Re: [ccp4bb]: Patterson maps with FFT

[Jay Pandit <pandit@pfizer.com>]

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Bernard Santarsiero wrote:
> 
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> I noticed recently that if I include a phase PHI in the LABIN command, the
> Patterson maps look different than when a phase is not included.  Does the
> inclusion of a phase overwrite what should be used to generate a Patterson
> map?
> 
> In particular, I'm doing an anomalous Patterson map, so F1=DANO.
> Including PHI was an accident, but I was surprised that it changed the
> map.
> 
> Bernie Santarsiero

Hi Bernie,
 I think you may have come up against an unexpected quirk of the
program.

 The LABIN command defines which items are used for map calculation, and
essentially determines what kind of map you get.

Normally, LABIN F1=DANO,PHI=PHI will calculate an 'anomalous Fourier'
map with amplitude DANO and phase 90-PHI

Also normally, the keyword PATTERSON forces a Fourier summation with
amplitudes F1 squared and phases set to zero.

By combining PATTERSON with F1=DANO, you probably calculated a Fourier
summation with amplitudes DANO squared and phases = 90.0 !!

Cheers,
Jay Pandit

-- 
 Jay Pandit
 MS 4039
 Pfizer Global Research and Development         Phone:  (1) 860 441 3738
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