Recently, Keinan and Nimri reported an interesting antibody-metalloporphyrin that mimics natural oxidation enzyme. 105 On the basis of the catalytic Scheme 14 Scheme 15 Scheme 16

The specific interaction of the isolated B domain of wheat germ agglutinin (WGA-B) with N, N H , N HH-triacetylchitotriose has been analyzed by 1 H-NMR spectroscopy. The association constants for the binding of WGA-B to this trisaccharide have been determined from both 1 H-NMR titration experiments and microcalorimetry methods. Entropy and enthalpy of binding have been obtained. The driving force for the binding process is provided by a negative DH which is partially compensated by negative DS. These negative signs indicate that hydrogen bonding and van der Waals forces are the major interactions stabilizing the complex. NOESY NMR experiments in water solution provided 327 protein proton-proton distance constraints. All the experimental constraints were used in a refinement protocol including restrained molecular dynamics in order to determine the refined solution conformation of this protein/carbohydrate complex. With regard to the NMR structure of the free protein, no important changes in the protein NOEs were observed, indicating that carbohydrate-induced conformational changes are small. The average backbone rmsd of the 35 refined structures was 1.05 A Ê , while the heavy atom rmsd was 2.10 A Ê. Focusing on the bound ligand, two different orientations of the trisaccharide within WGA-B binding site are possible. It can be deduced that both hydrogen bonds and van der Waals contacts confer stability to both complexes. A comparison of the three-dimensional structure of WGA-B in solution to that reported in the solid state and to those deduced for hevein and pseudohevein in solution has also been performed. Carbohydrates are one of the most extended families of biomolecules in nature. They play a role in energy storage and as constituents of the structural framework of cells and tissues. In addition, due to their extraordinary capacity to encode information stereochemically these molecules take part in a wide variety of recognition processes of biological significance. Thus, carbohydrate recognition by proteins has been shown to be involved in viral and microbial infection, inflammatory responses, innate immunity, fertilization, tumor spread and growth regulation [1±6]. The elucidation of the biochemical and cell biological processes in the cascades from the initial molecular rendezvous to the triggered response has established a burgeoning research field in glycoscience with obvious perspectives for medical application [7±9]. Detailed information on the three-dimensional structure of protein-carbohydrate complexes has frequently been obtained from X-ray crystallography data [10±14] and modeling [15], as the commonly high molecular mass of lectins has prevented their direct studies by means of NMR spectroscopy. However, in favorable cases, NMR may also provide information about the driving forces behind protein±carbohydrate interactions in solution [16±20]. The hevein domain is one of the most common chitin-binding motifs. Its presence in several lectins [such as hevein, pseudohevein, Urtica dioica agglutinin (UD...

The reaction of some structures to different external stimuli can be used with therapeutic purposes. In particular, in Photodynamic Therapy (PDT) a light-sensitive compound or structure, commonly named as photosensitizer...