Computer graphics image showing a detail of an enzyme, tyrosyl t-RNA synthetase. The image was produced on an Evans & Sutherland vector scanner used by the Biophysics Group in the Physics Department at Imperial College, London, for studies in protein engineering. Such powerful modelling tools have largely replaced the need for the construction of large ball & stick" type models of complex biological molecules. A three- dimensional image of the whole or parts of the molecule may be readily manipulated on screen and details of sections of the structure magnified."