Poly-gamma-methyl-L-glutamate

Date:
1952
Reference:
PP/CRI/H/1/7
Catalogue details

Licence: In copyright

Credit: Poly-gamma-methyl-L-glutamate. Source: Wellcome Collection.

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    Let F = Transform of main-chain Fg = Transform of side-chain Then the observed Patterson has the transform (F 0 + Pg)(P 0 + Pg 1 ) The calculated Patterson of the main-chain is F^F^,*» and if we subtract this» we have left p c F s* + ¥c + Vs*. If we now insert this onto the electron density of the main chain (that is, if we carry out the superposition procedure described above), then the transform of the result is F^ + FF^ + wtp CTS r S C ~ S~ S ; C which is F„F„F* + F„F„F * + F„F„F* CCS see CSS and writing F F ^ P C C = C (where P is therefore the transform ^ s _ p of the appropriate Patterson) Vs = S We obtain FP + F P + FFF aC SC CS CCS We must now consider the three terms of this expression. The term F^Pg respresents the transform of the density one would obtain by inserting the side chain Patterson in the main-chain electron density. As the main feature of the Patterson is its central peak, we get mainly a rather slurred version of the main-chain. Similarly FgPg represents mainly a slurred version of the side chains, which is what we want. As these two will not overlap much, these two terms alone would be very satisfactory But the third term, F^F^Fg*, adds confusion. Let us suppose, for a moment, that^Fg is the transform of a centrosymmetric distribution, so that Fq = Fq , then F C F C = F c Fq £ = P c and our term becomes Fg*Pc « Now Fg* is the transform of the side-chain electron density inverted through