# SLA, SLAB

NAME
SLA, SLAB - change slab.
SYNOPSIS
SLA keyword
SLA FRONT shift
SLA BACK shift
SLAB keyword
SLAB FRONT shift
SLAB BACK shift
DESCRIPTION
Change the slab. Slab is used to cut the slice out from the structure and to hide the rest. Two slab surfaces are used: the front slab surface, which is the one closer to the observer and the back slab surface. There are three versions of this command:
(1) SLAB FRONT shift ----> move the front slab surface;
(2) SLAB BACK shift ----> move the back slab surface;
(3) SLAB keyword ----> switch slab off or change the type of the surfaces.
SLAB FRONT shift
This command moves the front slab surface. It is recommended to use this command in scripts - in interactive mode, use controls (keys DEL and ENTER on numeric keypad). The shift value should be given in angstroms. Positive shift moves the front slab surface away from the observer. FRONT may be abbreviated to FRO.
SLAB BACK shift
This command moves the back slab surface. It is recommended to use this command in scripts - in interactive mode, use controls (keys 1 and 3 on the numeric keypad). The shift value should be given in angstroms. Positive shift moves the back slab surface away from the observer. BACK may be abbreviated to BAC.
SLAB keyword
Some keywords may be used to change the type of slab surfaces and to switch slab off. Here is the list of keywords:

SHORT FORM | LONG FORM | DESCRIPTION
OFF | OFF | Switch slab off: all parts of the structure should be visible.
PLA | PLANE | Use planes as slab surfaces
SPH | SPHERE | Use spheres as slab surfaces
CYL | CYLINDER | Use cylinders as slab surfaces
HALF-SPH | HALF-SPHERE | Use spheres as slab surfaces, but hide the back half of the structure.
HALF-CYL | HALF-CYLINDER | Use cylinders as slab surfaces, but hide the back half of the structure.

For most structures, the planar slab is the best choice. Spherical and semi-spherical slab may be useful when working with large globular proteins, while cylindrical and semi-cylindrical slab is useful when working with beta-barrel proteins (like porins). The cylinder axis is parallel to y axis (vertical from users standpoint).
EXAMPLES

COMMAND | DESCRIPTION
slab off | Switch slab off
slab front 4.5 | Move the front slab surface 4.5 angstroms away from the observer
slab back -2.8 | Move the back slab surface 2.8 angstroms closer to the observer
slab half-sph | Change slab to semi-spherical