density.read() -- read an EM (electron microscopy) density map file

file = <str:1>	'default'	input electron density map file
em_density_format = <str:1>	'XPLOR'	input density map file format for EM_GRID_SEARCH; 'MRC' | 'XPLOR'
density_type = <str:1>	'SPHERE'	Function used to calculate density map cross-correlation in EM_GRID_SEARCH; 'SPHERE' | 'GAUSS' | 'HYBRID' | 'GAUSS_NORM' | 'TRACE'
voxel_size = <float:1>	0	EM density map voxel size for EM_GRID_SEARCH
resolution = <float:1>	0	EM density map resolution for EM_GRID_SEARCH
em_map_size = <int:1>	0	size of the density map, for EM_GRID_SEARCH
ccf_func_type = <str:1>		type of correlation 'CCF' | 'LCCF'

This command reads a density map from file, which should be provided as a cubic grid of intensities, in the X-PLOR ([Brünger, 1992]) or MRC format. The size of the cubic grid is given by em_map_size. The density map resolution and the map voxel size are given by resolution and voxel_size, respectively.

When fitting the probe into the EM grid, the probe structure is converted first into probe density, by using the function indicated in the density_type variable. Each atom can be represented by one of several atomic density functions, including, the uniform sphere model ('SPHERE'), the Gaussian function ('GAUSS'), a normalized Gaussian function ('NORM'), a hybrid Gaussian/sphere model ('HYBRID'), and an interpolation to the closest point on the grid ('TRACE'). The recommended function is 'SPHERE'.

When calculating the cross-correlation coefficient between a probe model and the density map, ccf_func_type specifies if you want the normalized cross-correlation coefficient ('CCF'), or the local cross-correlation coefficient ('LCCF').

Example: See density.grid_search() command.