Abstract: A method of determining common three-dimensional structural features of protein surfaces is provided, as is use of representations of these common structures in molecular database searching and in designing focussed molecular libraries. The method is particularly concerned with the analysis and representation of protein surfaces such as b-turns, loops and contact surfaces. In one form, the method identifies common locations and orientations of amino acid side-chains, simplified as C?-C? vectors. In another form, the method identifies common regions of surface charge represented by grid points in three-dimensional space. Further provided are common three dimensional structural features of proteins that can be used to search molecular databases for the purposes of identifying molecules that match these common three dimensional structural features.