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Re: [ccp4bb] twinning in monoclinic space group |
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CCP4bb navigationCCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999Subject: Re: twinning in monoclinic space group From: Eleanor Dodson ccp4 {- at -} YSBL {- dot -} YORK {- dot -} AC {- dot -} UK Date: 2008-10-23 Those plots dont look too bad to me - not ideal but acceptable.. There are not many centric reflections so any stats are a bit suspect.. So I would go on working assuming no twinning - and try for a solution from MR or exptl phasing.. That is not so easy I know, but IF you can get an MR solution then those phases may be good enough to find anomalous scatterers.. Eleanor Michael Karl Uhl wrote: > Hello again, > > we looked at the graphs produced by truncate in the monoclinic SG --> > that's why we thought about twinning. The cumulative intensity > distribution does not fit to a sigmoid (indicates twinning) curve but > shows a strange distribution for the centric reflections. If I look at > the acentric and centric moments there is no straight line > (particularly for the centric reflections), the distribution is more > or less something in between twinned and not twinned. > > If we index the dataset triclinic and look at the truncate graphs > again, we can find the same distribution for the acentric reflections > (no straight line). The observed cumulative intensity distribution > fits very well to the theoretic one. > > Thanks for the fast answer and the help, > > Michael. > > > > > Eleanor Dodson schrieb: >> I dont think that is a twinning law, and that SG and cell dimensions >> are unlikely to be twinned. >> >> It could be really P1 I suppose with a twin operator -h,k,-l - ie the >> SYM op is actually a twin operator.. >> But twinning usually shows up in the intensity statistic plots - have >> you looked at the TRUNCATe plots (Import scaled task if you are >> reading scalepack output to convert to mtz file) >> >> Eleanor >> >> Michael Karl Uhl wrote: >>> Hello everyone, >>> >>> >>> I have collected a dataset with a resolution of 1.5 A. The indexing >>> with >>> denzo went very well with the monoclinic cell (62.3120 84.2860 >>> 72.8720 >>> 90.0000 111.9620 90.0000). >>> After many trials to determine the structure with MR as well as SAD I >>> thought that my dataset might be twinned. I reindexed the dataset >>> triclinic and used detwin to analyse it. The found twinning law >>> corresponds to "-h,-k,l". But nevertheless it was not possible for >>> me to >>> determine the structure. >>> I was thinking about a possible twin law in P21 and tried refmac5 with >>> the keyword "twin" and the monoclinic dataset. Refmac5 found a twinning >>> law of "-h, -k, l+h" with a twinning fraction of about 20%. Detwin was >>> not able to deal with these data and gave following error: >>> >>> *** FATAL ERROR *** >>> One of Twin related reflection indices -15 0 52 exceed maximum >>> allowed values ( 43 59 51) >>> Increase PARAMETER MAXIND and recompile. >>> >>> >>> Is this twinning law correct? For me it looks more like a cell >>> transformation than a twinnnig law. >>> >>> >>> Thanks for any help. >>> >>> Best wishes, Michael >>> >>> >>> -- >>> >>> Mag. Michael Karl Uhl >>> Research Centre Applied Biocatalyses >>> c/o Department of Molecular Biosciences - Structural Biology >>> Karl-Franzens-University Graz >>> Humboldtstraße 50/3th floor/room 186 >>> 8010 Graz, Austria >>> >>> Phone: +43 316 380 5466 >>> Fax: +43 316 380 9897 >>> michael.uhl@a-b.at >>> http://www.Applied-Biocat.at/ >>> http://strubi.uni-graz.at/ >>> >>> >>> >> > > ------------------------------------------------------------------------ > > > ------------------------------------------------------------------------ > > > ------------------------------------------------------------------------ > > > ------------------------------------------------------------------------ > > > ------------------------------------------------------------------------ > > > ------------------------------------------------------------------------ > CCP4bb navigationCCP4bb <-- 1999 <-- November 1999 <-- 30 November 1999 |
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