MALDI versus ESI: The Impact of the Ion Source on Peptide Identification.

For mass spectrometry-based proteomic analyses, electrospray ionization (ESI) and matrix-assisted laser desorption/ionization (MALDI) are the commonly used ionization techniques. To investigate the influence of the ion source on peptide detection in large-scale proteomics, an optimized GeLC/MS workflow was developed and applied either with ESI/MS or with MALDI/MS for the proteomic analysis of different human cell lines of pancreatic origin. Statistical analysis of the resulting data set with more than 72 000 peptides emphasized the complementary character of the two methods, as the percentage of peptides identified with both approaches was as low as 39%.

New sensitive high-performance liquid chromatography-tandem mass spectrometry method for the detection of horse and pork in halal beef.

The accidental or fraudulent blending of meat from different species is a highly relevant aspect for food product quality control, especially for consumers with ethical concerns against species, such as horse or pork. In this study, we present a sensitive mass spectrometrical approach for the detection of trace contaminations of horse meat and pork and demonstrate the specificity of the identified biomarker peptides against chicken, lamb, and beef. Biomarker peptides were identified by a shotgun proteomic approach using tryptic digests of protein extracts and were verified by the analysis of 21 different meat samples from the 5 species included in this study.

Peptidomics-based phylogeny and biogeography of Mantophasmatodea (Hexapoda).

The insect order Mantophasmatodea was described in 2002. Prior to that time, several generations of entomologists had assumed that all major insect taxa were known; thus, its description was a sensation for zoologists. Since then, a surprising abundance and species diversity of this taxon have been found, particularly in the winter rainfall region of South Africa.

Prevalidation of potential protein biomarkers in toxicology using iTRAQ reagent technology.

Today, toxicoproteomics still relies mainly on 2-DE followed by MS for detection and identification of proteins, which might characterize a certain state of disease, indicate toxicity or even predict carcinogenicity. We utilized the classical 2-DE/MS approach for the evaluation of early protein biomarkers which are predictive for chemically induced hepatocarcinogenesis in rats. We were able to identify statistically significantly deregulated proteins in N-nitrosomorpholine exposed rat liver tissue.

A second outer-core region in Klebsiella pneumoniae lipopolysaccharide.

Up to now only one major type of core oligosaccharide has been found in the lipopolysaccharide of all Klebsiella pneumoniae strains analyzed. Applying a different screening approach, we identified a novel Klebsiella pneumoniae core (type 2). Both Klebsiella core types share the same inner core and the outer-core-proximal disaccharide, GlcN-(1,4)-GalA, but they differ in the GlcN substituents.

New fragmentation mechanisms in matrix-assisted laser desorption/ionization time-of-flight/time-of-flight tandem mass spectrometry of carbohydrates.

The spectra recorded by matrix-assisted laser desorption/ionization time-of-flight/time-of-flight tandem mass spectrometry (MALDI-TOF/TOF-MS/MS) of complex carbohydrates from human milk are presented. Besides ions originating from glycosidic cleavages and from sugar ring fragmentations, these spectra show intense peaks that may be assigned to ions produced by three new fragmentation pathways involving a six-atom rearrangement. These ions, together with the A fragments from sugar ring fragmentations, open the possibility of obtaining a complete mapping of the linkage positions present in the carbohydrates investigated by MALDI-TOF/TOF.

Deamidation of labile asparagine residues in the autoregulatory sequence of human phenylalanine hydroxylase.

Two dimensional electrophoresis has revealed a microheterogeneity in the recombinant human phenylalanine hydroxylase (hPAH) protomer, that is the result of spontaneous nonenzymatic deamidations of labile asparagine (Asn) residues [Solstad, T. and Flatmark, T. (2000) Eur.

Separation and first structure elucidation of Cremophor EL-components by hyphenated capillary electrophoresis and delayed extraction-matrix assisted laser desorption/ionization-time of flight-mass spectrometry.

The polyethoxylated heterogeneous components of the so far poorly characterized nonionic emulsifier Cremophor EL (polyoxyl 35 castor oil) (CrEL) were fractionated by cyclodextrin-modified micellar electrokinetic capillary chromatography (CD-MEKC). Due to the low UV absorbance of most of the CrEL-components an indirect UV detection was used with phenobarbital-sodium as background absorber. For a precise assignment of the resulting peaks to the corresponding components capillary electrophoresis (CE) had to be combined with delayed extraction-matrix assisted laser desorption/ionization-time of flight-mass spectrometry (DE-MALDI-TOF-MS) as detection system.