D-printing, and experimental parameters were all investigated to better understand the excitation capability and obtain optimal analytical performance. Under optimized conditions, As, Bi, Ge, Hg, Pb, Sb, Se, and Sn were successfully detected, with detection limits of 2.5, 0.44, 1.6, 0.10, 2.8, 1.5, 31, and 0.24 μg L-1, respectively, and relative standard deviations all less than 4%. It was applied to the analysis of Certified Reference Materials (water, soil, and biological samples) and real water samples with satisfactory results. Because of its advantages of compactness, robustness, easy fabrication, and cost-effectiveness, it has a great prospect as a portable spectrometer for field analytical chemistry.
- Published
- 2019
3. Fluorescence Aptameric Sensor for Strand Displacement Amplification Detection of Cocaine
- Author
-
Hui Zhou, Ru-Qin Yu, Jing-Lin He, Guo-Li Shen, Jian-Hui Jiang, Hong-Qi Wang, and Zai-Sheng Wu
- Subjects
DNA Replication ,Electrophoresis ,Time Factors ,Stereochemistry ,Aptamer ,Molecular Sequence Data ,Fluorescence spectrometry ,DNA, Single-Stranded ,Biosensing Techniques ,Primer extension ,Analytical Chemistry ,chemistry.chemical_compound ,Cocaine ,Humans ,DNA Primers ,Base Sequence ,Chemistry ,Inverted Repeat Sequences ,Multiple displacement amplification ,DNA replication ,Nucleic acid amplification technique ,Aptamers, Nucleotide ,Spectrometry, Fluorescence ,Biophysics ,SYBR Green I ,Primer (molecular biology) ,DNA Probes ,Nucleic Acid Amplification Techniques - Abstract
A new fluorescence method based on aptamer-target interactions has been developed for cocaine detection with target-induced strand displacement. Here we describe new probes, the hairpin-probe and the single strand-probe (ss-probe), that possess two recognition sequences of cocaine aptamer. In the presence of cocaine, both probes would associate with the target to form a tripartite complex. The conformational change in the hairpin-probe causes the opening of a hairpin structure and the hybridization to primer. With polymerase and the dNTPs, the replication of the single-stranded domain of hairpin-probe triggers the process of primer extension. When the hairpin-probe is converted into a fully double-stranded form, the ss-probe and cocaine are displaced to bind another hairpin-probe and initiate new amplification cycles. Fluorescence signal generation would be observed upon SYBR Green I intercalating into the new DNA double helix. The new protocol design permits detection of as low as 2 nM cocaine in a closed tube, offering a convenient approach for a homogeneous assay. Compared with previously reported cocaine aptameric sensors, our new method is highly sensitive, selective, and economical.
- Published
- 2010
4. Detection of Protein Binding Using Activator Generated by Electron Transfer for Atom Transfer Radical Polymerization
- Author
-
Lin He and Hong Qian
- Subjects
chemistry.chemical_classification ,Polymers ,Atom-transfer radical-polymerization ,Activator (genetics) ,Chemistry ,Radical polymerization ,Polymer ,Photochemistry ,Electron transport chain ,Analytical Chemistry ,Electron Transport ,Electron transfer ,Immobilized Proteins ,Polymerization ,Polymer chemistry ,Animals ,Living polymerization ,Cattle ,Protein Binding - Abstract
A purge-free controlled living polymerization method, activator generated by electron transfer for atom transfer radical polymerization (AGET ATRP), is used to amplify the occurrence of protein binding events. Detection of ovalbumin is demonstrated where binding of femtomole protein is differentiable from the background using ellipsometry. Moreover, binding of subpicomole protein leads to visually distinguishable spots on the sensor surface within 15 min, which signifies its potential in future development of point-of-need devices.
- Published
- 2009
5. Electrochemical Biosensing Using Amplification-by-Polymerization
- Author
-
Songqin Liu, Yafeng Wu, and Lin He
- Subjects
chemistry.chemical_classification ,Glycidyl methacrylate ,Polymers ,Atom-transfer radical-polymerization ,Radical polymerization ,Analytical chemistry ,Biosensing Techniques ,Polymer ,Photochemistry ,Methacrylate ,Analytical Chemistry ,chemistry.chemical_compound ,Electron transfer ,Acrylates ,chemistry ,Polymerization ,Limit of Detection ,Electrochemistry ,Epoxy Compounds ,Methacrylates ,Biosensor - Abstract
A novel signal amplification strategy for electrochemical detection of DNA and proteins based on the amplification-by-polymerization concept is described. Specifically, a controlled radical polymerization reaction is triggered after the capture of target molecules on the electrode surface. Growth of long chain polymeric materials provides numerous sites for subsequent aminoferrocene coupling, which in turn significantly enhances electrochemical signal output. Activators generated electron transfer for atom transfer radical polymerization (AGET ATRP) is used in this study for its high efficiency in polymer grafting and better tolerance toward oxygen in air. 2-Hydroxyethyl methacrylate (HEMA) and glycidyl methacrylate (GMA) are examined to provide excess hydroxyl or epoxy groups for aminoferrocene coupling. A limit of detection of 15 pM and 0.07 ng/mL is demonstrated for DNA and ovalbumin, respectively. More than 7-fold signal enhancement in ovalbumin detection has been achieved comparing to the unamplified method. In addition, a more than 5 orders of magnitude of dynamic range is achieved with a linear correlation coefficient (R(2)) of 0.997 for DNA, and a more than 3 orders of magnitude with R(2) of 0.999 for ovalbumin. Together, the results show that the coupling of amplification-by-polymerization concept with electrochemical detection offers great promises in providing a sensitive and cost-effective solution for biosensing applications.
