naccess 2.1.1 Atomic Solvent Accessible Area Calculation Software: Developed at UCL by Simon Hubbard and Janet Thornton, this program calculates absolute and relative surface accessibilities of protein and nucleic acid structures. The program can also be used in conjunction with the Ligplot program to provide information on buried and accessible residues. naccess is a program that automatically performs accessible area calculation of a molecule from a standard Protein Data Bank (PDB) file input. The output includes a file of atomic accessible areas, a file of summed absolute and relative residue accesible areas, and a calculation log file.The algorithm is based on work described in the paper of Lee and Richards as referenced below. Program author Simon Hubbard curently holds the position of Professor in the Faculty of Life Sciences at Manchester University.