An ESR Study on the
Effect of Hydration on the Dynamic Property of RNase A
FU Ya-Zhen*, YANG Jing-Wen
(Institute of Biophysics, the Chinese Academy of Sciences, Beijing
100101, China)
Abstract A method
is described for the measurement of dynamic property of RNase A by ESR under
xeric conditions. The relationship between relative humidity and hydration
degree of RNase A was determined by hydration isotherm. A solution of RNase A
was allowed to react with a solution containing maleimide nitroxide label at 25
℃, then was dialysed and lyophilized. The stable powder of RNase A – maleimide
nitroxide label compound was put into the tubules, then was hydrated under
different relative humidity for 11 days. After hydration, the tubules were
closed and measured by ESR. The relationship between hydration value and Amax was detected. The results
showed that the lowest water content that could induce motion of RNase A by
water is about 0.20 g of water per g of RNase A. That means the motion of RNase
A molecule becomes detectable when there are 152 water molecules around one
RNase A molecule.
Key words hydration； RNase A； ESR
Received: June 7,
1999 Accepted: August 20, 1999
This work was supported by a grant from the National Sciences Foundation of
China, No. 39470153
* Corresponding author: Tel, 86-10-64888584; Fax, 86-10-64871293; e-mail,
[email protected]