- Published
- 2009
6. Surface-Initiated Activators Generated by Electron Transfer for Atom Transfer Radical Polymerization in Detection of DNA Point Mutation
- Author
-
Lin He and Hong Qian
- Subjects
chemistry.chemical_classification ,Time Factors ,Base Sequence ,Atom-transfer radical-polymerization ,Oligonucleotide ,Reducing agent ,Radical polymerization ,Nucleic Acid Hybridization ,Ascorbic Acid ,Biosensing Techniques ,DNA ,Polymer ,Ascorbic acid ,Sensitivity and Specificity ,Combinatorial chemistry ,Catalysis ,Analytical Chemistry ,Electron transfer ,chemistry ,Polymerization ,Point Mutation ,Organic chemistry ,Oxidation-Reduction - Abstract
Amplification-by-Polymerization reportedly offers a sensitive and detector-free approach for DNA detection. However, the requirement for an oxygen-free environment when classic radical polymerization reactions are used in signal amplification significantly limits the mobility of this approach for point-of-need applications. We report here the employment of a purge-free controlled/"living" polymerization reaction, activators generated by electron transfer for atom transfer radical polymerization (AGET ATRP), to achieve signal amplification upon DNA hybridization. Its aptitude in simplifying assay procedure and shortening assay turn-around has been demonstrated in this report, which substantiates the feasibility of using Amplification-by-Polymerization for high throughput or portable screening of genetic mutations. In addition, employment of water-soluble ascorbic acid as the reducing agent has overcome the hurdles encountered by heterogeneous AGET ATRP reactions. Optimization of AGET ATRP in the presence of oligonucleotides has been conducted where tris[(2-pyridyl)methyl]amine (TPMA) was selected as the catalyst ligand for its mild reaction rate. Effective polymer growth has been achieved when the concentration of the Cu(II) catalyst was controlled at 20 mM and ascorbic acid at 18 mM. The propagation and termination reaction constants have been derived, purporting the speculated controlled growth kinetics during polymer grafting. A linear relationship between the grafted polymer film thickness and the amount of captured DNA target sequences has been established, which provides the quantification basis during DNA detection. Detection of DNA sequences with single-point mutations has been successful regardless of the mutation site.
- Published
- 2009
7. Mass Spectrometry Imaging of Small Molecules Using Desorption/Ionization on Silicon
- Author
-
Lin He, Qiang Liu, and Zhong Guo
- Subjects
Diagnostic Imaging ,MALDI imaging ,Silicon ,Lasers ,Cytological Techniques ,Desorption/ionization on silicon ,Analytical chemistry ,Mass spectrometry ,Small molecule ,Mass Spectrometry ,Mass spectrometry imaging ,Cell Line ,Analytical Chemistry ,Mice ,chemistry.chemical_compound ,Liver ,chemistry ,Ionization ,Phosphatidylcholines ,Animals ,Humans ,Sample preparation ,Propidium iodide ,Propidium - Abstract
Development of novel tools to image spatial distribution of small molecules in biological samples is essential in disease diagnosis and biomarker discovery. To simplify sample preparation and reduce background noise in the low-mass region, we describe here the use of a matrix-free mass spectrometric imaging method, i.e., desorption/ionization on silicon (DIOS), for biological surface analysis. The imaging parameters, such as the laser beam diameter and the translation stage movement, were studied and optimized to improve imaging performance. The use of DIOS imaging to map small molecules on mouse liver tissues was demonstrated. In addition, phosphatidylcholine (PC) and propidium iodide (PI) were used as the cell membrane and nucleus markers, respectively, to "visualize" the presence of HEK 293 cells. The reconstructed ion maps of PC and PI were compared with the optical images collected from the same sample using bright-field and fluorescence microscopy. A good correlation of the spatial distribution of cells confirmed the validity of this DIOS imaging approach.
