The three dimensional structures on an atomic level of a number of proteins are being determined by the method of single crystal X-ray diffraction analysis. The proteins presently under investigation are Canavalin and Concanavalin B from the Jack Bean, gene 5 product of fd bacteriophage which unwinds DNA, beef liver catalase, and pig pancreas alpha-amylase. The solution of these structures will permit a correlation of general biochemical and mechanistic properties with architectural features and patterns of structure within the molecules. The structural models derived from these studies will further permit detailed investigation of the functional properties of proteins by virtue of the difference fourier technique.