Microscale sample deposition onto hydrophobic target plates for trace level detection of neuropeptides in brain tissue by MALDI-MS

A sample preparation method that combines a modified target plate with a nanoscale reversed-phase column (nanocolumn) was developed for detection of neuropeptides by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). A gold-coated MALDI plate was modified with an octadecanethiol (ODT) self-assembled monolayer to create a hydrophobic surface that could concentrate peptide samples into a approximately 200-500-microm diameter spot. The spot sizes generated were comparable to those obtained for a substrate patterned with 200-microm hydrophilic spots on a hydrophobic substrate. The sample spots on the ODT-coated plate were 100-fold smaller than those formed on an unmodified gold plate with a 1-microl sample and generated 10 to 50 times higher mass sensitivity for peptide standards by MALDI-TOF MS. When the sample was deposited on an ODT-modified plate from a nanocolumn, the detection limit for peptides was as low as 20 pM for 5-microl samples corresponding to 80 amol deposited. This technique was used to analyze extracts of microwave-fixed tissue from rat brain striatum. Ninety-eight putative peptides were detected including several that had masses matching neuropeptides expected in this brain region such as substance P, rimorphin, and neurotensin. Twenty-three peptides had masses that matched peaks detected by capillary liquid chromatography with electrospray ionization MS.     

Die Bestimmung von o-Nitrotoluol in Nitrocellulosepulver mittels des Eintauchrefraktometers

Ohne Zusammenfassung     

Emulsion polymerization of supermicron,monodisperse acrylic copolymer particles with core-shell structures

The emulsion polymerization of large MMA/BA copolymer particles with narrow particle size distributions and core-shell structure is described. A series of sequential seeded growth emulsion polymerizations were used to obtain monodisperse particles with diameters of at least 3 μm, at 30% solids contents. Because the core and shell polymers used here were chemically similar, core-shell structures could not be verified by differential staining tech-niques. Core-shell structure was demonstrated by minimum film-forming temperature studies and by scanning electron microscopy in conjunction with energy dispersive x-ray analysis, using chlorine-labeled core polymers. © 1995 John Wiley & Sons, Inc.     

Experimental observation of traveling waves in the transverse section of a laser

The selection of a transverse traveling wave by an inhomogeneous pump profile has been experimentally observed in a class B laser structure. The laser structure consisted of a wide-aperture edge-emitting laser diode operating in pulsed mode to avoid thermal guiding effects. The injection current's profile was modified from the usual top-hat configuration to a Lorentzian-like profile by the inclusion of a 10-mum p-type expitaxial spreading layer. Spatial dependance of the far field on the near field was observed. The same behavior is also demonstrated numerically by use of Maxwell-Bloch equations for semiconductor lasers.