The theme of this work is to develop a useful, accurate science of the forces that organize biomolecules. To this end we have accelerated our efforts to measure forces between proteins, DNA double helices, and polysaccharides. We have also concluded a set of studies on the release of water upon DNA/protein and DNA/drug binding. Force measurements between collagen triple helices have shown how decreasing temperature, lowering pH, or adding glycerol can remove the attractive forces that reconstitute collagen from solution. At least in this case, the independent action of these different changes in condition provides strong evidence against the popular assumption that """"""""hydrophobic interactions"""""""" stabilize protein assembly. This year, we published the first of our intended """"""""toolbox"""""""" papers, which codify measured DNA-DNA forces in a form that can be used in computation and analysis of molecular assembly. These forces are themselves the center of our own investigation into the packing of DNA and its packaging into ordered assemblies, such as in viruses. We have begun an extensive series of measurements on forces among stiff polysaccharides, the most neglected of all bio-materials. There is a strong technological as well as biological motivation for understanding these interactions. This year has seen the first quantitative measurement of the amount of water released upon specific vs. non-specific binding of DNA to protein (lac repressor) or upon the binding of DNA to various drugs. There is an immediate energetic connection between these changes in molecular hydration and the powerful """"""""hydration forces"""""""" measured between large molecules when they are brought into contact. The growing catalog of information about these interactions continues to create a new logic of thinking about molecular recognition and folding.
