Re: [ccp4bb] AIMLESS unmerged MTZ output

[Phil]

ISYM/2 is the symmetry number used to generate the unique hkl from the 
original. If ISYM is odd then it is the symop. If even then the symop is 
negated. Thus ISYM = 1 = h,k,l. ISYM = 2 = -h,-k,-l
Symmetry number is order of operators 
There is some code in C in the CCP4 library and in C++ in eg Aimless
Phil


Sent from my iPhone

> On 23 Jun 2017, at 18:46, wtempel  wrote:
> 
> Hello Phil,
> the order of reflections, or the order of operators? How would I reproduce 
> "Orig." H K L, as VIEWHKL appears to do?
> Thank you.
> Wolfram
> 
>> On Fri, Jun 23, 2017 at 1:50 AM, Phil  wrote:
>>  Yes. With the caveat that ISYM refers to the symmetry operators in the 
>> order they are stored in the MTZ file
>> Phil
>> 
>> Sent from my iPhone
>> 
>> > On 22 Jun 2017, at 17:04, wtempel  wrote:
>> >
>> > Hello all,
>> >
>> > Are the following statements regarding AIMLESS unmerged mtz output 
>> > accurate?
>> > - the H, K, L, M/ISYM columns are sufficient to recover the "original" H K 
>> > L indices.
>> > - a combination of "original" H K L and the BATCH value is unique inside 
>> > the file.
>> >
>> > Thank you in advance.
>> > Wolfram Tempel
> 

Re: [ccp4bb] AIMLESS unmerged MTZ output

[wtempel]

Hello Phil,
the order of reflections, or the order of operators? How would I reproduce
"Orig." H K L, as VIEWHKL appears to do?
Thank you.
Wolfram

On Fri, Jun 23, 2017 at 1:50 AM, Phil  wrote:

>  Yes. With the caveat that ISYM refers to the symmetry operators in the
> order they are stored in the MTZ file
> Phil
>
> Sent from my iPhone
>
> > On 22 Jun 2017, at 17:04, wtempel  wrote:
> >
> > Hello all,
> >
> > Are the following statements regarding AIMLESS unmerged mtz output
> accurate?
> > - the H, K, L, M/ISYM columns are sufficient to recover the "original" H
> K L indices.
> > - a combination of "original" H K L and the BATCH value is unique inside
> the file.
> >
> > Thank you in advance.
> > Wolfram Tempel
>

Re: [ccp4bb] Se-Met and Se-Cys double labelling

[Kay Diederichs]

Hi vito,

I don't think you need double labelling. Two (if there is a Met at the N-term 
it might be less ordered) or three SeMet should suffice to phase 360 residues. 
It was true in the old days that a Se could phase less than a hundred residues, 
but if your measurement is good (resolution better than 3A, 360° rotation 
range, fine slicing, PAD, little radiation damage, stable beamline) then I see 
no reason why SeMet-SAD (or even better MAD) shouldn't work.

One should mine the literature to find how many residues can be phased with one 
SeMet nowadays - sorry, lost track.

good luck,
Kay


On Wed, 21 Jun 2017 17:46:56 +0200, Vito Calderone  
wrote:

>I am working on a protein having 360 residues. In its sequence there are 3
>Met and 5 free Cys.
>I will need MAD to solve the structure since based on the sequence the
>closest homologue has 20% identity�I suppose MR would be very unlikely to
>work�so I would like to express a selenium derivative to exploit MAD.
>Looking in the literature 1 Se-Met every 120 residues seems not to comply
>the threshold to get a good anomalous signal. For this reason I would like
>to exploit both Met and Cys so I would have 8 seleniums per 360 residues.
>Could somenone suggest a reference to a protocol to express the double
>mutant protein in NON auxotrophic strains of E. coli which you have
>experienced working efficiently?
>Thanks