Crystalline fibrin
Yesterday I decided that it might be possible that the chains in fibrin are parallel,
and that the unit is only half as large as previously assumed: namely, with a = 4.75
A, b = 135 A, c = 10.03 A, β = 85.1º. on checking this possibility I found that the
small unit accounts for all of the reflections that I had measured except one, a faint
equatorial reflection with spacing 3.16 A. However, the possibility then suggested
itself that this reflection be a β reflection. If it is assumed that it is due to
copper Kβ – Rudall stated “probably trace of β” – then the spacing becomes 2.84 A,
which is that of the strongest equatorial reflection.
On checking the other reflections I had found another very faint reflection that
is to be interpreted as β, corresponding to the strongest non-equatorial spot, with
spacing 2.81 A.