- Published
- 2007
8. Altered Levels of Acute Phase Proteins in the Plasma of Patients with Schizophrenia
- Author
-
Huafang Li, Hui Zhu, Yifeng Yang, Chunling Wan, Yujuan La, Lei Jiang, Guoyin Feng, Lin He, Zhengrui Xi, and Yongshuo Chen
- Subjects
Adult ,Male ,medicine.medical_specialty ,Apolipoprotein B ,Complement factor B ,Analytical Chemistry ,Internal medicine ,mental disorders ,medicine ,Humans ,Electrophoresis, Gel, Two-Dimensional ,Gel electrophoresis ,Chromatography ,biology ,Chemistry ,Haptoglobin ,Acute-phase protein ,Middle Aged ,medicine.disease ,Transthyretin ,Endocrinology ,Schizophrenia ,Proteome ,biology.protein ,Acute-Phase Proteins - Abstract
Schizophrenia is a relatively common psychiatric syndrome that affects virtually all brain functions. We investigated the plasma proteome of 22 schizophrenia male patients and 20 healthy male controls using two-dimensional gel electrophoresis and mass spectrometry. In total, we have identified 66 protein spots in human plasma and found that seven of them showed altered changes in schizophrenia patients, as compared to healthy controls, which mainly were acute phase proteins (APPs). Among these APPs, haptoglobin alpha2 chain (p0.001), haptoglobin beta chain (p0.001), alpha1-antitrypsin (p = 0.001), and complement factor B precursor (p = 0.022) showed overexpression in schizophrenia patients, whereas apolipoprotein A-I (p = 0.034) and transthyretin (p = 0.035) were found to be significantly decreased in patients. In addition, the expression of apolipoprotein A-IV (p = 0.018) was significantly up-regulated in schizophrenia patients, as compared to controls. We also found these APP genes, which were differentially expressed in this study, overlap in the schizophrenia susceptibility loci. Our findings further support the hypothesis that the inflammatory response system is linked to the pathophysiology of schizophrenia.
- Published
- 2006
9. Electrochemical Interrogation of DNA Monolayers on Gold Surfaces
- Author
-
Lihua Wang, Chunhai Fan, Lin He, Haiping Wu, Shiping Song, Ruojun Lao, and Zhizhou Zhang
- Subjects
Surface Properties ,Chemistry ,Hybridization probe ,Nanotechnology ,DNA ,Electrochemistry ,Combinatorial chemistry ,Chemical sensor ,Analytical Chemistry ,Dna immobilization ,chemistry.chemical_compound ,Homogeneous ,Monolayer ,Gold ,Cyclic voltammetry - Abstract
In this report, we systematically investigated DNA immobilization at gold surfaces with electrochemical techniques. Comparative cyclic voltammetric and chronocoulometric studies suggested that DNA monolayers immobilized at gold surfaces were not homogeneous. Nonspecific Au-DNA interactions existed even with the treatment of mercaptohexanol, which was known to competitively remove loosely bound DNA at gold surfaces. While both thiolated and nonthiolated DNA formed monolayers on gold surfaces, their hybridization abilities were distinctly different. In contrast to thiolated DNA probes, nonthiolated DNA probes immobilized at gold surfaces were essentially nonhybridizable. The experimental results presented here might be useful for the design of high-performance electrochemical DNA sensors.
- Published
- 2005
10. Raman Spectroscopy
- Author
-
L. Andrew Lyon, Christine D. Keating, Audrey P. Fox, Bonnie E. Baker, Lin He, Sheila R. Nicewarner, Shawn P. Mulvaney, and Michael J. Natan
- Subjects
Nucleic Acids ,010401 analytical chemistry ,Humans ,Proteins ,02 engineering and technology ,Spectrum Analysis, Raman ,021001 nanoscience & nanotechnology ,0210 nano-technology ,Lipids ,01 natural sciences ,0104 chemical sciences ,Analytical Chemistry - Published
- 1998
11. A Laminar Flow Nebulizer for Aerosol MALDI
- Author
-
Lin He and Kermit K. Murray
- Subjects
Chromatography ,Chemistry ,Analytical chemistry ,Laminar flow ,Mass spectrometry ,Angiotensin II ,Dissociation (chemistry) ,Analytical Chemistry ,Aerosol ,law.invention ,Nebulizer ,Reflectron ,law ,Mass spectrum - Abstract
A laminar flow nebulizer was developed for use with aerosol matrix-assisted laser desorption/ionization mass spectrometry. The nebulizer consists of a glass pneumatic nebulizer combined with a laminar flow tube. Particles formed at the pneumatic nebulizer are entrained in an auxiliary gas stream that dries the particles in the laminar flow tube. The mass range of the reflectron time-of-flight mass spectrometer has been extended to greater than 5000 Da: a mass spectrum of bovine insulin is reported at a mass resolution of 100. Mass spectra of bovine insulin and the peptides bradykinin and angiotensin II contain features resulting from prompt analyte dissociation prior to ion acceleration.
