"The height of the vector rods in the three-dimensional Patterson of haemoglobin"

Date:
1951
Reference:
PP/CRI/H/1/4
Catalogue details

Licence: In copyright

Credit: "The height of the vector rods in the three-dimensional Patterson of haemoglobin". Source: Wellcome Collection.

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    the skeleton Patt arson, putting 01a« for «ach point of the latter» and where for «zampi© 6 points fall ©.» top of on® another, we insert it there 6 tiaes. there the vector densities overlap we add the® up. How what we prove in the Appendix is that this synthetic Patterson is identical with the one calculated in the normal ay. This is all very obvious and well-known. However It is worth while malting a few consents. Firstly, there is nothing in the proof about electron densities not baiag. .Negative,, so the results apply when we are thinking in temi of fictitious densities (see page 3). If we do this, when we say 'there is nothing sise in the crystal except the identical parts' we œean that the flctitlou density is stero elsewhere. In terms of real electron density this means that all the space whtre the parts are not is filled in with our average liquid. Slisilarlly when ws say 'we consider a single .Isolated part' we really reean an Isolated part surrounded by zero fictitious electron density. Is real terms, a part embedded ill an infinite sea of our average liquid. Also note that (assuming the salt has the saine average electron density as the protein ) the average value of our Patterson, in tens® of fictitious electron density, is zero. Thus at one step we allow for the salt, and achieve our aia of calculating directly the height-ahove-average» instead of by difference. Finally note that our part need not be the (fictitious) density of actual atoms. It can be any pattern of electron density. In practice it will be due to atoms distorted and smeared by heat motion and diffraction, but if we can split it up as described above our method still works* 2nd example This time consider a orystal »ade up of 3 kisisxnf parts called A B and €„ These may be quite different, or simply identical bodies in different orientations* We think of the skeleton a lattice as before, but this time we have to label our pointa-a..
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