34 Mr. E. G. Young. On the Optical Rotatory 



rosette formation. When the serum is ether-washed previously to crystallisa- 

 tion, the crystals show sharp angles, are of uniform size and more quickly 

 deposited. 



The above observation shows how the nature of the medium may affect the 

 structure of the crystals and is of interest in the consideration of all the 

 work which has been done in the endeavour to link up crystalline form of 

 proteins with plant or animal species from material which has been crystal- 

 lised but once from its natural medium. It is also interesting in showing the 

 possible physical associations between lipoid and protein material in protoplasm 

 and the difficulty of removing the one constituent without affecting others. 



Summary and Conclusions. 



Crystalline Ovalbumin. 



The specific rotation of crystalline hen ovalbumin is found to be — 30'81 c 

 for [«] D 15 and — 37'53° for [»] E 15 . The value for [a] is constant within the 

 limits of experimental error after the second crystallisation if recrystallisation 

 be carried out about the isoelectric point (P-i 4 - 9-5T). 



At a lower hydrion concentration (Pu 5 - 3-5'4) a constant lower specific 

 rotation is obtained, [*]„ 15 = -3014° and [«] B 15 = -36'80°. The results 

 were identical by two different methods of analysis. 



The optical rotation of an albumin solution at its isoelectric point remains 

 constant. If it be made slightly acid a prompt rise in rotatory power is 

 observed to a new constant level. If the solution be made alkaline to Ph 49 

 a prompt fall in rotatory power ensues which very slowly rises to the previous 

 value. This phenomenon can be brought about from either side of the 

 isoelectric point and is reversible. The variations in optical rotation are 

 explained on the basis of a tautomeric equilibrium of the lactam-lactim type. 



Experiments are recorded which tend to show that globulith formation is 

 no indication of the power of a protein to crystallise, but probably indicates 

 hydrate formation. 



Crystalline Serum Albumin. 

 Two methods have been used for the preparation of pure serum albumin 

 (horse). The first method involves the precipitation and complete dehydration 

 of the mixed proteins of serum at a temperature of - 4° C, by means of 

 absolute alcohol and ether, removal of fatty substances by Soxhlet extraction, 

 and crystallisation of albumin from aqueous ammonium sulphate solution ; 

 70"4 per cent, of the total albumin was obtained in crystalline form. After 

 the first crystallisation the product possesses a constant rotatory power, 

 [«]„"= -62-8°, [a] E 18 = -78-3°. 



