TNT is a program package which is used to "refine" models of macromolecules. It has been used for a number of years to produce improved models based upon X-ray diffraction data and the knowledge of chemical structures learned from small molecules. This web site provides the documentation for the package and instructions for aquiring it.
The current version is Release 5F
Release 5F of TNT was recently released. It has been tested on Compaq Alpha's running either VMS or Unix, SGI systems runing Irix, Pentium systems runing Linux, and Sun systems runing Solaris. The improvements introduced in 5F are incremental, i.e. your current input files will not need to be changed for this version. The principle improvments are the introduction of overall anisotropic scaling, the generalization of ncs operators to allow molecules to differ in average B factor, and the simplification of the handling of water molecules. A detailed list of the changes can be found here.