Fachbereich Chemie, Universität Konstanz, Konstanz
Carbohydrates are involved in a myriad of cellular functions. In the
form of glycoconjugates they modulate activity and physicochemical properties
of proteins and lipids, and they are themselves involved in molecular
recognitions processes. However, our understanding of
the underlying mechanisms is just at the beginning and methods for their
elucidation need further development. Challenges in current glycobiology
include the elucidation of the mechanisms of multivalent carbohydrate-protein
interactions and the development of tools to monitor glycan structures in cells
and organisms. This lecture gives an overview of our group's activities in
these fields. To unravel the molecular details of carbohydrate-protein
interactions we employed X-ray crystallography and, more recently, distance
measurements in the nanometer range by EPR spectroscopy using spin-labeled
carbohydrates. In contrast to proteins, that are routinely labeled by genetic
methods, such as expression as GFP fusion proteins, comparable methods are not
available for glycans. We employed metabolic oligosaccharide engineering for
monitoring glycans in different cell lines as well as in zebrafish. To increase
the repertoire of existing bioorthogonal ligation reaction, we developed a new ligation method based
on a Diels-Alder reaction with inverse-electron-demand of electron
deficient 1,2,4,5-tetrazines and terminal alkenes. Since this reaction is
orthogonal to the azide-alkyne cycloaddition (click reaction), detection of two
different sugars (one alkene-labeled the other azide-labeled) is possible
within one experiment.
