[ccp4bb]: molecular replacement woes!

[schakrav <schakrav@lamar.colostate.edu>]

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hi,
my name is srinivas chakravarthy (cheenu) and i am a graduate student in 
Dr.Karolin Luger's lab at Colorado State University. I am an absolute beginner 
in the field of crystallography and would deeply appreciate any input that 
comes my way pertaining to the problem i am now facing which is-
   I have synchrotron data from a nucleosome crystal which was indexed and 
scaled without any major problems in the space group p222(1). I get an overall 
completion of 96.7%. I run into problems at the molecular replacement stage 
(using CNS). the spacegroup of the model is p2(1)2(1)2(1). when i do a cross 
rotational search, going by the rotation function peak height values it seems 
to have worked. (highest values are .1591 and .1496 and the rest of the values 
are in the .06 range). this is on using "fastdirect". i havent tried "direct". 
when i do a translational search i do get a solution with a correlation 
coefficient (E2E2) which is significantly higher than the other solutions 
(monitor no. is .262) but on minimization refinement i get unreasonable r and 
free_r values. my final r is 0.5163 and the final free_r is 0.5231. the model 
and my molecule supposedly have a high degree of homology. 
my questions are 1.should i expect problems in molecular relacement on account 
of the model and my molecule being in different space groups (i've been told 
that i shouldnt)? if so what would be the nature of the problem? 2. what could 
be the possible reasons for the high r and free_r values?
Do forgive the lack of precision in expressing my problem. My excuse is I am 
just beginning to use the terminology and the concepts.
thanks for your patience,
cheenu.

Srinivas Chakravarthy
Colorado State University
Fort Collins
CO-80521