Angles split

Parameters

selection=string

(default: none)

structures=integer

(default: 1)

decrease=real

(default: 4.0)

all

Description

Command to identify torsion angles that have a strong bimodal distribution in the selected conformers. The analysis is performed for the torsion angles matched by the selection string. By default, the selection made in the most recent angles select command is used, or all angles if no selection has been made so far. However, torsion angles that rotate only hydrogen atom , e.g. methyl groups rotations, are considered only when the option all is present.

Torsion angles whose values in the selected conformers cluster into two distinct groups are identified by calculating the unimodal standard deviation from a single mean value and the bimodal standard deviation from two different mean values. A torsion angle distribution is considered as clearly bimodal, or "split", if the bimodal standard deviation is at least decrease times smaller than the conventional unimodal standard deviation, and if the there are at least structures conformers clustered in the smaller of the two groups. Split torsion angle distributions are reported in a table.

For example:

   Split angles:    mean1  mean2    dev   # 1   5   10   15   20
   CHI1  VAL   33  -174.1  -73.2    2.1   4 +        +  +    +

In the example, CHI1 of Val 33 exhibits two distint conformations with a small bimodal standard deviation of 2.1 degrees. The 4 conformers 1, 10, 13 and 18 that are marked with + are clustered around the secondary mean value of -73.2 degrees. The other 16 conformers are close to the first mean value of -174.1 degrees.

The angles split command is included in the detailed overview produced by the overview macro.

See also

• overview