Amino-acid residues asparagine

Fig. 7. Conformations of (a) tetraantennary and (b) biantennary glycans. The amino acid residue asparagine (ASN) is at the bottom in both cases.

In addition to the amino acids described above, several other amino acid residues are also reactive toward compounds containing heavy atoms. These are the side chains of arginine, asparagine, glutamine, lysine, tryptophan, and tyrosine. Those that are not reactive are alanine, glycine, isoleucine. 

Fig. 19. Efficiency of RPC in protein separation. Isocratic RPC separation of murine epidermal growth factor (after elution as a single peak from a diethylaminoethyl cellulose column). Column RP 18 (300x7.8 mm dP = 10 pm) 40 °C eluent 0.04 M triethylamine acetate in water — acetonitrile (74 26), pH 5.6 flow rate 0.8 ml/min UV detection at 254 nm, 0.05 AUFS injection 100 pg in 100 pi. The a peak was due to the polypeptide of 53 amino acid residues (M =6040 g/mol), the p component did not contain the asparagine residue in position 1. (From Ref.77) with permission)...

For small peptides, the amount of color increases with the size of the peptide. The presence of any of five amino acid residues (tyrosine, tryptophan, cysteine, histidine, and asparagine) in the peptide or protein backbone further enhance the amount of color produced, because they contribute additional reducing equivalents for further reduction of the phos-phomolybdic/phosphotungstic acid complex. With the exception of tyrosine and tryptophan, free amino acids will not produce a colored product with the Lowry reagent however, most dipeptides can be detected. In the absence of any of the five amino acids listed above, proteins containing proline residues have a lower... 

Holtje and Sippl selected a representative training set of twelve superimposed structures. The aforementioned Y AK process resulted in a pseudoreceptor that consists of six amino acid residues (Figure 5). In this pseudoreceptor model, the imidazole ring of the ligands is bound to a tyrosine residue that donates a proton to the imidazole and an asparagine residue that accepts a proton from the imidazole. Hence, two distinct H-bond have been found, which explain the strict binding mode of the imidazole. It has to be noted that the position of these receptor residues relative towards the imidazole is a consequence of... 

The linear assembly of glycosylated amino acids in particular usually provides well-defined products following this approach, the required carbohydrate structure is attached to an amino acid residue, typically serine and threonine for O-linked glycopeptides and asparagine for N-linked glycopeptides (Fig. I).16... 

FIGURE 17.7 Some important direct interactions between conserved amino acid residues of the active site of influenza A virus sialidase and a-Neu5Ac. Ala, alanine Arg, arginine Asn, asparagine Asp, aspartic acid Glu, glutamic acid His, histidine lie, isoleucine Typ, tryptophan Tyr, tyrosine. 

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