The Experts below are selected from a list of 11028 Experts worldwide ranked by ideXlab platform
Gunther K Bonn - One of the best experts on this subject based on the ideXlab platform.
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nanostructured diamond like carbon on digital versatile disc as a matrix free target for laser desorption ionization mass spectrometry
Analytical Chemistry, 2008Co-Authors: Muhammad Najamulhaq, Matthias Rainer, Christian W Huck, Peter Hausberger, Harald Kraushaar, Gunther K BonnAbstract:A nanostructured diamond-like carbon (DLC) coated digital versatile disk (DVD) target is presented as a matrix-free sample support for application in laser desorption/ionization mass spectrometry (LDI-MS). A large number of vacancies, defects, relative sp2 carbon content, and nanogrooves of DLC films support the LDI phenomenon. The observed absorptivity of DLC is in the range of 305−330 nm (nitrogen laser, 337 nm). The Universal Applicability is demonstrated through different analytes like amino acids, carbohydrates, lipids, peptides, and other metabolites. Carbohydrates and amino acids are analyzed as sodium and potassium adducts. Peptides are detectable in their protonated forms, which avoid the extra need of additives for ionization. A bovine serum albumin (BSA) digest is analyzed to demonstrate the performance for peptide mixtures, coupled with the material-enhanced laser desorption/ionization (MELDI) approach. The detection limit of the described matrix-free target is investigated to be 10 fmol/μL fo...
Huwei Liu - One of the best experts on this subject based on the ideXlab platform.
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graphite coated paper as substrate for high sensitivity analysis in ambient surface assisted laser desorption ionization mass spectrometry
Analytical Chemistry, 2012Co-Authors: Jialing Zhang, Chengsen Zhang, Baosheng Feng, Zhigui Zhou, Yu Bai, Huwei LiuAbstract:In this work, an extremely simple and quite sensitive mass spectrometric method termed ambient surface-assisted laser desorption/ionization mass spectrometry (ambient SALDI-MS) was developed to analyze different kinds of compounds, just using a piece of graphite-coated paper for the sample introduction. This provides great advantage in simplifying the analysis process. The method is quite easy to use, and there is no need to worry about the source of graphite, that is, the brands or the types of pencil. And the whole process was carried out under atmospheric pressure, offering all the merits that could occur in ambient MS. The improved sensitivity of this method is mainly because of the graphite, which serves as energy-transfer medium to absorb the energy of the photons and release it to the analytes that are adsorbed on the graphite surface. Also, three different laser wavelengths (1064, 532, and 355 nm) was tested to investigate the desorption mechanism. Fifty-one compounds, with varied chemical structures, were tried to prove that this new method possessed Universal Applicability to detect different kinds of small organic molecules.
Frank Schnorrer - One of the best experts on this subject based on the ideXlab platform.
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a versatile two step crispr and rmce based strategy for efficient genome engineering in drosophila
G3: Genes Genomes Genetics, 2014Co-Authors: Xu Zhang, Wouter Koolhaas, Frank SchnorrerAbstract:The development of clustered, regularly interspaced, short palindromic repeats (CRISPR)/CRISPR-associated (Cas) technologies promises a quantum leap in genome engineering of model organisms. However, CRISPR-mediated gene targeting reports in Drosophila melanogaster are still restricted to a few genes, use variable experimental conditions, and vary in efficiency, questioning the Universal Applicability of the method. Here, we developed an efficient two-step strategy to flexibly engineer the fly genome by combining CRISPR with recombinase-mediated cassette exchange (RMCE). In the first step, two sgRNAs, whose activity had been tested in cell culture, were co-injected together with a donor plasmid into transgenic Act5C-Cas9, Ligase4 mutant embryos and the homologous integration events were identified by eye fluorescence. In the second step, the eye marker was replaced with DNA sequences of choice using RMCE enabling flexible gene modification. We applied this strategy to engineer four different locations in the genome, including a gene on the fourth chromosome, at comparably high efficiencies. Our data suggest that any fly laboratory can engineer their favorite gene for a broad range of applications within approximately 3 months.
