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Re: finding sites

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> I have two different space groups...P21 and P1.  Most of my work is on 
> the P21 form as the P1 form is a recent discovery.  I have collected 

> Theoretically, the 3 dimensional arrangements of the sites should be the 
> same in both space groups, so I was wondering if I can use the known 
> sites as a sort of MR search model against the isomorphous signal from P1 
> Native vs. Semet.  I don't know exactly how I would go about doing that, 
> but if anybody has some suggestions, they would be greatly appreciated.

1.  Use |Fph-Fp| as the "native" data
2.  You didnt say if you knew how the Se sites "clustered" (i.e. know
    which belong to the same molecule), but assuming that you do:
	Isomorphous difference Se-S = 18 electrons, which is approximately
	that of sulphur (16 electrons), so you could create a "SeMet"
	MR model of a set of sulphurs at each SeMet site.
3.  Run MR in the normal way.

Alternatively, by creatively editing the script in X-PLOR for doing
Patterson space rotation functions, you could probably do the same
analogous thing using the anomalous difference patterson in P1.

I've had some success using |Fph-Fp| in translation functions to find
heavy atom sites in proteins, although this is certainly not a new idea,
but I've never tried rotation functions before.

| Phil Jeffrey                                  |                             |
| Crystallography Facility Manager              | If you lie to the compiler, |
| Memorial Sloan-Kettering Cancer Center, NYC   | it will get its revenge     |
| phil@xray2.mskcc.org                          |     - Henry Spencer         |
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