- Published
- 2011
12. Reversible addition-fragmentation chain transfer polymerization in DNA biosensing
- Author
-
Lin He, Weiming Zheng, Peng He, Eric Tucker, and Christopher B. Gorman
- Subjects
chemistry.chemical_classification ,Base Sequence ,Chemistry ,Oligonucleotide ,Hybridization probe ,Chain transfer ,Polymer ,Biosensing Techniques ,DNA ,Analytical Chemistry ,chemistry.chemical_compound ,Biopolymers ,Polymerization ,Polymer chemistry ,Spectroscopy, Fourier Transform Infrared ,Biophysics ,Fragmentation (cell biology) ,DNA Probes ,Biosensor ,Nuclear Magnetic Resonance, Biomolecular ,Chromatography, High Pressure Liquid - Abstract
Reversible addition-fragmentation chain transfer polymerization is employed here to allow detector-free visualization of specific DNA sequences for which dynamic polymer growth is used in signal amplification. In particular, surface-initiated polymer growth was regulated by the immobilization of chain transfer agents on the Au surface where DNA hybridization occurred. A linear polymer growth was observed as a function of the reaction time, characteristic of "living" polymer reactions. Significant improvement in assay sensitivity was realized in comparison to the previously reported polymerization-based sensing method by enhancing polymer growth rate and reducing background noises caused by nonspecific adsorption. Direct visualization of fewer than 2,000 copies of a short oligonucleotide sequence was demonstrated in a detector-free fashion.
- Published
- 2008
13. Detection of DNA point mutation by atom transfer radical polymerization
- Author
-
Lin He, Xinhui Lou, Matthew S. Lewis, and and Christopher B. Gorman
- Subjects
chemistry.chemical_classification ,Free Radicals ,Molecular Structure ,Atom-transfer radical-polymerization ,Spectrum Analysis ,Analytical chemistry ,Infrared spectroscopy ,(Hydroxyethyl)methacrylate ,Polymer ,DNA ,Photochemistry ,Microscopy, Atomic Force ,Analytical Chemistry ,Contact angle ,chemistry.chemical_compound ,chemistry ,Molecule ,Point Mutation ,Naked eye ,Polyhydroxyethyl Methacrylate - Abstract
We report here a new DNA detection method in which polymer growth in atom transfer radical polymerization (ATRP) is used as a means to amplify detection signals. In this method, DNA hybridization and ligation reactions led to the attachment of ATRP initiators on a solid surface where specific DNA sequences were located. These initiators subsequently triggered the growth of poly(hydroxyethyl methacrylate) (PHEMA) at the end of immobilized DNA molecules and formed polymer brushes. The formation of PHEMA altered substrate opacity, rendering the corresponding spots readily distinguishable to the naked eye. A second ATRP reaction to form branched polymers on the surface drastically improved the visibility of DNA hybridization and significantly shortened the detection time. The resulting polymer film was characterized using infrared spectroscopy, ellipsometry, contact angle measurements, and atomic force microscopy. Direct visualization of 1 fmol of target DNA molecules of interest was demonstrated. A proof-of-principle experiment to detect DNA point mutation was conducted. The perfectly matched DNA targets were distinctively differentiated from those with mutations. The demonstrated capability to detect DNA mutation with direct visualization laid the groundwork for the future development of detector-free testing kits in single-nucleotide polymorphism screenings.
- Published
- 2005
14. Ordered silicon nanocavity arrays in surface-assisted desorption/ionization mass spectrometry
- Author
-
Brian G. Prevo, Lin He, Orlin D. Velev, and Nancy Finkel
- Subjects
Silicon ,Surface-assisted laser desorption/ionization ,Nanotubes ,business.industry ,Analytical chemistry ,Arabidopsis ,chemistry.chemical_element ,Thermal ionization ,Mass spectrometry ,Plant Roots ,Analytical Chemistry ,chemistry ,Etching (microfabrication) ,Ionization ,Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization ,Optoelectronics ,Wafer ,Reactive-ion etching ,business - Abstract
We report here a simple method to generate ordered nanocavity arrays on a Si wafer and use it in surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS). A close-packed SiO2 nanosphere array was first deposited on a low-resistivity Si wafer using a convective self-assembly method. The nanoparticle array was then used as a mask in a reactive ion etching (RIE) process to selectively remove portions of the Si surface. Subsequent sonication removed those physically adsorbed SiO2 nanoparticles and exposed an ordered nanocavity array underneath. The importance of this approach is its capability of systematically varying surface geometries to achieve desired features, which makes detailed studies of the impacts of surface features on the desorption/ionization mechanism feasible. We demonstrated that the in-plane width and out-of-plane depth of the cavities were adjustable by varying etching times, and the intercavity spacing was controllable by varying the number of particle layers deposited. MS detection of small peptides on these substrates showed comparable sensitivity to conventional porous Si substrates (DIOS, desorption/ ionization on porous silicon). The desorption and ionization efficiency of these roughened surfaces exhibited a nonmonotonic relationship to the increased total surface area. Several possible factors contributing to the observed phenomenon are speculated upon. The application of this arrayed surface in metabolite detection of Arabidopsis thaliana root extracts is also demonstrated.
