Gold nanoparticles coated with a pyruvated trisaccharide epitope of the extracellular proteoglycan of Microciona prolifera as potential tools to explore carbohydrate-mediated cell recognition

The species-specific cell adhesion in the marine sponge Microciona prolifera involves the interaction of an extracellular proteoglycan-like macromolecular complex, otherwise known as aggregation factor. In the interaction, two highly polyvalent functional domains play a role: a cell-binding and a self-interaction domain. The self-recognition has been characterized as a Ca2+-dependent carbohydrate-carbohydrate interaction of repetitive low affinity carbohydrate epitopes. One of the involved epitopes is the pyruvated trisaccharide beta-D-Galp4,6(R)Pyr-(1 -> 4)-beta-D-GlcpNAc-(1 -> 3)-L-Fucp. To evaluate the role of this trisaccharide in the proteoglycan-proteoglycan self-recognition, beta-D-Galp4,6(R)Pyr-(1 -> 4)-beta-D-GlcpNAc-(1 -> 3)-alpha-L-Fucp-(1 -> O)(CH2)(3)S(CH2)(6)SH was synthesized, and partially converted into gold glyconanoparticles. These mimics are being used to explore the self-interaction phenomenon for the trisaccharide epitope, via TEM aggregation experiments (gold glyconanoparticles) and atomic force microscopy (AFM) experiments (self assembled monolayers; binding forces).