THE TRANSLATION PROBLEM IN MOLECULAR REPLACEMENT TECHNIQUES - I - ABOUT THE ROLE OF TRIPLET INVARIANTS

The case of a well oriented but randomly positioned molecule has been treated in a pioneering paper by Main (1976) [in Crystallographic Comp uting Techniques, edited by F. R. Ahmed. Copenhagen: Munksgaard]. The formula proved quite effective for small molecules but in its original form is inadequate for solving the translation problem in molecular r eplacement techniques applied to proteins. The Main formula has been s uitably modified: applications to test structures show that the use of direct methods may be a valid alternative to the widely used translat ion functions.