- Published
- 2005
15. Barcoding the microworld
- Author
-
Nancy H, Finkel, Xinhui, Lou, Cuiyang, Wang, and Lin, He
- Published
- 2004
16. Particles for multiplexed analysis in solution: detection and identification of striped metallic particles using optical microscopy
- Author
-
Arjuna Balasingham, Dimpy Gupta, Dominador F. Oviso, and Michael J. Natan, Ian D. Walton, R. Griffith Freeman, Lin He, Paul A. Raju, and Scott M. Norton
- Subjects
Diagnostic Imaging ,Reproducibility ,Electronic Data Processing ,Microscopy ,Microscope ,Chemistry ,business.industry ,Nanoparticle ,Nanotechnology ,Multiplexing ,Particle identification ,Analytical Chemistry ,law.invention ,Identification (information) ,Optical microscope ,law ,Metals ,Optoelectronics ,Data striping ,Particle Size ,business - Abstract
In this report, we present data demonstrating that cylindrical metallic particles, with various submicrometer striping patterns, may be readily distinguished in an optical microscope. Accurate particle identification is discussed relative to synthesis reproducibility and the limitations of optical microscopes. Results from a library of these particles, of which over 100 different striping patterns have been produced, are presented. For these particles, made with Au and Ag stripes, more than 70 patterns may be identified with greater than 90% accuracy. The ability to chemically modify the surface of these particles, making them useful for bioanalytical measurements, is also demonstrated. Finally, we discuss improvements in our manufacturing and identification processes that will lead to both larger numbers of striping patterns and improved identification accuracy.
- Published
- 2002
17. Surface-enhanced Raman scattering: a structure-specific detection method for capillary electrophoresis
- Author
-
Christine D. Keating, Lin He, and Michael J. Natan
- Subjects
Chlorophenol ,Analyte ,Chromatography ,Aniline Compounds ,Silver ,Specific detection ,Pyridines ,Tryptophan ,Analytical chemistry ,Electrophoresis, Capillary ,Spectrum Analysis, Raman ,Analytical Chemistry ,chemistry.chemical_compound ,symbols.namesake ,Capillary electrophoresis ,Column chromatography ,chemistry ,Spectrophotometry ,symbols ,Tyrosine ,Raman scattering ,Vibrational spectra ,Chlorophenols ,Nitroso Compounds - Abstract
A new approach to detecting capillary electrophoresis (CE) eluent components by interfacing CE with a surface-enhanced Raman scattering (SERS) system is described. In this approach, CE-based separation of a mixture of trans-1,2-bis(4-pyridyl)ethylene and N,N-dimethyl-4-nitrosoaniline has been detected by SERS in a postcolumn geometry. The retention time obtained from SERS corresponds well with that from conventional UV−visible detection. Meanwhile, CE eluants are identified by their characteristic vibrational spectra, demonstrating the validity of SERS as a structure-specific detection method for CE. In addition, the ability to monitor SERS intensity changes at molecule-specific frequencies makes selective detection of individual analytes possible, even when separation is incomplete. Finally, CE-SERS is evaluated for separation of amino acids (tyrosine and tryptophan) and environmental pollutants (chlorophenol mixtures).
- Published
- 2000
18. Extracting Accurate Precursor Information for Tandem Mass Spectra by RawConverter.
- Author
-
Lin He, Diedrich, Jolene, Yen-Yin Chu, and YatesIII, John R.
