DEFS Instruction
DEFS sd [0.03] sf [0.2]
su [0.01] ss [0.05] maxsof
[1]
DEFS may be used to change the default effective standard deviations for the
following DFIX, SAME, SADI, SIMU restraints, and is
useful when these are to be varied systematically to establish the optimum
values for a large structure (e.g. using R(free)). sd is the default for s
in the SADI and DFIX instructions (excluding DFIX instructions with negative
d , for which the default s remains at 0.1), and also for s1 and s2 in the SAME
instruction. sf is the default effective standard deviation for CHIV and
FLAT, su is the default for both s1 and s2 in DELU, and ss is the default s
for SIMU. The default st for SIMU is set to twice the
default s .
maxsof is the maximum allowed value that an occupation factor can refine
to; occupation factors that are fixed or tied to free variables are not
restricted. It is possible to change this parameter (to say 1.1 to allow for
hydrogen atoms) when refining both occupation factors and U's for solvent
water in proteins (a popular but not uncontroversial way of improving the R
factor).