How to infer the crucial participation of aromatic residues of diagnostical relevant endogenous lectins for ligand binding: A biophysical contribution to lectin histochemical results

Carbohydrate protein interactions are involved in many biological processes such as intercellular communication and differentiation. Therefore, structural and functional aspects concerning the interplay between proteins and carbohydrates are of great interest in medicine. X-ray crystallographic studies of numerous protein-carbohydrate complexes show that Tyr, Trp and His residues are often important constituents of the binding pocket. In the case such amino acid residues are fully or partly surface exposed they can be detected by the laser photo CIDNP (chemically induced dynamic nuclear polarization) method. In the case these CIDNP sensitive amino acids are located in the binding pocket the corresponding CIDNP-NMR-signal can be suppressed by addition of a ligand. Furthermore, by use of this method it is also possible to detect alterations of the surface accessibility between glycoproteins with and without an intact carbohydrate chain. However, in all cases the CIDNP-studies have to be supported by a molecular modelling analysis. The combination of CIDNP-NMR-techniques and molecular modelling leads to valuable models describing the structural and dynamic behaviour of lectin-carbohydrate-complexes and glycoproteins in solution.