Glycoproteins labeling with

In investigations by Morell et al. (1968), later by Ash well and Morell (1974), and by others (Pricer and Ashwell, 1971 Morell et al., 1971), it was demonstrated that all serum glycoproteins, with only one known exception, transferrin, require the presence of bound sialic acid for continuous circulation. By the use of glycoproteins labeled with either, or both, and Cu, it was shown that the sialic-acid-free... 

FIGURE 7-7 Structure of the P0 glycoprotein protomer. (A) In this ribbon diagram of the extracellular domain of P0, each P strand is labeled with a letter and two antiparallel P sheets are formed. The disulfide bridge is indicated in dark orange and a hypothetical path for disordered amino acids 103-106 is shown in black in the FG loop. (B) Lattice formation by P0. A view of the intraperiod line, or extracellular apposition, of myelin in the PNS. The orange tetramer sets emanate from one bilayer and the blue tetramer interacts with all four of them. This is a view perpendicular to the plane of the myelin membrane. 

Glycoproteins derivatized with DTPA at surface lysine residues and labelled with Gd(III) (or In(III)) are internalized by cells and metabolized to Gd(-DTPA-lysine), which is released only slowly from cells (323). Some Gd(III) may dissociate from this complex since the pH in lysosomes, where the metabolism occurs, is low (pH 5). 

The flexibility of the sugar linkages in glycoproteins results in multiple conformations that can be detected by time-resolved fluorescence experiments. Figure B9.1.1 shows an example of a triantennary glycopeptide labeled with a... 

Fig. 3. Intracellular transport route of the SFV spike glycoproteins from the endoplasmic reticulum (ER), over the Golgi apparatus, to the plasma membrane (PM). The cis cisternae do not react positively for add phosphatase or thiamin pyrophosphatase, and do not label with ridn in thin frozen sections. The medial cisternae do not react positively for thiamin pyrophosphatase or acid phosphatase, but label with ridn. The trans cisternae are positive for all of these markers.

Glycoprotein was digested using the peptide N-Glycosidase F (PNGase F) to release N-linked glycan, then labeled with 8-aminopyrene-l,3,6-trisulfonate (APTS). The detection used LIF with a argon-ion laser. 

Figures Selective protein modification using a keto amino acid, p-acetyl-L-phenylalanine. (a) Labeling of fluorescein hydrazide to the Z domain protein. Only the mutant protein containing p-acetyl-L-phenylalanine was labeled and became fluorescent, (b) A general method for preparing glycoprotein mimetics with defined glycan structure.

Lectins, or proteins with specific binding sites for carbohydrates, can be used as targeting molecules to localize particular glycoconjugates such as glycoproteins or glycolipids on cell surfaces (Fig. 373). Labeled with gold particles, lectins are important probes for detection of cell surface components and intracellular receptors and in immunological or biochemical assay procedures (Bog-Hansen et al., 1978 Kimura et al., 1979 Nicolson, 1978 Roth, 1983 Benhamou et al., 1988 Nakajima et al., 1988). 

The galactose moiety of the cell surface GSL and glycoproteins was labeled with [2H] following treatment of the cells with galactose oxidase, followed by reduction with KB[ H]4, as previously described (30,60,61). 

Other possibilities of protein labeling have been described. For instance, glycoproteins can be labeled with H-fucose or glucosamine Examples of H-labeling methods are included in Table 4. 

Besides amino acids, labeled saa harides are suitable for the labeling of glycoproteins. In this manner, glycoproteins have been labeled with H-mannose H-glucosamine N-acetylmanosamine Saccharides may also be allowed to react with proteins after periodate oxidation... 

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