Computer model of the most abundant protein in the circulatory system, Human Serum Albumin (HSA), important for the maintenance of plasma volume and the transport of a number of substances. The three dimensional structure of this protein was revealed using X-ray crystallography. Knowledge of the structure, including how and where substrates such as minerals and therapeutic drugs bind to the molecule, should open the way for pharmaceutical companies to design new drugs or alter existing ones to allow them to be carried more efficiently by the protein molecule through the body. The red spheres represent the binding locations of aspirin (right) and diazapine (left).