Investigation of the desorption process in UV matrix-assisted laser desorption/ionization with a liquid 3-nitrobenzyl alcohol matrix by photoacoustic analysis, fast-flash imaging, and UV-laser postionization
Rohlfing A.,University of Munster |
Rohlfing A.,Sequenom |
Leisner A.,University of Munster |
Leisner A.,Soft Solutions |
And 2 more authors.
Journal of Physical Chemistry C | Year: 2010
Ultraviolet matrix-assisted laser desorption/ionization mass spectrometry (UV-MALDI-MS) is a widely used method for the analysis of a variety of biomolecules. The technique relies on the codesorption of matrix and intact analyte molecules from the condensed to the gaseous phase and subsequent analyte ionization. In spite of numerous studies, the MALDI processes are not yet fully understood. Here, we used 3-nitrobenzyl alcohol as a liquid matrix and employed three complementary analytical techniques to monitor the phase transition and development of the ejected material plume. Each of these methods provided a time resolution in the nanosecond range. (i) Photoacoustic stress waves, generated by the recoil momentum of the ejected material, were recorded simultaneously with the corresponding MALDI-generated analyte ion signals. (ii) The MALDI plume expansion was monitored by using a second illumination laser for imaging the plume in dark-field and in scattered-light geometries, allowing discrimination between ejected droplets and gaseous plume domains. (iii) Time-and space-resolved UV-laser postionization of desorbed matrix molecules complemented these studies. The photoacoustic data indicate the transition from a primarily molecular ejection according to a quasithermal model at low laser fluences to a (layer-by-layer) phase explosion above a fluence threshold of about 170 J/m 2. Notably, this threshold coincides well with the onset of sizable ion generation. A few distinct droplets are detected over the whole of the investigated fluence range. © 2010 American Chemical Society. Source
Li X.,German Electron Synchrotron |
Li X.,Soft Solutions |
Kumar Y.,German Electron Synchrotron |
Kumar Y.,German Center for Neurodegenerative Diseases |
And 8 more authors.
EMBO Journal | Year: 2011
Missorting of Tau from axons to the somatodendritic compartment of neurons is a hallmark of Alzheimer's disease, but the mechanisms underlying normal sorting and pathological failure are poorly understood. Here, we used several Tau constructs labelled with photoconvertible Dendra2 to analyse its mobility in polarized neurons. This revealed a novel mechanism of sorting-a retrograde barrier in the axon initial segment (AIS) operating as cellular rectifier. It allows anterograde flow of axonal Tau but prevents retrograde flow back into soma and dendrites. The barrier requires binding of Tau to microtubules but does not require F-actin and thus is distinct from the sorting of membrane-associated proteins at the AIS. The barrier breaks down when Tau is phosphorylated in its repeat domain and detached from microtubules, for example, by the kinase MARK/Par1. These observations link the pathological hallmarks of Tau missorting and hyperphosphorylation in neurodegenerative diseases. © 2011 European Molecular Biology Organization. Source
Kawano Y.,Olympus America Inc. |
Higgins C.,Olympus America Inc. |
Yamamoto Y.,Olympus Corporation |
Nyhus J.,Allen Institute for Brain Science |
And 4 more authors.
PLoS ONE | Year: 2013
We present a new method for whole slide darkfield imaging. Whole Slide Imaging (WSI), also sometimes called virtual slide or virtual microscopy technology, produces images that simultaneously provide high resolution and a wide field of observation that can encompass the entire section, extending far beyond any single field of view. For example, a brain slice can be imaged so that both overall morphology and individual neuronal detail can be seen. We extended the capabilities of traditional whole slide systems and developed a prototype system for darkfield internal reflection illumination (DIRI). Our darkfield system uses an ultra-thin light-emitting diode (LED) light source to illuminate slide specimens from the edge of the slide. We used a new type of side illumination, a variation on the internal reflection method, to illuminate the specimen and create a darkfield image. This system has four main advantages over traditional darkfield: (1) no oil condenser is required for high resolution imaging (2) there is less scatter from dust and dirt on the slide specimen (3) there is less halo, providing a more natural darkfield contrast image, and (4) the motorized system produces darkfield, brightfield and fluorescence images. The WSI method sometimes allows us to image using fewer stains. For instance, diaminobenzidine (DAB) and fluorescent staining are helpful tools for observing protein localization and volume in tissues. However, these methods usually require counter-staining in order to visualize tissue structure, limiting the accuracy of localization of labeled cells within the complex multiple regions of typical neurohistological preparations. Darkfield imaging works on the basis of light scattering from refractive index mismatches in the sample. It is a label-free method of producing contrast in a sample. We propose that adapting darkfield imaging to WSI is very useful, particularly when researchers require additional structural information without the use of further staining. © 2013 Kawano et al. Source
Soft Solutions | Date: 2012-07-17
Soft Solutions | Date: 2013-07-16
A method and system for providing a marketplace that enables enterprise collaboration. The method includes allowing an agent to receive a request for purchasing a product and place an order to provide the products to a customer. Further, the method includes allowing the agent to receive the requested products from a vendor and charge the customer for the products with a price as received from the vendor.