Methodology for determining amino acid sequences of proteins by tandem mass spectrometry is described. The approach involves enzymatic and/or chemical degradation of the protein to a collection of peptides which are then fractionated by high-performance liquid chromatography. Each fraction, containing as many as 10-15 peptides, is then analyzed directly, without further purification, by a combination of liquid secondary-ion/collision-activated dissociation mass spectrometry on a multianalyzer instrument. Interpretation of collision-activated dissociation mass spectra is described, and results are presented from a study of soluble peptides produced by treatment of apolipoprotein B with cyanogen bromide and trypsin.Current strategy for sequencing proteins in our laboratory by tandem mass spectrometry (1) involves digestion of the protein with site-specific reagents such as cyanogen bromide or trypsin followed by fractionation of the resulting mixture by high-performance liquid chromatography (HPLC). Peptides in each fraction are then ionized by liquid secondary-ion mass spectrometry (LSIMS) (2) on a triple-quadrupole mass spectrometer. Sample is dissolved in a viscous matrix such as glycerol or monothioglycerol and then exposed to a beam of 6-to 8-keV (1 eV = 1.602 x 10-19 J) Cs' ions in the ion source of the mass spectrometer. Peptides are sputtered into the gas phase under these conditions, and the resulting mass spectrum consists largely of (M+H)+ ions characteristic of the molecular weight of each peptide in the sample (3). In a second experiment, the first quadrupole of the instrument is used to select a single (M+H)+ ion from the mixture and to transmit it to quadrupole 2, a collision chamber, where the peptide undergoes collisions with argon atoms and suffers fragmentation primarily at the various amide linkages in the molecule. The resulting fragment ions are then transferred to the third quadrupole, which separates them according to mass. The end result is a mass spectrum containing ions characteristic of the sequence of amino acids in the selected peptide. Repetition of this process under computer control provides sequence information on each peptide in the mixture. Presently, the above approach is limited by the 1800-Da mass range of our triple-quadrupole instrument. Maximum sequence information is obtained only when the protein under investigation is cleaved into peptides of molecular mass under this ceiling. New instrument developments should remedy this situation shortly (4).The major strength of the tandem mass spectrometry method is that it provides extensive sequence information over the whole length of a protein chain in a single series of experiments that involve minimal effort directed toward separation and purification of oligopeptide fragments. Total time for biochemical manipulation, HPLC fractionation, and instrumental analysis of samples from a single protein digest seldom exceeds 4 or 5 days. Even with the limited mass range of our existing instrumentation, it is usually possible ...

Airborne LiDAR Bathymetry (ALB) has been rapidly evolving in recent years and now allows fluvial topography to be mapped in high resolution (>20 points/m 2 ) and height accuracy (<10 cm) for both the aquatic and the riparian area. This article presents methods for enhanced modeling and monitoring of instream meso-and microhabitats based on multitemporal data acquisition. This is demonstrated for a near natural reach of the Pielach River, with data acquired from April 2013 to October 2014, covering two flood events. In comparison with topographic laser scanning, ALB requires a number of specific processing steps. We present, firstly, a novel approach for modeling the water surface in the case of sparse water surface echoes and, secondly, a strategy for improved filtering and modeling of the Digital Terrain Model of the Watercourse (DTM-W). Based on the multitemporal DTM-W we discuss the massive changes of the fluvial topography exhibiting deposition/erosion of 10 3 m 3 caused by the 30-years flood event in May 2014.Furthermore, for the first time, such a high-resolution data source is used for monitoring of hydro-morphological units (mesohabitat scale) including the consequences for the target fish species nase (Chondrostoma nasus, microhabitat scale). The flood events caused a spatial Remote Sens. 2015, 7 6161 displacement of the hydro-morphological units but did not effect their overall frequency distribution, which is considered an important habitat feature as it documents resilience against disturbances.

No abstract