- Subjects
- *
COMPUTER software development , *MASS spectrometry , *DATA extraction , *PEPTIDES , *PROTEIN research - Abstract
Extraction of data from the proprietary RAW files generated by Thermo Fisher mass spectrometers is the primary step for subsequent data analysis. High resolution and high mass accuracy data obtained by state-of-the-art mass spectrometers (e.g., Orbitraps) can significantly improve both peptide/protein identification and quantification. We developed RawConverter, a stand-alone software tool, to improve data extraction on RAW files from high-resolution Thermo Fisher mass spectrometers. RawConverter extracts full scan and MSn data from RAW files like its predecessor RawXtract; most importantly, it associates the accurate precursor mass-to-charge (m/z) value with the tandem mass spectrum. RawConverter accepts RAW data generated by either data-dependent acquisition (DDA) or data-independent acquisition (DIA). It generates output into MS1/MS2/MS3, MGF, or mzXML file formats, which fulfills the format requirements for most data identification and quantification tools. Using the tandem mass spectra extracted by RawConverter with corrected m/z values, 32.8%, 27.1%, and 84.1%, peptide spectra matches (PSMs) produce 17.4% (13.0%), 14.4% (11.5%), and 45.7% (36.2%) more peptide (protein) identifications than ProteoWizard, pXtract, and RawXtract, respectively. RawConverter is implemented in C# and is freely accessible at http://fields.scripps.edu/rawconv. [ABSTRACT FROM AUTHOR]
- Published
- 2015
- Full Text
- View/download PDF
19. Peer Reviewed: Barcoding the Microworld
- Author
-
Cuiying Wang, Lin He, Nancy Finkel, and Xinhui Lou
- Subjects
Chemistry ,law ,business.industry ,Nanotechnology ,Computer vision ,Artificial intelligence ,Combinatorial method ,Tracking (particle physics) ,Barcode ,business ,Multiplexing ,Analytical Chemistry ,law.invention - Abstract
The familiar concept of the barcode for tracking may be coming to a chemical reaction near you in the form of coded microparticles.
- Published
- 2004
20. Fluorescence Aptameric Sensor for Strand Displacement Amplification Detection of Cocaine.
- Author
-
Jing-Lin He, Zai-Sheng Wu, Hui Zhou, Hong-Qi Wang, Jian-Hui Jiang, Guo-Li Shen, and Ru-Qin Yu
- Subjects
- *
COCAINE , *DNA polymerases , *NUCLEOTIDE sequence , *NUCLEIC acids , *OLIGONUCLEOTIDES , *ELECTROPHORESIS - Abstract
A new fluorescence method based on aptamer-target interactions has been developed for cocaine detection with target-induced strand displacement Here we describe new probes, the hairpin-probe and the single strand-probe (ss-probe), that possess two recognition sequences of cocaine aptamer. In the presence of cocaine, both probes would associate with the target to form a tripartite complex. The conformational change in the hairpin-probe causes the opening of a hairpin structure and the hybridization to primer. With polymerase and the dNTPs, the replication of the single-stranded domain of hairpin-probe triggers the process of primer extension. When the hairpin-probe is converted into a fully double stranded form, the ss-probe and cocaine are displaced to bind another hairpin-probe and initiate new amplification cycles. Fluorescence signal generation would be observed upon SYBR Green I intercalating into the new DNA double helix. The new protocol design permits detection of as low as 2 nM cocaine in a closed tube, offering a convenient approach for a homogeneous assay. Compared with previously reported cocaine aptameric sensors, our new method is highly sensitive, selective, and economical. [ABSTRACT FROM AUTHOR]
- Published
- 2010
- Full Text
- View/download PDF
21. Detection of Protein Binding Using Activator Generated by Electron Transfer for Atom Transfer Radical Polymerization.
- Author
-
Hong Qian and Lin He
- Subjects
- *
CHEMICAL reactions , *PROTEIN binding , *CHARGE exchange , *POLYMERIZATION , *BIOCHEMISTRY , *ANALYTICAL chemistry - Abstract
A purge-free controlled living polymerization method, activator generated by electron transfer for atom transfer radical polymerization (AGET ATRP), is used to amplify the occurrence of protein binding events. Detection of ovalbumin is demonstrated where binding of femtomole protein is differentiable from the background using ellipsometry. Moreover, binding of subpicomole protein leads to visually distinguishable spots on the sensor surface within 15 min, which signifies its potential in future development of point-of-need devices. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
22. Electrochemical Biosensing Using Amplification-by-Polymerization.
- Author
-
Yafeng Wu, Songqin Liu, and Lin He
- Published
- 2009
- Full Text
- View/download PDF
23. Surface-Initiated Activators Generated by Electron Transfer for Atom Transfer Radical Polymerization in Detection of DNA Point Mutation.
