Q.742 - Mask overlap

I am trying to generate a mask using MAMA, of my molecule in its p41212 space group. However, when I get to overlap trim, it seems to not calculate the assymetric unit correctly, and gives the error ERROR --- Not an asymmetric unit ! the output is:

 Nr of points in unit cell  : (    1552320)
 Nr in your asymmetric unit : (     202300)
 Nr of symmetry operators   : (          8)
 Asymm. unit * symm. opers. : (    1344800)

so it is apparently not multiplying correctly? please can you advise?

From: XRAY::GERARD "Gerard 'CD' Kleywegt" 20-OCT-1995 17:06:41.83

which numbers did you type for overlap origin and overlap extent ? And what is the asu for your spacegroup (0-1 0-1 0-1/8 ?)

If your grid is e.g. 120 * 120 * 160, you would use:

 ov ori 0 0 0

 ov ext 121 121 21

From: SMTP%"eads@zugbug.bioc.aecom.yu.edu" 20-OCT-1995 18:28:24.26

Thanks for your quick reply, I have set

 ov ori 0 0 0
 ov ext 85 85 28

So I thought this should be ok.

From: XRAY::GERARD "Gerard 'CD' Kleywegt" 20-OCT-1995 18:40:57.70

The problem is with the C axis grid: 220 is not a multiple of 8 (i presume this gives problems in the FFT in CCP4 as well ??)

Use 216 or 224 instead & it should work (if you use 1/8*224 + 1,2or3 in MAMA)