The human serum immunoglobulins IgG and IgA1 are produced in bone marrow and both interact with specific cellular receptors that mediate biological events. In contrast to IgA1, the glycosylation of IgG has been well characterized, and its interaction with various

Rearrangement reactions involving migration of fucose and, occasionally, other residues have been found in the CID spectra of [M + H]+ and [M + 2H]2+ ions, but not [M + Na]+ ions, generated from several O-linked carbohydrates and milk sugars derivatized at their reducing termini with aromatic amines such as 2-aminobenzamide. Such rearrangements, which are similar to those reported by other investigators from several underivatized carbohydrates and glycosides, cause an apparent loss of sugar residues from within a carbohydrate chain and can produce ambiguous results during spectral interpretation. A mechanism, involving initial protonation of the amine nitrogen atom of the derivative, is proposed to account for the formation of the observed ions.

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Patient serum or plasma is frequently monitored for biochemical markers of disease or physiological status. Many of the rapidly evolving technologies of proteome analysis are being used to find additional clinically informative protein markers. The unusually high abundance of albumin in serum can interfere with the resolution and sensitivity of many proteome profiling techniques. We have used monoclonal antibodies against human serum albumin (HSA) to develop an immunoaffinity resin that is effective in the removal of both full-length HSA and many of the HSA fragments present in serum. This resin shows markedly better performance than dye-based resins in terms of both the efficiency and specificity of albumin removal. Immunoglobulins are another class of highly abundant serum protein. When protein G resin is used together with our immunoaffinity resin, Ig proteins and HSA can be removed in a single step. This strategy could be extended to the removal of any protein for which specific antibodies or affinity reagents are available.

Gelatinase B is a matrix metalloproteinase (MMP-9) involved in tissue remodeling, development, cancer, and inflammation. Neutrophils produce three major forms of (pro)gelatinase B: 92 kDa monomers, homodimers, and complexes of gelatinase B covalently bound to neutrophil gelatinase B-associated lipocalin (NGAL). In contrast to the case for other proteinases, little information about the glycosylation of any natural human MMP is available. Here, both gelatinase B and NGAL were purified from human peripheral blood neutrophils, and the entire contents of the released N- and O-glycan pools were analyzed simultaneously using recently developed high-performance liquid chromatography-based technology. The results are discussed within the context of the domain structure of gelatinase B and a molecular model of NGAL based on data from this study and the three-dimensional nuclear magnetic resonance (NMR) structure of the protein. More than 95% of the N-linked glycans attached to both gelatinase B and NGAL were partially sialylated, core-fucosylated biantennary structures with and without outer arm fucose. The O-linked glycans, which were estimated to comprise approximately 85% of the total sugars on gelatinase B, mainly consisted of type 2 cores with Galbeta1,4GlcNAc (lactosamine) extensions, with or without sialic acid or outer arm fucose. This paper also contains the first report of O-linked glycans attached to NGAL. Although both proteins were isolated from neutrophils and contained O-linked glycans mainly with type 2 cores, the glycans attached to individual serine/threonine residue(s) in NGAL were significantly smaller than those on gelatinase B. In contrast to NGAL, gelatinase B contains a region rich in Ser, Thr, and Pro typical of O-glycosylated mucin-like domains.