12.1. Core functions of MDAnalysis¶
The basic class is an AtomGroup
; the whole
simulation is called the
Universe
. Selections are computed on an
AtomGroup
and return another
AtomGroup
.
To get started, load the Universe:
u = Universe(topology_file, trajectory_file)
A simple selection of all water oxygens within 4 A of the protein:
water_shell = u.select_atoms('name OH2 and around 4.0 protein')
water_shell.n_atoms # how many waters were selected
water_shell.total_mass() # their total mass
AtomGroup
instances have various methods that
allow calculation of simple properties. For more complicated analysis, obtain
the coordinates as a numpy array
coords = water_shell.positions
and write your own Python code.