TEMPERATURE-FAVORED ASSEMBLY OF COLLAGEN IS DRIVEN BY HYDROPHILIC NOTHYDROPHOBIC INTERACTIONS

It has become almost axiomatic that protein folding and assembly are d ominated by the hydrophobic effect. The contributions from this, and o ther, hydrophilic interactions can now be better distinguished by dire ct measurement of forces between proteins. Here we report the measurem ent of forces between triple helices of type I collagen at different t emperatures, pH and solute concentrations. We separate repulsive and a ttractive components of the net force and analyze the origin of the at traction responsible for the collagen self-assembly. In this case the role of the hydrophobic effect appears to be negligible, Instead, wate r-mediated hydrogen bonding between polar residues is the most consist ent explanation.