Dissertation in Draft: Chapter VIII

Date:: 1953

Reference:: PP/CRI/F/1/8

Credit: Dissertation in Draft: Chapter VIII. Source: Wellcome Collection.

2/31

$arranged, at regular intervals along the locus of a coiled-coil has *W\ \jkjV CAtvpl&f öjtrt-.lr*- I been given • The^method of using this to calculate the structure factors of a real coiled-coil structure is explained in the introduction to that The gradual helix followed by the axis of the curved -helix is called the major helix. It has radius i , a repeat ° distance of P in the Z direction, and its pitch angle ©¿ is given )y túv* . The helix which approximates to the o¿ -helix itself is called the minor helix. The complete structure is assumed c z to repeat after a distance^ in the 2 direction, the major helix making turns, and the minor helix turns in its own frame in that distance. The précise definition of is given in the original paper. There are M atoms, equally spaced along the C- coiled-coil locus, in the repeat distance The cylindrical co-ordinate of reciprocal space are denoted by R, ^ and Z. The Fourier transform G(R,^, Z) is non-zero only on the layer-lines (we shall call P the number of the layer-line$) since the structure is periodic in the § direction (the fibre axis) but \ non-p eriodic in the òther two directions^/ From equations (%$) and •£ ljj, [liJT-liiiMjin ■- ■ ~far (\l) oá í --@E±r±r4±Í5^') Tire write down ¿the result for a right-handed major helix and a left-handed minor helix. This is P î ' * ¿fp(l++) +î(l' + )+ sJ ] ^ ^ {W Subject to the restriction that one only includes terms for which Nop t + M,s '■ ? + *M . _ , (g) where j> , ^ and m can take any integer values positive or negative.$

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Dissertation in Draft: Chapter VIII

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