Hi, Having a discussion with a colleague yesterday on differences in Phenix and Refmac representations of TLS B-factors in the PDB file I came across two different definitions for what the PDB ANISOU U's correspond to as written by Phenix: 1. From necat.chem.cornell.edu/workshops/.../WK04_PavelAfonine.pdf on p.20 U(TOTAL)= U(ATOM) + U(TLS) + U(CRYST) and only U(atom) + U(tls) is stored in the PDB ANISOU card. 2. From http://proteincrystallography.org/ccp4bb/message8948.html "Utotal = Utls + Ulocal + Ucryst. So, the ANISOU records always contain Utotal and ATOM records contain isotropic equivalent of Utotal" Which is not the same thing. I suspect it's #1. Am I right ? I would think that U(cryst) is potentially a non-zero contribution to atomic ANISOU values but is actually applied before the TLS/Anisotropic B-factors are refined. As a tie-breaker between #1 and #2 the program documentation suggest that it is just U(tls)+U(atom) but the paragraph that nominally explains it is not short of of inconsistencies, referring to the ANISOU record as having the "the total B-factor (B_tls + B_individual)" whereas they're not only not B's (they are U's) but it's also not the *total* U or B by its own definitions. IMHO it would warrant a rewrite for clarity since B and U are used interchangeably and "total" has variable usage. Phil Jeffrey Princeton