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End date: 2019 × Start date: 2016 × DDC: 540 × WGL Institute: ISAS ×

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Now showing 1 - 8 of 8
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    Why phosphoproteomics is still a challenge
    (Cambridge : Royal Society of Chemistry, 2015) Solari, Fiorella A.; Dell'Aica, Margherita; Sickmann, Albert; Zahedi, René P.
    Despite continuous improvements phosphoproteomics still faces challenges that are often neglected, e.g. partially poor recovery of phosphopeptide enrichment, assessment of phosphorylation stoichiometry, label-free quantification, poor behavior during chromatography, and general limitations of peptide-centric proteomics. Here we critically discuss current limitations that need consideration in both qualitative and quantitative studies.
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    Nuevo sistema integrado cromatografía líquida de alta resolución / nebulizador hidráulico de alta presión y temperatura (HPLC/HT-HHPN) para la separación automática de la matriz en la determinación de metales en salmueras con espectrometría de absorción atómica (FAAS)
    (Sao Paulo : Scielo, 2000) Yáñez, J.; Berndt, H.
    An integrated HPF-system using HPLC and HT-HHP-nebulizer is used for matrix separation by the determination of heavy metals in highly concentrated solutions with FAAS. The separation of the matrix (NaCl) is achieved in a HPLC RP-C18 column after heavy metal complexing with trans-1,2-diaminciclohexane-N,N,N ,N -tetraacetic acid (CDTA). Matrix separation and the metal determination can be realized in less than one minute, without any interference from the matrix. The detection limits of Cd(II), Co(II), Cr(VI), Cu(II), Mn(II) and Zn(II) by FAAS were improved in one order of magnitude in compare with the direct determination by pneumatic nebulization nebulizer.
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    The proteome of cholesteryl-ester-enriched versus triacylglycerol-enriched lipid droplets
    (San Francisco, CA : Public Library of Science, 2014) Khor, Victor K.; Ahrends, Robert; Lin, Ye; Shen, Wen-Jun; Adams, Christopher M.; Roseman, Ann Nomoto; Cortez, Yuan; Teruel, Mary N.; Azhar, Salman; Kraemer, Fredric B.
    Within cells, lipids are stored in the form of lipid droplets (LDs), consisting of a neutral lipid core, surrounded by a phospholipid monolayer and an outer layer of protein. LDs typically accumulate either triacylglycerol (TAG) and diacylglycerol or cholesteryl ester (CE), depending on the type of tissue. Recently, there has been an increased interest in the proteins that surround LDs. LD proteins have been found to be quite diverse, from structural proteins to metabolic enzymes, proteins involved in vesicular transport, and proteins that may play a role in LD formation. Previous proteomics analyses have focused on TAG-enriched LDs, whereas CE-enriched LDs have been largely ignored. Our study has compared the LD proteins from CE-enriched LDs to TAG-enriched LDs in steroidogenic cells. In primary rat granulosa cells loaded with either HDL to produce CE-enriched LDs or fatty acids to produce TAG-enriched LDs, 61 proteins were found to be elevated in CE-enriched LDs and 40 proteins elevated in TAG-enriched LDs with 278 proteins in similar amounts. Protein expression was further validated by selected reaction monitoring (SRM) mass spectrometry (MS). SRM verified expression of 25 of 27 peptides that were previously detected by tandem mass tagging MS. Several proteins were confirmed to be elevated in CE-enriched LDs by SRM including the intermediate filament vimentin. This study is the first to compare the proteins found on CE-enriched LDs with TAG-enriched LDs and constitutes the first step in creating a better understanding of the proteins found on CE-enriched LDs in steroidogenic cells.
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    Fast IR laser mapping ellipsometry for the study of functional organic thin films
    (Cambridge : Royal Society of Chemistry, 2015) Furchner, Andreas; Sun, Guoguang; Ketelsen, Helge; Rappich, Jörg; Hinrichs, Karsten
    Fast infrared mapping with sub-millimeter lateral resolution as well as time-resolved infrared studies of kinetic processes of functional organic thin films require a new generation of infrared ellipsometers. We present a novel laboratory-based infrared (IR) laser mapping ellipsometer, in which a laser is coupled to a variable-angle rotating analyzer ellipsometer. Compared to conventional Fourier-transform infrared (FT-IR) ellipsometers, the IR laser ellipsometer provides ten- to hundredfold shorter measurement times down to 80 ms per measured spot, as well as about tenfold increased lateral resolution of 120 μm, thus enabling mapping of small sample areas with thin-film sensitivity. The ellipsometer, equipped with a HeNe laser emitting at about 2949 cm−1, was applied for the optical characterization of inhomogeneous poly(3-hexylthiophene) [P3HT] and poly(N-isopropylacrylamide) [PNIPAAm] organic thin films used for opto-electronics and bioapplications. With the constant development of tunable IR laser sources, laser-based infrared ellipsometry is a promising technique for fast in-depth mapping characterization of thin films and blends.
