Hi Folks, Section 3 - Protein Geometry - of the course is now ready for you, it can be found at :- http://pps9900.cryst.bbk.ac.uk/ppscore/section3/index.shtml Cheers and seasons greetings, Dave H. David Houldershaw, PPS Tech. Coord. Principles of Protein Structure Crystallography Department, Birkbeck College, University of London Malet Street, London WC1E 7HX