BALL-AND-STICK MODEL OF RESIDUE CHARGES Lysozyme is an anti-bacterial enzyme found in tears and saliva. It dissolves bacterial cells in the human body. The image shows how colour can be used to represent the distribution of charge over the molecule. The charge is colour coded as follows: - white: neutral (i.e. charges cancel out) - yellow: non-charged - red: positive - blue: negative The molecular surface is actually generated using constructive solid geometry, the image being comprised of spheres and cylinders (two of the geometric primitives). The atomic coordinates are maintained in a relational data base.