The crystallisation procedure followed was that described by Blundell and
Johnson [18] (page 69). This batch method used 400 mg of lysozyme dissolved in 5
ml 0.04 M acetate buffer at pH 4.7. After stirring for five minutes 5 ml of 10
(w/v) sodium
chloride solution was slowly added over a further five minutes. The solution was then filtered into
small glass containers and left undisturbed at room temperature for two days after which time
crystals had appeared.
Derivatives of the iridium complex were prepared by soaking the crystal in a 
solution of
in 
at 
. After a few days the crystals began to turn a
pale yellow/brown colour which gradually turned to a dark brown over a period of several weeks.
Attempts at preparing derivatives using other elements of the third transition series were also
made. The choice of which heavy atom compounds to use for trial derivatives was based on the
commercial availability of the substances and also on whether they were at all soluble in the
protein mother solution. Solutions of 
, 
, 
and 
were prepared at concentrations ranging from to 
. It was found that for each of
these complexes solutions of greater than 
immediately caused cracks to appear in the
crystals but at lower concentrations some crystals retained their integrity.