Spin-label oximetry: kinetic study of cell respiration using a rapid-passage T1-sensitive electron spin resonance display.

Publisher Website
Google Scholar
Abstract
An unusual ESR display was 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 .mu.M, requiring only 1 .mu.l 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 was used in a close-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 incompatible with the data. The theory of diffusion limitation also is developed and is inconsistent with experiment. The average oxygen concentration decreases as Vmaxt, where t is the time after sealing the chamber, to a critical oxygen concentration of 5.2 .mu.M. Below 5.2 .mu.M, the concentration can be fitted to an exponential form, exp(-t/.tau.), where .tau. = 15 s for 4000 cells per .mu.l. This experimental behavior is determined by complex enzyme kinetics.

This publication has 13 references indexed in Scilit: