Froncisz W, Lai C S, Hyde J S
Proc Natl Acad Sci U S A. 1985 Jan;82(2):411-5. doi: 10.1073/pnas.82.2.411.
An unusual ESR display has been developed that exhibits sensitivity to bimolecular collisions of dissolved oxygen in water with nitroxide radical spin probes at oxygen concentrations as low as 0.1 microM, requiring only 1 microliter of sample. The method involves observation of the ESR rapid-passage signal when tuned to the dispersion using a loop-gap resonator. The bimolecular collision rate determines the phase of the signal. The method has been used in a closed-chamber geometry to study respiration of asynchronous populations of Chinese hamster ovary (CHO) cells. An integral of the Michaelis-Menten equation permits direct comparison with experiment and is shown to be incompatible with the data. The theory of diffusion limitation also is developed and shown to be inconsistent with experiment. The average oxygen concentration is found to decrease as Vmaxt, where t is the time after sealing the chamber, to a critical oxygen concentration of 5.2 microM. Below 5.2 microM, the concentration can be fitted to an exponential form, exp(-t/tau), where tau = 15 sec for 4000 cells per microliter. It is believed that this experimental behavior is determined by complex enzyme kinetics.
一种不同寻常的电子自旋共振（ESR）显示技术已被开发出来，它对水中溶解氧与氮氧化物自由基自旋探针的双分子碰撞具有敏感性，在氧浓度低至0.1微摩尔时即可检测，仅需1微升样品。该方法包括使用环形间隙谐振器调谐到色散状态时观察ESR快速通过信号。双分子碰撞速率决定信号的相位。该方法已用于封闭腔室装置中，以研究中国仓鼠卵巢（CHO）细胞异步群体的呼吸作用。米氏方程的积分允许与实验进行直接比较，结果表明它与数据不相符。扩散限制理论也已得到发展，结果表明它与实验不一致。发现平均氧浓度随Vmax t下降，其中t是封闭腔室后的时间，直至临界氧浓度5.2微摩尔。低于5.2微摩尔时，浓度可拟合为指数形式exp(-t/τ)，对于每微升4000个细胞，τ = 15秒。据信，这种实验行为是由复杂的酶动力学决定的。
