Fig. 1.

MALDI TOF analysis of the acidic N-glycans from serum transferrin shows a remarkable underglycosylation mainly due to the lack of a terminal sialic acid (increased peaks at m/z 1932, m/z 2078, m/z 2588, m/z 2735) and, to a much lesser extent, also due to the presence of truncated biantennary glycoforms at m/z 1770 (lacking a terminal sialic acid and a galactose unit) and at m/z 1567 (trace amount of a species lacking a terminal trisaccharide composed of a sialic acid, a galactose and an N-acetylglucosamine residue). Blue squaresN-acetylglucosamine; green circles mannose; yellow circles galactose; red diamonds sialic acid