Jurgen G. Schmidt

Botulinum Neurotoxin Detection and Differentiation by Mass Spectrometry

A new rapid, mass spectrometry-based method to detect and differentiate botulinal neurotoxins is described.

Immunomagnetic Separation and Quantification of Butyrylcholinesterase Nerve Agent Adducts in Human Serum

A novel method for extracting butyrylcholinesterase (BuChE) from serum as a means of identifying and measuring nerve agent adducts to human BuChE is presented here. Antibutyrylcholinesterase monoclonal antibodies were conjugated to protein-G ferromagnetic particles and mixed with 500 microL serum samples. The particle-antibody-BuChE product was rinsed and directly digested with pepsin. Native and isotopically enriched nonapeptides corresponding to the pepsin digest products for uninhibited BuChE, and sarin, cyclohexylsarin, VX, and Russian VX nerve agent-inhibited BuChE were synthesized for use as calibrators and internal standards, respectively. Internal standards were added to the filtered digest sample, and the samples were quantified via high performance liquid chromatography-isotope dilution-tandem mass spectrometry. The ratio of adducted to total BuChE nonapeptides was calculated for each nerve agent-exposed serum sample using data collected in a single chromatogram. Nerve agent-inhibited quality control serum pools were characterized as part of method validation; the method was observed to have extremely low background noise. The measurement of both uninhibited and inhibited BuChE peptides compensated for any variations in the pepsin digestion before the internal standard peptide was added to the sample and may prove useful in individualizing patient results following a nerve agent exposure.

Specific aspects of roughness and interface diffusion in non-periodic Mo/Si multilayers

Most of the currently used reflective coatings for EUV and X-ray mirrors are periodic nanometer multilayers. Depending on the number of periods and the absorption in the multilayer stack a certain band width of the incoming radiation can be reflected. In order to increase the integral reflectance or to accept larger ranges of incidence angles, non-periodic multilayers are needed. With the transition from periodic to non-periodic multilayers new challenges arise for the deposition process. Since the reflectance spectra are sensitive to every single layer thickness a precise coating control and an exact knowledge of the interface reactions are required. Furthermore substrate roughness influences the reflectance spectra. With an advanced coating process using additional ion bombardment during thin film growth the integrated reflectance of broadband mirrors can be conserved even for an initial substrate roughness of about 0.7 nm rms.

A photophysical study of two fluorogen-activating proteins bound to their cognate fluorogens

We are exploring the use of fluorogen-activating proteins (FAPs) as reporters for single-molecule imaging. FAPs are single-chain antibodies selected to specifically bind small chromophoric molecules termed fluorogens. Upon binding to its cognate FAP the fluorescence quantum yield of the fluorogen increases giving rise to a fluorescent complex. Based on the seminal work of Szent-Gyorgyi et al. (Nature Biotechnology, Volume 26, Number 2, pp 235-240, 2008) we have chosen to study two fluorogen-activating single-chain antibodies, HL1.0.1-TO1 and H6-MG, bound to their cognate fluorogens, thiazole orange and malachite green derivatives, respectively. Here we use fluorescence correlation spectroscopy to study the photophysics of these fluorescent complexes.

Melt Spinning Preparation of Bismuth Telluride and Partially Alloying with IV-VI Compounds for Thermoelectric Application

The melt spinning technique (MST) combined with post annealing processes is evaluated for the development of thermoelectric nanocomposites. The evaluated ones are based on two components almost immiscible in solid state but with crystallographic correlation. One is taken from the V-VI-components system and the other one from the IV-VI-components system. This concept was applied to p-(Bi 0,2 Sb 0,8 ) 2 Te 3 and to p-[(Bi 0,2 Sb 0,8 ) 2 Te 3 ] 1-x PbTe x composites. MST samples of all types were characterised for some structural and thermoelectric properties. All V-VI materials are clearly textured after MST and show no deterioration concerning the thermoelectric properties even after subsequent annealing processes. Structural analysis of p-[(Bi 0,2 Sb 0,8 ) 2 Te 3 ] 1-x PbTe x composites gave significant hints for oriented precipitates of a IV-VI-rich phase incorporated into the V-VI-rich matrix. The thermoelectric figure of merit of the evaluated composites could be enhanced by suitable annealing procedures of both the quenched bulk materials and the melt spin material.