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MRC file format
This information is taken from http://ami.scripps.edu/prtl_data/mrc_specification.htm
The MRC file header is of 1024 bytes long, organized as 56 LONG words followed by space for 10 80 byte text labels. The full specification, listed in Table 1, is abstracted from the image2000 Announcement of the MRC Image Processing package by Crowther et al., which is currently freely available to academic workers. Use of the programs is described in published papers which are referred to in the publication "Crowther, Henderson and Smith, J. Struct. Biol. (1996) 116, 9-16."
For further information about the MRC file format and MRC Image Processing package which includes routines to read/write MRC image, you may contact Jude Short at jms@mrc-lmb.cam.ac.uk.
| LONG Word # | Specification |
|---|---|
| 1 | NX number of columns (fastest changing in map) |
| 2 | NY number of rows |
| 3 | NZ number of sections (slowest changing in map) |
| 4 | MODE data type : 0 image : signed 8-bit bytes range -128 to 127 1 image : 16-bit halfwords 2 image : 32-bit reals 3 transform : complex 16-bit integers 4 transform : complex 32-bit reals |
| 5 | NXSTART number of first column in map (Default = 0) |
| 6 | NYSTART number of first row in map |
| 7 | NZSTART number of first section in map |
| 8 | MX number of intervals along X |
| 9 | MY number of intervals along Y |
| 10 | MZ number of intervals along Z |
| 11-13 | CELLA cell dimensions in angstroms |
| 14-16 | CELLB cell angles in degrees |
| 17 | MAPC axis corresp to cols (1,2,3 for X,Y,Z) |
| 18 | MAPR axis corresp to rows (1,2,3 for X,Y,Z) |
| 19 | MAPS axis corresp to sections (1,2,3 for X,Y,Z) |
| 20 | DMIN minimum density value |
| 21 | DMAX maximum density value |
| 22 | DMEAN mean density value |
| 23 | ISPG space group number 0 or 1 (default=0) |
| 24 | NSYMBT number of bytes used for symmetry data (0 or 80) |
| 25-49 | EXTRA extra space used for anything - 0 by default |
| 50-52 | ORIGIN origin in X,Y,Z used for transforms |
| 53 | MAP character string 'MAP ' to identify file type |
| 54 | MACHST machine stamp |
| 55 | RMS rms deviation of map from mean density |
| 56 | NLABL number of labels being used |
| 57-256 | LABEL(20,10) 10 80-character text labels |
| Symmetry records follow - if any - stored as text as in International Tables, operators separated by * and grouped into 'lines' of 80 characters (ie. symmetry operators do not cross the ends of the 80-character 'lines' and the 'lines' do not terminate in a *). Data records follow. | |
