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Dr. Cremer
http://www.chem.tamu.edu/rgroup/cremer/ Studies include trying to understand the role of water
and ions in protein folding, the adsorption behavior of soluble proteins
from the clotting cascade onto cellular and artificial interfaces, and
multivalent protein-ligand interactions. This last subject is of particular
interest because
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ligand-receptor binding at the surfaceof solid supported
fluid lipid bilayers can be profoundly affected by the chemical makeup of
membranes. Varying surface ligand density
can modulate the equilibrium dissociation constant, KD, between
lipid-conjugated ligands and proteins possessing multiple binding sites
(Figure 2 - the binding of a protein (green) to a fluid phospholipids
bilayer containing 2-dimensionally fluid ligands). If the ligands behave
ideally, KD(app) will be strengthened by increasing the ligand
density because the fluid surface facilitates multiple binding events to
occur. This occurs for the binding of anti-2,4 dinitrophenyl IgG antibodies
and lipid conjugated 2,4 dinitrophenyl haptens. Control experiments with
monovalent Fab fragments from the IgG molecules show that KD can
be strengthened 10-100 fold just for this bivalent binding system. Systems
with a higher degree of multivalency may be strengthened even more. In
contrast, cholera toxin binding to the glycolipid GM1 is weakened
by increasing ligand density which may have implications for the mechanism
by which cholesterol- and sphingomyelin-rich raft regions could attract
glycolipids and allow for enhanced binding and signaling.