###
*PROCHECK sample plots*

# Plot 8. Main-chain bond angle distributions

## Description

The histograms on this plot show the distributions of each of the different
main-chain bond angles in the structure. The **solid** line in the
centre of each plot corresponds
to the **small-molecule mean value**, while the **dashed** lines
either side show the **small-molecule standard deviation**, the data
coming from Engh & Huber
(1991).

Highlighted bars correspond to values more than **2.0**
standard deviations from the mean, though the value of **2.0** can be
changed by editing the **procheck.prm** file.

If any of the histogram bars lie off the graph, to the left or to the
right, a large arrow indicates the number of these outliers (as in the
**CA-C-O** and **CB-CA-C** plots above).

Significant outliers are shown on the **Distorted
geometry plots**.

## Options

The main options for the plot are:-

- Number of standard deviations for highlighting outliers (default is
**2.0**).
- The plot can be in colour or black-and-white.

These options can be altered by editing the parameter file,
**procheck.prm**, as described here.

###
*PROCHECK sample plots*