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a versatile two step crispr and rmce based strategy for efficient genome engineering in drosophila
bioRxiv, 2014Co-Authors: Xu Zhang, Wouter Koolhaas, Frank SchnorrerAbstract:The development of CRISPR/Cas9 technologies promises a quantum leap in genome-engineering of model organisms. However, CRISPR-mediated gene targeting reports in Drosophila are still restricted to a few genes, use variable experimental conditions and vary in efficiency, questioning the Universal Applicability of the method. Here, we developed an efficient, two-step strategy to flexibly engineer the fly genome by combining CRISPR with recombinase-mediated cassette exchange (RMCE). In the first step, two sgRNAs, whose activity had been tested in cell culture, were co-injected together with a donor plasmid into transgenic Act5C-Cas9, Ligase4 mutant embryos and the homologous integration events were identified by eye fluorescence. In the second step, the eye marker was replaced with DNA sequences of choice using RMCE enabling flexible gene modification. We applied this strategy to engineer four different loci, including a gene on the fourth chromosome, at comparably high efficiencies, suggesting that any fly lab can engineer their favourite gene for a broad range of applications within about three months.
Thierry Deutsch - One of the best experts on this subject based on the ideXlab platform.
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accurate and efficient linear scaling dft calculations with Universal Applicability
arXiv: Materials Science, 2015Co-Authors: Stephan Mohr, Laura E Ratcliff, Luigi Genovese, Damien Caliste, Paul Boulanger, Stefan Goedecker, Thierry DeutschAbstract:Density Functional Theory calculations traditionally suffer from an inherent cubic scaling with respect to the size of the system, making big calculations extremely expensive. This cubic scaling can be avoided by the use of so-called linear scaling algorithms, which have been developed during the last few decades. In this way it becomes possible to perform ab-initio calculations for several tens of thousands of atoms or even more within a reasonable time frame. However, even though the use of linear scaling algorithms is physically well justified, their implementation often introduces some small errors. Consequently most implementations offering such a linear complexity either yield only a limited accuracy or, if one wants to go beyond this restriction, require a tedious fine tuning of many parameters. In our linear scaling approach within the BigDFT package, we were able to overcome this restriction. Using an ansatz based on localized support functions expressed in an underlying Daubechies wavelet basis -- which offers ideal properties for accurate linear scaling calculations -- we obtain an amazingly high accuracy and a Universal Applicability while still keeping the possibility of simulating large systems with only a moderate demand of computing resources.
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Accurate and efficient linear scaling DFT calculations with Universal Applicability
Physical Chemistry Chemical Physics, 2015Co-Authors: Stephan Mohr, Laura E Ratcliff, Luigi Genovese, Damien Caliste, Paul Boulanger, Stefan Goedecker, Thierry DeutschAbstract:Density functional theory calculations are computationally extremely expensive for systems containing many atoms due to their intrinsic cubic scaling. This fact has led to the development of so-called linear scaling algorithms during the last few decades. In this way it becomes possible to perform ab initio calculations for several tens of thousands of atoms within reasonable walltimes. However, even though the use of linear scaling algorithms is physically well justified, their implementation often introduces some small errors. Consequently most implementations offering such a linear complexity either yield only a limited accuracy or, if one wants to go beyond this restriction, require a tedious fine tuning of many parameters. In our linear scaling approach within the BigDFT package, we were able to overcome this restriction. Using an ansatz based on localized support functions expressed in an underlying Daubechies wavelet basis -which offers ideal properties for accurate linear scaling calculations -we obtain an amazingly high accuracy and a Universal Applicability while still keeping the possibility of simulating large system with linear scaling walltimes requiring only a moderate demand of computing resources. We prove the effectiveness of our method on a wide variety of systems with different boundary conditions, for single-point calculations as well as for geometry optimizations and molecular dynamics.
Klaus Mullen - One of the best experts on this subject based on the ideXlab platform.
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new aspects in matrix assisted laser desorption ionization time of flight mass spectrometry a Universal solvent free sample preparation
Rapid Communications in Mass Spectrometry, 2001Co-Authors: Sarah Trimpin, Ali Rouhanipour, Hans Joachim Rader, Klaus MullenAbstract:A method of solvent-free sample preparation is shown to be of Universal Applicability for matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Results obtained were compared with those of traditional solvent-based sample preparation for MALDI-MS in order to demonstrate their similarities with respect to accuracy, sensitivity and resolution for polymers such as polystyrene and poly(methyl methacrylate) in a mass range from 2 to 100 kDa. The results revealed that there is fundamentally no difference in the quality of the obtained mass spectra, and we conclude that the mechanism of desorption and ionization remains unchanged. However, the solvent-free sample preparation turned out to have some advantages over the traditional method in certain cases: quick and easy Applicability is shown for polyetherimide avoiding time-consuming optimization procedures. In particular, industrial pigments that are insoluble in common solvents were characterized without interfering signals from fragments. The method even showed improvements with respect to reproducibility and mass discrimination effects in comparison to traditional sample preparation. Additionally, this contribution provides new insight regarding the analyte/matrix preorganization for the desorption step which now appears to be independent of crystallinity.
