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Biomedical subjects

A Dell

Publications and source records attributed to A Dell.

At least 199 records · Page 11Linked to original sources
PubMed1981

Extended performance using a high field magnet mass spectrometer.

The development of a high field magnet for high mass electron impact, chemical ionization, field desorption and fast atom bombardment mass spectrometric studies is described. Its utility is illustrated with examples from structural studies of vitamin B12 biosynthetic intermediates, oligosaccharides, glycopeptides and the bleomycin antibiotics. The technique has also greatly assisted sequence studies of protein derived peptides.

Bleomycin↗
PubMed1981

Field desorption mass spectrometry of oligosaccharides.

Field desorption mass spectrometry has been used to analyze carbohydrate polymers with 5 to 14 hexose units without prior derivatization. In all examples, the molecular weight of the oligosaccharide could be determined by means of the abundant quasimolecular ions of the type MNa(+), MH(+), MNa(2) (2+), and MNa(3) (3+). Fragmentation at glycosidic linkages was observed in varying extents. The reduced oligosaccharide Man(8)GlcNAcH(2), obtained from IgM [Cohen, R. E. & Ballou, C. E. (1980) Biochemistry 19, 4345-4358], gave quasimolecular ion signals MNa(+) at m/z 1544, MH(+) at m/z 1522, MNa(2) (2+) at m/z 784, and MNa(3) (3+) at m/z 530, all corresponding to its assumed molecular weight of 1519.5. Mycobacterial methylmannose polysaccharides with the general structure Man(x)MeMan(y)-OCH(3) [Yamada, H., Cohen, R. E. & Ballou, C. E. (1979) J. Biol. Chem. 254, 1972-1979] were also successfully analyzed. Man(1)MeMan(13)-OCH(3), the largest homolog, gave the expected signal of the quasimolecular ion MNa(+) at m/z 2506. The larger polysaccharides were analyzed by using a KRATOS MS-50 mass spectrometer with a high-field magnet enabling full sensitivity to be maintained up to 3000 atomic mass units. Polysaccharides up to m/z 1978 were analyzed by using a KRATOS MS-9 mass spectrometer operated at 4 Kv. The signal-to-noise ratio, which becomes a serious problem in field desorption mass spectrometry at low accelerating voltages, and the low instrument sensitivity were improved considerably by our use of a method of adding scans with low total ion currents obtained over a longer desorption time. In this way, we obtained complete sequence information on methylmannose polysaccharides up to Man(1)MeMan(9)-OCH(3)(MNa(+) at m/z 1802). Analysis of a presumed Man(1)MeMan(7)-OCH(3), gave a spectrum consistent only with the structure Man(2)MeMan(6)-OCH(3), revealing the existence of a methylmannose homolog with 2 unmethylated mannoses at the nonreducing end of the chain.

Carbohydrate Sequence↗
PubMed1980

Characterisation of an adrenal zona glomerulosa-stimulating component of posterior pituitary extracts as alpha-MSH.

The secretion of aldosterone from the zona glomerulosa of the mammalian adrenal cortex is stimulated by ACTH, potassium, angiotensin II and III, growth hormone, serotonin and E series prostaglandins. Some experimental and clinical studies suggest that additional stimulants of the zona glomerulosa must exist, possibly including pituitary factors other than ACTH. The possibility that posterior pituitary extracts may contain a zona glomerulosa stimulant was first suggested 20 years ago, but has since received little attention. We describe here the purification from posterior pituitary extracts of activities that stimulate rat glomerulosa cells and whole tissue in vitro. One of the active compounds has been identified as alpha-MSH (melanocyte stimulating hormone).

18-Hydroxydesoxycorticosterone↗
PubMed1976

Mass-spectrometric identification and sequence location of the ten residues of the new amino acid (gamma-Carboxyglutamic acid) in the N-terminal region of prothrombin.

The detailed mass-spectrometric evidence for our original findings [Magnusson et al. (1974) FEBS Lett. 44, 189-193] of ten gamma-carboxyglutamic acid residues in the N-terminal calcium-binding polypeptide of prothrombin is presented. The identification and sequence location of gamma-carboxyglutamic acid was made by electron-impact and field-desorption studies on acetyl permethyl peptide derivatives, and on the free amino acid. Details of the derivatives formed, and how this new amino acid may be easily recognized and sequenced from the mass spectrum, are given as a basis for future work.

Amino Acid Sequence↗