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2009-01-28T23:35:41Z

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== Parameters ==

; function=''string'' (required)
; selection=''string'': (default: ''none'')

== Description ==

This command defines relationships between dihedral angles in a grid
search. For instance, the dihedral angles of a sugar ring can be
represented by a single degree of freedom, the pseudorotation angle.

To represent a group of dihedral angles as a single degree of
freedom in a grid search, this command has to be called once for each
correlated dihedral angle. If exactly one angle within the fragment
is matched by the '''selection''' parameter, then this dihedral angle
will be related by the given '''function''', a Fortran expression of type
real, to a variable, p. The variable p will be the single degree of
freedom during the grid search during which it will vary from 0 to
2*pi. If exactly two angles within the fragment are selected, one of
which has occurred in a previous angle correlate command, then the
"new" angle will be correlated by the given '''function''' to the same
parameter p as the "old" angle.

For example, a molecular fragment consisting of the sugar ring of
nucleotide residue 4 in a DNA or RNA molecule can be defined, and the
dihedral angles of the sugar ring, DELTA, NU1, and NU2 be correlated
to the pseudorotation angle, as follows:

grid fragment "DELTA NU1 NU2 4"
numax=40.0*pi/180.0
grid correlate numax*cos(p+4*pi/5)+2*pi/3 "DELTA 4"
grid correlate numax*cos(p-4*pi/5) "DELTA NU1 4"
grid correlate numax*cos(p) "DELTA NU2 4"

== See also ==

* [[sugarring]]

CYANA Commands: grid correlate - Revision history

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