Crystal Structure of Horse Myoglobin 



iO 20 

 Angstrom Units r] 



c 

 > 



* 



■■ -<- 



Figure 3. Suggested mode of packing of myoglobin molecules 

 in the unit cell. 



THE PATTERSON PROJECTIONS AND THEIR INTERPRETATION 



I now proceed to give an account of various Patterson projections of 

 the wet myoglobin unit cell, and to indicate how they support, and add 

 further detail to, the molecular model just described. So far it has not 

 been practicable to collect the data which would be required for a 

 three-dimensional Patterson synthesis on the lines of that described by 

 Perutz for haemoglobin (p. 138) ; fortunately the structure of myo- 

 globin is so much more simple that two-dimensional projections con- 

 tain many features which can be interpreted. 



The three most important projections are illustrated in Figure 4, 

 showing the main peaks of vector density. Each projection shows the 

 whole of the unit cell, and in each the origin is drawn at the centre of 

 the cell. In a monoclinic unit cell it is convenient to project, not on to 

 the ab and cb faces of the cell, but on to planes through b and respec- 

 tively perpendicular to c and a ; these projections have dimensions 

 b X a . sin /? and b x c . sin fi and may be referred to as the c and a 

 projections. The third projection, perpendicular to b, is on to the ac 

 face of the cell and has dimensions a and c. 



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