I wonder if anyone attempted to write a historic book on development of crystallography. That generation of crystallographers is leaving this world and soon nobody will be able to say how the protein and non-protein structures were solved in those days.
Alex
On Jun 6, 2012, at 8:48 AM, Gerard Bricogne wrote:
> Dear Fred,
>
> May I join Phil Evans in trying to dissipate the feeling that anomalous
> differences were fictional before flash-freezing and all the mod cons. I can
> remember cutting my teeth as a PhD student by helping Alan Wonacott with the
> experimental phasing of his B.St. GAPDH structure in 1973-74. The data were
> collected at room temperature on a rotating-anode source, using film on an
> Arndt-Wonacott rotation camera (the original prototype!). The films were
> scanned on a precursor of the Optronics scanner, and the intensities were
> integrated and scaled with the early versions of the Rotavata and Agrovata
> programs (mention of which should make many ccp4 old-timers swoon with
> nostalgia). Even with such primitive techniques, I can remember an HgI4
> derivative in which you could safely refine the "anomalous occupancies"
> (i.e. f" values) for the iodine atoms of the beautiful planar HgI3 anion to
> 5 electrons. This contributed very substantially to the phasing of the
> structure.
>
> In fact it would be a healthy exercise to RTFL (Read The Fascinating
> Literature) in this area, in particular the beautiful 1966 papers by Brian
> Matthews in Acta Cryst. vol 20, to see how seriously anomalous scattering
> was already taken as a source of phase information in macromolecular
> crystallography in the 1960's.
>
> In spite of that, of course, there would always be the unhappy cases
> where the anomalous differences were too noisy, or the data processing
> program too unsophisticated to filter them adequately, so that only the
> isomorphous differences would be useful. It was in order to carry out such
> filtering that Brian Matthews made another crucial contribution in the form
> of the Local Scaling method (Acta Cryst. A31, 480-487).
>
>
> With best wishes,
>
> Gerard.
>
> --
> On Wed, Jun 06, 2012 at 11:02:05AM -0400, Dyda wrote:
>>> I suspect that pure MIR (without anomalous) was always a fiction. I doubt that anyone has ever used it. Heavy atoms always give
>>> an anomalous signal
>>
>>> Phil
>>
>> I suspect that there was a time when the anomalous signal in data sets was fictional.
>> Before the invent of flash freezing, systematic errors due to decay and the need
>> of scaling together many derivative data sets collected on multiple crystals could render
>> weak anomalous signal useless. Therefore MIR was needed. Also, current hardware/software
>> produces much better reduced data, so weak signals can become useful.
>>
>> Fred
>>
>> [32m*******************************************************************************
>> Fred Dyda, Ph.D. Phone:301-402-4496
>> Laboratory of Molecular Biology Fax: 301-496-0201
>> DHHS/NIH/NIDDK e-mail:[log in to unmask]
>> Bldg. 5. Room 303
>> Bethesda, MD 20892-0560 URGENT message e-mail: [log in to unmask]
>> Google maps coords: 39.000597, -77.102102
>> http://www2.niddk.nih.gov/NIDDKLabs/IntramuralFaculty/DydaFred
>> *******************************************************************************[m
>
> --
>
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