INTERACTION OF COLLAGEN MAC ROMOL EC U L ES 



47 



but definite amount of tyrosine (Highberger, 1956), and the ability 

 of the TC to form highly ordered fibrous structures is lost if the 

 purification treatment is such that the tyrosine is removed. In them- 

 selves, these results suggest that the tyrosine is located in relatively 

 accessible regions of the macromolecules, perhaps at the ends. This 

 possibility was given further force by the observation of Bensusan 

 ( 1959 ) that iodine markedly accelerates the thermal gelation of 

 neutral salt solutions of collagen, especially in view of the fact that, 

 with the exception of histidine which reacts much more slowly with 



/>/t ¥.tr 



7A- 



a, I ?00 - 



o 



"5/ 



_ *^ 



2 4 6 8 10 f2 14 (6 18 20 22 24 26 28 30 32 34 36 38 40 



Tabe number 



Fig. 27. The distribution of 1^-^' activity in paper-curtain electrophoresis of 

 denatured collagen incubated with trypsin (Run B-l of Fig. 26), together with 

 the relative specific activities of the various fractions indicated in Fig. 26. At 

 top is shown the electropherogram of the same run after staining, first with 

 ninhydrin (positive reaction indicated by N), then with amido-black (A). Note 

 that Fraction I escaped detection by staining with ninhydrin and amido-black, 

 but has by far the highest specific activity of the various fractions examined. 

 (From Hodge ef a/., 1960.) 