- Author
-
Hong Qian and Lin He
- Subjects
- *
POLYMERIZATION , *MOLECULAR genetics , *DNA , *GENES , *CHEMICAL reactions - Abstract
Amplification-by-Polymerization reportedly offers a sensitive and detector-free approach for DNA detection. However, the requirement for an oxygen-free environment when classic radical polymerization reactions are used in signal amplification significantly limits the mobility of this approach for point-of-need applications. We report here the employment of a purge-free controlled/"living" polymerization reaction, activators generated by electron transfer for atom transfer radical polymerization (AGET ATRP), to achieve signal amplification upon DNA hybridization. Its aptitude in simplifying assay procedure and shortening assay turn-around has been demonstrated in this report, which substantiates the feasibility of using Amplification-by-Polymerization for high throughput or portable screening of genetic mutations. In addition, employment of water-soluble ascorbic acid as the reducing agent has overcome the hurdles encountered by heterogeneous AGET ATRP reactions. Optimization of AGET ATRP in the presence of oligonucleotides has been conducted where tris[(2-pyridyl)methyl]amine (FPMA) was selected as the catalyst ligand for its mild reaction rate. Effective polymer growth has been achieved when the concentration of the Cu(II) catalyst was controlled at 20 mM and ascorbic acid at 18 mM. The propagation and termination reaction constants have been derived, purporting the speculated controlled growth kinetics during polymer grafting. A linear relationship between the grafted polymer film thickness and the amount of captured DNA target sequences has been established, which provides the quantification basis during DNA detection. Detection of DNA sequences with single-point mutations has been successful regardless of the mutation site. [ABSTRACT FROM AUTHOR]
- Published
- 2009
- Full Text
- View/download PDF
24. Reversible Addition-Fragmentation Chain Transfer Polymerization in DNA Biosensing.
- Author
-
Peng He, Weiming Zheng, Tucker, Eric Z., Gorman, Christopher B., and Lin He
- Published
- 2008
- Full Text
- View/download PDF
25. Surface-Enhanced Raman Scattering: A Structure-Specific Detection Method for Capillary....
- Author
-
Lin He and Natan, Michael J.
- Subjects
- *
CAPILLARY electrophoresis , *SURFACE enhanced Raman effect - Abstract
Examines a structure-specific detection method for capillary electrophoresis (CE) eluent components. Interface between CE and surface-enhanced Raman scattering system; Separation of mixture of trans-1,2-bis(4-pyridyl)ethylene; Application of CE-SERS in tyrosine, tryptophan and chlorophenol mixtures separations.
- Published
- 2000
- Full Text
- View/download PDF
26. Mass Spectrometry Imaging of Small Molecules Using Desorption/lonization on Silicon.
- Author
-
Qiang Liu, Zhong Guo, and Lin He
- Subjects
- *
MASS spectrometry , *NUCLEAR spectroscopy , *SPECTRUM analysis , *MATHEMATICAL optimization , *ELECTRON-stimulated desorption , *SURFACE analysis , *DIPOLE moments , *PROPERTIES of matter , *ELECTROLYSIS , *ANALYTICAL chemistry - Abstract
Development of novel tools to image spatial distribution of small molecules in biological samples is essential in disease diagnosis and biomarker discovery. To simplify sample preparation and reduce background noise in the low-mass region, we describe here the use of a matrix-free mass spectrometric imaging method, i.e., desorption/ionization on silicon (DIOS), for biological surface analysis. The imaging parameters, such as the laser beam diameter and the translation stage movement, were studied and optimized to improve imaging performance. The use of DIOS imaging to map small molecules on mouse liver tissues was demonstrated. In addition, phosphatidylcholine (PC) and propidium iodide (PI) were used as the cell membrane and nucleus markers, respectively, to ‘visualize’ the presence of HEK 293 cells. The reconstructed ion maps of PC and PI were compared with the optical images collected from the same sample using bright-field and fluorescence microscopy. A good correlation of the spatial distribution of cells confirmed the validity of this DIOS imaging approach. [ABSTRACT FROM AUTHOR]
- Published
- 2007
- Full Text
- View/download PDF
27. Altered Levels of Acute Phase Proteins in the Plasma of Patients with Schizophrenia.
- Author
-
Yifeng Yang, Chunhing Wan, Huafang Li, Hui Zhu, Yujuan La, Zhengrui Xi, Yongshuo Chen, Lei Jiang, Guoyin Feng, and Lin He
- Subjects
- *
ANALYTICAL chemistry , *SCHIZOPHRENIA , *PSYCHIATRIC diagnosis , *PATIENTS , *TWO-dimensional electrophoresis , *MASS spectrometers , *BLOOD plasma , *ACUTE phase proteins , *HAPTOGLOBINS , *APOLIPOPROTEINS - Abstract
Schizophrenia is a relatively common psychiatric syndrome that affects virtually all brain functions. We investigated the plasma proteome of 22 schizophrenia male patients and 20 healthy male controls using two-dimensional gel electrophoresis and mass spectrometry. In total, we have identified 66 protein spots in human plasma and found that seven of them showed altered changes in schizophrenia patients, as compared to healthy controls, which mainly were acute phase proteins (APPs). Among these APPs, haptoglobin α2 chain (p < 0.001), haptoglobin β chain (p <0.001), α1-antitrypsin (p = 0.001), and complement factor B precursor (p = 0.022) showed overexpression in schizophrenia patients, whereas apolipoprotein A-I (p = 0.034) and transthyretin (p = 0.035) were found to be significantly decreased in patients. In addition, the expression of apolipoprotein A-IV(p = 0.018) was significantly up-regulated in schizophrenia patients, as compared to controls. We also found these APP genes, which were differentially expressed in this study, overlap in the schizophrenia susceptibility loci. Our findings further support the hypothesis that the inflammatory response system is linked to the pathophysiology of schizophrenia. [ABSTRACT FROM AUTHOR]
