Quantitative field desorption mass spectrometry. V. Discussion of methodology and examples of applications

The possibilities for the application of field desorption mass spectrometry in quantitative analyses are described and evaluated. The advantages of and the sources of errors in the use of different standards as well as in the application of different methods such as photographic detection, single ion monitoring, repetitive scanning, selected ion monitoring, and double ion detection are illustrated by representative examples. Sensitivity and precision of the different techniques are evaluated. Most importantly, the use of stable isotope labelled compounds as internal standards has enabled quantitative determination with good precision, accuracy, and sensitivity. In order to demonstrate the capabilities of the methods, examples of applications are presented and the scope of quantitative analysis with field desorption mass spectrometry is discussed.     

3-Azi-1-methoxybutyl D-maltooligosaccharides specifically bind to the maltose/maltooligosaccharide-binding protein of Escherichia coli and can be used as photoaffinity labels

Maltooligosaccharides with two to six (alpha 1-4)-linked glucose residues, carrying at their reducing end a 3-azi-1-methoxybutyl group in either alpha or in beta glycosidic linkage, were synthesized. These maltooligosaccharide analogues inhibit maltose uptake via the maltose-binding-protein-dependent transport system in Escherichia coli. The concentration of half-maximal inhibition of maltose transport, at 15 nM concentration, decreases with increasing chain length of the analogue, levelling off at 40 microM after a chain length of four glucose residues in the alpha series and at 350 microM after a chain length of three glucose residues in the beta series. The inhibition of maltose transport occurs at the level of the periplasmic maltose-binding protein. 3-Azi-1-methoxybutyl alpha-D-[3H]maltotrioside was bound by the maltose-binding protein with a Kd of 0.18 mM. Irradiation at 350 nm of purified maltose-binding protein in the presence of 4 microM of this substrate labeled the protein covalently; labeling was prevented by 1 mM maltose. Using a crude preparation of periplasmic proteins two proteins were labeled, the maltose-binding protein and alpha-amylase. Thus, 3-azi-1-methoxybutyl alpha-D-maltooligosaccharides are potent photoaffinity labels for proteins with maltooligosaccharides-binding sites.     

Über das Vorkommen vakuolenhaltiger Ganglienzellen im Ganglion cervicale uteri trächtiger und nichtträchtiger Ratten

Zusammenfassung An einem Material von 32 gesunden, geschlechtsreifen Ratten wird das Ganglion cervicale uteri histologisch untersucht. Besonders in dem apikalen Bereich des Ganglions lassen sich regelmäßig vakuolenhaltige Ganglienzellen nachweisen. Die Zahl dieser Ganglienzellen erfährt in der Schwangerschaft eine statistisch gesicherte Zunahme, was an einem Material von 7 trächtigen und 9 nichtträchtigen Ratten belegt wird. Die Bedingungen für das Auftreten vakuolisierter Ganglienzellen und die Frage nach ihrer Bedeutung müssen in weiteren Untersuchungen geklärt werden.     

The product environmental footprint communication at the crossroad: integration into or co-existence with the European Ecolabel?

The International Journal of Life Cycle Assessment - Since 2013, the European Commission (EC) is developing and testing the Product Environmental Footprint (PEF)—a product evaluation method,...