1. The hydrodynamically effective volume,
Ve of Taka-amylase A was calculated according to the treatment of Scheraga and Mandelkern. It was found to be nearly equal to
M_??_/N, the anhydrous volume of the protein.
2. The hydrodynamically effective volume,
Ve, of some other proteins were also calculated and compared with
M_??_/N values of the respective proteins.
Ve is far less than
M_??_/N with flexible and hydrated protein, whereas both volumes are nearly equal with rigid anhydrous protein.
3. The observed partial specific volume by density measurement of Taka-amylase A is 0.700ml./g. and markedly less than the calculated value of 0.723ml./g. by the Cohn-Edsall method. The deviation may be caused by the occurrence of prosthetic sugar groups in the interstices between polypeptide helices in the molecule without any contribution to the molecular volume.
These facts mentioned above support the view that Taka-amylase A molecule may be rigid and compact and scarcely hydrated.
In conclusion, the authors express their hearty thanks to Prof. S. Akabori and Mr. T. Ikenaka for supplying the valuable sample. The authors are also indebted to the Ministry of Education for a grant.
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