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    Synthetic glycopeptides and glycoproteins with applications in biological research
    (Frankfurt am Main : Beilstein-Institut, 2012) Westerlind, Ulrika
    Over the past few years, synthetic methods for the preparation of complex glycopeptides have been drastically improved. The need for homogenous glycopeptides and glycoproteins with defined chemical structures to study diverse biological phenomena further enhances the development of methodologies. Selected recent advances in synthesis and applications, in which glycopeptides or glycoproteins serve as tools for biological studies, are reviewed. The importance of specific antibodies directed to the glycan part, as well as the peptide backbone has been realized during the development of synthetic glycopeptide-based anti-tumor vaccines. The fine-tuning of native chemical ligation (NCL), expressed protein ligation (EPL), and chemoenzymatic glycosylation techniques have all together enabled the synthesis of functional glycoproteins. The synthesis of structurally defined, complex glycopeptides or glyco-clusters presented on natural peptide backbones, or mimics thereof, offer further possibilities to study protein-binding events.
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    Alignment of retention time obtained from multicapillary column gas chromatography used for VOC analysis with ion mobility spectrometry
    (Heidelberg : Springer, 2010) Perl, Thorsten; Bödeker, Bertram; Jünger, Melanie; Nolte, Jürgen; Vautz, Wolfgang
    Multicapillary column (MCC) ion mobility spectrometers (IMS) are increasingly in demand for medical diagnosis, biological applications and process control. In a MCC-IMS, volatile compounds are differentiated by specific retention time and ion mobility when rapid preseparation techniques are applied, e.g. for the analysis of complex and humid samples. Therefore, high accuracy in the determination of both parameters is required for reliable identification of the signals. The retention time in the MCC is the subject of the present investigation because, for such columns, small deviations in temperature and flow velocity may cause significant changes in retention time. Therefore, a universal correction procedure would be a helpful tool to increase the accuracy of the data obtained from a gas-chromatographic preseparation. Although the effect of the carrier gas flow velocity and temperature on retention time is not linear, it could be demonstrated that a linear alignment can compensate for the changes in retention time due to common minor deviations of both the carrier gas flow velocity and the column temperature around the MCC-IMS standard operation conditions. Therefore, an effective linear alignment procedure for the correction of those deviations has been developed from the analyses of defined gas mixtures under various experimental conditions. This procedure was then applied to data sets generated from real breath analyses obtained in clinical studies using different instruments at different measuring sites for validation. The variation in the retention time of known signals, especially for compounds with higher retention times, was significantly improved. The alignment of the retention time—an indispensable procedure to achieve a more precise identification of analytes—using the proposed method reduces the random error caused by small accidental deviations in column temperature and flow velocity significantly.
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    High spatial and temporal resolution cell manipulation techniques in microchannels
    (Cambridge : Royal Society of Chemistry, 2016) Novo, Pedro; Dell’Aica, Margherita; Janasek, Dirk; Zahedi, René P.
    The advent of microfluidics has enabled thorough control of cell manipulation experiments in so called lab on chips. Lab on chips foster the integration of actuation and detection systems, and require minute sample and reagent amounts. Typically employed microfluidic structures have similar dimensions as cells, enabling precise spatial and temporal control of individual cells and their local environments. Several strategies for high spatio-temporal control of cells in microfluidics have been reported in recent years, namely methods relying on careful design of the microfluidic structures (e.g. pinched flow), by integration of actuators (e.g. electrodes or magnets for dielectro-, acousto- and magneto-phoresis), or integrations thereof. This review presents the recent developments of cell experiments in microfluidics divided into two parts: an introduction to spatial control of cells in microchannels followed by special emphasis in the high temporal control of cell-stimulus reaction and quenching. In the end, the present state of the art is discussed in line with future perspectives and challenges for translating these devices into routine applications.