14 research outputs found
Determination of the primary structures of 16 asialo-carbohydrate units derived from human plasma α1-acid glycoprotein by 360-MHz 1H NMR spectroscopy and permethylation analysis
The present study was initiated in order to determine
the primary structures of the carbohydrate units of
desialyzed human plasma al-acid glycoprotein. In an earlier
investigation I6 glycopeptides which originated from four of
the five glycosylation sites of this protein were prepared in the
homogeneous state. Since the elucidation of the structures of
such a large number of carbohydrate units by the conventional
chemical and enzymatic procedures would require a very long
period of time and considerable amounts of material, a new
method-360-MHz H NMR spectroscopy-in combination
with methylation analysis and partial acetolysis was introduced
i n the present study. This highly sensitive method allowed the
elucidation of the structures of the carbohydrate units of the
mentioned glycopeptides to be carried out in a very short period of time. The present investigation revealed that the structures
of the 16 heteroglycans can be grouped into five classes, and,
except for those of two classes, the structures are new. Two
classes designated A and B possess the known bi- and trimtennary
structures, respectively. A third class designated C
proved to be tetraantennary in its structure, whereas the other
classes designated BF and CF are, in comparison with the
structures of classes B and C, characterized by an additional
fucose residue in a hitherto unknown position and linkage.
The latter monosaccharide residue is attached in an a( 1-3)
bond, vicinal to Gal@(1 +4), to the GlcNAc residue 7. The
present study also revealed that each glycosylation site of
pooled a]-acid glycoprotein possesses carbohydrate units with
different structures
Steps toward determination of the size and structure of the broad-line region in active galactic nuclei. I. An 8 month campaign of monitoring NGC 5548 with IUE
This is an electronic version of an article published in The Astrophysical Journal. Clavel, J. et al. Steps toward determination of the size and structure of the broad-line region in active galactic nuclei. I. An 8 month campaign of monitoring NGC 5548 with IUE. The Astrophysical Journal 366 (1991): 64-8