(a): solid contour
lines
(spaced at
intervals of 0.05) represent the linking number Lk(alpha,beta) computed
for alpha ranging from 0° to 180°, beta from 0° to 360°
and n=192 bp so that beta0=125°. Color scale gives the fiber
compaction defined as the number of nucleosomes per unit volume.
Black regions correspond to sterically forbidden regions. Points 1 to 4
are particular reference states: structure 1 is the most compact fiber
structure allowed, paths 1-2, 1-3 and 1-4 correspond respectively to
decondensation at constant beta, constant alpha and constant
Lk(alpha,beta).
(b): fiber structures corresponding to points 1 to 4 in (a), top view and frontal view drawn for 24 nucleosomes. For clarity the first and the last NCP orientations are outlined by a yellow and a dashed violet line. The twist change between any two fiber structures is the angle swept out by the dashed violet line (namely, -0.70 between 1 et 2, -1.10 between 1 et 3, 0 between1 and 4).
(b): fiber structures corresponding to points 1 to 4 in (a), top view and frontal view drawn for 24 nucleosomes. For clarity the first and the last NCP orientations are outlined by a yellow and a dashed violet line. The twist change between any two fiber structures is the angle swept out by the dashed violet line (namely, -0.70 between 1 et 2, -1.10 between 1 et 3, 0 between1 and 4).