- Published
- 2006
- Full Text
- View/download PDF
28. Electrochemical Interrogation of DNA Monolayers on Gold Surfaces.
- Author
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Ruojun Lao, Shiping Song, Haiping Wu, Lihua Wang, Zhizhou Zhang, Lin He, and Chunhai Fan
- Subjects
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DNA , *GOLD , *ELECTROCHEMICAL analysis , *MONOMOLECULAR films , *DIFFUSION , *OXIDATION - Abstract
In this report, we systematically investigated DNA immobilization at gold surfaces with electrochemical techniques. Comparative cyclic voltammetric and chronocoulometric studies suggested that DNA monolayers immobilized at gold surfaces were not homogeneous. Nonspecific Au-DNA interactions existed even with the treatment of mercaptohexanol, which was known to competitively remove loosely bound DNA at gold surfaces. While both thiolated and nonthiolated DNA formed monolayers on gold surfaces, their hybridization abilities were distinctly different. In contrast to thiolated DNA probes, nonthiolated DNA probes immobilized at gold surfaces were essentially nonhybridizable. The experimental results presented here might be useful for the design of high-performance electrochemical DNA sensors. [ABSTRACT FROM AUTHOR]
- Published
- 2005
- Full Text
- View/download PDF
29. Detection of DNA Point Mutation by Atom Transfer Radical Polymerization.
- Author
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Xinhui Lou, Lewis, Matthew S., Gorman, Christopher B., and Lin He
- Subjects
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DNA , *GENETIC mutation , *POLYMERIZATION , *CHEMICAL reactions , *ADDITION polymerization , *CARBOCATIONIC polymerization - Abstract
We report here a new DNA detection method in which polymer growth in atom transfer radical polymerization (ATRP) is used as a means to amplify detection signals. In this method, DNA hybridization and ligation reactions led to the attachment of ATRP initiators on a solid surface where specific DNA sequences were located. These initiators subsequently triggered the growth of poly(hydroxyethyl methacrylate) (PHEMA) at the end of immobilized DNA molecules and formed polymer brushes. The formation of PHEMA altered substrate opacity, rendering the corresponding spots readily distinguishable to the naked eye. A second ATRP reaction to form branched polymers on the surface drastically improved the visibility of DNA hybridization and significantly shortened the detection lime. The resulting polymer film was characterized using infrared spectroscopy, ellipsometry, contact angle measurements, and atomic force microscopy. Direct visualization of 1 fmol of target DNA molecules of interest was demonstrated. A proof-of-principle experiment to detect DNA point mutation was conducted. The perfectly matched DNA targets were distinctively differentiated from those with mutations. The demonstrated capability to detect DNA mutation with direct visualization laid the ground-work for the future development of detector-free testing kits in single-nucleotide polymorphism screenings. [ABSTRACT FROM AUTHOR]
- Published
- 2005
- Full Text
- View/download PDF
30. Particles for Multiplexed Analysis in Solution: Detection and Identification of Striped Metallic Particles Using Optical Microscopy.
- Author
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Walton, Ian D., Norton, Scott M., Balasingham, Arjuna, Lin He, Oviso Jr., Dominator F., Gupta, Dimpy, Raju, Paul A., Natan, Michael J., and Freeman, R. Griffin
- Subjects
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METALS , *MICROSCOPY - Abstract
Focuses on the detection and identification of striped metallic particles using optical microscopy. Discussion of accurate particle identification; Analysis of synthesis reproducibility; Limitations of optical microscope.
- Published
- 2002
- Full Text
- View/download PDF
31. Raman spectroscopy.
- Author
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Lyon, L. Andrew, Keating, Christine D., Fox, Audrey P., Baker, Bonnie E., Lin He, Nicewarner, Sheila R., Mulvaney, Shawn P., and Natan, Michael J.
- Subjects
- *
RAMAN spectroscopy - Abstract
Discusses various aspects and applications of Raman spectroscopy. Reference to books and periodicals on this topic; Details on instrumentation, data analysis and theory relating to Raman spectroscopy; Biological applications of Raman spectroscopy; Use of Raman scattering in materials science; Information on nonlinear Raman techniques.
- Published
- 1998
- Full Text
- View/download PDF
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