With the advent of recombinant deoxyribonucleic acid (DNA) technology which allows a wide range of manipulation of genes and their expression in cell lines other than the natural ones, many aspects of protein structure have become more important than ever. In addition to the determination of the amino acid sequence questions relating to homogeneity, the nature of post-translational modifications, the verification of the structure of a protein produced by a synthetically modified gene or the detection of a natural mutant are all questions that are more and more frequently asked and with the demand for more detail. Mass spectrometry has emerged as an important contributor to this field, particularly since the advent of fast atom bombardment (FAB) ionization, which makes it possible to ionize directly large polar molecules such as peptides and small proteins. As such, FAB mass spectrometry provides mainly molecular weight information which, in itself, often suffices to answer certain questions, particularly because the mass of many peptides can be determined directly from a single mass spectrum of a mixture. However, in order to obtain detailed structural information, such as the amino acid sequence, fragmentation has to be induced by collision processes and the product ions separated, preferably in the second mass spectrometer of a tandem system. This approach is particularly suited for the determination of the sequence of N-blocked peptides and the nature of the blocking group; the type and location of modified (i.e. phosphorylated, sulfated, glycosylated) amino acids; detection or verification of amino acid replacements; confirmation of the structure of synthetic peptides; and last but not least, the determination of the primary structure of proteins.

A total of four Martian samples, one surface and one subsurface sample at each of the two Viking landing sites, Chryse Planitia and Utopia Planitia, have been analyzed for organic compounds by a gas chromatograph‐mass spectrometer. In none of these experiments could organic material of Martian origin be detected at detection limits generally of the order of parts per billion and for a few substances closer to parts per million. The evolution of water and carbon dioxide, but not of other inorganic gases, was observed upon heating the sample to temperatures of up to 500°C. The absence of organic compounds seems to preclude their production on the planet at rates that exceed the rate of their destruction. It also makes it unlikely that living systems that behave in a manner similar to terrestrial biota exist, at least at the two Viking landing sites.

No abstract

No abstract

No abstract

The protein MetAP2 is a common molecular target for both AGM-1470 and ovalicin. This finding suggests that MetAP2 may play a critical role in the proliferation of endothelial cells and may serve as a promising target for the development of new anti-angiogenic drugs.

No abstract

No abstract